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·PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA

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·Principles and Practice of
OBSTETRIC
ANAESTHESIA
By
J SELWYN CRAWFORD
M.B ch.B, D A (ENGLAND) FFA R.C.S
Anaesthesia Service
The Presbyterian Hospital New York
Late Senior Registrar and First Assistant Department of Anaesthesia
Central Middlesex Hospital London
BLACKWELL
SCIENTIFIC PUBLICATIONS
OXFORD

·Blackwell Scientific Publications Ltd 1959
This book is copyright It may not be reproduced by any means
in whole or sa part without permission Application wrth regard
to copyright should be addressed to the publishers
Published simultaneously in the United States of America by
Charles C Thomas Publisher 301 327 East Lawrence Alenue
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Published simultaneously in Canada by The Ryerson Press
Queen Street IVest Toronto 2
First printed 1999
PRINTED IN GREAT BRITAIN FOR BLACKWELL SCINTIFIC PUBLICATIONS LTD
BY BILLING AND SONS LIMITED GUILDFORD AND LONDON
AND BOUND AT THE KEMP HALL BINDERY

·TO MY MOTHER AND FATILER
WITH GRATITUDE
FOR THEIR UNDERSTANDING AND SACRINCE

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·CONTENTS
LNTRODUCTION
1
1 TIIE MOTHER
6
I THE PLACENTA
16
III ANALCESIA
32
IV FORCEPS DELIVERY AND CAESAREAN SECTION
$2
V OTHER INDICATIONS FOR ANAESTHESIA
79
VI TEE CHILD
94
VII EQUIPMENT AND ADMINISTRATION
115
EPILOGUE
123
INDEX
126

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·INTRODUCTION Trte adding of a new title to the cataloguc of medical works is a responsibility wluch may be justifiably undertaken on onc of only cho counts of the aim is to fill a gap m the literature or if the author feels apable of presenting in a more palatable manner facts and ideas such have already reached the library shches in the present case the pica is based on the former indication At the tinic of wrining no Brush textbook of obstetric anaesthesia remains in print. Although the subject us dealt with in tcribooks of both obstetrics and anaesthetics discussion necessanly tends to be somewhat cursory It as axiomatic that sound practice stems from knowledge scdded to expenence and an attempt has been nuade here to gather together the facts and many of the theones which must be understood by an anaesthetist before he can intelligently apply himself to the management of an obstetric patient. The days of empiriasm in anaesthesia for general surgery are fase passing for obstetric anaesthesia they still flourish. The pages wluch follox real that we remun ignorant of many aspects of the subject, notably regarding the problems of placental transmussion and of neonatal respiracion Howeser there is much known sluch as unmediately applicable to sound obstetric anaesthetic procedure and it is surely time that the prinaples were put into more general use Repeatedly throughout this decade the pages of the Lancet and the British Afedical Journal haic rescaled that there is considerable disquict regarding our standards of anaesthesia for obstetrics The Citicisms may be resolved into two categones the one concerned ynth method and the other with service The primary aim of this book is to prevent an evaluation of the range of methods of anaesthesia and analgesia with reference to physiological and pharmacological proces.cs Some mention must also be made however of the deficiencies in our anaes. thesia service Despite the fact that we have a large and still blowing population of anaesthouses whose work is confined almost entucly to hospital practice in recent years obstetric needs have been met by an increase in neither quantity nor quality of attention Obstetric anaesthesia remains the B I

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·INTRODUCTION 3 Anacsthetists must also bear considerablc responsibility for the current failure to reduce the perinatal mortality and morbidity rates but the analysis of the factors concerned is difficult The United States las similar problems in 1955 the maternal mortality was o 47 per Iooo live births with a total of about four million deliverics Referring to a somewhat carlier penod (1944-53), Matson and Jacoby have indicated that surveys reveal 3-10 per cent of the deaths to be the result of anaesthesia In response to this situation leading Amencan anaesthetists notably Hingsons and Apgar? have urged a 24-hour anaesthetic service for obstetrics combined with a closer collaboration between anaesthetists obstetricians and paediatriaans in both routine work and in the investigation of the problems involved. That such proposals can be advanced for immediate adopton in a country which soll suffers from a senous shortage of anaesthetisks delincates even more sharply the poverty of our own efforts Obstemnc anaesthesia and analgesia cannot be satesfactorily undertaken merely by transposing to the labour ward the methods learned in the general operating theatre Further specialızed knowledge and techniques are needed The welfare of the child, also is a direct responsibility of the obstetno anaesthetist. By virtue of his special training the anaestherist has a unique contribution to make towards the problems of ensuring an adequate oxygen supply for the foctus of avoiding centrally-induced neonatal depression of resuscitating the newborn and of preventing or treating regressing pulmonary efficiency in the newbom As in the casc of maternal morbidity these problems become of increasing concern as the previous major causes of perinatal death arc reduced in importance On a national scalc anaesthetists are not yet facing their responsibilities in thus field. The problems in terms of both research and of day-to-day application can be attacked satisfactorily only by the concerted action of obsternaans paediatricians and anaesthetists (physiologists and other laboratory workers have of course a great part to play in the special centres) cach of whom is willing to work under the direction of the others depending upon the shifting requirements of the situation This is no place in which to discuss the larger questions involved in an expansion of the anaesthetic service fully to meet these requirements It might be suggested, however that the urgent demands of obstetrics are likely to be met to a greater extent by a reorganization than by a reinforcement of cach anaesthetic department The common function of an Introduction is to survey the environment -both hustonical and contemporary of the subject to be dissected in the ·2 PRINCIPLTS AND PRACTICE OF OBSTETRIC ANAESTHESIA Cinderella of the speciality in most hospitals—including those of considerable repute-and all too frequently anaesthesia for forceps delivery is left in the hands of the junior resident unsupervised, and with only the smatterings of experience in the general theatre That most obstetric operations are emergences occurring at awkward hours is the basic cause of this administrative failure but it is also the very reason why increased skill and attention are called for in these cases The national maternal and infant mortality rates have been falling in a gratifying manner during the past twenty years These declines have resulted from improvement in many lines of therapy notably in the combating of sepsis and of shock, but not from improvement in standards of anaesthesia The latter is now by contrast becoming a prominent cause of maternal mortality and must thus be indicted as a major factor in infant mortality and morbidity In 1955 there were 667 811 live births 439 maternal deaths and a maternal mortality rate of o 66 per 1000 in England and Wales 1 of the maternal deaths 251 were associated with complications of pregnancy (excluding urinary tract infection and ectopic pregnancy) or with delivery (Brews P 713) One hundred and twenty of these were associated with actual delivery and failure of complete anaesthetic management must have played a significant part in many of these tragedies The Report just quoted indicated that in the three-year period 1952-54 in England and Wales 49 maternal deaths were directly attributable to complications of anaesthesia and in another 20 cases anaesthesia was a contributing factor To thus total of 69 must be added an unspecificd number in which the anaesthetist was at fault in his role as resuscitator Comparable figures will certainly apply to the whole of the United Kingdom Dinnick' has shown that in England and Wales in 1954 general anaesthesia was administered for 67 600 of the 432 000 deliveries occurring in hospitals and regional methods were used in a further 19 000 cases When considered in relation to the round total of two million anaesthetics (excluding dental gases )' administered annually in the United Kingdom these figures speak for themselves If we relegate to a position of neglect one patient out of every twenty-five requiring anaesthesia we are failing in our professional duty This is the very least of the matter for no menuon has been made of the 900 ooo deliveries occurring each year in the United Kingdom dunng the course of whuch techniques and drugs of direct concern to the anaestheast are regularly used. The negligence of Brush anaesthetists in this regard ill-becomes the country in which was first demonstrated a rationally controlled method for the relief of pain 212 childbirth ·INTRODUCTION $ Bert B Hershenson Robert A Hingson, Clement A Smith Virginia Apgu, F H Seward, Hilda Roberts lan Donald and R Bryce-Smith. It is largely duc to thc initiatic of these men and women that case of pain in childbirth luas been and continues to be icndered more efficient and more safe for both mother and cluld Finally my thanks go to Miss Alarjonchuck MRCOG in Toronto and to Dr R E Molloy FFA RCS nou returned to London from Pittsburgh for rcading the draft text with the um of discovering any gross crrors of fact in obstetric and anaesthetic matters They are not to be held responsible for any of the opinions assessments or recommendabons cypressed. JSC September 1958 REFERENCES Report on Confidential Enquincs into Maternal Deaths in England and Wales 196. 54 Ministry of Health Reports on Public Health and Medical Subjects No 97 HMSO London 1957 2 Brews A (1957) Edm and Hollands Alanual of Oi stetrics Tith cd London Churchill 3 Dannick O P (1957) Discussion on general anaesthesia for obstetrics Proc roy Soc Mied 50 547 4 Compiled from vanous unofficial sources no authoritative figures are to hand s Cull W A and Hingson RA (1957) Dedication education and organization in the round the clock staffing of a modern obstetrical analgesia and anesthes12 service Bull Alat 11 elfare Scpt-Oct 6 Matson J E and Jacoby J (1957) Material mortality and morbidity from anesthesia ) in Coll Surg 28 172 7 Apgar V (1995) Role of the anesthesiologist in reducing neonatal mortality NY SI J Med 55 -365 & Hershenson B B (1955) Obstetrical Anesthesia Its Prisciples and Practice 1st ed P 176 Sprngfield Ili Thomas Burge E S and Baldwin CE (1956) Usc of spinal anesthesia un obstetrics at the Evanston Hospital Amer J Obstet Gynec 71 973 ·4 PRINCIPLES AND PRACTICE OF OBSTETRIC ANALSTHESIA patient in body of the book In this respect it is felt that two further matters must be presented one a warning and the other a tribute Most hospital practitioners regularly consult the leading journals concerned with their speciality and published in other lands In the English-speaking communities reading is probably confined to the Journals from the Commonwealth the United States and Scandinavia Interpretation of the views expressed and of the results reported in these articles must to some extent be based upon an appreciation of the medicosocial background of the community under investigation In the field with which this book is concerned the point assumes great importance when attention is directed to the literature of the United States and Canada Readers on the eastern shores of the Atlantic would do well to bear in mind the following facts The midwife system is virtually non-existent in North America almost all deliveries being conducted by the attending physician or obstetrician (in the USA 85 per cent of the total occur in hospitals) Outside of the renowned institutions this not infrequently leads to a call to delay the progress of delivery in order that the accoucheur may reach his time 8 9 The vast majority of deliveries are instrumental the practice being founded upon well-engrained views on saving the perineum and avoidmg prolonged pressure on the foetal head. Consequently the very large numbers of forceps deliveries often quoted are in effect biased by the inclusion of many cases of normal women undergoing normal pregnancies and having normal infants In North America active participation by the mother in her labour is not generally observed and there is a vociferous demand for the obliteration of all awareness of the birth process for sedation and for if possible amnesia Hingson s introduction of the regime of continuous caudal analgesia has to some extent offset the latter two requirements It is important that these factors be borne in mind whenever articles from Canada or the US A are consulted just as it is necessary for North American readers to appreciate the working conditions in Britain and Scandinavia when assessing the results published in these countries As was said earlier this book was conceived mainly because there appeared to be a need to collect and to analyse the plethora of pronounce mnents and observations on the subjects of obstetric analgesia and anaesthesia and of neonatal resuscitation Inevitably therefore it is founded upon the work of many people who have been prominent in this field during the past century A very personal call is felt to pay tribute to the following inspiring workers Sir James Young Simpson John Snow Carl Gauss Sir James Barcroft R J Minnitt Stewart H Clifford ·TIB MOTIIER 7 the guin us notably accelerated during the course of the third trimester reversal of the process being instrated only after delery The intravascular water retendon increases only slightly during the first trunester the gradient steepens thereafter until just before the onset of labour when thercu a sharp and sigruficant fall Salt retention closely accompanies water setengon throughout progo nancy Both processes arc probably related to the secretion of steroids by the placenta. In the post-partum penod following a normal pregnancy on the ascrage about 5 gm sodium u 'shed by the mother The other components of the blood also follow a pattern of solumetric change during pregnancy Total blood solume decreases during the first two months and thereafter Tises gradually unal thc ame of delivery Plasma volume increases steadily throughout pregnancy just before the onset of labour when there is a significant fall Red cell volume after an urutal fall during the first to months nses with the progress pregnancy unul the time of delivery However the increasing hypervolaemua outstrips the rise in red cell volume and haemoglobin mass leading to bacmodelugon and an apparent anaemua as terma approaches A red cell count of 3-75 million per com a haemoglobin of ri-sz gm per cent, and a haematocrit of 35 per cent have been suggested as the lone levels of normal at term Because of foetal demands made upon the maternal iron supplies there is always a tendency for a true anaema to develop It is almost always necessary to supplement a normal good diet with iron throughout pregnancy in order to buuld a score with which the heavy demands of the final anmester may be met. It us the duty of the anaesthetist in co-operanon with the obstetrician to watch for anaemua and to treat it should it occur in a patient under lus care. It is generally accepted that the maternal blood loss during a normal delivery might reach 500-600 ml The platelets which semain farly constant a concentration during pregnancy increase abruptly in number during the late stages of labour There is ui addigon a total increase and a relative increase in the fibrinogen content of the plasma, the total amount bang 40 per cent greater thas normalm despite a diminution of plasma protein concentration there is actually a gun of about 18 per cent in the total arculating mass nicar term Although these two factors are important in curbing haemorrhage they might also lead to an increased liability to chrombo-embolic phenomena during the pucrperum and should spur the anaesthetist to theteascd care in the matters of foot-sorrups leg-rests and general positioning of the pacerit ·CHAPTER 1 THE MOTHER EVERY anaesthetist is a doctor It is to be expected therefore that obstetric anaesthetics will be admistered always by practiooners having some knowledge of the significant changes accompanying pregnancy Furthermore the anaesthetist will be aware of the general mechanics and physiology of labour and of how these might vary It is only by weaving his specialized skill into the framework of this basic knowledge that he is able to offer maximum aid to both the patient and the obstetrician As in all medicine co-operation is the key-word. The anaesthetist must be able to anticipate the difficulties which the obstetrician might encounter during delivery and must be prepared to allow him the best operating conditions compaable with the safety of his two patients Reciprocity is of course impliat in co-operation A good obstetrician apprecates the limitations of anaesthesia and the dangers which it presents to mother and child In addition in any good team each doctor will know the individual adequacies of the other and will modify hus technique accordingly In the years of his training and in the case of the occasional obstetric anaesthetist-during the long summer of lus consultancy recollections of his undergraduate tuition in obstetrics will fade in the mind of the anaesthetist Thus chapter is an attempt to present a resume of the important anatomical and physiological considerations of pregnancy and labour relative to the practice of anaesthesia In emphasis and approach it is a considerable distortion of the obstetric viewpoint this is natural enough as obstetrician and anaesthetist contemplate the patient from opposite poles Normal Pregnancy and Labour 1 VARIATIONS IN BLOOD AND BODY FLUID Water retention is a normal concomitant of pregnancy There 15 general retention throughout the assues but the proportions held in the intra- and extra-vascular compartments vary in each trimester Thc extra-vascular flud increases gradually during the first six months and 6 ·TT MOTHER 9 contraction The subject will be further discussed m dius and subsequent chapters Although the general enous pressure remuns relatively uncluanged, the mercasing size of the gravd utcrus leads to a gradual se m the femoral venous pressure conaming through the sccond and turd trimesters At term the pressure scaches about 18 mm Hg compared with the normal o mm Hg It should be noted that u hen the patient : supine 2$ in operatic obstetrics the inferior Cha cavawhich receives the uterine crous outilosdirectly subject to these pressure changes 3 ALTERATIONS IN THE MECHANICS or RESPIRATION Despite the encroachment of the diaphragm into the thoracic cavity pulmonary venalanon is actually increased during pregnancy INCTCase Is initiated in the first trimester and continues gradually throughout pregnancy It is a result of a nuse in both respiratory rate and adal olumne The rate is increased to the point of dyspnoea in about 60 per cent of women during the final trimester Broadening of the chest and 2 change from abdominal to thoracic breatlung contabute to the physiological compensaaon for a decreased thoracic height and the tidal volume increases by an average of about 35 per cent during the months from early pregnancy to term Vital capacity and inspiratory reserie remain unchanged, and thus the expiratory reserve is inevitably decreased The respiratory mucosa exhibits a generalized hyperacrua due to capılm lary engorgement Thues is to be accepted as increasing however slightly the hazard of intubacon especially if the nasal route is used It also tends to increase the discomfort of the dyspnoea of late pregnancy - an increase which is emphasized in the presence of even minor upper respiratory infection These points are of some importance in regard to the applicacon of a face-mask as nose-breathing becomes extremely difficult for some women al term 4 BIOCHEMICAL CHANGES As pregnancy advances both the orygen and the carbon dioxide dissociation curves of the mother s blood ate stufted slightly to the right Tlus means that dunng late pregnancy in a low oxyget-tension environ ment oxygen is more readily released and carbon dioxide more readily taken up by the blood than is the case in the non-pregnant state Oxygen consumption is increased, having by term risen to a level about 10 per cent lugher than that obtaming prior to pregnancy Carbon dioxide tension ·8 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA 2 CARDIOVASCULAR CHANGES uterine contractions occur The dynamics of the circulation undergo important changes during pregnancy The size of the heart increases slightly but only in proportion to the general weight gain Its position changes as might be deduced from the mechanics of a rapidly growing tumour causing upward displacement of the diaphragm Cardiac output is increased considerably dunng the middle trimester and thereafter gradually falls reaching a rate a little above normal just before term. During the first stage of labour cardiac output rises again increasing markedly when strong At no time however is the myocardial reserve of the pregnant woman without heart disease demonstrably depleted. During pregnancy the resting pulse-rate increases on the average by 12-20 beats per minute Vanlous changes of rhythm in otherwise normal hearts have been observed they invariably disappear following delivery and are probably of no significance Systolic blood pressure is unchanged by normal pregnancy The diastolic pressure falls slightly dunng the greater part of the gestation penod, with a resultant increase m pulse pressure but it returns to the pre-pregnancy level duning the final month As would be expected, uterine blood flow increased vastly with the progress of pregnancy It has been computed that towards term blood reaches the uterus at the rate of soo ml per minute 1 Due to the demands of the foetus oxygen consumption is extremely high (see Chapter II) Furthermore there are during labour greatly significant changes in the continuity of uterine blood flow It has been shown that in the course of a normal contraction the pressure within the uterine muscle rises to about so mm. Hg As the venous pressure is only about 4 mm Hg there is a temporary interference with the venous return from the uterus and consequently by retrograde resistance with the arterial supply It has been suggested that this period of relative ischaemia dunng each contraction is compensated for by a local hyperaemia-induced by the accumulated metabolites --W hulst the utenne muscle is at rest The changes in uterine blood flow are said to be accompanied by simular variations in placental blood flow leading to a adal variation in the amount of oxygen available to the foetus The second of these propositions has not yet been satisfactonly demonstrated, and it is interesting to speculate upon the significance of the large blood-filled intervillous spaces in this respect. Possibly in normal labour the intervallous blood acts as a reservoir from which the foetus can draw an adequate amount of oxygen during a ·11 THE NOTHIER is prolonged, the use of drugs w łuch are excrete inchanged by the kidney must be limited 7 MECITANICS AND PAY LABOUR Towards the end of a nomal pregnancy, the uterus is an extra-peluc structurc. The onset of labour may be heralded by the phenomenon of lighterung in wluch the presenting part descends into the pelvas Prior to thus, although the well-known contractons of Braxton-Hicks accur with considerable frequency there is no pain of 201y significance associated with normal pregnancy The nene-pathways insoked in labour are now well-recogmzed, their final denuficazon being based largely on the results of Cleland s original worl. The propulsore efforts of the uterus contributed largely by the longitudinal muscle fibres of the corpus and fundus are initiated by stamuh travelling via sympathcac fibres whose central ongus lic above the lord of the axth thorzac segment The onconung factus as accommodated by acuyc dilatagon of the lower segment of the uterus that us by the arcular fibres of the lower thurd of the corpus uteri and those of the CCVI. The motor pathways by wluch this is effected art contuned in the parasympathetic outflon from $2 3 and 4 In addiqon to the neural clement, there is a hormonal factor of possibly equal importance in the control of myometrial activity It is understood that a pituutary dennove closely related to pitoan plays an important part in the initiation of uterine contraction. The sensory acne supply is best described in conjunction with an account of the course of labour The inmal contractions are felt as a oghtening in the lower abdomen and the lower part of the back. Such sensagons are not to be construed as evidence of true labour unless each acco ucd by a palpable uterine contraction The lower abdominal discomfort us reflexly produced by stimuli ansing in the body of the Uterus Afferent nerses from the latter pass via vanous plexuses of interchung fibres to the cell stadions as the closench and Melfth thorac ganglia of cach sympathetic cham From these the assoaned wlute ramı communicantes travel with the approprate dorsal nerve root to synapse in the cleventh and twelfth thonac segments of che spinal cord In accordance with the general findings regarding visceral sensaon pain us therefore referred to the areas supplied by the somatic afferent nenes arising from these segments Under some circumstances the first lumbar segment might also become involved. The low backache component of early labour is 25ociated with the start of cervical dilatation Saumul from the cervix are transmitted 122 ·to PRI QULES AND PRACTICE OF OBSTETRIC ANESTHESL and carbon donde conset are both dished. The carbon donde combmong poker of the blood dearezses from the normal of about sa volumes per cent to approximate 45 volumos per coat. This recados malbalı restes 200ompued bra redococa m bosal bati base. It does not, however represent a tice zadoss. The sum FH rents consult The cond.sons apparendy one of compensated carbon donde deficie a defiat resulong from the increased palconary venalason referred to above. These factors are of comederable mportance m the mastering of questions concernang neonatal respiras02 In relaqon to the foregong 1 is as well to remember the doming normal pregnancy the basal metabolic rate rises gradually and they a. term 1 migh. be more than 10 per cent above tha. obrang in the case Con-rregnant site. In addision, there is a creased f. absorpion 223 a rise in plasına fars concern abon. Ketoss is no a normal 2000mm ment of pregnancy but these two stufis, together with the fall malkab reserve, make the pregnant woman moreasingly Lable to do so a ketonic st2.. Glucosina, persistent or term.ttent, is a communal feature of many Fregnanas. It is rela.ed to a los ered real threshold, and to a decreased abilt on the part of the liver to store glycoga Non-pro.em mtrogen and blood urna levels are significant reduced dunng normal Fregnancy S DIGESTIVE DISTCRSANCE The only disturbance of digestion which is of n.erest to the anchest occus duong labous It has long been held that there is a congderable reductos n the rate of empiring of the swomach dung labour This tenet is based almost cadrely on dm.cal impression, and is said to bold for both find and solid stomach-cn.cats. Radiographic restgagon* has tended to throw some doubt on the correctness of the new 25 far 35 Aud contenus are concerned, but it would still serve the anaesthenes well not to tzke chances in cius respect. 6. REAL TRACT Of som-wpormace to the passtheast is the fact tha dimag Feazacy 2 slight degree of hydrometer and brdson proses developspoorly on the agh side. This effect tends to be cocertad dung labour dus to mechanical factors, and can be a frommet cause of labour The pand is reforced to the tenth and derech thorzac segmos. If, as in grotracted labour thus process of daruming back the Eow of urme pain andra ·TIT NOTHIER 13 involve brcath-holding for most of the period of cach contracuon with two important implications firstly no inhalatonal analgesia can be given dunng the bearing-down period and consequently a storc of thc drug must be built up within the patient during thc 20 seconds prior to cach such episode secondly, for a 30-40 second penod during cach contraction the mother is deprived of oxygen and at the same time she performs a vanation of Valsalvas manocuvic These factors arc of the greatest concern in the conduct of cases of maternal heart disease and of foctal distress In some mothers duc to reasons of anatomy (unpliablc fascial sheaths resistance to stretching of scar tissue) or psychology (involuntary contracnon of muscle by an apprehensive patient) the pelvic floor which term implies in effect the levator ani and its attendant fascia con nues to resist the passage of the presenting part Such an event is liable to cause increased pain in the S2 S3 and S4 segments and, if untreated to result in some soft-tissue perineal injury It is the latter prospect added to the postulated possibility of danger to the infant because of delay in the second stage plus undue pressure on the foetal skuli which has led North Amencan doctors to favour the practice of routine episiotomy and forceps delivery The sense of distension of the vagina and vulva as they are traversed by the foetus is transmutted by somatic afferents leading to the mid-sacral segments To allow the accoucheur better control of the rate of delivery and thus to help to avoid teanng the perineal skin and subcutaneous tissue the mother is instructed to stop bearing-down when the head is about three-quarters crowned. To help her to do so she is encouraged to breathe deeply and rapidly through her mouth, thus effectively preventing a Valsalva manoeuvre At the same time she is usually given some additional relief in the form of inhalational analgesia After delivery of the head, there is usually a quiet interval of about a minute before the next contraction initiates delivery of the shoulders To reduce the chances of obtaining a bad tear during delivery of the shoulders the mother is discouraged from beating down at this time Any pain during the third-stage of labour will be associated with a strong uterine contraction (T11 and T12) vaginal discomfort due to the passage of the placenta is fleeting 8 SOME ASPECTS OF PATHOLOGY a Pre-eclamptıc toxaemia To the anaesthetist the outstanding aspects of this condition are ·I2 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA the second, third and fourth sacral components of the parasympathetic system Sensation is appreciated as coming from the sites of distribution of the appropriate somatic afferent fibres As labour progresses contractions assume a greater regularity and increase in strength and frequency Pain is likely to supercede discomfort when the degree of cervical dilatation has reached about two fingers in the primipara and about three fingers in the multipara From this time and until the end of the first stage of labour each contraction is characteristically accompanied by a waxing-peak-waning pattern of pain The waxing and waning components take the form of a dull ache-respectively increasingly and decreasingly severemfelt in the lower abdomen the low back area and the front and inner aspects of the upper thighs in effect over the area of distnbution of Tui T12 L1 S2 S3 and S4 At the peak period there is in addition a severe graping pain which is usually referred to the areas supplied by TII and T12 When the foetal lie is occipito-postenor the most severe pain in the first stage is nearly always felt in the back often under such circumstances backache persists even between contractions Classically contractions during the latter-half of the first stage of labour occur about every 3-5 minutes and last for about 1 minute Pain or discomfort is felt dunng approximately the last 40 seconds of each contraction, and thus there is about a 20-second warning period The remembrance of this fact is of great importance in the successful conduction of inhalational analgesia. At the end of the first stage the mother becomes a much more active participant in her labour In many cases thus change from the era of passivity guckens the interest of the patient and in so doing helps to diminish her appreciation of the pain involved. At the same time both the character and the source of pain are somewhat changed Contractions occur more frequently and give only about 5 seconds warning of the start of pain Hence to provide adequate inhalation analgesia reliance must be placed upon the regularity with which the contractions occur Although the pain of uterine propulsion—transmitted via Tri and T12- persists that due to dilatation of the lower segment 15 of course ended In place of the latter stimuli arise from the pelvic floor area upon which the head descends with some force following full dilatation of the cervix The afferent fibres here concerned likewise have their central connections situated in the second, thud, and fourth sacral segments but are somatic rather than parasympathetic Stimulation of the pelvic floor leads reflexly to an increase in the strength of uterine contractions it also provokes the mother into making voluntary bearing-down efforts The latter 4 ·TIIC MOTUER IS ton dunng or following the third stage with an attendant danger of Screrc post partum lacmorthage As an additional factor the placental site is about twice the normal size in these cases and not infrequently extends to the lower uterine segment whicrc rctraction is rclatis cly inefficient The rouunc use of ergometrinc has lielped to decrease the frequency of this occurrence but recourse might hasc to be made to a pitoan drp Significant aspects of pathology in cases of placenta praevia, malpresentations disorders of utcrinc function prolapsed cord and retained placenta will be discussed subsequently together with the role of the anaesthetist in ther management. REFERENCES 1 Romney S L Red D E Metcalf ) and Burwell CS (1955) Oxygen utilization by the human fetus in utero Amet > Obstet Gynec 70 795 Crawford, J S (1956) Some aspects of obstetne anaesthesu Brit j Anaesth 28 201 3 Cleland, J GP (1933) Paravertebral anaesthesia in obstetrics experimental and clinical basis. Surg Cynes Obstet 57 31 4 Seward E H and Bryce Smith R (1957) Inhalation Analgesia in Childbirth Ist ed. Oxford Blackwell. s Gibberd, G F (1955) Short Textbook of Midwifery Och ed. P 142 London Churchill In addition to the above the following works have been frequently consulted during the preparation of the present chapter 1 Marx G F and Orkin, LR (1958) Physiological changes during pregnancy 2 review Anesthesiology 19 258 . Hingson, R. A and Hellman, L. M (1956) Anesthesia for Obstetrics ist ed Philadelphia Lippincott 3 Brews A. (1957) Eden and Hollands Manual of Obstetrics Irth ed. London Church ·14 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA hypertension interference with renal function placental infarction and retroplacental haemorrhage In severe cases the diminished renal output will be such as to lead the anaesthetist to limit his choice of drugs in the manner suggested previously (part 6) There is strong support in obstetric circles for the suggestion that the renal failure and the hypertension result at least in part from renal cortical arteriolar constriction initiated by a utero-renal reflex similar to the Trueta-shunt phenomenon The possible role of the anaesthetist in the treatment of such a condition and in the treatment of eclampsia will be discussed later in this book. In the presence of pre-eclampsia the anaesthetist must assume that there as a significant diminution in the efficiency of oxygen transport from mother to child This can result from three causes gross placental infarction haemorrhage into the placental site diminution in the rate of maternal blood-flow through the decidual essels Whatever reason pertains it behoves the anaesthetist to take care that he does not decrease maternal oxygenation by his choice of analgesia or anaesthesia The more active measures he can take to counteract the effects of placental deficiency will be discussed later b Multiple Pregnancy Multiple pregnancies tend to result in the delivery of small premature infants Furthermore toxaemua of pregnancy occurs relatively frequently in association with this condition Thus an extra attention to the details of inaternal oxygenation is indicated The first stage of labour is often prolonged on account of weak and infrequent uterine contractions according to Gibberd 5 who also teaches that the persistence of this uterine inefficiency during the second-stage leads frequently to the necessity of a forceps-assisted delivery despite the small size of the foetus In the case of twin pregnancy there is usually an interval of about twenty minutes between delivery of the first infant and the resumption of uterine contractions During this period if there is any placental separation it is likely to be only slight It is rarely that the presenang foetus does not lie longitudinally The second infant however is frequently not so conveniently situated. If the obstetrigan has not been able to carry out a version on the second twin before the membranes rupture the mother will probably have to be anaesthetized for the operation. Possibly because of the excessive stretching to wluch the uterus is subject during pregnancy there is an increased risk of inadequate retrac- ·TIIT TLACT-TA 17 tissue of foctal ongin It inclosos a broad, swiftly-running current of maternal blood, and lies witlun the uterinc cavity being fed from artenoles which pass through the myometrium from the uterine and oranan artones and drained by a comparable 1cnous System in any arca of adjacency, the matcmal blood flows in a direction opposite to that taken by the foetal strcam' Tlus description pertains to conditions casting after about the thirtieth wech of pregnancy The speafiary and rate of placental transmission are governed by the following factors I. The effective crient of the placental site IL The rates of flow of both foctal and maternal blood. III. The permeability of the endothelial barrier IV The partial gas-pressure osmouc pressure and hydrostatic pressure gradients across the endothcuum, v The relaase concentrations of electrolytes VI The capsary of the placenta to undertake active transmission Acterm the placental site is generally arcular in outline with a diameter of about 6-8 inches Koncict it has by this aime passed its peak of efficiency The process of placental degeneraaon normally begins to reach significant proportions at about the thirty-cighth fleek of prega nancy It consists of a progressive obliteratrc endarteritis of the foctal ressels which by causing a coagulatic necrosis of the chorionic villus leads to clic appearance of localized placental infarctos representing discrect areas of fusion of such necrosed villi Concomitant with, though distinct from, the areas of infarction are localized areas of haemorrhage mto the placenta. In these regions the ville have been destroyed or disorganized by haemorrhage from the matemal aspect of the chorodecidual space The process of ageing of the placenta thus leads directly to a reduction of the efficiency of the organ by diminishing its area of acavity Starting between one and three weeks before term degeneration continues progressively and thus becomes of considerablc significance when pregnancy is prolonged beyond the expected date of delivery A recent study' kas suggested that the placetira ages much more rapidly at least between the thirty-sixth and fortieth wecks when the maternal Rh blood-group is negative A similar picture of placental infarcuon and haemorrhage of variable seventy is associated with toxaemia of pregnancy essential hypertension and chronic nephntıs Placenta praevia is the remaining notable condition in which the placental site might be drastically diminished. It is convenient to consider the factors of the hydrostatic pressure C ·CHAPTER 11 THE PLACENTA 3 General Considerations PLACENTAL fuocoon is the crux of most problems in obstetne anacsthesia It is by way of thus fasanaong organ that the foetus recases its oxygens its nourishmeat and its share of drugs administered to and abaormal substances produced by the mother The placenta also provides virtually the sole route of excretou open to the foctus Some recent studies 2 have indicated that certain substances might pass berseen the chonon laeve and the foerus via the aminoac Amd, but for the moment these matters lie outside the range of thus book. The differential manner i wluch the placenta segulates its two-way trafic, the factors influencing the degree and selectivity of 10s action and, in great measure the norms of sach action are woefully l-understood Hobeses the sum of facts and hypotheses regarding the subject has progressively increased sunce Barcroft initiated serious rescarch into the physiologr of the placentam and recently Dotably in New York a determined attack has been made on many of the problems The anaesthetist is especially concerned with questions regarding foetal respiration, and with the possibilin of placcotal transference of the drugs which he administers to the mother An approach to these problems acrossitates some understanding of the physiology and pathology of the placenta. It is not considered that the placepta u an organ of mternal secretion, possibly acting also as a storchouse for vanous products necessary to foctal metabolison. These matters are of little practical concern to the anaesthetiss, to whom the organ is represented solely as a vast area of juxtaposidon of the maternal aod foeral arculadons Foctal blood passes from the umbilical antenes to the umbilical sein by way of a huge network of capillary loors contained within the chorionic vill. The latter are loed only by a synapal epihchal layer and bathed in the maternal blood of the intervallous spaces in the mature placenta, the intervallous spaces coalesce to a marked degree, forming what is termed the chono-deadual space This mupally maternal structure is bounded on one side by chorionic 16 ·TULE. PLACENTA 19 arteriovenous difference in oxygen content of the umbilical vessels is close to that of the uterine vessels the blood flow of the two arculations should, in accordance with the Fick principle be of the same order, namely soo ml per minute We have no micans of controlling ather the rate of blood-How or the hydrostatic pressure withun the foctal capillanes of the placenta The influence of molecular size and ionic charge upon the degree of permeability of the placenta is apparently of little immediate practical concern to the anaesthetist as there exists no well-founded theoretical exposition of these matters u luch can be applied to the problems of drug transference * What is known empincally about the behaviour of cach drug is detailed in the second half of this chapter It is unlikely that the factors of osmouc equilibrium and electrolytic concentradon play any significant part in the transmission of anaesthetic agents The placental transmission of gases is obviously of pressing interest to the anaesthetist. Details regarding the anaesthetic agents will be discussed in the general secuon on drugs preceded by a consideration of the passage of oxygen and carbon dioxide. It has been demonstrated that placental transmission ceases on complem aon of delivery and before the cord is cut but is still in progress between the times of delivery of the presenting part and of the conclusion of the second stage of labour Thus there can never be any point in attempting to oxygenate the chuld via its mother once delivery is complete and nor is there any danger to the child in giving the mother more anaesthetic at thus stage Cord pulsation is not indicative of continuty between maternal and foetal crculations though of course there might be a dwindling storc of oxygen within the placenta on which the apnoerc infant might usefully draw No studies of the time of cessation of transmission 13 cases of Caesarean section have been reported, but it would obviously be of interest to know this b Placental Transmission of the Respiratory Gases Foctal survival is dependent upon the oxygen supply received via the placenta, and upon the efficiency with which carbon dioxide is passed to the matemal arculanon along the same route The mechanics of the two arculations as described above provide a gross control of the rate * For a review of aspects of this subject with reference to the influence of toraemua the reader is referred to McGaughey H S Jones HC Talbert L and Anslow WP (1958) Placental transfer in normal and toxac gestation Amer J Obstet Gynet 75 482 ·18 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTUIESTA gradient and the rates of blood flow together According to Page 8 between uterine contractions the pressure within the foetal capillaries 15 30-36 mm Hg and that in the chono-deadual space w 5-10 mm Hg Dunng a contraction both pressures rise to maintain this gradient coincidentally cnsuring that the arculaton of foetal blood does not cease Page concludes that hydrostatic pressure plays no part in the transfer of any substance esther way However, changes in the local maternal arculanon must influence the rate of flow of blood within the chono decidual space There is increasing evidence replaong previous speculanon that placental transmission is altered in conditions affecting the afferent sauses of this space These condisons include nocably toxaemia of pregnancy essendal hipertension uterine hypertonis and spinal and epidural block. As previously indicated, both pre-eclampuc toracmua and essendal hypertension may reduce the extent of the effective placenta) site by producing areas of infarction. Lately it has been demonstrated by Johnson and Clayton amongst others, chat in severe coxaemia placental function is much improved by an epidural block. Obviously such a block is unlikely to cause a reversal of the process of pathology sa the infarcted areas It can be effective only by relieving the constriction of uterine vessels whuch is a characterisac of the condizon Sularly part of the considerable relief of foetal distress afforded by epidural block during the strong contractions and throughout the prolonged laboumno of cases of tocoordinate uterine activity lave been attnbuted to uterine vaso-dilatation.o 7 Paylıng Wright and her colleagues" further believe that even in the course of normal labour fauly strong uterine contractions by interrupting blood-flow through the afferent vessels of the chono deadual space can temporary reduce placental transmission of oxygen. Indeed, foetal bradycardiam-possibly sigrufying foetal hypoxia_-45 frequently observed at the height of a contraction and is well-recognized as being assoaated with sustained utenne hypertoniary under conditions of prolonged spraal analgesi. Variation in the calibre of the uterine arteroles whether of intrinsic or extrinsic ongin leads to altered transmission from mother to child, not by changrag the hydrostaac pressure within the chorio-decidual space bur by affecting the rate of blood-How In cases of protracted uteruc vaso-constrcaon the flow of blood through các interviſlous spaces becomes so sluggish that the pathological process of infarcoon is initiared. Other than the self-evident effects of compression of the umbilical cord, little us known regarding the factors influeang the rate of blood-flow through the foetal capillanes Romney and his controrkers have suggestad, on the basis of findings quoted later in this chapter that as the ·MIT PLACINTA mlת 19 arterio-senous difference in ogen content of the umbilical vessels is close to that of the uterinc vessels the blood flow of the two arculations shoud, in accordance with the Fick prinaple bc of the samcorder namely 500 per minute We have no means of controlling either the rate of blood-fox or the hydrostatic pressure within the foctal capillanes of the placenta. The influence of molecular size and ionic charge upon the degree of permeability of the placenta is apparently of loc immediate practical concern to the anacsthetist as there exists no well-founded theoretical exposition of these matters wluch can be applied to the problems of drug transference * What us known empincally about the behaviour of cach drug us detailed in the second half of this chapter It is unlikely that the factors of osmotic equlibrum and clectrolyac concentration play any significant part in the transmission of anacsthetic agents The placental transmission of gases is obviously of pressing interest to the anaesthetist. Details regarding the anaesthetic agents will be discussed in the general sccoon on drugs, preceded by a consideration of the passage oxygen and carbon dioxide. It has been demonstrated that placental transmission cases on complonon of delivery and before the cord is cut but is still in progress between the time of delivery of the presenting part and of the conclusion of the second stage of labour Thus there can never be any point in attempung to oxygenate the child via jis mother once delivery is complete and nor is there any danger to the child in giving the mother more anaesthetic stage Cord pulsabon is not indicabye of continwry berween maternal and foctal arculations, though of course there might be a dwindling store of oxygen within the placenta on which the apnoeic infant might usefully draw No studies of the time of cessation of transmission in cases of Caesarean section have been reported, but it would obviously be of saterest to know thuis of at thus b Placental Transmission of the Respiratory Gases Foctal survival is dependent upon the oxygen supply received via the placenta, and upon the efficiency with which carbon dioxide is passed to the maternal arculation along the same route The mechanics of the two arculations as described above provide a gross control of the rate * For a review of aspects of this subject with reference to the influence of toxacmia the reader is referred to McGaughey HS Jones K C. Talbert L and Anslow WP (1998) Placental transfer in normal and toxic gestation Amer Obstet Gytuce 75 482 ·20 utero PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTIITSIA and quantity of these transfers The conditions existing at the matema) foetal interface merit further discussion Aspiration of blood from the intervallous space is now an established technique and thus analysis of the matemal blood involved in the process of placental transmission can be obtained with considerable accuracy The difficulties of obtaining blood samples from the foctal capillaries have however proved much more intractable and it has been customary to rely upon analysis of umbilical vein blood, taken at the moment of delivery as giving a fairly reliable reflection of the condoons custing in In the course of two noteworthy articles Apgar and her col leaguesto 11 have suggested that the partial pressure of oxygen found m the umbilical vein at birth will be lower than that which had obtained in the villous capillanes immediately prior to delivery The difference it is postulared is due to interference with placental transmission dunng parturition subsequent to the analgesia--whether regional or general.com and to physical factors associated with the mechanics of delivery These workers indicate that the partial pressure of oxygen withun the umbilical vein of a normal infant at the time of delivery is about so mm Hg Baston and Meschia 12 and later Page " presented the following equation rclating to the rate of oxygen transference across the placenta QƏDW (PⓇP) where is the total quantity of oxygen transferred from mother to child each minute D is the diffusion coefficient for oxygen expressed in mg/kg of foetus per mm Hg difference mpo, W is the weight of the foetus in kilograms PAP, are the average values for the partial pressure of maternal and foetal blood respectively Com nting on thus equation Page noted that P, will alwavs exceed P, for two reasons there is a rapid withdrawal of oxygen from the foctal blood by the foctal tissues and secondly the dissociation of foctal oxyhaemoglobin occurs at a lower po, than does the dissociation of adult oxy haemoglobin lower even than that of the pregnant woman The latter point is of further importance for the corollary holds true foctal haemoglobin has an increased affinity for oxygen in the high partial pressure range and consequently when compared with adult haemoglobin has an increased capacity to take up oxygen at the placental site Page discusses the equation in the light of results published by Romney and his colleagues * These workers analyse their findings in 13 cases of Caesarean section performed under spinal analgesia and present the following figures orygen in ·21 TIIE TLACENTA Utcrinc blood-flow Foctal weight Placental Baght Waght of myometrium assessed at soo ml/min as crage 3 300 gm average soo mg average 1,500 gm Uterine artery Utcrrc vcin Umbilical artery Umbilical icin Ai crage Orygon Content (ml /100 ml) 132 10 S 33 80 Romneys group considers the oxygen consumption of the placenta and of the myometrium to be about 45 ml/kg /mn Thus from a total uterine consumption of 23 s ml, oxygen per minute the foctal demand accounts for about so ml/kg /min Reverting to the equation the following may be substituted Q=165 W=3 3, (Px--Py)=37 and thus D=0 135 (Page in obtaining a result of D=02 is considering the transfer of oxygen from the uterinc artery to the uterus and its contents) The values quoted by Romney and hus co-workers appear to indicate that the uterinc arculation carries oxygen in considerable excess of the focral requirements at term Gross disruption of the placental site would undoubtedly interfere senously wich the pasage of oxygen to the foctus as already indicated, but the above-quoted figures lend some point to the more recent views on post-matunity expressed notably by Bancroft- Livingston and Fisher 13 These workers claim that other things being equal, there is no evidence of an association between post-matunty and foetal hypoxia, and that the mcreased perinatal mortality rate attendant upon post-maturity is a reflection of other factors namely disproportion excessive size of the infant, and prolonged labour As the debate is sall proceeding the possibility of a Ielationship between post-maturity and foetal hypoxia will continue to be pressed. Assuming that there is maximal flow of maternal blood through the chanodecidual space and that its haemoglobui is fully oxygenated the amount of oxygen presented to the foetus can be increased only by adding to the quantity of oxygen dissolved in the plasma McClure claims that this can be done by allowing the mother to breathe pure oxygen He presetats the argument that 100 ml of adult blood contains o 25 ml of orygen and 104 ml of nitrogen in the dissolved state and that thus by replacing the nitrogen with oxygen an additional 10 ml of oxygen per ·22 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA 100 ml of maternal blood is made available to the foetus McClure goes on to say that as the arterial blood of the neonate is usually so per cent saturated with oxygen (an estimate rather lower than that suggested by Pages and by James and his colleagueslo u) and the foetal oxyhaemo globin dissociation curve is steep in the vicinity of so per cent saturation this slight increase in maternal po, will result in a significant rise in the oxygenation of the foetal blood. He reports a series of 15 mothers undergoing normal delivery under pudendal block. They were given to 1 of 100 per cent oxygen via a closely-fitting BLB mask for an average of 45 minutes pnor to delivery The infants in the series had a mean umbilical vein po. of 38 21 mm. Hg whilst the comparable figure in a control series of 19 mothers who breathed air but were otherwise similarly treated, was 28 93 mm. Hg That maternal inhalation of a hugh oxygen concentration might benefit the foetus was first suggested nearly thirty years ago 15 and the therapy 15 now generally practised in cases of foetal distress Carbon Dioxide As stated in the previous chapter the patient at term has a low partial pressure of carbon dioxide in her blood (pco,) and a low concentration of buffer base (42 mEq/l) compared with that of the normal adult The findings presented from Apgar s Unitio 11 in the articles previously referred to indicate that the blood of a normal foetus at term exhubits the same tendencies In response to the transient anoxaemia associated with delivery per vaginum the neonate rapidly develops a marked degree of respiratory acidosis but metabolic acidosis does not occur unless the period of anoxaemia is prolonged. The fall in pCO, following adequate oxygenation of the newborn infant is of equal rapidity In view of the fact that under conditions of adequate oxygenation foetal pCO, and buffer base concentration are both maintained at about the levels found in maternal blood, it would seem that the placenta permits the very rapid diffusion of carbon dioxide from foetus to mother without the incentive of a steep gradient It is also apparent that the foetus is not as has so often been claimed used to a high partial pressure of carbon dioxide in utero These matters will be referred to again in Chapter VI c The Placental Transmission of Anaesthetic Agents Our routines of anaesthesia need modification when applied to the obstetric case The basic feature necessitating this modification is the fact that in such a case there are two subjects involved one of whom can ·TUIE PLACENTA usefully be regarded as a poor risk patient The anacsthetist can be in only indirect communicanon with his second, more vulncrable patient Just as it is upon the pharmaco-physiology of the placenta that the de clopment of the foctus of a healthy mother depends so also it is upon the transmitting attributes of the placenta that many of our rules an obstetric anaesthesia fundamentally hinge Yet cien today little is known regarding the placental filtradon or active transport of our analgesic and anaesthetic agents from maternal to foctal arculauon Equally important is the fact that we are also ignorant of the time-factor involved in many instinccs. A fauly cursory perusal of the literature indicates that the first laboratory evidence of placental transmission of a drug in which we are interested was published in 1907 Snyder states that Holzbach in that year showed scopolamine to already present in a chuld s urne when delivery occurred Is minutes after injection of the drug into the mother the route of administradon not being indicated. Fifty years later we find that there has been virtually no progress in our knowledge of the possible transmission of other drugs having a primary action at the autonomic nerve endings. Pages has stated that monoaminc oudose in the placenta prob ably breaks down adrenaline and noradrenaline as they leave the matemal arculanon and that thus these agents do not reach the foctus Zachs and Wislockal have shown that there is present in the placenta a large storc of cholinesterase though for some rcason as yet unexplained, the acetyl cholinesterase and scrum cholinesterase of the placenta are comparaosely resistant to prostgmine. We remain completely ignorant regarding the possible entry into the foetal arculanon of other para-anaesthetic agents If scopolamine why not atropine and, of even greater importance especially in respect to the conduct of spinal and epidural analgesia, why not the s aso-pressor agents? We appear to know nothing regarding the the degree or rate of transference of these drugs yet in the presence of established foetal distress their exhibition could conceivably be a final determining factor on the outcome of the case The tale as regards the inhalational anaesthetic agents is somewhat bnghter la 191. Whipple (quoted by Snyder18) recorded hus observations that, following chloroform anaesthesia for delivery concentration of the drug in foeral maternal and placental blood was about the same There is no record of any subsequent confirmation of this work. Although Whipple makes no comment on time factors it can probably be correctly assumed that there is only a very short interval betsy een commencement of induction of anaesthesia and the passage of chloroform to the infant ·24 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA Smith and Barker 18 in 1942 published the results of their observations on the placental transmission of ether They concluded that the relation between maternal and foetal blood ether levels was generally, though not always individually a directly proportional one The low amounts which were found in the umbilical arterial blood suggested that the foetal tissues received less ether than did the maternal These workers made significant note of the possibility of trans-amniotic passage of ether from maternal to foetal circulation and also of the pos ible propensity of the placenta for storing ether thereby aiding the production of a gradient These two matters though beyond the scope of this book, obviously merit considerable thought and investigation Again as with chloroform there is no intimation of the rapidity with which ether first reaches the foetus but presumably the delay is equally short The only analytical study of the passage of nitrous oxide is recorded in another earlier article by Smith 20 He quotes only four figures which are said to be the average of an unspecified number of assays--times are not mentioned Smith studied the volumes per cent of nitrous oxide in foetal and maternal bloods The figures for matemal arterial and venous blood were 28 and 21 7 respectively and for umbilical vein blood and umbilical artery blood 13 5 and 9 8 respectively The striking feature of these figures is the steep maternal/foetal gradient Further investigation of this problem mught serve to clanfy the picture The picture regarding cyclopropane is rather confused—and confusing Smith 20 in the same article as the one just referred to reported the following findings Volumes Sample taken from cyclopropane Maternal artery 75 Maternal vein 67 Umbilical vein 60 Umbilical artery per cent SI It will be observed that the foetal concentration is about 75-80 per cent of the maternal blood level and that no times are discussed Rovenstine 1 in 1955 said that the foetal blood concentration of cyclopropanc approached that of the mothers blood only after 15--0 minutes but he gave no details of investigations supporting this Hingson and Hellman? state that the maternal cyclopropane blood level reaches 16-20 mg per cent in 10 minutes and that simultaneously the foctal blood levels (whether artenal or venous is not indicated) nise to 13-16 mg per cent during the same period There are no details given of the number of cases ·DIE PLACINT imeshiqareds of the amc clapsing before a clopropanc begins to appear in the foctzl arculation or of what happens after 10 minutes Apgar and her co-workers reported a study of as mothers to whom cclom propane was given They found in 2 c2505 that the amount of anacsthetic in the umbilicals ein blood was usually less than but was proporuonal to the amount m the venous blood of a maternal cxtremuts As marcmal aztero-scous studies suggested that the concentraton of cyclopropane un dhe materna) tissues was not in equilibrum with that in the blood ac che ume of sampling it was suggested thuac che matemalfortal gradient was probably greater than that shown by comparison of matemal venous blood and umbilical ren blood A source of confusion us inherent in the facts that, in the series chec clopropane was given brickly or intermittently and that a nigrogen svashout techmquc was used in some cases Again there was so suggcuon of how much of a lag might be present It does appear that the placents presents some form of pargal barnes to the transmission of cyclopropane from mother to child. In view of Apgar s recent expose of the increased risks wluch the foctus runs when copropane is used in obstetric anaesthesia it would be as well of our knon ledge could be more sharply defined on such matters as the ome factor A further matter to wluch bracf reference will be made later concerns the possibility and if so the rate of re-transference of cyclopropanc from foetus to mother Of the transmission of trichlorethylene (Trilene) by the placenta, virtually nothing is knorn Helliwell and Hutton "nho were investgaang the safety and potcntialıues of Tulane as an absectric analgesic discovered chat in ewes wluch are given Tnlene a higher concentragon of the drug Is attained in the coctal circulation than in the maternal circulation Hon ncr these workers supply of sheep failed, and they had to resort to using goats in these animals the foetal blood concentraton was found not to be higher than the maternal blood concentration An important inference may be drawn from this The application of results obtuned in experamenes in one species to the postulation of pharmaco-physiological prom cesses in another is of very doubtfisl value u the study of the function of the placenta. We do not know how soon and to what extent Trlene Teaches the foccus nor do we know hon significant as the high fat content of the full-term foetus in relatonsłup to Talene binding-power Work by Roberts seems to indicate that there I 2 sbghtly raised madence of neonatal depression when Trlene is used, especially when perludine is exhibited as an adjunct Hon much of this s due to the producaon of mild material depression with associated foetal hypoxia, semains to be discovered ·26 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTZIESIA Our knowledge of the placental transmission of analgesics and sedatives presents a bizarre picture Paraldehyde according to Snyder 16 readily passes into the foetal circulation The umbilical cord blood concentration at delivery is approximately the same as that in the matemal blood Methylpentynol (Obisvon) was shown by Boumezs to be absent from cord blood at delivery, cien though the mothers were given as much as 10 gm of the drug ar 3-hourly intervals during the first stage of labour Recently Katz and hus co-workers 27 in a preliminary report have claimed on the basis of chemical analysis that promethazine does not penctratc the placental barrier Clinical experience to which reference will be made in the next chapter suggests that little if any, of the drug does indeed reach the foetus and that the same observation might be extended to cover all the phenothiazine dernatives in common use Dihydrocodeine apparently does traverse the placenta according to Myers, 28 though no direct assays of drug levels were reported The narcotics form an interesting part of the general theme Apgar and Pappera' are the authors of the only paper in which reference is made to actual assays of pethıdıne the most widely used narcotic They state that the cquivalent of 60-70 per cent of the maternal blood concentration of the drug is found in the blood of the newborn They give no details of measurement and do not refer to the time intervals involved Lund and Harris39 discussed heroin They found no significant difference in the incidence of asphyxia of infants whether delivery occurred 1 2 3 or 5 hours after administration of the drug to the mother Referring primarily to morpha McNabii has written that the peak of on the foctus occurs 90-120 minutes following administration of the drug to the mother and that some depressive action may be observed even 4 hours after This is the traditional view but it has not received the support of pharmacological investigation On the basis of extensive clinical observation it is generally accepted that pethudine should be given not less than 2 hours and morphua not less than 3 hours prior to the expected time of delivery and that appreaable quantities of these drugs do reach the foctus Recently increased favour has been accorded the view that provided thesc drugs are given within 15-20 minutes of delivery they will not reach the foctus in significant amounts Thus importanr deviation remains to be justified by analysis of cord blood Furthermore it should be noted that McNabs! clums elsewhere in his article that N-allyimorphine (Nalline) readily traverses the placenta and he advises that it be given intramuscularly or stravenously to the mother opiate action ·TILE PLACENTA 27 at least s minutes before delivery, if it is suspected that the child might be depressed by a narcobc. It is luard to bclicve that the small change in molecular structure which conscrts Nallınc to morphua is suffiaent to lead to a prolongation of the interval of transmission from under s minutes to 15--0 minutos Although la allorphan/pethidine and levallorphan/ alphaprodine (Nesentl) mixtures arc currently advocated weknow nothing of the rate and extent of transmission of this antidote of possible significance in thus respect is a detail in the work on pethudinc/levallorphan mixtures reported by Roberts ** Infants of mothers who received their last injection of the mixture 3 hours prior to delis cry were on the whole morc depressed than those whose mothers received thar final dose closer to the time of delivery Possibly there is a differential rate of metabolism by the foctus favouring the more rapid destruction of levallorphan but possibly too levallorphan finds a more casy transit to the foetus than docs pethidinc. Gillam and his colleagues *3 appear to favour extending the safe period of narcotic administration to one hour In reporting a study involving pethidine and Nisenal they state that asphyxaated infants were never encountered in the 20 per cent of their patients who were delivered within one hour of the time of ther last dose of either analgesic agent. Regarding the other group of antagonists Holmes) claims that amiphenazole (Daptazol) crosses the placenta, as administration of the drug to mothers under his care counteracted morphine-induced depression in the foetus The time factor was not indicated. No work has been reported on the possible antagonism by Daptazol and Megimide of barbiturates in the foetal tissues The position regarding the transmission of the barbiturates themselves is becoming clearer Snyder16 implies that all barbiturates cross the placenta very promptly once they have entered the maternal blood-stream A number of workers35 have in the past three or four years shown that thiopentone sodium administered intravenously to the mother appears in the foctal arculation certainly within 2-3 minutes—thereafter the level of concentration in the two blood-streams remains equal falling in an exponental manner provided, of course that the drug is not given repeatedly The old 8 10 II or i, minutes rules—unfortunately still laboured in authoratitive textbooks and articles—are falsely premised and must be abandoned. If a single dose of thiopentone is used in obstetric surgery it does not call for a humed delivery Indeed, it may be argued that the longer the time elapsing before delivery occurs the less likely is the child to suffer from depression of barbiturate origin Recently Flowers & showed that sodium barbital traverses the placenta ·28 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESLA very quickly, and that maternal and foetal concentrations soon achicve cquality falling gradually over a period of 15 hours or longer Ploman and Perssons 37 using the 47 months foetuses nvolved in therapeutic tertunations of pregnancy demonstrated that amylobarbitone phenobarbitone and barbitone all crossed the placental barner without delay, although in the case of amylobarbitone administered intramuscularly about 30 minutes elapsed before the level of foctal blood concentration reached that of the maternal concentranon. Fealya has shown that the placental transference of pentobarbital sodium (Nembutal) occurs almost immediately following intravenous injection of the drug The foetal blood concentration level is 74 per cent of the maternal concentration within 1 minute The foctal and maternal blood levels persist at the same equilbrium for at least 185 munutes Nyberg and bus colleagues have demonstrated that w vinbarbital sodium is administered to the mother prior to delivery concentrations of the drug in maternal blood and in cord blood rapidly become almost equal. Happily with the exception of one or two dissidents there is general and informed agreement on the question of the transfer of the muscle relaxants It had been taatly assumed, since Gray sa original work, that d-tubocurarıne did not pass the placenta. Crawford showed that this was indeed the case, by analysis of specimens of cord blood in a relevant series of patients He was also able to demonstrate thit gallamıne frethodide (Flaxedil) did reach the foetus though in very small--probably insignificant-amounts In view of the greater sensitivity of infants as compared with adults to the non-depolarizing relaxants a d-tubocurarınc should be preferred to Flaxedil in obstetrics The possible transmission of succinylcholine has not been investigated pharmacologically However there have been no 21-reports following its use in many thousands of cases Even if the drug did reach the foctus the rapidity of its breakdown would seem to guard against its producing nconatal depression especially in view of the infants relatively raised tolerance to depolarızıng agents No thorough investgation of the possibility of the transference of decamethonium iodide has been undertaken Duchesne and his co-workers are the only ones to have recorded doubt of the general assumpoon that thus relaxant does not pass to the foetus un significant amounts However they used the drug as an adjunct to analgesia produced by pethidine and hyoscine and noted an increase (from 15 per cent to 27 per cent) in their rate of production of neonatal asphyxia when decamethonium was included. There is no indication that they took steps to combat materna) ·TiT PLACEVTI 39 sub-oxygenation and, under such arcumstances their results must be viewed with crtreme reserve In conclusion the following general remarks might be thought worthy of consideration If wc agree that certain substances cross the placenta with case then it is surcly rcasonable to postulate that the samic substances are able to traverse the barrier in the opposite direction? If such is the case at wluat ratc does the foctus nd itself of the non-metabolized drugs such as cthes Trlene, cyclopropane and nitrous Onide, when adınınistration to the mother has coised? Furthermore is it being rathcr precious to press the point and to inquire about the relative metabolic activities of the foctal and matcrual organisons espcaally regarding liver function. And to note elut cxcrction occurs only via the maternal organismi Perhaps the maternal liver can merabolize drugs such as the barbiturates and the narcotics miorc rapidly than can the foctal liver and some time after the initial administration of the drug a recrse gradient results Docs thus initiate a retum of the drug from foctus to mother? Some of these questions might seem of academic interest only Suci might well be the case but so long as the sub-speciality of obstetric anaesthesia continues in its present uncasily-founded state no query wluch comes within its province can lightly be dismissed as being unworthy of investigation REFERENCES 1 Brambell F WR (1954) Transfer of proteins across the fetal membranes Cold Spring Harbor Symposia on Quantitative Biology The Manimalien Tetus 19 71 2 Chinard FP (1954) Biochemical evaluation Cold Spring Harbor Symposia on Quangstative Biology The Mammalian Tehus 19 2017 3 Drowne J C McC (1954) Utero-placental circulation Cold Spring Harbor Symposia on Quantitative Biology Tlie Afamınaſtar fetus 1960 4 Shanklu D R (1958) 'The human placenta Obstet and Cynec II 129 5 Page E W (1957) Transfer of materials across the human placenta Amor J Obstet Gynet 74 705 6 Johnson T and Clayton C G (1955) Studies in placental action during prolonged and dysfunctional labours using radioactive sodium J Obstet Gynaec Brut Emp 62 513 7 Paylıng Wnght H Morts N Osbome S B and Hart A (1958) Effective uterine blood flow during labor Amer ) Olstet Gyne 75 3 & Romney S L Red DE Metcalf ) and Burwell C S (1955) Oxygen utilization by the human fetus in utero Amer } Obstet Gynet 70 791 ·30 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA 9 Crawford J S (1956) Somc aspects of obstetric anaesthesia Brui Anaesth 28 146 10 James L S Weisbrot I M Prince CE Holaday D A and Apgar V (1958) Acid base status of human infants in relation to birth asphyxaa and the onset of respiration J Pediat 52 379 11 Weisbrot I M James L.S Prince C E Holaday D A and Apgar V (1958) Acid base homeostasis of the newborn infant during the first 24 hours of life ) Pediat 52 395 12 Barton D H and Meschi3 G (1954) Comparative study of the exchange of the respiratory gases across the placenta Cold Spring Harbor Symposia on Quantitative Biology The afammalian Fetis 19 93 13 Bancroft-Livingston Gand Fisher O D (1958) Studies in prolonged pregnancy J Obstet Gynaec Brit Emp 05 147 14 McClure J H (1958) Newborn blood oxygen a method of increasing the partial pressure of orygen in the blood of the new born infant Obstet and Gynec 11 696 15 Waters R. M and Harris J W (1931) Carbon dioxid and orygen problems in obstetric anesthesia Anesth & Analg 10 59 16 Snyder F F (1949) Obstetric Analgesia and Anesthesia Isted p _61 Phila delphia Saunders 17 Zacks ST and Wisłocki G B (1953) Placental esterases Proc Soc erp Brol (NY) 84 438 18 Snyder F F (1949) Obstetric Analgesia and Anesthesis ist ed P 331 Phila delphia Saunders 19 Smith C A and Barker R H (1942) Ether in the blood of the new born infant Amer J Obstet Gynet 43 763 20 Smith C A (1939) Effect of obstetrical anesthesia upon the orygenation of material and fetal blood with particular reference to cyclopropane Surg Gynec Obstet 69 384 21 Rovenstine E A (1955) In Report of Section of Anaesthesia of Australasian Medical Congress Afed Aust2 577 22 Hingson R A and Hellman L M (1956) Anestliesia for Obstetrics Ist ed PIS. Philadelphia Lippincott 23 Apgar V Holaday D A James LS Prince CE and Weisbrot I M (1957) Comparison of regional and general anesthesia in obstetrics with special Icfercace to transmission of cyclopropane actoss the placenta J Amer med Ass 165 2755 24 Helliwell PJ and Hutton A M (1949) Analgesia in obstetrics Anaesthesia 4 18 25 Roberts H and Please N W (1958) Respiratory minute-volume in the newborn infant J Obstet Gynart Brut Emp 63 33 26 Bourne G (1954) Methylpentynol in Labour Lancet 2 522 27 Adelman MH Fisch J Jacobson E and Katz J (1958) Studies of promcthazine with measurement of concentrations in venous blood fetal cord blood and cerebrospinal fiud. Anesthesiology 19 93 -8 Myers JD (1998) Preliminary clinical evaluation of dihydrocodeine bitartrate in normal partuntion Amet į Obstet Gynec 75 1096 29 Apgar V and Papper E M (1932) Transmission of drugs across the placenta Anesth & Anals 31 309 ·T}IC PLACTYTA 31 Jo Lund C. and Hams J W (1943) Ux of hetoin in labor Amet J Obstet Gynet 45 930 31 McNab JA (1955) Obstetrical analgesia and anaesthesia Cmad med As 72 681 32 Roberts H hane M 'Taal N Snow P and Mease NW (1957) Effects of some analgesic drugs used in childtirth with special reference to variations in respiratory minute volume of the new bom Lancet 1 128 33 Gillam J S Hunter GW Damer C 13 and Thompson CR (1958) Mependine hydrochloride and alphaprodine hydrochloride ai olsteinc analgesie agents Ame] Obstet Gynec 75 1805 34 Holmes, JM (1956) Amipherazole in obstetne analgesia Lancet 2 765 35 Mchechnie F B and Conserse J (1955) Placental transmision of thion pental. Amet J Obstet Gynec 70 619 36 Flowers, C. E. (1957) Placental transmission of sodium barbital Obstet and Gymtec 9 332 37 Ploman, L. and Persson, B H (1957) On the transfer of barbiturates to the human foctus, and their accumulation in some of its vital organs J Obstet Gynaec Brut Emp 64 700 38 Fealy J (1958) lacental transmission of pentobarbital sodium Obstet and Gynec II 342 39 Nyberg FF hendrick J G Evans J A and Stofer B E (1958) Infant depression following Delvinal analcesia Obstet and Gynec ut 184 40 Gray T C (1947) d-Tubocurarine in Cacsarean section Brit med ) i 444 41 Stead A L (1955) Response of the newbom infant to muscle relirants Brilj Anaesth 27 124 42 Duchesne R. Lamontagne A Lacasse J L aradus R Surous P and Bertuier A (1956) Barbiturates in obstetrics effects on the newbom Canad Anacsth Soc ) 3 97 ·CHAPTER IT ANALGESIA The method of reheving pain in labour has formed almost as controversial a topic as has the question of anaesthesia itself in obstetrics There seems Little point in here recounting yet again details of the hustory of obstetric analgesia or alluding to the international flavour of the debate Chapter II contains an account of the anatomy and physiol of the present chapter will be concerned with methods of relief contemporarily in common use in Britain pain in labour a Sympathetic Reassurance The confidence of the patient is a prime factor in the success of any inethod of analgesia The most knowledgeable and adept doctor or midwife will have to work very much harder~and even so often unsuccessfully-to achieve some relief for a patient who is unprepared uncomprehending and terrified than will be necessary for one who has been well-rehearsed in the active role which she must play in her labour The exhortations and crusades of Grantley Dick Read are well enough known to need no recounting here it is appreciated that some women of greater or lesser intelligence can by following the Dick Read regime successfully carry through labour and delivery without recourse to analgesics More important to our thesis however it must be acknowledged that the call for analgesia is greatly diminished in patients who have been sympathetically prepared in a manner allied to the Dick Read technique possibly the onginal evangelistic tone should be modified somewhat specifically with regard to the promise of absolute freedom from pain or discomfort (a fault in technique which is shared equally by cxponents of methods deffenng radically from that of Dick Read) Once confidence has been shattered by even one overwhelmingly painful contraction it is extremely difficult to re-establish a rapport by the fasty use of analgesic drugs if no preliminary proviso had been made regarding their possible exhibition There is no doubt that many individuals wall break down under stress however well-prepared they have been to meet 32 ·AVAITIVA 16 and the culminaoon of a pregnancy must be accepted as being a spressing carenience The patient must be confident in the knowledşc that supplementary analgesia will be available to her without rccriminabon es reluctance-should her own efforts fail to relieve the tmunn sluch according to Dick Read, as the basis of the pain of labout Confidence is rarely an expression of blind futh but rather a product of education An orporunity u offered by the attendance of the majonty of pregnant women in Dnuain at the anto-naual Clinic to discuss with ach the process of labour and delnery flow often tlus benefit » conferred upon those not atending the Clinics is unknown Usually a semuar Suster, the obs etric registrat, or possibly a consulezne obstetrain conducts che Analgesia class' an the Clnic. Too rarely u an anaesthetust involved As the obstetri, anaesthesia service of the country cokos thus must undoubtedly be remedied. In the Analgesit lectures, expectant mothers are told what they arc likely to experience danng the course of a normal labour and delivery and, of equal importance they are given a simple account of the relatonshup bern con cause and effect to a greater or a lesser degree, depending upon the prevailing medical temper in cach particular area or hospital, they are taught how best chey can ally themselves with the progress of labour the better to avoid or to diminish pain-provoking tensions The range of analgesic drugs used by the hospital is reviewed, and the patients are alloned to acquant themselves with the odours of rutrous oxide and Talene Apparatus is demonstrated, and every woman should be allowed to realize the feel of a mask on her face Each pacient for whom there is an increased possibility of abnormal labour should have special instruction This should be concerned nocbly with the type of anaesthesza she is likely to encounter, and with the avoid. ance of heavy meals when labour is felt to be immunent Inhalational Techniques Nitrous oxide remains the foundation upon wluch us bult the whole structure of analgesia in Brash obstetric practice This was so for many years even before 1933 when Minnutt' evolved a gas-air apparatus which could be sanctioned for use by unsupervised midwives Since that time, is has held undisputed sway but there are indications that its place in routine schemes will soon be shared by Tnlene The outstanding advantage of nitrous onde over all other analgesic agents is its great flexbilty combined with a very high safety factor when it is used in the approved manner Because of the rapid produca ·34 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA in an tion of analgesia and the equally rapid dissipation of the drug at the end of administration the pain of each contraction can be combated as an enaty On a theoretical basis this is a much more rational approach than is the swamping of the entire penod of labour and delivery aura of analgesia produced by the repeated injections of such drugs as pethudine or by regional block techruques Although the latter methods are in many cases superior in the efficiency with which they counteract the painful peaks of contraction we must be realistic and humble enough to admit that when employing such techtuques we are exposing our patients to drugs for which during many hours in each labour, they have no requirement This is a situation possibly unique in the field of medicine and it adds greatly to our responsibility for any adverse sidereactions Other than ritrous oxide Trilene is the only agent in common employ. ment as an intermittent analgesic Aspects of the history methods of administration associated apparatus and contraindications regarding the two drugs have been recounted in many publications The subject was admirably presented recently by Seward and Bryce-Smuth and there seems little point in recapitulating all the details here Therefore there follows only a summary of the important aspects of inhalational analgesia Midwives may administer nitrous oxide only when the gas is mixed with an equal quantity of air Consequently the machines which the anaesthetist will meet in most upics-andin domucilary practicem are those which deliver such a mixture and are approved by the Central Midwives Board They are Minnitt gas-air analgesia apparatus Jecta gas-air analgesia apparatus Talley gas-air analgesia apparatus The CM attachment which permits an initial inhalation of two or three breaths of pure nitrous oxide is not authorized by the Central Midwives Board for use by midwives Thiene vapour may be administered in a range of concentration up to 043-05s volume per cent in air and the machines delivering such quantities must contnue to do so within a reasonable range of respiratory activity on the part of the patient and under variations of room temperature from $5°F to 95° F The machines so far endorsed by the Board are The Tecota Mark 6 trichlorethylene inhaler The Emotnl Automatic trichlorethylene analgesia unlialer Fifty per cent rutrous oxide in ar administered in the approved fashion may be used without fear of untoward effects for all healthy women ·ETUIGEN 35 modergomg pormal labour Talene na 15 Bs equally safe m rios of soch aases but, des to the cumslagse scoon of the drug there is the possibily the contm zous adornwrigor for core than aboc se how's must resu! m some drones on the part of the mother and a7 250cua..d degree of foccal depression Thew: of so so nitroos onde and ur obnoul emails cher mer mhailanon of 10 XT cent onge minut. I patents who have simptoms assocua.ed with heart disease or anam, bas rrethod of froduang analgosua mig! -Il crore dangerous, edo bercer aoided. Simulark mens na włom there Blies to exis consderab's flaconal cfare assocu od male greeclampsc toasa, posmart and possible severe hypertens.cn or diabetes, shorld preferable no be micred class form of analgesi. ln all such as, Trilece, or modically supertred so to Futros ondeforsgen nagua, Es rot fourrundu.ed. L all cases, the mother becoms udal exaad, dressed o-dowy or of seas of focul digeress affect addrizon of the analgesic mute should be immediately disconomied ad the posicion reassessed Seward and Boyce-Serba suggest thao Tolose2: gises a more Sasfaktor, degree of analgesuz chan does so SO IZOWS onder and is equivalent in analgesic potency to 75 29 msons ondelorrgoth. T: Latter mixture B not available for use by mudoties but can be emploved adriagcously by the anaesticos Finally the danger of sodalume consumago Mula pretiocircled Trile should be borrem mind whenever a geral 2.00 bend become imperative c. Sustemose Agents Pettude hidrochlonde has asumed the same starure n the field of $ww.em.cally adams ered analgesics as char of risos ouden mhalasonal techniques. The man effort to produce a precise delerenon of the place of path.dine in obs.cuic practice has been indtaken by Hilda Roberts The general rules as tech she onginally published as those used for gendarce in the Obstetric Department of the Postgrad Medical School of London are still followed. They are (t) labour not be cableed before administrazon of the walgesic uterine contract2005 must be of good amplitude and our 2. regolat a.crtals (z) dilaranon of the es uten mu have reached uleisc cree fingers as a primipiza and to fiogers 17 a mulapara In stie aracio just quoted, Roberts suggesed gisug scopolamute eh each dose of periud.zen za efort to decrease the rz.coffulare to product analgesia la a seniss reported sobsegaends scopolamune was on teda ·36 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESTA а and this is the usual practice today Scopolamine appears not to increase the chances of obtaining adequate analgesia with sufficient significance to justify its use in the face of its propensity to produce maternal disorientation However there is here a point to be noted perbudine is not completely reliable analgesic in labour and workers in general agree that given as the sole agent it will fail in 5-10 per cent of cases when used in combination with nitrous orde/aic the failure rate is apparently 4-5 per cent Pethidine is usually given in doses of 100 mg though it is apparent that in many centres the initial dose, at least has crept up to iso mg The timing of subsequent doses must depend upon the progress of labour The second dose may be given about one hour later if progress is satisfactory and thereafter at three-hourly intervals until about two hours before the predicted time of delivery As with all drugs given by injection the intramuscular route should be used unless intravenous administration is indicated It is neither safe not rational to give subcutancous injections --which so often are found to be in reality placed intradermally--as the rate of absorption from this site and hence the period of activity of the drug is completely unreliable It is generally agreed that 100 mg pethudine exerts a respiratory de pressant action about equal to that obtained with morphia gr (10 mg) In the mother this action will inevitably lead to a mild degree of anoxaemua and a slight carbon dioxide retention especially of the drug as administered repeatedly over a long period Such maternal reactions cannot fail at least to tend to produce deleterious effects upon the foetus This aspect of pethidine analgesia has not been studied probably for the reason that it would be difficult to differentiate such effects from those produced by the placental transmission of the drug The effect of maternal respiratory depression is likely to be significant in a proportion of cases and the situation must not be tolerated The likelihood of resulting sub-oxygenation is undoubtedly increased if nitrous oude/air analgesia is being used to supplement the pethidine and under these circumstances close watch must be kept for evidence of foetal distress Recent reports 5 indicate that when pethidine is given in dosages as suggested above to supplement nitrous oxide/air analgesia about 15 per cent of infants will suffer significant depression of respiration Roberts and her colleagues* showed that on the average a diminution of 10-15 per cent in the minute volume of the newborn infant occurred if pethidine was added to the basic nitrous oxide/aur scheme of analgesia. Such findings are not lghtly to be discounted and they together with carlier impressions of a similar nature have led to dissatisfaction with the simple pethidine/ ·ANALGESTA 37 nitrous oxde/ax technique and to a scarch for means of avoiding or of combating the central depression Because of the greates analgesic effect of Talone in air, as compared with that of so so nitrous onde/air, use of the former results in a slight reduction in the amount of pethudine needed to produce an cqui-analgesic effect. However even with the dimrushed total dase of petkedinc thcrc is no doubt that a rate and degree of fortal depression of severity approximately equivalent to that obtained with petludinc/nitrous oxide/217 results from the use of the pethudinc/Tnlene routint it is most unwise to mc a routine iniaal dose greater than 100 mg pethidine in conjunction 17th Thiene and subsequent doses given in response to the same indications as ti beni tucrous oude/aur inhalational analgesia is used should for safety be limuted to 75 mg at a ame The admunistration of phenothazine denvatives to supplement, and coinadentally to reduce, the use of pethudinc is becoming increasingly popular Chlorpromazine (Largactl) and promethazine (Phenergan) are the drugs most commonly employed. Each is given by intramuscular injecaon in a dosage ranging from 25 mg to so mg The phenottuazine denvalves are said to exert a selective depressant action upon the brain-stem reacular formanon Clinically their exlubecon leads to a varying degree of sedation often associated with amnesia, a general diminugon of autonomic tonal activity a speafic deterrence of nausea and vomiting and a potentation of the action of other sedatives and analgesics Chlorpromazne has been shown to cause hver damages occasionally fatal.following a prolonged course of administration, but although in very rare instances a similar result has been claimed as followng a single dose, the hepatotoxic effect of the drug is probably of no significance in obstetric practice Reports on the use of chlorpromazine in labout appeared earlier than those on promethazine and are more numerous The former drug will therefore be discussed first. There is fairly general agreement that the Rise of chlorpromazine permuts a reduction in the previously established dosage scheme of pethuidine without causing loss of analgesia There is no authontative account in the English literature of the potentialities of chlorpromazine as the sole relieving agent in labour and there would seem to be lile justification for pursuing such an investigation There are vaned views regarding the direct effect of chlorpromazine on the progress of labour Caldeyro-Barcia and Jus colleagues have suggested that the drug in no way alters the force and frequency of contracnons Injualy several workers? ' reported that labour was prolonged and that the forceps-rate was increased under the influence of chlorpromazine ·38 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA due to the mother's decreased awareness of her surroundings and her consequent lack of co-operation It is probable that these views resulted from an early tendency to overdosage and it is now generally agreed 10 that if the duration of labour is altered in any way it is more probably decreased, due to the enhanced relaxation (vide Dick Read) of the mother The effects of chlorpromazine in terms of neonatal well-being are still not completely assessed. On the whole because of the narcotic-sparing action of the drug infants of mothers given chlorpromazine/pethidine are probably as lively as those in a series in which pethudine alone has been used in conjunction with nitrous oxide/air or with Trilene Indeed It has been suggested'i .. 13 that in a large series the former group of infants will show less depression However it must be accepted that there has been an unpleasantly large number of instances in which gross neonatal depression has followed the use of a chlorpromazine/pethidine mixture Some of these must undoubtedly have resulted from abuse of the narcotic which must at all times be given more sparingly when used in this combination Other causes have probably been associated with an unexpectedly high potentiation of pethidine and the possibility of thus occurrence must cause considerable uneasiness in the minds of doctors charged with the control of these patients A third suggested explanation of the sporadic encountering of undue neonatal depression has to do with an important side-action of chlorpromazine itsel?-namely the production of hypo- In various reports 13 hypotension has been cited as a feature noted in up to 33 per cent of obstetric patients who have been given chlorpromazine In many cases the hypotension is mainly orthostatic and by ensuring that the patient lies flat her blood pressure can be maintained at the normal levels However thus leads to obvious difficulties in many cases It is well known that a fall of maternal blood pressure from any cause during labour inevitably tends to lead to foetal distress It should be realized therefore that the price of using this extremely impressive augmentation to obstetric analgesia might well be very hugh perinatal morbidity and mortality It is likely that in practice it will be abandoned in favour of the other phenothiazine derivatives Promethazine potentiates narcotic analgesics and sedatives almost to the same degree as does chlorpromazine In addition although it does tend to produce some measure of dissociation the effect is much less pronounced than that obtained with the latter drug "and mothers given comparable doses of promethazine appear to be considerably more amenable to direction and encouragement & As with chlorpromazine though apparently to a lesser degree—there is the danger of untoward tension in terms of ·ANALGESIA 39 potentiation of pethsdine by promethazine The outstanding difference is however that neither the degree of hypotension nor the ratc of appearance of this side effect is nearly as marked with promethazine as with chlorpromazine 14 In consequence of the foregoing it will be found that whilst the effects of the two drugs on the course and symptoms of labour are about the same promethazine is considerably less liable to lead to perinatal depression than is chlorpromazıne to which it is thus to be preferred No hepatotoxic effects have been noted as following the administration of small amounts of promethazine It cannot be too strongly stressed that when used in combination with a phenothuazıne derivative the dose of pethidine must be reduced from the normal range A reduction of 40-50 per cent is advocated Despite the finding previously referred to that chlorpromazine has no effect upon uterine contractibility there is evidence that if given early in the first stage it completely inhibits the progress of labour 10 Presumably promethazine shares thus property It follows that the phenothiazine derivatives should be withheld until such time as the first injection of pethidine is indicated The initial dose of either chlorpromazıne or promethazine should be not more than 50 mg With thus is given so- 75 mg pethidine depending upon the weight of the patient Pethidine may be repeated at 3-hourly intervals in doses of 25-50 mg with the usual provisos The phenothuazine derivative should be given with every alternate pethidine injection in a dose of 12 5--5 mg It is considered most unwise to give a total exceeding 100 mg of phenothiazine compounds in the course of a labour The normal careful observation accorded a woman in labour must be sharpened and if chlorpromazine has been chosen for use the liability of the production of sudden and alarming hypotension must be borne in mind For the healthy patient undergoing normal labour the combination of pethudine and a phenothuazine derivative can be recommended for general use in both hospital and domiciliary practice and should be considered as an advance in therapy As previously stated promethazine is much to be preferred to chlorpromazine The combination may be used in association with Talene/air or nitrous oxide/air analgesia but it will probably be found that there is a considerably diminished call for the inhalational agents except in very recalcitrant cases The use of promethazme should generally and the use of chlorpromazine should specifically-be avoided in abnormal obstetric cases especially in the suspected presence of placental insufficiency It is quite possible that promethazine will be shown to be of great advantage in such patients ·38 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA from an due to the mother s decrcased awareness of her surroundings and her consequent lack of co-operation It is probable that these views resulted early tendency to overdosage and it is now generally agreedº 10 that if the duration of labour is altered in any way it is more probably decreased, due to the enhanced relaxation (vide Dick Read) of the mother The effects of chlorpromazine in terms of neonatal well-being are still not completely assessed. On the whole because of the narcotic-sparing action of the drug infants of mothers given chlorpromazınc/pethudene are probably as lively as those in a series in which pethidine alone has been used in conjunction with nitrous oxide/air or with Trilene Indeed It has been suggested11 12 13 that in a large series the former group of infants will show less depression However it must be accepted that there has been an unpleasantly large number of instances in whuch gross neonatal depression has followed the use of a chlorpromazine/pethudine mixture Some of these must undoubtedly have resulted from abuse of the narcotic which must at all times be given more sparingly when used in this combinanon Other causes have probably been associated with an unexpectedly high potentiation of pethidine and the possibility of this occurrence must cause considerable uncasiness in the minds of doctors charged with the control of these patients A third suggested explanation of the sporadic encountering of undue neonatal depression has to do with an important side-action of chlorpromazine itself-namely the production of hypo- In various reports 13 hypotension has been cited as a feature noted in up to 33 per cent of obstetric patients who have been given chlorpromazine In many cases the hypotension is mainly orthostatic and by ensuring that the patient lies flat her blood pressure can be maintained at the normal levels However thus leads to obvious difficulties in many cases It is well known that a fall of maternal blood pressure from any cause during labour inevitably tends to lead to foetal distress It should be realized, therefore that the price of using this extremely impressive augmentation to obstetric analgesia might well be very high in terms of perinatal morbidity and mortality it is likely that in practice it will be abandoned in favour of the other phenothuazine derivatives Promethazine potentiates narcotic analgesics and sedatives almost to the same degree as does chlorpromazine In addition although it does tend to produce some measure of dissociation the effect is much less pronounced than that obtained with the latter drug 14 and mothers given comparable doses of promethazine appear to be considerably more amenable to direction and encouragement & As with chlorpromazinethough apparently to a lesser degree-there is the danger of untoward tension ·41 ANALGESIA les allorphan and in addition to its action in opposing directly-induced neonatal depression the drug will also be of bcncfit in the avoidance of secondary depression subscquent to maternal sub-oxygenation and hypercapnia There are no data available on the effective dosage of levallorphan necessary to counteract narcotic depression in the presence of phenothiazine denvaaves It is possible that the levallorphan/petludmc ratio might have to be incrcased slightly under such arcumstances It should be noted that the specific narcotic antagonists and the phenothazine denvatives all oppose the tendency of pethidinc to produce nausea and vomiting As pethudine-induced cmesis has been vanously reported as occurring in 10-25 per cent of cases 18 this property is of considerable significance in the pursuit of maternal comfort Amuphenazole is not a specific narcotic antagonist It has cxcited considerable interest as a possible direct antagonist to the action of barbiturates on the central nervous system in addition to its postulated effect as an inhubitor of narcotic-induced depression Despite the work of the Melboume School 19 20 there is still general doubt regarding the precise site and mode of action of the drug Speculation persists that it is a general central nervous system excitor Overdosage can certainly lead to evidence of central nervous stimulation and this is not a property calculated to encourage the routine use of the drug in obstetncs Holmes21 has recommended that 30 mg amiphenazole be given with each injection of morphia gi ţ (16 mg) With such a mixture he claims that an analgesic effect equal to that of 130 mg pethidine is obtained As he had previously found 150 mg pethudine be equivalent in analgesic activity to morphia gr he concludes that amıphenazole does diminush to some degree the pain-relieving quality of narcotics Furthermore the antagonist does not oppose the tendency of morphia to produce nausea and vomitng In his report Holmes concludes that when given in the doses recommended amphenazole reduces but does not entirely eliminate the incidence of neonatal apnoea caused by morphia It would appear that levallorphan is a better choice of antagonist in obstetric anaesthesia Scopolamine has had an honoured place in obstetric practice since the introduction by Gauss of the concept of twilight sleep It has commonly been given intramuscularly together with pethidine in doses of gr iso (04 mg) The general routine has been to repeat the administration of scopolamine gi ito at a time with each subsequent dose of pethidine omitting the former drug if the mother shows signs of becoming disorientated or unco-operative and also if delivery is expected within the forthcoming two hours As Roberts has indicated administration of ·40 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA but for the moment the investigation of this must be left in the hands of well-trained observers in special centres Recently a third phenothiazine derivative promazine (Tnlafon, Sparine) has been favourably reported on in the United States 15 Compared with the other two it is said to be less toxic and to be several times more effective as an analgesic potentiator It is stall too carly to make even an initial assessment of the place of thus drug in obstetric practice The narcotic antagonists are assuming increasing importance in obstetric practice There are three members in general use levallorphan (Lorfan) nalorphine (Lethidrone Nalline) and amiphenazole (Daptazole) Levallorphan and nalorphine are specific narcotic antagonists acting centrally as substrate competitors at the cell surface They may be gives by either intramuscular or intravenous injection and their rate of onset of activity is about equal to that of similarly administered pethidine or morphia. The duration of their activity specifically in relation to the question of neonatal depression has not been convincingly demonstrated (see Chapter II and below) It is generally agreed that whilst opposing the central depressant action of narcotics these drugs do not greatly affect the degree of analgesia or of sedation produced. There is one important difference between the actions of the two drugs Levallorphan even when given in considerable quantity appears to exert no deleterious effect upon the patient If on the other hand nalorphine is given alone or 15 over-titrated against a narcotic respiratory depression can result 16 17 There seems, therefore to be every justification for abandoning this drug in favour of levallorphan Should nalorphine be preferred, it is usual to give 5 mg for each 100 mg pethidine Reference has already been made (in Chapter U) to the somewhat anomalous findings of Roberts and her co-workers in their investigation of the effects of the combined administration of pethudine and levallorphan As has been suggested these phenomena might be due in part to an inadequate dose of the antagonust It is advisable to maintain a ratio of 1 mg levallorphan to 100 mg pethidine Levallorphan can usefully be given intravenously of delivery is imminent and narcotic-induced neonatal depression is feared. Under such circumstances the drug must be given at least 15 minutes before delivery of full effect is to be achieved (sec Chapter II) The dosage 15 1 mg for there is absolutely no point in stunt There should be little reason however for such an emergency to arise Sufficient evidence now exists to favour the teaching that levallorphan be given with each dose of pethidine with or without an accompanying dose of promethazine There is no danger involved in the use of ·ANALGESIA 41 Levallophan and in additon 10 is action in opposing directly-induced nconatal depression the drug will also be of benefit in the avoidance of secondary depression subsequent to matemal sub-oxygenation and hypercapnia There are no data available on the effectise dosage of levallorphan Trecessary to counteract narcoac depressson in the presence of phenom thazine derivatnos It is possible that the levallorphan/petludinc ratio mught have to be increased slightly under such circumstances it should be noted that the specific narcotic antagonists and the phenon thuazine denvauves all oppose the tendency of pethudine to produce nausca and vonuting As pethidine-induced cmesis has been variously reported as accurring a 10-25 per cent of cases 18 thus property is of considerable significance at the pursuit of maternal comfort Amphenazole is not a specific narcotc antagonist It has cxatcd considerable interest as a possible direct antagonist to the action of barbiturates on the central nervous system in addigon to its postularcd effect as an indubitor of narcotic-induced depression Despite the work of the Melbourne School 1 so there is still general doubt regarding the prease site and mode of action of the drug Speculation persists that it is a general central nervous system exator Overdosage can certainly lead to endence of central nervous simulation and this is not a property calculated to encourage the routine use of the drug in obstetrics Holmesz! has recommended that 30 mg amuphenazole begiven with each injection of morphia gt # (16 mg) With such a mixture he claims that an analgesic effect equal to that of 130 mg pethidinc is obtained. As hc had previously found 150 mg pechsdisc to be equivalent in analgesic activity to morphia gt 1 he concludes that amuphenazole does dimrush to some degree the pur-relieving quality of narcotics Furthermore the antagonist does not appose the tendency of morphu to produce nausea and vomiting in his report Holmes concludes that when given in the doses recommended amiphenazole reduces but does not entirely clımınate the incidence of nconatal aynoca caused by morplua It would appear that levallorphan is a better choice of antagonist in obstetric anacsthesia Scopolamuse has had an honoured place in obstetric practice since the introduction by Gauss of the concept of twilight sleep It has commonly been given intramuscularly together with perludine in doses of gr the (04 mg) The general routine has been to repeat the administration of scopolamine gi tha at a time with each subscquent dose of pethudine omítug the former drug if the mother shows signs of becoming disorientated or unco-operative and also if delivery is expected within the forthcoming two hours As Roberts has indicated administration of ·42 PRINCIPLES AND PRACTICE OF OBSTLTRIC ANAESTILESIA Scopolamine within two hours of delivery can lead to some respiratory depression of the infant The two principal reasons for the use of scopolamine in labour have been firstly to achieve some slight potentiation of a simultaneously exhibited narcotic analgesic and secondly to promote a degree of amnesia for the more unpleasant episodes Promethazine offers a greater degree of certainty in the production of narcotic potentia tion and a wider margin of safety than does scopolamine Furthermore, unpleasant side-effects notably dryness of the mouth and a tendency to disorientation are much less likely to occur with promethazine than with scopolamine It is probable that the place of the latter in common practice will be taken bv promethazine or an allied drug The barbiturates have a well-defined function in the management of labour Their role will not be fulfilled unless it is remembered that thus class of drugs possesses no analgesic properties If barbiturates are relied upon as the sole medication at times of severe pain a state of unmanageable exatement is likely to result The place of these drugs is complementary to that of the analgesics previously discussed in thus chapter They should primanly be used to promote rest for the mother in the early stages of labour especially at night If a primipara starts in labour at any time between the late afternoon and early morning (6 pm to 4 a m would be a useful rule-of-thumb guide) a barbiturate will serve admirably to give her a good rest before regular strong contractions begin At other times of day probably a better plan is to give chloral hydrate gr 30 The mother will probably not be able to sleep or wish to do so during the daytime either at home or in hospital, and the latter drug is more likely than are the barbiturates to produce a refreshingly quiet sedation When a multipara as first seen in labour it is advisable to assess the rate of progress for an hour or two before deciding upon giving a barbiturate if the first stage seems likely to last for several more hours then treatment should be instituted as outlined above In multipara and primipara barbiturates are also indicated when the first stage is prolonged progress remains slow and the mother u tiring or is losing confidence it is in such a situation that many practitioners consider morphua (gr 4 11-16 mg) or Omnopon ( gu) to be specifically indicated, as these drugs possess both sedative and analgesic qualities of great potency If under such circumstances an oplate is gnen it would be advisable to reduce the suggested dose of a phenom thuazine derivative has been previously administered it is also advisable that levallorplan (1 mg for morphia gi & 128 mg for Omnopon gr }} be given at the same time The use of barbiturates in the treatment of eclampsia and of severc ·ANALGESIA pre-eclampsia will be mentioned in a later chapter, but the matter as morc the prerogatic of the obstciscan than of the anaesthetist The barbiturates in common usc are quinalbarbitonc sodium (Scconal) pentobarbitone sodium (Nembutal) and butobarbitonc soduum (Soncryl) The recommended dosage of cach vanes batucen gr it (100 mg) and gr 48 (300 mg) depending upon the weight of the patient and the degree of apprehension she colubiss The actual choice of barbittirate usually depends more upon the personal preference of the sudwife in charge or on the tradiaon in the department than upon slighe variations between the pharmacology of cach product There is scally little signuficant difference between the three All doctors newly mining upon a Department or a General Practice would be sc!-advised to accept the established regunc In general se must be admitted that most sedatives and analgesics tend to appear to be more effectue af the Ward Sister has faith in them Her prejudice or hostałty can often wreck a theoretically sound scheme of therapy Barbiturates should be avoided during the second half of labour especially if possible during the period 4-6 hours prior to delivery Recenity methylpentynol (Obliron) has achuered some populanty as 2 muld ataractic and as a potentiator of analgesic drugs Roberts has lately substantiated Boume s** observations on thus drug Gren orally 121 Kater drachms (about 20 mi) of the Elixima dose wluch was repeated if the patient vomited witlun 10 minuteswappeared to be helpful in dimunıslung the stress of carly labour Later is labous subsequent doses of 3-6 drachms apparently increased the analgesic activity of tutous oxide/air and of perludine in the dosage given the drug scened to produce no deletenous effect upon the infast Notable macemal siden effects were drowsiness in 40 per cent of cases (though thus might be considered a hughly desirable side effect early in labour) euphoria (28 per cent) and vomiting within 10 munutes of recesvug the drug (10 per cent) Vomiting occurs in a comparable percentage of cases even when the drug us administered usthun a capsule though a repeat dose according to Boume is usually retained Whitehouse reports that in an effort to avoid this unpleasant action the rectal route of administration has been adopted in the Birmingham Maternity Hospital and by general practationers within the vicinity with very satisfactory results However there ss a well-ingrained and understandable prejudice against giving drugs per rectum during labour and it seems unlikely that Whitehouses suggesaon will become generally accepted Methylpentynol zs neither an analgesic for an ana-spasmodic Apart from helping to enhance the action of the analgesics its man att butc ·42 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA scopolamine within two hours of delivery can lead to some respiratory depression of the infant The two principal reasons for the use of scopolamine in labour have been firstly to achieve some slight potentiation of a simultaneously exhibited narcotic analgesic and secondly to promote a degree of amnesia for the more unpleasant episodes Promethazine offers a greater degree of certainty in the production of narcotic potentiation and a wider margin of safety than does scopolamine Furthermore unpleasant side-effects notably dryness of the mouth and a tendency to disonentation are much less likely to occur with promethazine than with scopolamine It is probable that the place of the latter in common practice will be taken by promethazine or an allied drug The barbiturates have a well-defined function in the management of labour Their role will not be fulfilled unless it is remembered that this class of drugs possesses no analgesic properties If barbiturates are reled upon as the sole medication at times of severe pain a state of unmanageable excitement is likely to result The place of these drugs is complementary to that of the analgesics previously discussed in this chapter They should pnmarily be used to promote rest for the mother in the early stages of labour especially at night If a pnmıpara starts in labour at any time between the late afternoon and early morning (6pm to 4 a m would be a useful rule-of-thumb gude) a barbiturate will serve admirably to give her a good rest before regular strong contractions begin At other times ofday probably a better plan is to give chloral hydrate gr 30 The mother will probably not be able to sleep or wish to do so dunng the daytime exher at home or in hospital and the latter drug is more lkely than are the barbiturates to produce a refreshingly quet sedation When a multipara as first seen in labour it is advisable to assess the rate of progress for an hour or two before deciding upon giving a barbiturate If the first stage seems likely to last for several more hours then treatment should be instituted as outlined above In mulapara and primipara barbiturates are also indicated when the first stage is prolonged progress remains slow and the mother is tiring or is losing confidence It is in such a situation that many practitioners consider morphia (gr H 11-16 mg) or Omnopon (se }) to be specifically indicated, as these drugs possess both sedative and analgesic qualines of great potency, If under such circumstances an opiate 15 grien it would be advisable to reduce the suggested dose of a phenothuazinc derivative has been previously administered it is also advisable that levallorphan (1 mg for morphia gr , 1 29 mg for Omnopon gt }) be given at the same time The use of barbiturates in the treatment of eclampsia and of severe ·ANALGESIA 43 pre-cclampsia sall be mentioned in a later chapter but the matter is morc the prerogatic of the obstetrician than of the anaesthetist Thc barbicurates in common usc arc quinalbarbitone sodium (Scconal) pentobarbitone sodium (Nembutal) and butobarbitonc sodium (Soncryl) The recommended dosage of cach varies between gr it (100 mg) and gr 4* (300 mg) depending upon the weight of the patient and the degrec of apprchcnsion she exhibits The actual choice of barbiturate usually depends more upon the personal preference of the midwife in charge or on the tradition in the department than upon slight variations between the pharmacology of cach product There is really little significant difference betny cen the three All doctors newly entering upon a Department or a General Practice would be well-advised to accept the established régime In general it must be admitted that most sedatives and analgesics tend to appear to be more effective of the Ward Sister has fasth in them Her prejudice or hostility can often wreck a theoretically sound scheme of therapy Barbieurates should be avoided dunng the second half of labour espeaally if possible dunng the period 4-6 hours prior to delivery Recently methylpentynol (Oblivon) has achieved some popularity as a mld ataracaic and as a potentiator of analgesic drugs Roberts has lately substantiated Boume sam observations on this drug Given orally in water 6 drachms (about - ml) of the Elixir-a dose si hich was repeated if the patient vomited withun 10 minutes appeared to be helpful in diminishing the stress of carly labour Later in labour subsequent doses of 3-6 drachms apparently increased the analgesic activity of nitrous oxadeau and of pethudine In the dosage given the drug seemed to produce no deleterious effect upon the infant. Notable maternal sideeffects were drowsiness in 40 per cent of cases (though this might be considered a highly desirable side-effect early in labour) euphora (28 per cent) and vomiting within 10 minutes of receiving the drug (10 per cent) Vomiting occurs in a comparable percentage of cases even when the drug us administered within a capsule though a repeat dose according to Bourne is usually retained. Whitehouse reports that in an effort to avoid this unpleasant action the rectal route of administration has been adopted in the Birmingham Maternity Hospital and by general practitioners withun the vicinity with very satisfactory results However there is a well-ingrained and understandable prejudice against giving drugs per rectum durung labour and it seems unlikely that Whitehouses suggestion will become generally accepted. Methylpentynol is neither an analgesic nor an anti-spasmodic Apart from helping to enhance the action of the analgesics its main attribute ·PRINCIPLES AND PRACTICE OF OBSTETRIC AVAESTHESIA is that of a mild tranquilizer with some emphasis on sedapon As such its place in carly labour is probably the same as that suggested for chloral hydrate In additon it might usefully be given in place of a barbiturate to relatively less apprehensive patients or to those who are known to react in an undesirable way to the latter group of drugs. The bitter taste of methylpentynol, its tendency to produce vonuang and the significant volume of fluid which its administration entails combine to make its place in the later stages of labour less well-defined. In summary there is here presented a suggested scheme for the managem pain and distress in labour Under no arcumstances is ngid observagon to be encouraged. At all times therapy must be related to thc candinon of the individual patient, to her raghs, and to the state of the foetus A Scheme of Obstetric Analgesia During Pregnancy Educagon and reassurance ment of Dining Labour First Stage A. From inception of labour to onset of regular, strong contractors (corresponding roughly to a dilatation of 3 fingers in primupara and fingers in mulapara) I General nursing care to combat uncasiness the provision of comfortable attractively furnished day-rooms well-stocked with books and magazines, and including a television set and a wireless is impliat in the term nursing care Chloral hy drate ge 30 or methylpentynol o drachms during day 3 A barbiturate, gr itt at right 4 If this period as prolonged, or discomfort becomes excessivo 100 mg pethudine or morphua gr I (plus 1 o mg levallorphan in other case) may be subsotured for or added to (2) or (3) B From onset of well-established labour to end of first stage 1 Inugalım dost pettudine mg 50-75 lezllorphan mg 0-75-10 promethazine mg 25-50 Subscqucnti m doses pethudine (mg 25-50) plus levallorphan (mg o'sa 0-75) at 3 or 4-hourly intervals and accompany alcemate injections with promethazne (mg 125--5) Total dose of promethazine not to exceed 100 mg : If peaks of contractions sall prosoke pain do not hesitate to use inhalatonal analgesic ·ANALCIMA Second Stage Intermittent inhalational analgesis one injection of petudinc/ les allorphan mixture may be gren and promcthazinc added af st was omutted from the previous injection 7 Danng delasery Conanuous inhalatonal analgesia (preferably Tnlene in air) from the time the attendant takes oser control of delivery to completion of delivery of the shoulders Thud Stage Preferably a few breaths of Talene NOTES AND PRECAUTIONS I In the presence of foctal distress and when there ss evidence or suspioon of placental insuffiancy (Cg cases of matemal hy pertension or gross anaemia pre-eclampuc toxaemia post-matunty history of previous unexplained still-buch) the use of so so jutrous oxide/aus and of the phenothuazunc denvases is contraindicated. 2 In cases of heart disease pusing symptoms towards the end of pregnancy the use of so so sistrous oxide/air, and of chlorpromazine is contraindicated. 3 Whea there is a reasonable possibility that a general anaestheac will be given using a closed-arctus technique Trilene should be avoided 4 If because of accompanying heart discasc opersave delivery is planned and the anaesthetst intends to use a closed-circut he must himself be responsible for adminiscerug * 75 zs sitrous oxide/oxygen mixture whenever mhalagonal analgesia is requed. 5 If the patient gives a hustory suggesting an undue reaction to barbiturarc mcthylpentynol or morphaflevallorphan should be substituted. Porphyna presents an absolute contraindication to barbiturates 6 The anaesthetus should cagerly encourage and assist the obstetrician in guarding against matemal dehydration by the liberal use of intravenous transfusions Apart from the importance especially in protracted labouraa on the grounds of general physiological prncples thus line of therapy not only counteracts a prominent cause of maternal discomfort in labour but it also helps to limut oral intake 7 Should the patient have luad any corticosteroid therapy during the previous eighicen months she should be given prophylactic hydrocorttsone on the loves used in general surgical cases ** Routine inquiry cvery obstetric patient should be made regarding this matter and pronunient nore made of the posiave replies mit is of increasing urgency ·46 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTIIESIA d Conduction Analgesia Since the introduction of the technique of continuous caudal analgesia by Hingson and Southworth in 1942 and its application to obstetrics by Hingson and Edwards”? in 1943 use of the method for the control of pain in labour has been held in very popular esteem in North America Hingson s visit to Britain in 1949 stimulated renewed interest in the subject here 8 and led to much common-room discussion but the fact remains that regional analgesia for obstetrics is sall out of favour in thus country It is often a difficult and puzzling task to try to explain an honest terms to an American practitioner why this should be A contnbution to the debate may be found in the Introduction to this book and in this and the two succeeding chapters If ether caudal or lumbar epidural analgesia is embarked upon an in-dwelling catheter technique should be employed No local analgesic even with added adrenaline is likely to be effective for more than three hours after injection and a scheme of repeated epidural punctures is painful and potentially dangerous to the mother and laborious to the staff The technique and equipment associated with the administration of continuous epidural analgesia need not be discussed here—they must be in the armoury of every competent anaesthetist and are admirably described in several publications 29 30 31 A note might usefully be inserted here however regarding the drugs to be employed and it can be taken to apply to all local techniques (other than spinal analgesia) discussed in this book Procaine (1 s per cent) and Xylocaine (I-1 s per cent) are the agents most generally used in the British Isles From published reports no authontative indication regarding supplementation with adrenaline can be gleaned It is well-recognized that the admixture of adrenaline (used in a dilution of about 1 400 000) will oppose—usually effectively-the general systemic distribution of drugs injected into such a well-vasculanzed area as the epidural compartment By so doing adrenaline helps to reduce the number and severity of toxac reactions to local analgesics and also significandy prolongs analgesia It is highly unlikely that the adrenaline will effect the foetus (sec Chapter II) and its use is therefore to be recommended. However care should be taken that the patient is not given cyclopropane or Talene during the period of action of the drug Xylocaine has achueved immense populanty in Britain because of the rapidity of onset of its action and because of its high spreading factor the latter allowing even the tyro to achieve gratifying success in the field of regional analgesia However as in the case of the other local analgesics ·Aral 11 with i Xyloxamc has on occasion produced unpleasant and oftcs serious toxic effects Many of these episodes han c not becse gencrally publicized and will be heard of only in the course of personal discussion Only a part of the total dose of Xylocaine 23 destroyed in the let the rest : cxcreted unchangad 122 thc Idney's Homer in labour when real flow us from quently diminished the possibility of toxic reactions duc to the drug is mcreased, as is the chance of its passage across the placental barrier In recent years 2-chloroprocainc hydrochloride (Nesicame) luas been increasingly strongly advocated (notably by Foldesso) as the local analgesic of choice when this drug reaches the systemic circulation it u rapsdly broken down by cholinesterase and thus its safety-factor 15 very hugh It is recommended that .-chloroprocainc be used in a . per cent solution for local infiltrabon and 3 per cent for epidural block when mixed 200 000 adrenaline it should be scadministered at so-minute mtervals An account of the anatoury and physiology of pain in labour will be found in Chapter I From tlus it will be apprcaned that to obtain satisfactory results epidural analgesia introduced by cither the lumbar or the caudal roure must extend from the eleventh thoraac to the fourth sacral segments inclusive Extension upwards to T4 or Ts will halt cho progress of labour If epidural analgesia is insatured very early in labour progress usually ceases as the necessary stimulation to the initiation of motor activity is removed. Hingson teaches that continuous caudal analgesta should not be started unul the presenting part is in the pelvis contractions lasting at least 40 seconds occur at not more than 3-minute wiervals and the cervix 15 at least 2 fingers dilated in the multiparous patient and 3 fingers in the primupara. The following contrandications to çpidural analgesia are listed by Hugson 2 Slow uregular and ineffective uterine contractions (but see later) Obstructive factors to labour foctal or maternal in origin 3 Severe haemorrhage 4 Hypotension s Infection at the site of injection 6 Lack of trained supervisors 7 Placenta pracvia with haemorrhage To the preceding are submitted the following additions 8 Known sensitivity on the part of the patient to local analgesics 9 Muluple pregnancymGuttmacher and Little and Friedmans have ·48 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIS recently shown that, under regional analgesia, the second twin us likely to suffer considerable depression at delivery 10 Probably all cases of suspect placenta practia. 11 Maternal opposition. 12 CNS pathology In reasonably skilled hands the failure rate with caudal analgesia is about 10 per cent-factors in this group include vanation in local anatomy The failure rate is probably slghtly less with lumbar epidural block, though with this method there is a greater chance of acadentally punctum ing the dura. The proportion of failures is thus about the same following regional analgesia as when pethudine plus nitrous oxade/aur analgesia is used. However in the event of failure after the insertion of an cpidural needle it is more difficult to regain the mothers confidence than is the case when a projected scheme of systemic analgesia has to be supplemented. Labour tends to be prolonged under the influence of conduction analgesia, and the rate of forceps delivenes undoubtedly rises sharply The latter result, of course occasions no displeasure or annetz in most North American hospitals The outstanding demands made by the regime of conduction analgesia are as follows 1 A doctor skilled in the management of these cases must constantly be present actually in the obstetric department. If the method is liberally employed, it will probably be found necessary to have two such doctors on duty progress of labour must carefully be watched for evidence of slowing 3 An unduly high level of analgesia must be guarded against by suitable positioning 4. Partly as a corollary to (3) the blood-pressure must be carefully checked and recorded every half-hour after stabilizazon has been obtained following the mbanon of analgesia. Hypotension is an cres-present posability especially if the patient is permitted to sit (propped or not) for long periods. The immediate therapeutic measures are to lay the mother flat and to raise her legs. 5 Saupulous attention must be pad the the bladder This organ is rendered insensible under conduction analgesia, and excessive filling occurs without the mothers knonledge The bladder mas seasonably free from distenuon by encouraging the mother to bear down strongly about asery three hours assistance being given by 2 The of the patient. be kept ·To gorofa ¢ AVC144 applying moderate suprapubic pressisse Thc alternati: o at repa or continuous catheterization The foregoing discussion might te lo dsunt the scale who come triplatcs introducing conducnon analgesia into radix such a response is not the object of the author The sethod fint mary very sigtificant attabutes to a credit firstly si ate 21 far al oí knowledge goes at the moment that after the initul surm of Labru no depressant drugs are transmitted to the foctus in care ulite thalani's hold on kafe us precarious sous cars be a factor of inestimabic impmistance There is some suggespon" that in case of prematurity of placa uzsufficiency the foctal selvage rate u lugher when conducuns rather tun systemis, analgesia us employed. In faimes it must be noted that patients in the systemic analgesia' seria 20 often subject to the father fucanicy sedason and larger doses of analgesics asdigonal in Anscrican hospiul Secondly conduction analgesia ensures an alert and compare mother in the luch proporcon of cases which are carried through successo fully the mother is completely free from apprehensions asid discomfort Eom the start of analgesia to die moment of dels cry lloscer a considerable number of paucnts do experience discomforimsometimes rather destressing during delivery This can be avoided by infiltrations of the perineum with a local analgesic It us chudly of agraficant benefit to panenes suffering from manife! cardiac insufficiency or from respiratory infection Fourthly as Jolmson' has stressed, conanuous epidural analgesi offers considerable advantage in the management of prolonged labour due to disordered uterinc function. It has been confidently reported that in cases of uterine incriza and cervical dystocia, the rate of progress un the first stage of labour w increased and the necessity of cventual Cacsarcas section decreased by the use of conduction analgesia. In addigon 25 Johnson and Claytonas have pointed out, thus treatment also helps to restore the assocated impoveruhed placental arculation by dulacatson of the decidual vessels Thus important observation introduces a fifth attribute of epidural analgesi2 There is good reason for supposing that placental insufficiency due to hypertension or to pre-eclamptıc roxacmia u likely to be countered so a significant degree by the vaso-dilatation 25sociated with conduction analgesia The following is a fale summary of the position as sc appears to the author In Britain amongst patients doctors and nurses tradition favours general analgesia for labour and should be respected. A corollary of this fact is that the implementacon of the techniques of general analgesia E ·SO PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA on both a local and a national scale is at a laudably high level of effecaveness and safety, reducing in some measure the invidious companson of these methods with regional techniques in North Amencan practice The hugh forceps rate associated with conduction analgesia does not help to commend it to British obstetricians As outlined above, there are cases in which regional block offers significant advantages over general analgesia, all obstetric anaesthetists should be competent and thar departments equipped to undertake conduction analgesia for such patients To extend the practice to a larger proportion of obstetric patients would entail a considerable reorganization of hospital and departmental ad minustration and a re-orientation of our obstetric practice in terms of possible decreased maternal distress and perinatal morbidity, the returns of any, for such efforts would probably be insignificant Epidural nalgesia is not recommended for use in domiciliary practice Its place in operative obstetrics and in the treatment of eclampsia will be discussed in subsequent chapters REFERENCES 1 Minnit R J (1934) Selt administered analgesia for the midwifery of general practice Proc R Soc Mei 27 1313 2 Sevard E H and Bryce-Smith R (195) Inhalation Analgesia in Culdborth Ist ed Oxford Blackwell 3 Roberts H (1948) Pethidine and scopolamme un labour Brit med J 2 590 4 Roberts H Kine K M Percival N Snow P and Pleas NW (1957) Effects of some analgesic drugs used in childbath with special reference to variation in respiratory minute volume of the newborn Lancet I 128 $ Baker FJ (1957) Pethidine and nalorphine in labour Anaesthesia 12 28. 6 Caldeyro-Barcia R Poseiro J J Alvarez H and Tost P (1958) Action of chlorpromazine on uterne contractility and attenal pressure in normal and toxemic pregnant women Amer J Obstet Gynec 75 1088 7 Savage D (1955) Chlorpromazınc as an analgesic un labour Britt Anaesth 27 346 8 Carroll J ) and Hudson 1 W (1955) Chlorpromazme and promethazine in obstetrics Cuand Anaesth Soc ) 2 340 9 Lindley J E Rogers S F and Moyer ) H (1957) Analgesia potentiating effects of chlorpromazine during labour Obstet and Gynec 10 $8. 10 Browne A DH and Mannion PJ (195) Application of chlorpromazine to obstetrics with a study of ss effects during labour Irish) med Sa bth Ser No 351 P 117 11 Davies ) I (1955) Use of largacti in obstetrics Canad Anaesth Soc J 2 327 12 Editorial (1956) Chlorpromazine in obstetrics Lancet 2 $63 13 Hatcr WB (1996) Chlorpromazine in normal labor Obstet and Gynet 91 14 Gordon L E and Ruffin C I (1958) Promethazine as an adjunct to obstetrical analgesia and sedation Amer y Obstet Gynee 76 147 ·A new ANALOTSIA Is Wegryn S P and Marks RA (1958) Promazine speridine and spinat anesthesta for labor and dchuery } Amet med Ass 167 1958 16 Eckenhoff J E Elder JD and hing B D (1952) N allyi normorphinc in the treatment of morphic or demorol narcosis Amer) med Sri 333 191 17 Tenne) S M and Mithocfor J C (1953) Respirstory depressant action of ally lnormophine in the normal salject and in patients with respiratory aadosis secondary to pulmonary emphysema New nel ] Act 249 886 18 Cillar js Hunter W Damer C B and Thompson GR (1998) Megendine hydrochlonde and alphaprodinc hydrochloride as obstetric analgesic agents Amor J Obstet Gynet 75 1tos 19 Shulman A Shax F H Cass, N A and Whyte H M (1953) treatment of barbiturate uto rication Bnt med i 1238 Gershon S Druce D K Orchard N and Shau F H (1958) Amiphenazole and morphine in the production of analgesia Brit med ] 2 366 21 Holmes M (1956) Amiphenazole in obstetric analgesia Lancet 2 765 22 Bourne G (1954) Methylpentynol a labour Lancet 2 $22 23 Whitchouse W L (1988) Rectal methylpentynol in labour Correspondence Lancet 1 743 24 Haukins D F and Noon W CW (1957) Blood clectrolytes in prolonged Labour J Obstet Gynaes Brut Emp 64 641 25 Dundee ) W (1957) Anacsthesia and surgery in adrenocortical insufficiency Brit ) Anaesth 29 166 26 Hugson R A and Southu orth L (1972) Continuous caudal anesthesia Amer } Surg 58 g -7 Hingson R A and Edwards W B (1943) Continuous caudal analgesia 10 obstetrics ] Amer med Ass 121 2.5 28 Edicorual (1949) Caudal analgesia Brit med } 2802 29 Hingson R A and Hellman L M (1956) Anesthesia for Obstetrics Ist ed Philadelphia Lippincot 30 Foldes FF Colavancenzo E and Birch JH (1956) Ep.dural anesthesia a reappraisal Anesth & Asalg 35 33 89 31 Dramage PR (1954) Spssal Epidural Analgesia ist ed Edinburgh Livingstanc 32 Guttmacher AF2 Special Committee on Infant Mortality 957) Panci discussion Obstetric anesthesia and analgessa NY SHJ Med 37 2532 33 Little W A and Fredman E A (1958) Anesthesia for the twin delivery Anestesiology 19 525 34 Johnson T (1957) k tolonged labour a clinical trial of continuous caudal analgesia Brinsed ] 2 386 35 Jahulsors T and Clayton, C G (1958) Studies in placental action during prolonged and dysfunctional labours using radioactive sodium J Obstet Gynaec Brut Emp 62 313 ·SO PANCIPLES LD PRACTICE OF OBSTHIC 4X4ESTHESIA on both a local and a national scale, o at a laudably builtd of caccata ness and safety reducing in some measure the undous compan of these methods with regional techniques - North American be The lugh forceps 13.e associated with condocom walesa doos no hay to commend i to Baosh obstetaan. As outlined abors, cara cases in which regional block offers significant adres oregoneral analgesia all obstetric anasstheasts should be competens, and that departments equired to undertake conduction analgesia for sach panorams. To extend the practice to a larger propornoa of obscene pancers woul! entail a considerable reorganizzson of hospital and departmental 23- muration, and a re-onentzoon of our obscetnic pracace. La comes of posable decreased maternal distress and permasal mondo che TEILTRES, if any for such efforts would probablr be mogubcat Epidural analgesia is not recommended for use n dorchart practic Its place m operaire obstetrics and m the treatment of edampsa will be discussed m subsequent chapers REFERENCES I Munnatt, R. J (1934) "Selt-adomessed analgesia for the monary of gammel practice Proc R. Soc 1.227 1313 - Seward, E H and Bryce-Smith, R. (1957) H_11. folesa - Clither Ist ed Oxfood. Blackwell 3 Roberts, H. (1945) 'Perhadine and scopolammen labour Brilr1,3492 4 Roberts, H, Kane, K. M Peroral, Snow Pad Picase, W (195) 'Effects of some analgesic dans used na daldharth, wah pecal reference to van bon m resor min. volume of the new born. Larur, LLS. 5 Baker F J (195) 'Pethined calorpne m labout 6 Caldeyro-Bartu, R., Posero, J, Alize Hand Tost, P (1956). fon of clorpromar oa gerade contractility and at pressure na pormal and taxtu fregnant women Am J O'siri G75, 1045. - Sarage, D (1955) Chlorpromana amalges. Lbour. Brt. 3.4.2 27 346 & Carroll J J and Hudson, P (1955) Chlomon and prone an Olsena Canal In2sh Sn). 343. 9 Ludly J E Rogeis, S F and Mover T H (195-) Anlessa-potesztens ccts of calorftomazne durmg labour. Obstetar: Gen 10 10 Browne, 4. D H 2nd Mant102, P J (1955). Application of chlorF2222 to obs tocs, wzba sods ofiseños dung labour Inst] 12252, 6. Sce No. 351 F 11" 11 Danes, JL (1955) Use of larga mobscene. Cal. Ara sı. So...243 1. Editonal (1956) Chorpromazmem obstedes. Laat, 3, 563 13 Harez V B (1956) Chorpromaze doimal labor. Ostend Game 8,1 14. Gordon L E. and Ram C. L (1955) 'Prometheme as an adone to obetaal analzesa and sedation, the joista Gykius ·TORCITS DELIVERY AND CAESARIAN SECTION 33 anaesthetic agent in obstetric practice The adtantages clamed on its behalf arc (f) In terms of general toxicity and central depression it offers a relaa cly hugh degree of safety for the mother (z) Satisfactory anaesthesia can be obtained together with adequate orygenation (3) It is one of the very few drugs which will provide relaxation of the users without at the same time causing dangerous maternal depression (4) should somang occi! It is likely to do so in a light plane of anaesthesia, when the laryngeal refleres are still able to offer some prosection aganst the aspiraton of volutus (s) it demands no cumbersome apparatus when used in general practice The disadvantages of ether may be classified as (1) It is frequently the cause of nconatal depression (2) k 1 notorious for provoking romang during inducton or the recosery period (3) Given as the sole agent, it is likely to be assocated with a prolonged and tempestuous induction (4) It 15 explosive and inflammable (s) It is unpleasant to take Dominant opinion in Britain is probably still in favour of ether as the mainstay ur obstetric practice Ethez haas been used as the sole anaesthetic for so long that its name is almost synonymous with obstetric anaesthesia s dhe minds of not a few specialists and general practitioners It must always be acknowledged that in questions of safety che man behund the anaesthetic is of far greater significance than is the agent or method used. There is no doubt that there are many consultants and general practitioners who from the long experience of giving ether anaesthesia can by their skull in manupulatng the drug ensure an irreducible degrec of danger and discomfort for their patients for these artists and the term is used with sincere respectuothu book is not intended. It is aimed, rather to interest the younger generations of anaestheasts and general practioners who are not satisfied with the standard of anaesthesia which they or their department can offer and for those who are concerned with the training of post-graduate and medical students The aut or us convinced that given equal standards of skill certainly a more pleasant and probably safer anaesthcac can be given by wing the more up-to-date techniques to be dsscussed, than by using ether Ifether as to be used the mother must be given a belladonna derivanve ·CHAPTER I FORCEPS DELIVERY AND CAESAREAN SECTION The general arms by the sausfaction of which any method of anaesthesia for operative obstetrics must be judged, may be listed as follows a Concerning the Mother * To provide a sure relief from pain - To provide continuous adequate oxygenation 3 To involve the muumal use of toxic drugs 4 To avoid the production of hypotension and vomitng and, if these should appear likely to occur to provide prophylaxis against their 11l-effects s To provide satisfactory working conditions for the obstetrician 6 To provide maximum physical and psychological comfort within the terms of the preceding and following conditions b Concerning the Child To guard against any diminution of oxygen supply 2 To ensure the minimal degree of central depression due to the anaestheac agents It is only with such an approach in mind with its object of ensuring the greatest safety for mother and child that a discussion on obstetric anacsthesia can be presented. For convenience methods of general anaesthesia will here be reviewed first followed by an account of regional techniques the chapter will conclude with a discussion of the senous problem of maternal vomutung 1 General Anaesthesia i INHALATIONAL AGENTS A Ether Since the eclipse of chloroform, cther has been the most honoured ·FOR CEPS DILTERY AND CATSARCAN SECTION 33 whuch an ainay may be maintained, and being sot as lable as an orom pharyngeal airway to provoke retchung or laryngcal spasm A manoeuvre wluch is mentioned only to be condemned, is that of giving carbon diondemmor of allowing rebreathing in the absence of a functioning absorber-In order to faalitate the rapidity of cther induction In the hands of a competent anaesthetist the amc gained by the usc of such a method is probably insignificant in respect to foctal depression under other arcumstances the ill-effects of the gas on a foctus akeady m distress would probably be considerable In domiciliary practice ether will almost exclusively be given by the open-drop method. The absence of a supply of pure orygon increases considerably the prospective danger of moderately deep anaesthesia However most instrumental delueties in the home are outlet forceps and for these anaesthesia need be only very light and of short duratonideed ether analgesia is probably a better connotaton It is likely that the latter face plus che greater caugon stimulated by the absence of faaliaes for resuscitation contnbuted in good measure to the relatively low inadence of matemal mortality in domualiary practice whuch was described by Parker Electve Cacsarcan section can provide one of the greatest challenges to the art of the obstetric anaesthetist in the emergency case if the mother objects to the incidents of induction of het recovery is marred by vomiting or a cough, if the operating condiaons are not endrely to the laking of the obstetncian or if there is nooceable neonacal depression the anaesthetist can by blunang hus insight somewhat persuade humself that elegance was sacrificed to expediency or that much of the distress was due to obstetric difficulties in the case of an elective Cacsarean section the anaestheast must accept total responsibility for any pre- or postoperatrve distress not of immediate surgical origin suffered by the patient and for any depression of the neonate at delivery The common sndications for clecave secbon are disproportion severe or increasingly severe toxaemia maternal diabetes placenta praevia and bacech presentation in an elderly pampara Should placental insufficiency be known or be expected to exist under any of these circumstances the anaestheast will plan his scheme of drug and oxygen admini stration accordingly If difficult operative conditions are likely to increase the time between incision and delivery such conditions as for example the myomata or dense scar tissue the anaesthetist will have been forewarned of this by the obstetrician There can be no excuse for failure When a pagent arrives in the theatre for an elective Caesarean section Presence of ·54 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA (atropine gr Tóg or scopolamine gr 1to) intramuscularly at least 5 minutes or intravenously at least 2 minutes before induction of anaesthesia For delnery in hospital, an anaesthetic maciune should be available, with a closed circut attachment for the use of the accomplished anaesthetist Anaesthesia should be induced with nitrous ovde or if soda-lime is not in use Tulenc It is claimed that anaesthesia can be surreputously induced by way of the mask which the mother has been applying for her unhalational analgesia Tlus implies that she has been receiving nitrous oxide oxygen from an anaesthetic machine or that the anaesthetist can induce anaesthesia by placing a finger over the au-ınlet of a nitrous owde/ass apparatus The former condition is likely to be of infrequent occurrence, and the latter manoeuvre is strongly to be deprecated, as it must lead to anoxia A total flow-rate of 10-12 ltres should be used in the proportion of 80 20 nitrous oxide to oxygen, in a semi-closed system when a closed-circut is in use the total flow may be kept down to 4 litres or less umg 2 so so mixture Ether or Talene followed by ether as introduced gradually into the mixture of inhaled gases with even more chan the usual Care to avoid straining and breath-holding Anaesthesia should be kept to the lightest plane compatible with satisfactory operating conditions In the case of forceps delivery the patient should if possible be placed in the lithotomy position catheterized and towelled before induction, because of the cumulative effect on the foetus of protracted ether anaesthesia For an outlet forceps delivery the ether should be discontinued as soon as cpisiotomy has been performed to be recommenced after complete delivery of the infant in cases in which some difficulty is expected ether administration should be continued unul the largest diameter of the head has been delivered For Caesarean section skin preparation catheterization and towelkng should precede induction and the other flow should be cut off just as the surgeon prepares to incise the The question of the use of an oro-pharyngeal airway remans a vexed one It is the author s opinion that such an aid should not be invoked unal after delivery when anaesthesia can be deepened if it is so desired, unless as in the case of a shost-necked or large-tongued patient the difficulties of maintaining an unembarrassed natural airway prove too great In the ordinary course of events anaesthesia before delivery should be so light that pharyngeal stimulation with an airway would be likely to provoke reflex activiy in a high proportion of patients Certainly thus condidon should appertain at the time of delivery A naso-pharyngeal tube mught be found to offer some compromise increasing the case with uterus ·$7 FORCEPS DELII CRY AND CACSAREAN SICTION (3) Significantly less post-operatse vomiting than with ether (4) Early relaxation of jan and pharyngeal musculature permutting carlier insertion of an airway should this be required. The disadvantages are (1) Matemal respiratory depression necessitates using the technique of assisted respiration (-) An appreciable inadence of neonatal depression (3) Difficulty of produang full uterinc relaxation without approaching levels of concentrapon which might prove dangerous to the mother (4) Virtually necessitates the use of a closcd-circuit apparatus () Danger of cardiac arrest in the presence of arculating pitressin (6) Incompatability with adrenaline-Important if the perincum has previously been infiltrated with a local analgesia (7) Hazards of explosion and fire When cyclopropane is used as the main agent for induction and mantenance of anaesthesia it is customary and wise to use nitrous onde as a vehicle for the cyclopropane Induction is carned out with cyclopropane nitrous oxde and oxygen at flon-rates of about 750 ml 1,500 ml and I 500 per minute tespectively by means of a closed-circut apparatus and using assisted respiration (this method is of course precluded if Tnlete has been used extensively for analgesia) As soon as a light and stable depth of anaesthesia has been reached the flow-rates should be ICadjusted to approximately 300 ml. 1000 ml 1 000 ml per minute cyclopropane ditrous oxide oxygen The same indications for stopping and recommencing the administration of cyclopropane and nutrous oxade at the time of delivery should be used as were described previously for ether However the speed of recovery from cyclopropane is comparatively greater and if it is anticipated that the actual process of delivery is likely to be prolonged, it is advisable to reduce the flow of anaesthetic gases rather more slowly Cyclopropane will provide reasonably saus factory working condisons for most forceps deliveries If the tone of the uterus or contraction of the pelvic floor muscles, cause considerable embarrassment to the obstetrician then there must be no hesitation in adding a small amount of ether to the mixture should incrcasing the cyclopropane flow to about 700 ml per minute not have proved helpful Under the circumstances postulated, the nconate would face far less danger from the cther than from the trauma of an unnecessarily difficult delivery Furthermore saying the mother from a degree of traumatic shock and local tissue damage is obviously of greater merit than is avoiding the prospect of increased post-operative vomiting ·SO PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESLA she is alert possibly apprehensive, and has not been subject to the long and probably wearying ordeal of labour which makes induction in an emergency section so much simpler If she is indeed apprehensive, then the anaesthetists record will already have become slightly camished. If nitrous oxide/ether is the chosen method of anaesthesia then in an unsedated patient it is likely that induction will be an unpleasant memory for mother and anaesthetist. In these patients anaesthesia will have to be fairly deep to provide ideal operative conditions and under such cur cumstances neonatal depression is more likely to result if ether is used than if some form of balanced anaesthesia is employed. Following operatron if ether has been used at least one-third of patients are likely to vomit pro- All patients should receive some form of sedation on the evening before the day of operation Preferentially a barbiturate with or without methazine should be given The sedanve given at 8 or 9pm- can be discounted in assessing the total of depressant drugs likely to affect the foetus at the time of delivery It is preferable and, if ether is to be used, very desirable that the mother should receive pre-operauve sedation If morphia (gr 4 intramuscularly about 60 minutes before operation) is prescribed, then levallorphan (1 o mg) should be given cither at the same time or injected intravenously at least 10 minutes before the start of anaesthesia Promethazac 25 mg intramuscularly gaven 45-60 minutes preoperatively might well become the drug of choice in this context b Cyclopropane At the time of writing cyclopropane holds an important place in the scheme of anaesthesia for hospital delivery Owing to lack of suutable apparatus it is little used in domaliary practice Possibly the widespread introduction of an easily portable machune-equpped with sparklet cylinders of cyclopropane-such as Hingson sº Westem Reserve Midget, mught spur an increase in the popularity of the agent in obstetric work in the home However considerations of the attendant dangers and the cost of cyclopropane anaesthesia are likely to weigh in favour of more recently introduced methods The advantages offered by cyclopropane in hospital practice are (1) A smooth and rapid induction associated with this factor a light plane of anaesthesia can be maintained with greater ease than is the case with ether (2) An case in raped manupulation of the depth of anacsthessa ·TORCITS DIUERY AND CAESAREAN SECTION 39 and hypercarbia of foctal distress Hoscice thus effect is unlikely to have becn of significance in the production of a similar result obscrved by thein in their series of clectic Cacsarcan sections Whatever the mode of action of cyclopropanc m leading to nconatal depression, it is apparent that considerable effort must be made to rcducc to a minimum the quantity of the drug administered beforc dclivery One method of doing thus is by inducing anacsthesia with thuopentonc a drug which will be discussed later It is also a sound practice to hyperventilate the patient with a high orygon flou keeping the expiratory valve partally opened, just before delivery The use of cyclopropane within about one hour of the most recent admirustration of pitressin constitutes an inexcusable risk for the patient Similarly of course the latter drug should not be used dunng or shortly after operation conducted under c clopropane anacsthesia Thc lugh madence of cardiac irregulanties with possible fatal outcome when thus combination of drugs is used as well cnough documented' to need no emphasis here The free use of cyclopropanc in the presence of circulating Patocan has generally been sanctioned on the grounds that the latter drug of synthetic ongin contains no pressor agent However there is some reason to doubt the accuracy of this views Lesser and Eason' have reported one case of fatal cardiac arrest seemingly caused by a combined action of cyclopropane and Patoan It is probably wise to ensure that a patient is never subjected to the influence of Pitocin and of cyclopropane simultancously < Other inhalational agents Aside from its occasional employment as an and to induction of ether anaesthesia it is not advisable to use Trilene for operative obstetrics Trilene anaesthesia usually entails a long period of induction though it is much less frequently associated with a tumultuous second-stage than is ether Excretion of the drug is an equally lengthy process and hence neonatal depression is a highly probable consequence of thus anaesthetic is used. Almost the oldest inhalational agent can usefully be considered in company with the newest Anaesthesia with both chloroform and Fluothane (Halothane) is characterized by rapidity of induction the production of marked uterine relaxation and a tendency to cardiac irregularities with possible syncope Owing probably to the fact that it was introduced within a more enlightened era devoted to precise measurement Fluothane is administered almost exclusively with the ad of standardized cquipment Chloroform is still given by the open- ·58 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA Cyclopropane can be used for the induction and maintenance of anaesthesia for emergency Caesarean section For this operation the flow-rates of cyclopropane nitrous oxide and oxygen should be the same as those advised for forceps delivery As in the case of the latter operation there will be less likelihood of neonatal depression of skin preparation cathetenztion and towelling precede induction Except in patients who have undergone exhausting labours or in whom multipanty has led to a considerable laxity of the abdominal wall the operative conditions under cyclopropane anaesthesia are likely to fall short of ideal This is particularly so if the obstetrician s technique includes firm packing of the intestines away from the fundus of the uterus and into the sub-diaphragmatic region These conditions are even more liable to be met with in an elective Caesarean section and may be circumvented by giving a small dose of a nondepolanızıng relaxant-preferably d-tubo-curarine about 10-15 mg -at the time of the initial skin incision The question of intubation will be discussed later in this chapter If delivery is made unduly difficult by contraction of the uterine muscle and the latter is not responsive to an increase of cyclopropane within the margins of safety then the addition of ether is indicated Results obtained in a recent study by Apgar suggested that cyclopropane given as the sole anaesthetic agent for Caesarean section and for premature vaginal vertex delivery occasions greater risk of neonatal depression than does spinal analgesia for such cases There was no significant difference in regard to neonatal mortality. It is likely that part of the difference in morbidity is due to placental transmission of a depressive agent though no significant correlation was found between the degree of neonatal depression and the concentration of anaesthetic present in the umbilical vein in Apgar a series A further factor whuch could be of contributory signuficance is the tendency of cyclopropane to cause a local arterio-venous shunting effect It is possible that this phenomenon might tend to cause a partial by-passing of the placental site by arterialized blood and that this in association with a strong tendency to matemal respiratory depression even under light cyclopropane anaesthesia might lead to neonatal depression due directly to oxygen-lack However Apgar and her co-workers failed to find any significant difference in terms of the oxygen saturations and carbon dioxide tensions of umbilical vein blood between infants delivered under regional block and those subject to cyclopropane These same workers present the interesting postulate that the relatively unsatisfactory state of neonates following cyclopropane anaesthesia might be related to the invidious effects of the drug on the foetal myocardium in the presence of the anoda ·PORCEPS DELIVERY AND CAESAREAN SECTION not increase the likelihood of producing nconatal depression duc to the single injection of thuopentonc The likchhood is indeed, probably diminished (3) Relative freedom from unpleasane post-operative scquclac Associated disadvantages are (1) It us a deadly wapon in the hands of the unwary of the inexpenenced. (-) Should vomiting occur, it is of more scrious significance owing to coinadental decrease in the efficiency of the laryngeal reflex (3) Increased danger of laryngeal spasm and, reputedly bronchospası, under light thuopentone anaesthesia Because of the rapıdıry with which maternal blood concentrations of thiopertone are mirrored in the foctus administrauon of the drug before delivery should be confined to the instal dose Depending upon the weight and general condition of the mother about 150--50 mg of thiopentone may be given for induction with an absolute maximum of 300 mg For forceps delivery maintenance of anaesthesia may be bascd upon nitrous oxide—80 20 nitrous oxide oxygen for 3-4 minutes followed by a so so mixturamor cyclopropane-300 1000 1000 cyclopropane nitrous oxide oxygen. The former technique is to be preferred, as the use of cyclopropane will still entail the disadvantages previously listed, despite the decrease in total dosage Esther of thesc methods should prove satisfactory for most forceps delivenes If there is a demand for increased uteric or pelvic floor relaxation cyclopropane or a trace of ether may be added. For emergency Caesarean section the routine injection of 10-15 mg d-tubo-curarine just before the skin is incised will be found to add to the efficiency of a balanced technique and in other respects the scheme just described for forceps delivery should be used If the patient is particularly alert as in the case of elective Caesarean secnon it will usually be found necessary to employ the cyclopropane technyque in order to achieve good operating condizons unless full relaxation together with intubation is substituted. Premedication with atropine must be part of any scheme of thropentone anaesthesia. If thiopentone is used for induction it is not necessary to place the patient in lithotomy or to prepare the abdomen before the patient is anaesthetized Indeed it is preferable not to permit these preparations whilst the patient is awake as the possibility of neonatal depression is decreased by prolonging the induction-deliycry interval This factor assumes even greater importance in the anaesthetic management of that irritating class of cases EUA Caesarean Section The object of the ·60 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESLA of his patient drop method. Both drugs must be preceded by atropne premedication. The dangers to heart and liver offered by chloroform administration are so well known that an anaesthetist who employs the drug must be prepared to accept an increased degree of responsibility for the welfare Chloroform anaesthesia m obstetrics is not advisable unless the admunistrator has had very considerable experience with the drug One of its main advantages has been the absence of an associated fire or explosion hazard. This is no longer a pressing indication, as such hazards can be arcumvented by removing the source of gaidon or by tising intravenous anaesthesia. Because of the apparatus involved in its use Fluothane is unlikely to become popular in domiciliary practice Too short a penod has passed since its introduction to assess the place it is likely to find in hospital practice However an initial survey seems to indicate that it offers few advantages and some disadvantages when compared with other techniques Use of the drug confers an easy and rapid induction comparative freedom from vomiting and apparently no striking degree of maternal depression There is however an ever-present danger of senous cardiovascular disturbance and the uterine dacadity produced by the drug 15 apparently so marked, that administration must cease or at least be drastically curtailed before the end of the operation in order to guard against its causing severe post-partum haemorrhage? 8 On the other hand, it must in fairness be added that Brown and Woods in alluding to sixteen Caesarean sections anaesthetized with Fluothane have nothing but praise for the drug and say that in their experience uterine contraction and retraction are not affected by it. Finally as the rate of production of cardiac arrhythmias is known to increase greatly when adrenaline is given in the presence of chloroform (though not apparently in the presence of Fluothane?0) it is probably correct to surmise that this anaesthetic should not be administered if the patient has recently been given pitressin 11, INTRAVENOUS AGENTS a Thiopentone The poor analgesic property of thiopentone when compared with its depressant central action, precludes its use as the sole anaestheac for any but the most rapid of operative deliveries The advantages of thiopentone as an induction agent are (1) Rapidity of action and freedom from subjective unpleasantness (2) Prolongation of the induction-parturition interval probably does ·in her FONCIN DIR) AVD WRII SITIO in an attempt to indicate that when the furthol is successfully employeche pabent, although rendered free from an apprchenion and general sascomfort is sall scrisibly aware of her environment In general the method in ohes the use of a phenothuazanc deware a nirwoc and a nascorse ancagonise ? Chlorpromazinc and promethazune base been the phenottuazione derivantes most commonly used in this count Their respecte meno m obstets have already been descussed in Chapter II) and further reference will be made only to promethazine Perhudenc is the sole narconc of choicchawthe employment of morphua has not been described, and that of alphaprodine is limited to the United Statesmand, whilst the choice of antagonist lies between levallorphan nalorphine and amuphenazole discussion will be limited to levallorphans, for reasons outlined in Chapter III As so far coled, the recommended method is as follows At least 10-15 minutes before the start of surgery with the pagentlying position of greatest case a siuxture of 100-150 mg perludine 10-2 mg lezallorphan and 25-50 mg promethazinc made up with water to a dilution of 10 mg perbudine per i ml solution as slowly injected utratmously over a period of --3 minutes The absolute quantues of perludine and promethazınc used (the le allorphan/pethidine rado must always be 1 100) will depend, as aluays upon the weight and general condidon of the patient, and upon the ampurude of her response to the initz) fev mulettres In the light of our present knowledge although it us felt with reasonable Certamey shat significant hypotension will not occur it is strongly advised thar frequent blood pressure readings be recorded during the course of hypoaesthesia After the necessary lapse of time during whuch the subjective response to each contracaon will be seen to diminish (there is no contraindicaton to allowing nitrous oxide or Trlene analgesia if already in use to conunuc for the first few mmutes after injection) the patent is placed into the lichotomy position having been fores arned of thus manocuvre Esch major step in the preparation and the process of delivery should be preceded by advising the pauent to expect a fresh series of sumul but ones wluch will be nother punful nor unpleasant It has been found necessary on occasion to provide extra analgesic cover by injecting the line of the proposed cpisiotomy with local anaesthetic This as possibly a reflection of an inadequate interval between induction of hypożesthesia and the start of surgery There ss some evidence that the phenothuazınc clement of the mixture helps to provide 2 degree of relaxation of che pelvic floor ti 13 However should thus struc- ·62 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESTA examination in these patients is usually to decide whether or not vaginal haemorrhage is due to a separating placenta praevia. Epidural and spinal analgesia are obviously contraindicated under such arcumstances and a thiopentone induction followed by maintenance with nitrous oxide and oxygen during the period of examination is the scheme of general anaesthesia least likely to lead to a dangerous depression of the foetus Naturally there is a certain equation involved in the likelihood of the production of neonatal depression following thropentone-induced anaesthesia Although the significance of the thiopentone decreases with the passage of time that of the agents used for maintenance increases If nitrous oxide is the sole other anaesthetic time is probably of little importance provided anaesthesia can satisfactorily be mamtained. If however cyclopropane is employed, delay of delivery for longer than about 20 minutes after induction of anaesthesia is likely to lead to neonatal depression caused mainly by the inhalational anaesthetic The optimum time of delivery under such a scheme of anaesthesia is probably 5-10 minutes after the start of the thiopentone injection Use of an oro-pharyngeal airway and failure to pay careful attention to the maintenance of a clear natural airway, are the main causes of laryngo-spasm and vomiting noted above as disadvantages of thiopentone in obstetric anaesthesia Adequate premedication with atropine care in holding the chin and avoidance of an oro-pharyngeal airway should virtually eliminate the possibility of laryngeal spasm A further method of providing analgesia in associadon with thiopentone induction-especially for elective Caesarean sections the use of the technique of intermittent intravenous injections of pechrdine as employed in balanced anaesthesia for general surgery Bingham" has described the use of such a technique in a series of 359 Caesarean sections, and the excellence of his results are strongly in its favour Neonatal depression consequent upon the pethidine should be avoided by giving i mg levallorphan before the start of anaesthesia or by the use of a pethudune/levallorphan mixture This technique offers considerable advantage in cases of trial of forceps when ulamate delivery-possibly by Caesarean section—is likely to be effected only after prolonged anaesthesia b Phenothiazine deri atives A recent approach to the problems of obstetric anaesthesia involves the use of phenothiazine derivatives The method does not lead to the production of anaesthesia but to a condition which has been termed ataralgesia 12 or hypoaesthesia 13 These terms have been introduced ·TURCHAS DIVERY AND CAISARLAY 11.7104 as takas to indicate not only blocking of the branches of both pudends! nenes, but to include adequate local infiltration of the perincum and labu. Used as the solc method of relieving the pain of certain types of forceps delvety pudendal block is probably attended by the Icast danger to mother and chuld it is generally accept that only about 60 per me of forcers dels series can be satisfactonis performed under local analgesia. Unranforced pudendal block doo not offer sufficiently exiensisc analgesia or adequate uterine relaxibon for opctauons involving conscrabic rosanon of the head, or for those in such the head ss not at the outlet. Recently Scott and Gaddh hxc described the use of praiendal block supplemented in certain cises with pothicine and chelorpromazing for extending the application of local analgesic teclunquc to about go per cent of all forceps deln erics Thar method w based on the employment of kallands forceps As indicated in the previous section full applicauon of hypoacsthesia, without pudendal block, might wall produce equally sausfactory results Houder u Pukce point out for those forceps requiring lade manipulation pudendal block must be placed very high on the list of methods of choice Worlun thus category of patients there are virtually no contraindications to pudendal block, and the only noteworthy complications are toxic effects due to overdosage of Of Scavity to the analgesic (which should be an extremely rare occurrence sf an accepted technique is closely followed) and the production of a vulval hacmatoma delseries 1. SPINAL ANALGESLA The use of spinal and extra-dural block methods of analgesia must of course be confined to hospital practice Before starting upon any discussion of the application of spinal and extra-dural analgesia to operative delivery it is necessary to supulate a number of factors which absolutely contraindicate the use of these methods 1 relative matemal hypotension 11, maternal anzernia 1 poor general condition of the mother wv absence of an immediately available source of pure oxygen v absence of means of resuscitadonmncluding a tilting table The majority opisyon in Britain is against the use of spinal analgesia for any surgery sscluding obstetric To an appreciable extent this bias is derived from the atitude of the general public Patients in this country F ·64 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA ture or the height of uterine tone, obstruct the obstetriaan unduly the anaesthetist can offer increased aid by administering 75 25 nitrous oxide oxygen or Trilene or a short spell of cyclopropane Resort to these latter aids should rarely be needed Atropine premedication is not a necessary preliminary to hypoaesthesia. An oro-pharyngeal airway is not indicated and there is very little reason Why vomiting should occur before during or after operation—indeed, the method can be said to preclude nausea and vomiting Oxygenation is adequate throughout but in cases of foetal distress (see below) increased oxygen should be given to the mother At present hypoaesthesia is recommended for general use—in both domiciliary and hospital practice only in cases of simple forceps delivery, not involving more manupulation than slight rotation of a malpositioned head and in the absence of foetal depression The impression is that it will prove to be safely and satisfactorily applicable to all cases of forceps delivery bur investigation of this must for the time being be confined to special hospitals with research facilities The place of the method in Caesarean section is as yet entirely without significant investigation < Relaxant drugs The choice of relaxant drugs is limited mainly by the factor of possible placental transmission of the agent and this has been discussed in Chapter II It is evident that d-tubocuratine is to be preferred to Flaxedil if a non-depolanzıng drug is to be used Recent observations recorded by Hodges16 suggest that if suxamethonium is utilized the possibility of the conversion of its action from depolarizing to non-depolarizing in the presence of Pitocin must be borne in mind 2 Regional Techniques For a discussion of the drugs used in regional analgesia the reader is referred to Chapter III 1 PUDENDAL BLOCK For obvious reasons of convenience the admirustration of a pudendal block is more properly within the province of the obstetrician than of the anaesthetist The anaesthetist should however be competent to perform such a block and of course be well acquainted with the anatomical considerations underlying the technique There are many published accounts of the general procedure 17 18 and to these the reader is referred for instruction It is to be noted that the term pudendal block is tactly ·prior to PORCEPS DELIVERY AND CACSAREAN SECTION 67 significance in thus regard is the time when the patient is returned from the lathotomy position at the end of operation For Caesarean section the injection should be made at the same site, and with the same precautions Analgesia is requred to extend to the level of T8 and the requisite dosage is 0608 ml of joo nupercainc in 6 per cent glucose or 6-8 mg pontocainc in 20-25 ml of 10 per cent glucose It is a common prophylactic practice to add a vaso-pressor such as s o mg methedrne to the local analgesic used for the skin weal spinal puncture The possible effect of this on the foctus which is already distressed has been noted in Chapter 11 If the practice is not followed there is need for even greater vigilance regarding blood-pressure changes after the spinal has been given Forthman and Adnanı 21 in a series of 391 Caesarean sections carned out under spinal analgesia noted a degree of hypotension in 82 per cent. Only 20 of their patients were given ephedrıne intramuscularly pror to the spinal and 2 of these developed hypotension. The average systolic blood-pressure fall for the series was 30 mm. Hg These findings alone in the hands of acknowledged leaders in the field of anaesthesia would seem to vitiate against advising the use of spinal analgesia in the presence of any degree of foetal distress Holmesz* has pointed out that the effects of peripheral vaso-dilatation attendant upon any spinal block rising above the level of L2 are likely noticeably to be increased by the partial occlusion of the imfenor vena cava by the uterus when the patient is supine The consequent sudden decrease in venous retum to the heart is a likely cause of acute circulatory collapse in obstetric cases the immediate treatment of such collapse or of any severe degree of hypotension must be to administer 100 per cent oxygen and to elevate the legs of the patient sufficiently to give an adequate autotransfusion of blood. Following these measures a vaso-pressor should be given intravenously It is unwise immediately to ult the patient into a Trendelenberg position lest the analgesic drug travel even further cephalad and also because the increased gravitational pressure of the uterus on the diaphragm is likely to add to the dangerous state of the mother Only when it is possible to institute the satisfactory administration of oxygen under intermittent positive pressure (preferably after the patient has been anaesthetized and intubated) should the table be tilted head-down As has been pointed out in Chapter I during pregnancy there is an increasing dependence upon the thoracic component of respiratory activity When Caesarcan section is performed under spinal analgesia the lower 4 or 5 intercostal muscles are paralysed, with resultant respira- ·66 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA apparently prefer to be asleep during the operations evidencing little curiosity about what is going on in the theatre The opinions of surgeons and anaesthetists is based upon a number of points the undoubted fear of ruinous (in terms of self-confidence reputation and money) legal proceedings which seemingly are an inevitable consequence of any but the most minor complications of spinal analgesia that the possible complications of regional analgesia outweigh any advantage offered somewhat paradoxically, the feeling that to give a spinal is a confession of failure that the standard of British anaesthesia is now so high that the use of such a blunderbuss technique in place of 'balanced anaesthesia is a retrogressive step The latter argument is undoubtedly a form of overswing following the introduction of the newer drugs primarily the relaxants and there is evidence that it is now being corrected Unfortunately the attitude carnes a very real danger in that it tends to cloud the important fact that certainly as great attention must be paid to the conduction of spinal analgesia as is paid to the most delicately balanced general anaesthetic That there is a place for spinal analgesia in general surgery is undoubted whether or not the indications in obstetric practice arc of significant dimensions as a more open question but truly the technique and safeguards must be understood by all undertaking obstetnc anaesthesia For a forceps delivery a low spinal is given with the objective of obtainıng analgesia up to the level of Tro The agents in general use are zdo nupercaine in 6 per cent glucose—the dosage being 04-06 mland pontocaine 4-6 mg made up to 2 0-2 5 ml in 10 per cent glucose The injection is made in the third or fourth lumbar interspace using a fine-pointed 22-guage spinal needle the patient should be in the lateral position and the table should be tilted 15-20 degrees head-up As soon as the injection has been completed the patient should be placed fat on her back and one minute later the table is returned to the honzontal. There is an apprecable number of departments in which the patient is made to sit whilst the spinal is being given This appears to increase the discomfort and distress of the mother and in the case of outlet forceps deliveries adds to the possible dangers to the infant Under no arcumstances should the analgesic drug be injected whilst the uterus is in contraction as the associated turbulence effects within the cerebro-spinal fluid are likely to lead to undue and possibly disastrous spread of the drug Blood-pressure readings must be taken before the block is instituted and at frequent intervals dunng the subsequent 10-15 minutes Of special ·TORCEPS DEUVERY AND CAESAREAN SECTION 09 Massey Dawkins25 advises the use of the twelfth thoracic Interspace Using 17 per cent Xylocainc with 1 250 000 adrenaline hc injects ---24 ml and thereby aims to achicve analgesia crtending from T8 to T12 inclusncly Foldesze advocates the use of a cathetes for though the operation is usually completed (in Britain) within the effective period of the first dose the catheter-method incrcases the safeguard against inadvertest puncture of the dura. Foldes using 3 per cent 2-chloroprocainc with added adrenaline injects an urutal dose (including the test dose) of about 24 ml of analgesic drug ualizing the third or fourth lumbar interspace He also makes the point that the patient should be alted 5-10 degrees foot-down during the period of drug-fixation as for some reason these patients appear to retain supra-pubic sensitivity of the in- Jection is made whilst they are in the horizontal position In cach of these methods the usual test dose is advocated as a preliminary Massey Dawkins son the basis of his considerable experience with the cxtra-dural technique considers that in 10 per cent of cases it is impossible to initiate a block because of local anatomical difficulacs mis per cent the method is a failure, in 10 per cent significant hypotension develops McKay' in the course of an account of 699 obstetric cases conducted under continuous epidural analgesia in Toronto General Hospital comments on the fact that the series included 76 Caesarean sections Almost all of these patients needed some form of general anaesthesia during part of the course of their operation This feature is an important and disturbing one Manipulation within the upper abdominal region-especially rather vigorous packing of the coils of small intestine away from the uterus—and in the same genre the slight Trendelenberg tilt requested by some obstetraans frequently provokc sharp complaints from the mother Objectively it is not uncommon for hiccoughing retching or vomiting to occur and, apart from the direct danger offered to the mother such episodes are liable to interfere with the course of the operation Under these arcumstances the intravenous injection to the mother of 25 mg promethazine with or without 25 mg pethidine plus o 25 mg, levallorphan can often restore the equanimity of both mother and surgeon Epidural block appears not to lead to the increase in uterine tone which is seen in association with spinal analgesia The gravity of dangers to the foetus are certainly far less from epidural analgesia than froni a spinal In cases of elective Caesarean section in which it is imperafange and ·69 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESLA of the patients tory embarrassment which is not infrequently very well marked. Such a state of affairs will persist unul extraction of the foetus permits a return to full-functioning of the diaphragm, and until that time oxygen must be given to the patient from the moment the spinal begins to take effect 3 Makepeace" in a recent review of 1840 deliveries conducted under spinal analgesia, noted that 18 per cent of the parents complained of headache of varying seventy--post-operatively undergong Caesarean section 108 per cent demonstrated this reaction, as did 20 i per cent of those delivered vaginally It is of interest to note in this context that in the senes reported by Forthman and Adnam, 21 and previously referred to 54 per cent of the patients receiving spinal analgesia exhibited post-operanve hypertension, compared with 25 per cent in another group who were given a general anaesthetic for delivery the average nase in systolic blood-pressure being 20 mm Hg Characteristically an increasing intensity of uterine tone follows the administration of spinal analgesik Thuis effect undoubtedly plays an important part in reduang the flow of blood through the placental site Once a spinal has been given no ame must be lost in delivering the baby or death in utero can result from primary anoxia. Because of this increased topiary spinal analgesia is contraindicated for forceps delivery involving any but the least amount of intrautenne manupulation. For a likereason spinal analgesia is contraindicated for those Caesarean sections in which operation is likely to be prolonged due, for example, to adhesions or in which the lower utenne segment is hkely to be thun, as in obstructed labour due to shoulder presentation 211. LPIDURAL BLOCK The employment of caudal or lumbar epidural block for the emergency operation of forceps delivery is not advocated. The ame invoked, and the relatively high failure rate diminish the appeal of a method which, on the posiuve sade, offers little or no danger of drug intoxication to the foetus and, a hen successful, ensures almost complete freedom from discomfort for the mother If either form of epidural analgesia us contemplated m a particular patients for instance one with severe heart disease-It is advisable to mitate the block carly in labour uthzing a polyvinyl catheter By so doing a satisfactory control of the lesel of analgesia is obtained, and the full co-operation and confidence of the patient is better assured The place of epidural analgesia in the management of Caesarean section 15 more firmly based. There is a small range in the choice of techniques ·TORCEPS DELIVERY AND CAESAREAN SECTION 71 or worse to other residents who huc never received and who are not receiving traning in any other aspect of the speciality Of these factors the last is probably the most important It will be discussed later in this book. It is traditionally held that the ame normally taken by the stomach to empty is increased in labour This is said to be somewhat akin to the delayed gastric cmptying following severe trauma and to be duc possibly to a like cause An attempt has been made30 to demonstrate that, in the first stage of Labour the range of gastric cmptying times us comparable with that accepted as normal in the non-pregnant This finding applied only to Aud contents However in cases of prolonged and exhausting labour there can be no doubt that there is considerable retention of stomach contents and on the whole it is most advisable to regard the obstetric patent as presenting with a sigmficant volume of intragastnc material unless there is extremely strong evidence to the contrary In addition it has been observed repcatedly since Mendelsons, first drew attendon to the syndrome that the aspiration of a very small quantity of highly acid gastric contents can rapidly lead to serious and con fatal consequences In this connection the suggestion made by Dinuck,28 of giving antaad tablets to women in labour-especially to those with a history of dyspepsia—is worthy of pursuance When it is known that a patient who is not in labour has eaten a substantial meal or drunk a considerable amount of flud within a penod of four to six hours prior to the proposed time of operation common sense urges that steps be taken to relieve her stomach of its contents before anaesthesia is induced. The comparable period in the case of a patient who last ate after commencement of her labour is approximately eight to ten hours It has been argued that under these condiaons the use of regional analgesia obviates the necessity of emptying the stomach Regarding this it must first be stated that the aspiration of vomited or regurgitated material is not necessarly precluded by the use of conduction analgesia Klein,sin his account of matemal mortality Kings County New York, refers to the deaths of eleven mothers in one year following the inhalation of vomited gastric contents during the course of delivery under spinal analgesia Indeed Stearns and Frederickson *** on the basis of their considerable experience with regional techruques remark that there is probably no more certain way to produce vomiting than by the administration of spinal anesthesia for Caesarean It is likely that the chance of the occurrence of such an accident is less under epidural analgesia than under spinal but it still exists and must therefore still be anticipated in section ·70 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA tive to keep to the minimum the amount of depressant drug reaching the foctus—as in severe toxaemia of pregnancy prematunty or pronounced post-matunty-and in cases of emergency Cacsarean section, where haemorrhage is not a complication and the start of operation not of the utmost urgency, epidural analgesia must be given high pronty in the choice of methods available to the competent anaesthetist past few years The Vomiting The number of deaths in England and Wales resulting from the 19- halation of regurgitated or vomited material during the course of anaesthesia for operative delivery has been vanously estimated as being from fifteen" to twenty- annually during the precise number is of Lttle significance to the present theme except in as much as it will help to reflect the degree of success of a national effort to cradicate this tragedy That the problem is still with us and is not confined to this country has been indicated most recently by an account of 3 maternal deaths following the administration of general anaesthesia for delivery, which occurred in one hospital during a period of 17 months 29 Related to the number of deliveries each year or even to the number of obstetric anaesthetics which it is estimated are given annually the number of deaths might appear to be small. However cach one must be stigmatized 2s having been a completely avoidable tragedy and anaesthetists bear the full responsibility of ensuring that the annual rate is rapidly reduced. It must also be recognized that matemal death is the end-point of a process and that for every death recorded there must be a considerable number of cases in which the final catastrophe was avoided, but maternal morbidity and possibly perinatal death or irreparable damage resulted. The notonous position held in the realm of obstetric anaesthesia by the aspiration of foreign matenal denives from the following factors most of which are interrelated (1) the very high proportion of emergency operations involving (a) the need for haste (6) a relatively unprepared patient (2) the tendency to retention of gastric contents especially in the event of prolonged labour (3) the raised intra-abdominal pressure consequent upon the size of the pregnant uterus (4) attempts to maintain ught anaesthesia without mmumuzing pharyngeal stimulation (s) delegation of respon.ibility in this field to very junior anaesthetists ·TORCEPS DELIVERY AND CAESAREAN SECTION 73 a recent reports of a wide application of the technique suggests that it holds considerable mcrit.* Both the passage of a stomach-tube and the injection of apomorphunc will, espcaally in the former case Icad to some degree of maternal discomfort--this is an insignificant price to pay for the vast increase in safety It has been claimed that the straining and breath-holding which occurs during the manocuvrc (again notably when a stomach-tube is passed) might lead to incrcased disruption of the placental site, or at least temporarily to further diminution in foetal oxygenation The flecting nature of the mcasure makes it unlikely that these factors will have any significance in terms of perinatal salsage but should they give rise to any real anxiety it would be advisable to employ apomorphinc rather than a gastric-tube However the apparent success of other of these methods must not be taken as indicating that the stomach has been empued. The only danger wbuch has been averted as that of massive regurgitation or vomiting and considerable though that lightening of the load might be the patient must subsequently be treated with the utmost circumspection In the cases under descussion (ic emergency Caesarean section either before the onset of labour or in the early stages of the first part of labour) the recommendations as outlined previously should be followed Any temporary obstruction to the airway must be avoided for as O Mullane36 has shown this condition especially in the presence of raised intraabdominal pressure strongly favours the production of regurgitation A rapid and smooth induction with thiopenfone in competent hands is advocated as that least likely to be attended by vomiting or laryngeal spasm The use of an oro-pharyngeal airway is deprecated for reasons previously given If the stature of the patient is such as to suggest that maintenance of an arway will prove difficult intubation must be undertakea Routine intubation is advocated by many authorities 37 10 There are two methods open to use conscious intubation following careful spraying of the mouth pharynx cords traches, and carina with a local analgesic and intubation following administration of a relaxant drug The former offers the danger of silent aspiration post-operatively the latter entails a dangerous period of delay between induction of anaesthesia * In a personal communication Professor Robert T Wlute of the Department of Medicine University of Colorado has reported that the use of apomorphine in seventy five cases has revcaled no unpleasant or dangerous side-effects in the mothers and no resultant barm to the infants He and Dr Robert E Dean--who us to read a paper on the subject to the Amencan College of Obstetricians and Gynecologists in October 1958 (later to be published in Obstetrics and Gynecology) have been quite impressed by the techtuque ·72 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESZA It will be found helpful to consider further the specific instances in which the prospect posed might anse Elective Caesarean section may be omitted from the discussion as only under conditions of gross mise management is vomiting likely to occur These patients must be treated pre-operauvely along the same lines as the general cold surgical patient and if they are diabetic must be given glucose and msulin only by the intravenous route in the traditional manner The patient who is not in established labour and who presents for an emergency Caesarean section will do so for one of the following reasons (a) vaginal haemorrhage--associated with either placenta praevia or toxaemia of pregnancy (6) prolapsed cord following premature rupture of the membranes (1) apparent foetal distress (d) she was booked for an elective section and has gone into labour prematurely In each of these situations other than (d) spinal analgesia is absolutely, and epidural analgesia relatively contraindicated Before general anaesthesia is induced the stomach should the volume of its contents be suspected of being appreciable—must be relieved of the greater part of its load Two methods are available to effect thus manoeuvre (a) a large-bore stomach-tube may be passed (a size 10 oesophageal tube is the smallest bore permissible) to act both as a means of siphoning-out the fluid gastric contents and of provoking active vomiting (b) apomorphine hydrochloride may be given to stimulate the vomiting-centre Holmessa initially advocated that apomorphine should be used in the following manner gr to (3 mg ) of the drug is dissolved in 10 ml of water and the solution given by slow intravenous injection until nausea and vomiting commence at which time the injection is stopped Holmes comments that from gr to to gr to with an average of gr 1 (1-2 mg average is mg ) is needed to produce a result and that nausea rapidly subsides as soon as the stomach is emptied a process which he states usually takes about 3 minutes Holmes found no side-effects of note other than a slight increase in sweating and lacrimation and a rise ir maternal pulserate of about 10-20 beats per minute Atropine sulphate gr Ido (o 4 mg) injected slowly intravenously after the episode of nausea and vomiting has ended tends to offset these mild vagal-stimulant effects of apomorphine There was no apparent consequent neonatal depression Dinnick28 strongly queries the efficiency and safety of this routine but ·uterine tonc TORCEPS DELNERY AND CAESAREAN STCTION 73 might have to be forceone It is in these cases that the attendance of an expert anaestheast is most desirable and Icast often realized if speed IS SO essential then obviously epidural analgesia is not practicable if the obstetnaan is adept at administering a pudendal block then this must be the method of choice in the act of intra-utenne manipulations being necessary pudendal block should still be performed, and will serve to allow the obstetnaan to undertake his preliminary manocuivres whilst the anaesthetist is preparing to cover the extra pain and to diminish In such a case light gclopropanc anacsthesia, or cther analgesia is probably all that will be required. Suction apparatus should, as Cher be on hand and working If the obstetrician is not adept at the techniquc of pudendal block then the patient will require general anaesthesia for a rather longer time She should be placed in a head-up uilt to decrcase the chances of silent rcgurgitation from the oesophagus and induced with a minimal amount of thiopentonc or cyclopropane followed only at the request of the obstetnaan by cther Sucanyl-cholinc-already drawn up in a syringe and the implements of intubation must be ready for instant usc should laryngeal spasm or vomiting occur The rather dramatic cases comprising thus group arc rclauvely rare being more usually associated with a prolapsed cord (see next chapter) More frequently the patient presents without a history of undue oral mtake and the obstetric indication for extreme haste is less marked. If the proposed operation is an outlet forceps (as will be most likely in domıçılary practice) the two methods of choice are pudendal block and hypoaesthesia. Both methods are accomparued by a minimal tendency to vomiting and regurgitation and in both the patient retains a fully-active laryngeal reflex Efficiently performed pudendal block will take s minutes being started after the towelling-up preliminaries have been completed hypoaesthesia will become effective 10-15 minutes after completion of the injection which is given before surgical preparation of the patient is begun lf further aid is needed during the course of intra-uterine manipulation inhalational analgesia may be administered The alternaaves to the above-suggested régimes are thuopentone cyclopropinc low spinal or ether anaesthesia in descending order of ment, and their respective roles in the possible production of vomiting bave already been discussed Epidural analgesia would appear to offer no more advantage than does pudendal block in avoiding the dangers of vomuang during forceps delivery and it involves a far more elaborate and ame-consuming ntual unless the epidural catheter is already in position ·74 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESLA and passage of the endotracheal tube In either case an adequately tested, cuffed endotracheal tube and a rehable laryngoscope are essential. When intubation is the method chosen the patient should preferably be placed about 15-20 degrees into a foot-down position unal after the tube has been inserted and the cuff inflated 38 thus measure helps to guard against the possibility of regurgitation of oesophageal contents past an incompetently-rendered crico-pharyngeal sphincter 38 One further point remains to be emphasized Under no circumstances must the business of anaesthesia be started—whatever the method to be employed—unal the anaesthetist has within his reach (and preferably lying beside the head of the patient) a length of wide-bore tubing which leads to a suction apparatus As a preliminary thus apparatus must be found to be working efficiently and it should be switched on throughout the proceedings To neglect these precautions would be an act of criminal folly The emergency Caesarean section which is undertaken after labour has been in progress for some time invokes a different range of possible anaesthetic techniques for avoiding the hazards of aspiration If there is good reason to suppose that the volume of gastric contents is considerable then the stomach should be emptied as descabed above There seems to be no point whatsoever in exposing the mother whether anaesthetized by regional or general techniques to the danger of massie vomiting or regurgitation when prophylaxis is so simple and so devoid of serious danger Again however it must be remembered that gastric and oesophageal evacuation is only a preliminary measure If it is reasonably certain that the volume of gastric contents is not very large but the mother is known to have been taking fluids orally during the previous 8-10 hours and there are no maternal or foetal contraindications to epidural analgesia then this is probably the method of choice for emergency Caesarean secnon The best alternative is probably a thiopentone induction with or without intubation using either of the methods previously descnbed. If intubation and a full relaxant technique is used a further danger must be appreciated The patient is of necessity kept in a light plane of anaesthesia until the infant is delivered. If she is completely paralyzed at the same time it is not inconceivable that she mught inadvertently be allowed to recover consciousness during the course of the operation The moral to be drawn from this supposition is obvious Proposed forceps delivery of a patient who is likely to have a full stomach involves the anaesthetist in yet a third dilemma Again if there is evidence that a heavy meal has recently been taken gastric emptying should be instituted. However the degree of urgency (referable to the foetus) in forceps delivenes is sometimes such that this initial measure ·FORCES DEUNTRY 4VDCISAUF SECTION 6. Lest M and Eron c A (1951) Carla grest war auchs danrg n'Acnc hư ra hºa: . ! ! ! + - Mahar L M. (1950) Chr alawon of flachan with specul reference to a corroth recent vann Cool text a 35 Russell, J T (1959) lal theme and Caesaran kan Correspone 9 Brna, T h. and Wood, MA (1968) Whehare shachar) in a country hospital Brug trekk, 30 333 10. "Flucchine" A report to the deal Recich Cound by the Comme carlosye Auskan harin (1950) Ens w} 11 Bahan I (1950) Balantdanachuf. Cauran soron trastene, 12,435 12. Harvard Buty T (1950) Aunluparts wubrunnarbeid Laut 2. 13 Crawford S. (194) Anaestheta for obogaty's motrit advances Brite! Bul. 14 34 14. Danes,] L(1055) Usoflırntil notons Call taxnh. Sac J-2, 3-² Is Vestyn. S. and Luts. R A (1955) Promethane me and full shesa for Liher and deliver met med L 167 1918 16 Hodges, RJ (1965) Interaction of sunmshot ur and oxytoan Corres foodance Brt.me!). I 1416. r GazeJ AL and Denton, AR (193) Furrers delivery und local anak Ets2 Brih :) ), 2.99. 18 WW, P L. (1956) Transiçmal fulliluostre tixck. Obstet Gyern 8 3$$ 19. Scott, J S and Gid.l.RL. (1957) Local analren and hellands furcogs Brt. med., 1971 so. Foldes, F F (1959) Personal communication of Forthman, H.) and Adrum.] (1957) 'Blool-pressure changes during Caesarean section Anes's, Aza's 36 (Lar-April) 63 Holmes, F (1987) Spioal analysis and Cicinsia section. J Ocrest Gym Brih Empf-9 3 Monrosh. R. R. (1950) Spinal analytsua for Caesarean section Correspond cnice Brit, mell, 1 1076 - Makepeace AW (1955) Spinal anesthesia in obstetrics Oestet zu Gynet.. II 438 25 Dawkins, CJM. (1956) Extra-dural analgesia in obstetrics and Syrhaetolosy Psigtsud mel 32.54 -6 foldes, F F and Crawford, JS (1958) Esutasl Argest mt Gyrun Iyy ! Obstetrics Paper presented at the Congress of the Seandinavzin Sasty of Anesthesiologists, Gausdal, Norway Sept 195$ -7 Machay LAL (1957) Lumbar epidural anaesthesu for obstetrics at th- Tororto General Hospital. Cural. Arst Sex J 4 112 9 Donuck, O P (1957) In Discusuon on anaesthese for obstetrics an evaluation of general and regional methods Prec roy Sex Vlah, 50 347 -9 Biker G Land Hubleng, GW (1955) Post-operave aspiration faeumorutis Am J Rett. L. 80 4- 34 Crawford, JS (1956) Some aspects of obstetric anaesthesu. Brzej Antesti 2S 01 ·76 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA prevention of After all operative deliveries whatever the method of pain-relief utilized, the mother should be treated on the lines adopted for general surgical patients she should be placed on her side Dinnick has drawn attention to the fact that in Hingson s series 30 per cent of the patients who vomited did so after the birth of the child. Aspiration under such conditons must, of course, be prevented by attention to the general prinaples of anaesthesia. It has frequently been suggested 39 40 that if the patient is to be delivered on a table s bich cannot be tilted (as for instance in domiciliary practice) general anaesthesia should be induced, and forceps delrery effected, with the patient lying in the lateral position. Whilst thus practice would undoubtedly decrease the danger of aspiration of any material which might be vomited or regurgitated, it is considered that the the initial occurrence is of greater urgency Alo insatution of the practice appears to be attendant more upon the wishes of the obstetrican than of those of the anaesthetist. Finally to further matters of prophylaxis must be emphasized If a mask is used for the administration of either pure oxygen or of an anaestheac, it must on no account be strapped upon the patient s face. A aghtly fitting mask can effectively conceal the presence of regurgitated material in the mouth. It is further to decrease this danger that Parker? adreses also the use of transparent masks in obstetric anaestheac practice Secondly any mother who gives evidence of entering upon a protracted labour should receive her fud and glucose intake intravenously Significant gastric retention is closely associated with prolonged labour and m such a case the patient should receive nothing orally except frequent refreshing mouth-washes which are to be retumed immediately Thus matter demands the vglance of both obstetricians and anaesthetists in toto REFERENCES i Parker R. B (1956) Maternal death from aspiration asphyxa. Brit med J 2 16 2. Hingson, RA (1958) 'Western Reserve anesthesia machine orygen mhalator and resuscitator ] Amer med. Ass 167 1077 3 Afgar y Holaday D A. James, L S Prince C. E and Wesbrot, I M (1957) Comparison of regional and general aacsthesia in obstetrics, with special reference to transmission of cydopropane actoss the placenta. Amet med As 165 ISS + Groenhill, JP (195-) Analgesia and Anesthesia m Obstetrics Ist cd Thomas Springfield, s Francs, H. H. and Francs, WJ A. (1956) Climaal mal of synthetic oxytocin. Brui med. J I 1136 ·CILATTER V OTHER INDICATIONS FOR ANAESTHESIA 1 Brench Presentation In one out of approximately thirty labours the breech forms the presenting part. However the ratio falls to one in sixty sf premature delssencs of shorter than 3. weeks gestauon arc excluded. From the point of view of the anaestheast, breech presentation may be classified roughly as 1. Complete brooch presentadon u Incomplete breech presentadon—implyzng usually breach with extended legs part due to the close alliance of this condiaon with prematunity and to the mechanics involved in effecting vaginal delivery there is a high perinatal mortality assoaated with breech labour-about 10 per cent in primapara, slightly less in mulapara.? Although some of the contburing factors are outside hus province the anaestheast has a very important part to play in the attempt to reduce this appalling deach-rate The methods of brecch delivery may be classified as 1. Spontancous delivery with minimal assistance, 11. Assisted delivery m. Extraction All delveries are usually carried out with the patient in the lithotomy position 1. SPONTANEOUS DELIVERY In these cases the obstetraan usually performs an episiotomy under local infiltragon and, correlating his actions with the expulsive efforts of the mother gendly cases the child along its path to complete delivery If the operation as successful, an anaesthetic will not have been required. However such success can never be guaranteed, and in many hospitals an anaesthetist is requested to attend all breech delivenes The fact that

·78
PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA
31 Mendelson, CL (1946) Aspiration of stomach contents to the lungs dunag
obstetric anesthesia Amer J Obstet Gynec 52 191
32 Klein M D Clahr J Tamı A B and Solkow M. L (1953) Maternal deaths
caused by anesthesia in the Borough of the Bronx from 1940 to 1951 N) SI
J Aled 53 2861
33 Stearns A B and Frederickson G C (1957) Promethazine hydrochlonde for
the control of nausea and vomiting during spinal anesthesia Ilinous med J
112 267
34 Holmes J M (1956) Prevention of inhaled vomit during obstetric anaesthesia
J Obstet Gynaec Brit Emp 63 -39
35 Editonal comment (1958) Obstet gynec Suy 13 333
36 O Mullane EJ (1954) Vomiting and regurgitation during anaesthesia
Lancet 1 1209
37 Coleman, D ) and Day B L (1956) Anaesthesia for operative obstetrics
value of a cuffed endotracheal tube Lancet 1 708
38 Morton H 3 V and Wylie WD (1951) Anaesthetic deaths due to regurgita
tion or vomiting Anaesthesia 6 190
39 Peel, J (1955) Discussion hazards of anaesthesia in obstetnes Proc roy Soc
Med 48 1089
40 Morley H A (1956) Maternal death from aspiration asphyxia Correspond
ence Brut med J 1 1416

·11 OTTI INCARIOS JOMALAISTUT 14 ml. Bidai EXTRACTION Dificulas m the second sage of breach labour may br due in diame uterine contractions or to relatise or absolu.c dapropotunc enim of the legs can contribue to the latter 17 adds con to catning delay by macerfeng uzch lacral fletion of the body The obicencun will almose manably wish to conduct a tho ough czamin 107 onder anaa hosua before he dads on a course of action In the cent of absolu e disa propordon or of foetal dis ross in the presence of incomplete coma! dilaanon, Cacare4.7 section will probably be arned out immediately and the anacs.hetus must be prepared to prolong bus anaesthesu on the unas already outlined for this operation Al.cmusdy of the CCTVIX S fully dila.cc, the obstetrain is likely to perform a bicech cxtracuor an operanon which will probably mioke considerable intra-u.crunc mansa pulason of the focal limbs. Should no focul distress be apparat and the certzz be only part-dilated, the usual course is to allow labour to continue though on occasion the obscernaan may bring down a leg It will be apparent that the mutual situagon demands that the anaesthetist be able to provide some diminution of uterme cone. It is gonerally agreed that regional analgesia-especially spinal block-- not saasfactory for breech extraction because of its cendency to be associated with a haghtening of u.cnne activity Recendy lethuena has reported a senes of twenty-four breach extractors successfully carried out under epidural analgesi bur for the present, anaesthetists would be well-advised to rely on gencral methods for the conduct of these cases lese they be embarra,sed by the need to induce general anaesthesia mid-way through the operation. General anaesthesia should be induced with thiopentonc and mancained with nitrous oude together with the least amount of cther required to produce adequate uterine relaxation. Injection of a perhidine-levallorphan mixture is likely to be of help in limang the amount of cther needed. Deeper cther anzesthesia will probably be called for if the operation is limited by incomplete dilatation of the cervix. In such a case however the foctus is not likely to suffer from the effects of the drug as delivery will not occur mal some ame after disconanuance of anaesthesia. It w possible that Fluothane will eventually prove to be preferable to cher in the latter technique should complete delivery be undertaken immediately the ethes administration should cease as soon as the legs have been brought down OTTIER CONSIDERATIOYS N BREECH DELIVERY On the whole breech labour tends to be prolonged, and hence there is C ·80 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA in most instances he apparently plays only a passive part should occasion absolutely no resentment. He can with advantage take over the management of the analgesic technique During breech delivery there is a considerable tendency for the umbilical cord or the placenta to be compressed, with consequent foetal anoxia By ensuring that the mother receives an orygen-rich mixture (Trilene in oxygen or 75 25 nitrous oxide oxygen) the anaesthetist can counteract the ill-effects of this to a possibly significant degree By using the same mixture of gases and encouraging the mother to overbreathe dunng delivery of the head, the anaesthetist can help greatly in reducing the rate of this delivery and with it the incidence of intracranial haemorrhage which is one of the main causes of perinatal mortality associated with breech delivery Finally there is no certainty that the obstetrician will not have to undertake an assisted breech delivery u1 ASSISTED BREECH DELIVERY For patients in this category the obstetrician delivers the head with the aid of forceps or by jaw and shoulder traction Diminution of uterine tone is not specifically required and the manoeuvre can be satisfactorily performed under pudendal block 2 However the block cannot be carried out easily or safely once the foetus has been delivered as far as the shoulders Although the obstetrician will wish to avoid haste in delivery because of the danger of producing intracranial haemorrhage delay must also be kept to a minimum because in these circumstances there is very frequently considerable compression of the cord persisting until delivery is completed Rapid induction of anaesthesia, without the provocation of breath-holding or straining is therefore essential and the use of either thuopentone (150 mg --50 mg) or cyclopropane is recommended The disadvantages of the latter drug in relation to foetal depression (see previous chapter) are not likely to be significant in these cases in which only a short time elapses between induction of anaesthesia and the cessation of placental transmission whereas thropentone followed by so so nitrous oxide oxygen would probably in a senes of patients give nse to more instances of dangerous struggling on the part of the mother The provisos regarding the possibility of vomiting or regurgitation as discussed in the previous chapter must always be borne in mind. If there is good reason to suppose that the volume of gastric contents is at all sigruficant then pudendal block performed before delivery starts must be the method chosen ·OTHER INDICATIONS TOR ANAESTIILSIA 83 under conanuous epidural analgesia are likcly to have been allowed to eat and to dank during their labour and thereby placed in greater jeopardy should general anaesthesia be required. 2 Other Abnormal Presentations Persistent ocapito-posterior position (deep transverse arrest of the head) is usually dealt with by manual or instrumental rotation of the head, followed by delivery with forceps The anaestheast must provide some measure of uterine relaxation together with complete relaxation of the pelvic floor musculature and the technique has been discussed in the previous chapter Many cases of facc presentation pose a similar anaesthetic problem when vaginal delivery is to be undertaken and the foetus remuns viable and the same remarks apply to cases of transverse lie with shoulder presentanon If the anaesthetist is suddenly and unexpectedly confronted with a patient whose labour falls into any of these categones he must immediately appreciate that there are several important concomutants to the condition labour will almost certainly have been prolonged and thus inquiry must be made regarding the state of Aud balance and details of oral intake There is notoriously a hugh perinatal mortality rate associated with thesc conditions partly referable to trauma—which thc anaestheast can help to reduce by providing adequate relaxanon--and partly to prolonged anoraemia—which must be reduced to a minimum by meticulous anaesthetic care and antiapated by the provision of resuscitative measures immediately following den Livery It is worthy of emphasis that in cases of shoulder presentation not only is the lower uterine segment extremely thunned but also owing to the draining away of the liquor the foetus is aghtly gripped by the uterus The use of spinal analgesia in these cases makes delivery--whether vaginal or abdominal—very difficult and greatly increases the danger to the child. 3 Mfultiple Births Delivery of mulaplc births is usually effected by the natural processes and the services of an anaesthetist are not required. However if anaesthesia is needed-possibly for version or forceps delivery of the second twinit must be remembered that these infants as in the case of breech presentation are very commonly premature Utenne tone does not provide a handicap in this condidon and only light anaesthesia will be required, Pudendal block together with hypoaesthesta or inhalation analgesia administered by the anaesthetist will usually be sufficient As previously noted, both Guttmacher and Little and Friedman' have ·82 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA popular concem about the danger of vomiting when general anaesthesia is employed. Such an attitude imples a complete inversion of the logical approach when a patient with a breech presentation is admitted in early labour it must be accepted that she is a very likely candıdate for anaesthesia during the subsequent 12-36 hours There is no excuse for failug adequately to maintain her hydration solely by the intravenous route Should the local feeling be strongly influenced by fears of the acidaspiration syndrome, then as further precautions a Ryles tube can be left in situ and a small volume of a suitable alkalı mixture regularly administered on the lines suggested by Dinnick 5 The considerable period of warning provides the anaesthetist with an excellent opportunity of giving the pethidine-levallorphan-promethazine mixture previously descnbed, about 15 minutes before a proposed operative procedure In association with pudendal block this will certainly be adequate for spontaneous breech delivery and for an assisted delivery in many instances it will provide sufficient hypoaesthesia for breech extraction or for bringing down a leg but should a deeper plane be requred or should Caesarean section be indicated, induction and maintenance of general anaesthesia will be carried out relatively easily with small amounts of the agents chosen There seems to be little point in confining the local analgesic block to the line of the proposed episiotomy as described for spontaneous breech delivery Because delivery so frequently becomes more complıcated obstetncians should be encouraged routinely to undertake pudendal block which takes only a couple of minutes longer and involves no increased risk for the patient The use of continuous epidural analgesia has been strongly recommended in many quarters for the conduction of breech labour and delivery An outstanding advantage of the method is the absence of centrally-depressant drug action on the foetus a factor of added importance because in a high proportion of cases breech presentation is associated However whilst epidural analgesia is undoubtedly relatively satisfactory for spontaneous and assisted breech delivery and under some circumstances Caesarean section it cannot be relied upon to give adequate operating conditions for thorough examination breech extraction or bringing down a leg Furthermore should the breech presentation be found to be associated with placenta praevia epidural analgesia is contraindicated The superimposition of general anaesthesia upon regional block is neither aestheacally satisfying nor conducive to ideal patient-doctor or anaesthetist-obstetrician relationships especially when the change of course occurs in mid-operation Further patients with prematurity ·OTHER INDICATIONS TOR ANAESTIESIA 85 ment of retained placenta associated with prolonged adherence to the placental site In these cases the anaesthetist must remember that resuscitation of the patient is within the scope of his speciality and he must assume full responsibility for secing that a transfusion is set up before the operation commences in a proportion of cases previous efforts by the obstetno attendant will have resulted in considerablc uterine haemorrhage and the only hope of saving the patient will lie in cmptying the uterus as quickly as possible Under these arcumstances the anaesthetist must arrange for a transfusion (if it is not already in progress) to be started immediately cather by himself or by another competent attendant Naturally blood is the transfusion flud of choice, and must eventually be given but af matched-blood is not immediately available whuchever of the usual intravenous fluds us to hand must be used. Induction should be rapidly carned out with the patient preferably in the Trendelenburg position in the shocked and exsanguinated patient thiopentone is contraindicated. Cyclopropane with a high oxygen flow presents probably the best form of anaesthesia under these circumstances because of the wellestablished property of this agent to conserve the coronary and cerebral blood-flows in the presence of hypovolaemia. However it is imperative to remember that cyclopropane should not be used if vaso-pressor agents or Pitoan have recently been administered. Ether given by open-drop in domicıbary practice or following a nitrous oxide/oxygen induction in hospital is the second-choice of anaesthesia but care must be taken to avoid the production or enhancement of uterine atony It is highly unlikely that decp anaesthesia will be required in these cases If there has been only slight overt or concealed haemorrhage and the patient is not in a state of shock, the time factor ceases to be of paramount importance in such cases induction of anaesthesia should be postponed until the transfusion is running and blood has been made immediately available Provided that the risks of vomiting and of the coincident admirustration of vaso-pressors are appreciated, any anaesthetic technique other than spinal block will be satisfactory Spunal analgesia is contraindicated because the associated increase in utennc tone is likely to make the operation both difficult and hazardous It is in these cases especially under conditions of domialary pracace that the hypoaesthesia technique of using a pethidine-levallorphanpromethazine mixture is likely to be of outstanding ment Delay in starting is of relaovely little importance in the conduct of this and the complete absence of the dangers of vomiting and regurgitation operation together with the modesty of the equpment necessary makes it seem ·84 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA recently reported that when conduction analgesia is used for twin delivery the second twin tends to run an increased risk. This is apparently related to the fact that there is often need to perform podalıc version and breech extraction at the second delivery, and under condinons of increased uterine tone a rise in perinatal mortality and morbidity must be expected The induction of general anaesthesia if it is to be used, must, of course be delayed unal after delivery of the first twin in order to keep to a minimum the amount of depressant drugs reaching the second infant 4 Prolapsed Cord This complication occurs most commonly in association with the conditions alrcady discussed in the present chapter Obviously, the danger is confined to the child, and it has been estimated that the overall foetal ortalıcy is so per cent being higher when the prolapse occurs before full dilatation of the cervix Management during the first stage of labour consists of either immediate Cacsarcan section or of digital repossaon of the cord Anaesthesia for the former will be on the lines previously discussed for the latter manoeuvre only a light plane of anaesthesia 15 required, but a hurried induction with possible straining, must be avoided The agents used for anaesthetizing for a reposition of the cord are not of significance as far as the foetus is concerned provided that full oxygenation is maintained, as there is likely to be an appreciable interval between the end of anaesthesia and delvery of the infant The anaesthepsı should therefore direct hus full attention to the avoidance of matemal vomiting the danger of which might be somewhat increased as cord prolapse can uccur in the early stages of labour Unfortunately regional analgesia 18 contraindicated in this condition because of the dictates of ame the danger inherent in positioning the patient for a spinal or an epidural block and the disadvantage of increasing uterine tone The obstetric treatment of cord prolapse during the second stage of labour consists of immediate delivery either by forceps or by breech extracoon and the anaesthetic management is the same as that previously discussed for these operations 5 Retained Placenta Treatment of simple retention of the placenta in which the placental site is completely disrupted and the organ remains unexpelled due to atony of the uterus or to an obstructing contraction ring requires the services of an anaesthetist only as a final resort when manual removal has to be undertaken Anaesthesia is called for however in the manage ·OTHER INDICATIONS FOR ANAESTHESIA 87 depend upon the views of the individual obstetaan regarding the safety of the manocuVTC Fluothane offers the possibility of a substitute for ether and would be much less likely to cause the mother an unpleasant period of recor cry 8 Eclampsia and Serere Toraemia of Pregnancy The aid of the anaesthetist is being sought on an increasing scale in the treatment of eclampsia and severe pre-eclampac toxaemua The pertinent aspects of toxacmua of pregnancy are hypertension which in the ulumate stage (eclampsia) becomes manifestsymptomatically as an encephalopathy progressive renal failure and progressive detcnoradon of placental funcnon The anaesthetist is likely to be consulted only in the later and more severe stages of the disease the patient having previously not received medical attendon or the initial therapeutic measures (consisting manly of bed-rest, muld sedadon and dietary restriction possibly with hypotensivc therapy) having failed. The treatment of only those cases in which the foetus is still alive will be considered here for if death in utero has already occurred, anaesthetic management simplified to the general techniques usually adopted for patients with acute renal failure If Caesarean section is to be performed whether the patient is in labour or not then epidural analgesia must be the anaesthetists method of choice As has already been observed there is considerable decrease of placental efficiency in this condition and the improvement of utenne blood-flow resulting from the sympathetic blockade together with the avoidance of drug-induced foetal depression offers the best chance of delivenng a viable chuld Premedication should be given lest the hypertension be increased by emotional stress and thus should consist of morphia (gr 4-11 mg) and les allorphan (10 mg) given intramuscularly 30 minutes before initiation of the block No vaso-pressor agent should be added to the local analgesic used for the skin weal Frequent bloodpressure readings should be noted, and if the systolic blood-pressure falls below 110 mm Hg a nor-adrenaline or neosynephrine transfusion should be started, the rate of administration being regulated to maintain the systolic pressure between 110 mm Hg and 140 mm Hg For patients in whom operative delivery is not immediately contemplated, congnuous and heavy sedation has unul recently been the prinapal form of treatment. There can be little doubt that such therapy Is pharmacologically unsound and is likely to lead to iatrogenic disease in both mother and child Attempts have been made to combine a lesser degree of sedauon with hypotension induced with systemically administered drugs O heefe and his colleagues have described the use of a lync ·86 PRECIPLES AND PRACTICE OF OBSTETRIC AESTHESLA likely to become the technique of choice for the management of retamed placenta in the home Recently Sauerl' has reported cases of retained placenta which he coduced sausfactorily mdas pudendal block alone. Sauer considers that manual removal of the placenta entails for the mother no pain of uterine ongis, though if cervical contraction renders entry into the uterine arity difficult, he encourages the patien to mhale some amyl nitrate 6 Other Operations The anaesthetic care of pan-nis undergoing emergency hysterectomy (folloung rupture of the uterus or unquenchable haemorrhage) or repair of perineal lacerations is, like that for abortion or ruptured ectopic pregnancy no different from the route used m general emergency surgery and will not be considered in this book 7 External Version External cephalic version as performed, almost exclusively before labour commences. It is thus derer an emergency operation, and the routine preparation of the patient by prelimmars avoidance of food and donk, and by the usnal preoperaore medicanon, may be undertaker Fear of depression of the foetras by the anaesthetic agents should not influence the choice of technique. Contemporary obstetric teaching donounces any strenuous attempt to turn the foetus. Before the anaesthetist 15 called, version will already have been attempted whilst the mother 1525 awake, and it is adrasable to delay subsequent attempts under anaesthesia until the uterus bas recovered from its traumatically-induced state of The first reqmsite of the anaesthede management is to provide good relaxation of the mother s abdominal wall muscles. This can be effected by any of the usual methods and dmg the use of a muscle-relaxant drug, Mios obstetricans do not demand a facad myometnum, as this would appear to offer an myitation to disaster of the operator becomes overeager However although the uterme muscle should be alloned to retain some tons, its relax activity shonld be dampened suffiaently to Degate the response of contraction when the operator applies more than slight pressure to the foetal parts. The operanon can be performed under chopen.one lods, giren m an average dose of 750 mg but this is not advisable of the obstetrica considers that he might have dificults disengagmg the breech, as the utene-relaxant effects of the drug are sery short-lasing The usual teaching is that ether is the onlr satisfactory zaostbeac for this operation. The depth of ether anaesthesia prouded will uitable toniaty ·OTHIER INDICATIONS TOR ANAESTHESIA 87 depend upon the views of the individual obstetrician regarding the safety of the manoeuvre Fluothanc offers the possibility of a substitute for cther and would be much less likely to cause the mother an unpleasant penod of recovery 8 Eclampsia and Sesere Toxacmia of Pregnancy The aid of the anaesthetist is being sought on an increasing scale in the treatment of cclampsia and severe pro-eclampoc toxacmia Thc pertinent aspects of toxacnua of pregnancy arc hypertension wluch in the ultimate stage (eclampsia) becomes manifestsymptomatically as an encephalopathy progressive renal failure and progressive deterioration of placental function The anaesthetist is likely to be consulted only in the later and more severe stages of the disease the patient having previously not received medical attention or the initial therapcuac measures (consisting mainly of bed-rest mild sedation and dietary restriction possibly with hypo tensive therapy) having failed. The treatment of only those cases in which the foetus is sall alive will be considered here for of death in utero has already occurred, anaesthetic management is simplified to the general techniques usually adopted for patients with acute renal failure If Caesarean section is to be performed whether the patient is in labour or not, then epidural analgesia must be the anaesthetists method of choice As has already been observed there is considerable decrease of placental efficiency in this condition and the improvement of uterinc blood-flow resulting from the sympathetic blockade together with the avoidance of drug-induced foctal depression offers the best chance of delivering a viable child Premedication should be given lest the hypertension be increased by emotional stress and this should consist of morpha (gr 11 mg) and levallorphan (10 mg) given intramuscularly 30 minutes before initiation of the block No vaso-pressor agent should be added to the local analgesic used for the skin scal Frequent bloodpressure readings should be noted and if the systolic blood pressure falls below 110 mm Hg a nor-adrenaline or neosynephrine transfusion should be started, the rate of administration being regulated to maintain the systolic pressure between 110 mm Hg and 140 mm Hg For patients in whom operative delivery is not immediately concemplated, continuous and heavy sedation has until recently been the priapal form of treatment There can be little doubt that such therapy is pliarmacologically unsound, and is likely to lead to iatrogenuc discase in both mother and child Attempts have been made to combwe a lesser degree of seda on with hypotension induced with systemically administered drugs Keefe and his colleaguesll have described the use of a lytic ·88 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTYLESIA cocktail in the treatment of cclampsia, and Centurol2 used, in addoon hypothermia in treating 6 mothers with eclampsia, s of whom were delivered of a living infant. Though the latter heroic measure is unlikely to be applied frequently the sedative-saving property of the phenothazine dentatives added to their properesity for tending to decrease blood-pressure render them of considerable value in the moderately longterm treatment of severe pre-eclampac toxaemja It is necessary, howcver to mterpolato a warning regarding the use of chlorpromazinc in this way The liver is particularly vulnerable in toxaemia of pregnancy and the repeated administrauon of chlorpromazine would very probably lead to severc, or even fatal, hepatic failure in a proportion of patients so treated. In cases of rapidly worsening pre-eclampac toxaemia and of established eclampsia, the anaesthetic treatment of choice is continuous epidural block. Aspects of this technique were recently discussed by Bryce Smith13 and by Foldes and Crawford. 14 A catheter is inserted into the cpidural space preferably via the first or second lumbar unterspace and threaded 2 or 3 inches cephalad, so that the drug may be injected dose to the region of the sympatheac outflon A vaso-pressor must not be used then making the local skin and subcutancous infiltration but adrenaline (1 200 000) should be added to the solunon injected into the cpidural space in order to prolong drug-action and to diminish the chances of rapid absorption into the systemic arculation Used in a concentration of 15-20 per cent, 2-chloroprocaine repeated three hourly appears to be the safest drug to use Though Xylocaine (1 o per cent) has been recommended, the fact that, in eclampsia both renal and hepatic function are depressed, makes the occurrence of toxic reactions to this drug highly probable. Blood-pressure readings should be regularly noted, and a dangerous degree of hypotension counteracted with nor-adrenaline or neosynephrine There should be no significant degree of muscle relaxation, or of respiratory depression, when 2-chloroprocaine is used in the concentration suggested. If labour is in progress it will probably be prolonged, though painless Bryce-Smith has noted that when I per cent Xylocaine is used, increasing increments of the drug are apparently needed to mantain the fall in blood-pressure for longer than 24 hours This phenomenon is possibly of a sumilar nature to that following partial sympathectomy u wluch vaso-constricton and hypertension recur in response to arculating adrenaline and nor-adrenaline and to increased activity of the intact sympathetic vascular fibres It is possible that the best way of counteracting this effect would be to give an Arfonad infusion but such a measure would necessitate constant supervision by an anaesthetist ·OTHER INDICAYONS TOR ANAISTHESIA 89 9 Disordered Uterine Function In this country Johnson's '* luas been a noteworthy propagandist of the part which the anacsthetist may play sn the management of certain cases of prolonged labour Johnson advocates the instituaon of continuous caudal analgesia should labour be prolonged for more than 48 hours owing to such disorders of exterinc activity as hypotonic inertsa hypertonic lower uterine segment inertia, and cervical dystocia. The rationale of the treatment lies in the fact that by snlubiting lower segment and cronical conc and relaxing the pelvic floor musculature the progress of labour ss hastened. There are two important addenda to this argument the concomitant ablation of labour pain it is claimed increases the potency and effectiveness of the upper uterine segment contractions and the assoaated local vasodilatadon replenishes the impoverished uterine blood-flow characteristic of prolonged labour Johnson echoes the warung issued by Hssigson and Edwards?? regard. ing caudal analgesia to the effect that the block must not be initiated unal the cervix has reached at least one-third dilatation, lest uterino contracuons be completely anhubited. He recommends the use of a 15 per cent solution of piperocaine hydrochlonde ('Mctycaine') given in an mital dose of 40 mi and subsequently in doses of 15 ml at intervals of 30 minutes over a total penod of approximately 6 hours Some of the papients in his reported series were delivered withun the whour period of the others those whose labous appeared to be progressing favourably cononued to receive reinforcement of the block, and the rest (a small proportion of the whole series) were delivered by Cacsarcan section Johnson claims that the creatment advocated resules appreciable shortering of labour with much diminuton of material distress Al though there is a raised incidence of malrotation of the head, with resultant increase in the difficulties of forceps delivery the associated Cacsarean section rate is decreased and these is a marked overall improve mene in the figures of perinatal salvage The author has had no personal experience of the application of thus technique but it undoubtedly is a radonal line of therapy and anaesthetists should be ready to offer such a service when the occasion presents However on general principles a contnuous lumbar cpidural block would probably be preferable to a continuous caudal în skilled hands (a requisite for both techniques) the total falure rate associated with lumbar block is lower than that with caudal there is less likelihood of contamination of the thurd or fourth lumbar nterspace s preferred to the sacral hiatus and the extent of the block can be obtained with simular case using ather technique For ·90 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA reasons previously discussed, 2-chloroprocaine with adrenaline it is suggested, offers a wider margin of safety than does piperocaine It will be noted that patients included in both this and the previous group who are treated with a contnuous epidural block, may be prepared for Caesarean section or for forceps delivery merely by altering the concentration and volume of the analgesic solupon injected. 10 Associated Maternal Disease A HEART DISEASE The cardio-vascular changes occurrmg during the course of normal pregnancy and labour have been discussed in the opening chapter Heart disease in pregnancy is almost solely rheumatic in origin, and the most commonly affected valve is the mitral. In untreated cases the mortality rate in pagents with heart disease who become pregnant is to per cent. 15 It is generally accepted that this rate can be reduced to less than 2 per cent when adequate treatment is instituted 19 However working under the influence of a community which disavows the practices of contracepton, sterilization and therapeutic abortion the Dublin school has demonstrated that the inadence can be reduced sall further Only patients with the more severe stages of heart failure with incipient or actual decompensation are likely to be presented as a problem for the anaesthetist. Heart disease alone is now not commonly accepted as an indication for Caesarean section Occasionally the operanon is performed upon primigravida or in patients who exhibit a degree of disproportion or other anomaly which makes it seem likely that labour will be prolonged. In such cases the anaesthetic management need not differ from that outlined in Chapter IV Analgesic technique for labour progressing in the presence of symptomatic heart disease must be directed towards ensuring continuously adequate oxygenation good relief from pain and emotional distress and avoidance of straining During the early stages the regime of medication should follow the lines laid down in Chapter III though if the mother 15 cognisant of her perł it would be as well to include a tranquillizing drug, such as promethazine in the scheme The relative merits of regional and general analgesia for the conduction of the second half of labour and of delivery pose some interesting problems Labour and delivery in the presence of heart disease are commonly accepted as being characteristically easy and rapid. Actually to cause a slowingoflabour and virtually to assure the necessity of a forceps delivery by instituting an epidural block would seem to be an unwarranted therapeutic intrusion However there can ·OTHER INDICATIONS TOR ANAESTICIA 91 be no doubt thae the almost complete relief from pairs and the virtual elimination of straining provided by epidural block play a significant part in protecting a badly over-burdened heart Furthermore 25 Hingson and Edwards is point out the bloodless phlebotomy produced by the epidural injection casi relieve she heart of the burden of a hugh venous return Montgomery and hus colleaguest have drawn attention to the fact that cardiac discess often increases dramatically immediately after de Levery as the venous tetum is increased by the great reduction in uterine blood-flow the releasc of the pressure exerted by the gravid uterus on the anfenor vena cava and the increased amplitude of respiration Vaso dilatation following epidural block would tend to perme a more gradual accommodation to the effects of emptying the uterus Fusther invesagation of the relaave merits of the methods of analgesia needs to be pursued. If general analgessa undertaken the commonly employed inhalagonal methods are concauidicated A qualified medical practitioner--preferably of course an anaestheast-must himself ada minister 50 50 nitrous oxide and oxygen or Trilene in oxygen if these agents are to be used Levallorphan must be given with each ingection of perhudine to avert any tendency to maternal respiratory depression Promethazine will be found to be a useful adjunct as already descnbed The patient should be encouraged to breathe from an oxygen-enriched source throughout the second stage and during the lattes part of the first stage of labour If a fotceps delivery is undertakery 16 would preferably be performed under a pudendal block, if continuous epidural analgesia is not already besnig conducted. Cacsarean section is probably best carned our under cpidural analgesia with the patient sedated with promethazine and possibly petludisie plus levallorphan if general anaesthesia is employed for Caesarean section or for forceps delivery the assaeschetst must ensure absolute avoidance of struggling and breath-holding Thiopentone induction followed by intubation under a relaxant drug and sustained intermittent positive pressure on the lines suggested by Montgomery and his colleagues * is presented as the best method for these patients B DIABETES Although since the introduction of insulin the diabetic woman is no longer specifically jcopardized by becoming pregnant the associated foetal mortality-rate is depressingly high estimates ranging from 25 to 40 per cent 22 The nsk of antra-uterine death occurring becomes significant after the thirty-sixth weck Furthermore the foetus teads to be larger ·92 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA than the average during the later stages of development and thus there is an increased possibility of disproportion at term. A thurd factor to be noted is that the incidence of pre-eclamptc toxaemia is very hugh in diabeaics and thus an unduly large foetus has to rely upon a relatively insufficient placenta Because of all these factors the customary management of pregnancy in the diabetic is to perform an elective Caesarean section at about the thirty-sixth week. Unfortunately, it is found that the neonatal death-rate is still alarmingly high (see next Chapter) but the overall perinatal mortality-rate has been reduced by this measure Because of the precarious state of the foetus the use of depressant drugs which cross the placenta must be kept to an absolute minimum in the anaesthetic management of these patients and epidural analgesia is strongly indicated. If this is beyond the technical ability of the physician concerned then spinal analgesia should be employed, but with meticulous attention to the details outlined in the previous chapter As in all other branches of surgery the anaesthetist must assure himself that the patient has received her pre-operative glucose intravenously and not by mouth, and that her insulin requirements have been satisfactonly met C RESPIRATORY DISEASE The anaesthetic management of a tuberculous patient in labour does not pose any great problem The routine methods of analgesia may be undertaken and equipment used for inhalation analgesia should be disinfected in the usual way after delivery Occasionally forceps delivery 15 performed to cut short the second stage of labour In such a case pudendal block or conduction analgesia is to be preferred to general anaesthesia These same general remarks may be applied also to the management of patients who develop an acute respiratory infection pnor to delivery Increased care must be taken to ensure that the patient does not suffer from any degree of oxygen lack. REFERENCES 1 Brews A (1957) Eden and Hollands Manual of Obstetrics IIth ed p 350 London Churchill Methuen, D (1958) In Discussion The breech Proc R Soc Med 51 163 3 Law RG and Ransom S G (1954) Anaesthesia in hospital breech delivery Brit med J I 562 4 Burge E S and Baldwin CE (1956) Use of spinal anesthesia in obstetnes at the Evanston Hospital Amer J Obstet Gynec 71 973 s Dinnick O P (1957) In Discussion on anaesthesia for obstetrics an evaluation of general and regional methods Proc roy Sơc Mled 50 547 ·OTHIER INDICATIONS TOR ANALSTIIESIA 93 6 Special Committee on Infant Mortality (1957) Panel discussion Obstetric anesthesia and analgesia NY St J Med 57 2532 7 Little W A and Friedman EA (1958) Anesthesia for the twin delivery Anesthesiology 19 SIS 8 Brows A (1957) Eden and Hollands Manual of Obstetrics IIth ed p 377 London Churchill 9 Ersten B Reynolds RN LTH (1953) Effects of controlled respiration on circulation during oclopropane anesthesia Anesthesiology 16 365 10 Sauer H HA (1958) Manual removal of the placenta under local anesthesia Obstet Gynec 12 221 11 O heefe WP Shanahan ) and Quine M B (1955) Chlorpromazine in eclampsia Irish] med Sa Sixth series No 351 p 124 12 Centuro A (1953) So-called artificial híbemation in the treatment of cclampsia Re Ostet Gmic 8 747 13 Bryce-Smuh R (1957) Role of the anaesthetist in cclampsia S Afr med ) 31 IOIS 14 Foldes, F F and Crawford J S (1958) Epidural Analgesia m Gynecology and Obstetrics Paper presented at the Congress of the Scandinavian Society of Anesthesiologists Gausdal Norway Sept 1958 15 Johnson T (1954) Continuous caudal analgesia experience in the minigoment of disordered uterinc function in labour Brit med J 1 627 16 Jobinson, T (1957) 'Prolonged labous a clinical trul of continuous caudal analgesia Brit med J 2 386 17 Hingson R. A and Eduards W B (1943) Continuous caudal analgesia in obstetrics J Amer med Ass 121 225 18 Hingson R A and Hellman, LM (1956) Anesthesia for Obstetrics Ist ed P.O. Philadelphia Lippincott 19 Gibberd, G F (1955) Short Textbook of Midwifery 6th ed p 258 London Churchill 20 Drury M. I O Driscoll M K. Hanratty TD and Barry A P (1954) Rheumatic heart disease complicating pregnancy Brit med J 1 70 26 Montgomery J B Parkhouse and Prebble SE (1958) Heart failure in obstetrical anaesthesia Anaesthesia 13 33 -2 Brews A (1957) Eden and Holland s Manual of Obstetrics 11th ed P 169 London Churchill ·CHAPTER VI THE CHILD EVEN a compressed review of contemporary knowledge of the Important physiological aspects of perinatal life would be of such length as completely to unbalance the present book as it was onginally conceived. In this chapter therefore remarks sall be confined to pertinent and very broad generalizations on aspects of this subject as they influence directly the day-to-day work of the obstetric anaestheast Apologies are offered to specialized workers in this important and advancing field, for any tendency to dogmatism which might appear in these pages Such a tendency is the penalty for abbreviation, and the general reader is asked to remember that our present views, aspecally on such matters as neonatal respiragon and pennatal arculation are in a state of marked flux which, though exating is on occasion bewildering 1 Physiology At birth the infant has a red cell count of so-s5 million per ccm with a normal range of about 1 million either way 1 2 The haemoglobin concentration is approamately 18 gm. per 100 ml. blood but is frequently found to be considerably higher it is worthy of note that samples of blood obtained from the heel capillaries consistently show a higher concentranon of red cells and haemoglobin than do those from the penipheral venous blood, and it is generally advisable to study blood from the latter source when haematological or biochemical investigations are undertaken The values just considered begin to change radically within a few hours of birth, but such matters are beyond the terms of reference of this book. There appears to be little general agreement on what figure represents the normal blood solume at birth Estimates range from 75 per cerca to 10 per cent (expressed in litres) of the body waght (expressed in kilograms) For a normal 74 lb (3 500 gm ) infant this would represent a range of 200-350 ml of blood. It is widely accepted that the full-term infant may receive 100-125 ml of blood from the placental vessels including about 15 ml from the umbilical cord.' The part which this 94 ·THE CHILD 95 extra volume may play in pulmonary function will be discussed lates As a mete systemuc circulation expander and an additional source of haemoglobin its importance to the nconate is still in doubt. It is claimed that rapid adjustnient wall result in the passage of most of the added extracellular fluid into the extravascular compartments and that the increased Iron supply becomics of possible advantage only when the infant is to or thice months old. We cannot with cercancy say whether or not the transfusion of thus extra 100 ml of blood is to be considered as being normal from a biological point of view for of delivery occurs in the squatang position the baby arrives at a les el probably only a little lower than that of the placenta, and the cord is likely often to be so taut as to make its value as a transmitting tube greatly danunished. Of greater moment is the question of drainage of blood from infant to placenta. Gunther has attempted to show that by holding the baby about 15 cm. above the level of the vulya with the cord intact-representing a hydrostaac pressure difference of 12 mm Hg between infant and placenta--for a very short ame the infant can be caused to lose up to 26 gm. waght, presumably due to sphonage of blood into the placental vessels Apgaro has quened the occurrence of such a process on the grounds that the force of uterinc contractions is likely to counteract any head of pressure which it is possible to produce by elevating the infant. Haseer as the tension within the resting uterus is said to be about 15-25 mm Hg the pressure being increased by 60-75 mm Hg during contraction? and the neonatal systolic blood pressure is varyingly stated to be between 69 mm. Hg8 and 80 mm Hg! 557th a diastolic of 46 mm Hgest would seem that the addition of a hydrostatic pressure-head of 12 mm Hg would make Gunthers suggestion qutc feasible The threat of a 7 s- 100 per cent depletion of neonatal blood volume makes it advisable that the infant should not be held above placental lecl prior to camping the corda especally when the infant is already in distress Apparently prematurc infants at least from the thirty-fourth sech onwards possess a range of haemoglobin concentration red cell count and blood volume scadonshup to body wacht denacal to that of the full-term infant. However the placenta associated with prematunity contains relatsely more blood than does that delivered at term with a consequent increase in the ratio of placental blood volume to infant blood Volume It is thus possible to produce a most significant degree of hypervolaemia, and a relaticly marked degree of hypovolaemia by holding the premature infant below or above the level of the placenta The pertinent biochemical data regarding foetal and neonatal blood have been bnefly discussed in Chapter 11 It has been pointed out that ·PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA 96 foetal blood has a higher affinuty for oxygen at low pressures than has adult blood Wintrobe states that whilst at the twentieth week of pregnancy 94 per cent of the haemoglobin of the foetus is of the foetal type the proportion at birth has fallen to between s5 per cent and 85 per cent Thus with progressing maturity there is decreasing specific affinity In the normal infant at birth, umbilical vein blood carries oxygen at a partial pressure of so mm Hg As already pointed out Apgar and her colleagues consider that this momentary asphyxia is a normal concomitant of the birth process These workers also reported very marked vanations in the oxygen tension found in blood taken from the umbilical artery, with saturations ranging from o to so per cent (mean 22 per cent) in apparently normal infants The variation in partial pressure of carbon dioxide was not so marked, the average values being about 55 mm Hg in the umbilical artery and 43 mm Hg in the vein Referring to the investigations of Dawes and his colleagueslo (see Fig 1) the New York group postulate that the values found in the umbilical artery blood represent those of the blood reaching the neonatal tissues—including the brain—at the moment of delivery The mean umbilical artery buffer base concentration was found to be 41 s mEq per litre Thus under optimal conditions the normal infant is born in a mildly asphyxiated condition and with a slight respiratory acidosis However it is becoming more definitely apparent that this phase is not reflective of the state of the child prior to delivery The previous concept characterized by Eastman"1 as one of Everest in utero is not to be accepted as applying under normal circumstances Recently some remarkable studies carried out in Stockholm12 have revealed by direct photography a satisfyingly pink foetus lying in utero attached to the placenta by a pink umbilical vein and blue umbilical arteries Admuttedly these investigations were made on mothers between the fourteenth and eighteenth weeks of pregnancy prior to the induction of therapeutic abortion but there is reason to believe that simular findings will result from studies carried out on more mature foetuses (In faimess it must be added that it is rather difficult to reconcile these findings especially that of a blue umbilical artery and a pink skin with those of Dawes and his colleagues 10 This is a matter for further investigation ) According to Apgar and her colleagues 13 the percentage oxygen saturaaon of arterial blood is not a satisfactory index of the degree of depression of a neonate and nor is the tension of carbon dioxide The seventy metabolic aadosis as indicated by a depressed pH or buffer base concentranon reflects more closely the status of the infant Under favourable circumstances respiratory and metabolic acidosis with associated of ·Tilt CHILD 97 anoxaemua, arc rapidly corrected by the initiation of pulmonary respiratory acuity It is now fairly well established that full ventilation of the lungs is normally achucted very shortly after delivery" Cross and lus collcagues! give the following details regarding pulmonary activity in the nconate BCA SVC 62 31 RV LV 67 DV IVC 80 58 FIG I Diagram of the foetal curculation. The figures indicate the percentage oxygen saturation of blood withdrawa simultaneously from various vessels and averaged from determinations on 6 lambs IV'C inferior vena cava SVC superior vena cava DV ductus venosus FO foramen ovale Da ductus arteriosus BCA brachiocephalic artery (Reproduced from Bom G V R. Dawes GS MottC and Widdıcombe J G (1954) Changes in the heart and lungs at birth Cold Spring Harbor Symposium on the Mammalian Fetus 19 102 By kind permission of Dr Dawes and of the publishers) H ·98 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA They are substantially the same as those published earher by Cook and his co-workers16 in Boston. 21 TABLE I Full-term Premature Infants Infants No of observations 47 No of infants Male 25 8 Female 17 6 Total 42 14 Age range (days) 0-19-II 13 o 56-14 31 Mean wt. in kg and standard deviation (SD) 3 26-0 404 1 87 0183 Mean min. vol. (ml) and SD 487 40-81 67 343 90-57 46 Mean respiratory rate and SD 30 99- 713 32 40-10-68 Mean tadal air and SD 16 SO- 353 II 42- 333 Mean O consumption/kg hr and SD 419 11-53 45 418 38-69 18 Mean CO2 production/kg/hr and SD 326 33 48 15 330 14 74 24 (Reproduced from Cross h. W Tizard, J P N and Trythall, D AH (1957) Gaseous metabolism of the new born infant Ada paediat 46 265 By kind per mission of Dr Cross and of the publishers ) I Cook and his co-workers16 concluded that average values for minute volume udal volume alveolar ventilation and functional dead space (the latter averaging s ml for a.skg infant) for infants of different size and matunty vaned directly with the infant body weight The respiratory rate appeared not to be closely related to body weight though a tendency for the smaller children to exhibit a higher rate was observed. THE FIRST BREATH The preceding data refer of course to established respiratory activity and are presented as a basis of reference to be used in assessing degrees of abnormality and as an objective to be pursued when treatment is instituted. Of prime interest to the anaesthetist is the mystery surrounding the initiation of sustained respiration There has been recorded a multitude of views on the stimulus which provokes the infant to take its first breath, much of the interest and knowledge stemming from Sir James Barcroft s onginal researches There seems little point in detailing these theories here as they are well established in the folk-lore of medicine Evidence of co-ordinated quasi-purposeful foetal respiratory activity is now generally accepted but the significance of this in the scheme of initiation of extra-uterine breathing is no better founded than is the significance of a relationshup of limb movements in utero to the activities of walking and runtung ·Tut CUILD 99 The most tenable ves appears to be that in the normal relauvely non-depressed infant respiration is iniaated reflexly by taculc stimulation In thus regard, the more sensitive parts of the body surface appear to bc the sout arca and, of considerably less significance the soles of the feet Once the initial full gasp has been taken in the presence of an adequately functioning nervous system the muntenance of respiragon appears de pendent upon preasely those factors which govern respiratory activity throughout life nanıcly central nervous and chemoreceptor response to oxygen carbon dionde and add-base shifts A few hours after delivery the intrathoracic pressure changes under conditions of quet respiration approach those found in the adult but a very much greater negatis c pressure is produced in the effort of drawing the first breath Donald! has been able to demonstrate a negatie intrathoraac pressure of 80 cm vater during the initial inspiration with a swing of over 40 cm water during the first few breaths of hfc The main provocation of this very great effort is the need to overcome the cohesion of the alıcolar and bronchiolar walls of the atelectaac lungs It is accepted that prior to delivery the lungs contain amniotic flud. The entry of such find, as P Gruenwaldia has pointed out docs not involve the combating of any degree of surface tension Houcier immediately upon normal delivery presumably in response to the iniaal inspiratory effort and to the opening up of the vast pulmonary capillary system much of the intraal colar flud is absorbed, the flud within the bronchioles either taking its place or itself being absorbed. The resultant suckiness of the terminal pulmonary ducts as the main cause of the greatly incrcased resistance to the entry of air A strong body of opinon now holds 17 that this re sistance is considerably reduced if the pulmonary capillary bed becomes thoroughly and rapidly engorged The turgidity of the vessels so produced possibly lessens the clasac resistance of the lungs to inflation and in addition helps acasely to push apart the applied surfaces of the alıcols and broncluoles It will be apparent that the premature infant with its relauvely weak respiratory musculature and its compliant bony thoracic cage is in urgent need of all the help it can get to reduce the effort requred to overcome resistance to its initial inspiration It is mainly for this reason that Gumthers urges that the premature enfant should not be held above the level of the placenta lest the resultant hypovolacmua lead to inadequate filling of the pulmonary vessels The same argument will hold good in the case of any infant whose efforts are hkely to be impared as a result of central depression Bonham Carter 17 has suggested that the production of a mild hypervolaemus in premature infants will by rusing the central venous ·100 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA 1 pressure ensure optimum conditions for rapid lung aeration but there are other aspects to this question and it will be discussed later I NEONATAL DEPRESSION AND RESUSCITATION In essence, neonatal depression implies complete or partial failure rapidly to establish adequate unaided ventilation A degree of hypoxia is therefore a concomitant though not, as explained earlier an index, of the state of depression It is most important for the purposes of analysing the causes of depression and the efficiency of therapeutic measures taken to counteract it as well as for providing an immediate guide to treatment that some accepted scale of connoting the general status of the newbom be established. The hallowed terms 'asphyxia pallıda and asphyxia livida are worthless in this regard. It is suggested that the scheme propounded by Dr Virginia Apgar18 (Table 2) be generally adopted, and that each neonate s score according to the Apgar scale be recorded on the appropriate case-sheet A further concept of Apgar $78 whuch could with advantage be brought into general use is that of the ame to sustained respiration (TSR), which is probably of greater worth than the recordings of breathing ame and crying time TABLE II Sixty seconds after the complete birth of the infant (disregarding the cord and placenta) the following five objective signs are evaluated and each given a score of 0 I or 2 A score of 10 indicates an infant in the best possible condition o I 2 Heart rate Absent Slow Over 100 (below 100) Respiratory effort Absent Slow Good Irregular Crying Muscle tone Limp Some flexion Active of extremities motion Response to catheter in Grimace Cough or nostril (tested after steeze oropharynx is clear) Colour Blue Body pink Completely pink Pale Extremitics blue (Reproduced from Apgar V (1953) Proposal for new method for evaluation of newbom infant Anesth & Analg 32 260 By kind permission of Di Apgar and of the Editor) No response The first measure xbuch must be taken following delivery is to clear the infants mouth and pharynx of mucous and amniotic flud. It is of course preferable that this be done after delivery of the head in cases of ·THE COLD 101 vaginal delivery As the normal infant tends to be a compulsive noscbreather attention should be paid to clearing the narcs The types of apparatus in use for this performance will be discussed in the next chapter Although Pottero has said that the contents of the mouth and pharynx are usually inhaled without ill-effect during the first inspiration and that plugging of a bronchus with mucus sufficient to interfere with the establishment of extra-uterinc respiration is of almost unknown occurrence it seems good sense to clear as much flwd as possible from the upper respiratory passages that the first inspiration may consist mainly of air The toilet described will take up sufficient time and involve enough sumulation of the sensitive snout arca to enablc a reasonablc estimate of the infant s condition to be made at the one-minute stage advocated by Apgar 18 If the childs score is 7 or over it is unlikely to need further active attention as regards its vital physiology and, its cord having been cut, it should be placed on a sloping surface with a head-down tilt of about 15-20 degrees Thereafter the mouth should be fairly frequently aspirated, as mucous and liquor invariably drain into it for some time after delivery There is a suggestion that following Caesarean secaon the infants stomach should be aspirated through a finc rubber catheter-after respiratory activity has become well established—lest subsequent regurgitation and inhalaton lead to pulmonary complications Whilst this might be a sensible prophylactic measure in the case of the premature infant, the value of its routine application has not been convincingly demonstrated If at the time of initial assessment the infant appears to be satisfactory this is no excuse for leaving it to fend for itself during the next couple of hours Its condition might well be likened to that of the general surgical patient who on extubation appears to react well and to have a satisfactory tidal volume but who in a few unfortunate instances is allowed by a negligent anaesthetist to return immediately to the ward, where depression and regurgitation supervene The custom of serving coffee or tea in the labour ward office at least after every operative delivery is one to be encouraged wholeheartedly by all-including the hospital administrators After the party a social call should be paid upon both mother and child by the obstetrician and the anaesthetist This does not of course preclude the necessity of having a nurse attendant upon the patients during the whole time If it is apparent that the child is depressed, then resuscitation must be undertaken immediately After the first 60 seconds there is absolutely ·IO2 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA no place for the attitude of watching to see if the child will take a gasp Depression means anoxaemia prolonged anoxaemia means increasing depression and in a spiral fashion the circulatory adjustments-especially of the pulmonary system—the viability of the cortex and the efficiency of the vital centres are increasingly compromised if time is wasted by a policy of waiting for the anoxic drive to become effective The first and only important measure after clearing of the upper air passages is the administration of oxygen Even should feeble respirations have started if depression is present oxygen must be given If there is no cardiac impulse or umbilical pulsation and the child is not obviously long dead attempts to stimulate the heart with needles drugs or electric shocks are sheer procrastination and will succeed only if adequate oxygenation would have succeeded—though the converse very likely does not hold Slapping the child throwing it around (albeit with the elegance of a rocking motion) anointing it with hot and cold water insulting its anus—all these indulgences one would have thought to have been long consigned to the dustbin of history but they are unfortunately, still to be observed on occasion They have no place in sane medical (or nursing) practice Oxygen is the sole agent of resuscitation and if it is not immediately obtainable in pure form the attendant must give of his own supply (see next chapter) There was a fashion for giving carbon dioxide with the oxygen this too makes no sense As previously described, the infant has been building up an embarrassing surplus of carbon dioxide since the moment when delivery started and it continues to accumulate the gas as apnoea persists In a depressed infant the stimulant phase of the actions of carbon dioxide and acidosis has passed and only depression of increasing severity is to follow To supplement thus with yet more carbon dioxide is sheer folly Neonatal depression is likely to be due to one of two main causes primary anoxia occurring during labour or delivery with or without associated intra-cranial haemorrhage and central nervous depression due to drugs administered to the mother The main line of treatment is the same whatever the cause but whilst inaugurating resuscitative measures the anaesthetist should make a rapid assessment of the likely aetiology If any of the narcotics is implicated levallorphan (o 1 mg) should be injected into the umbilical vein It is possible that barbiturate-induced depression might be counteracted by the administration of amiphenazole but there is no dosage which can be reliably advocated, and the danger of overdosage with consequent excessive central stimulation is sufficient to make it advisable not to use this antagonist in neonates at the present There is no point and indeed probably danger in attempting a time ·TILE CIDLD 103 pharmacological reversal of depression due to other analgesic and anaesthetic agents For a mildly depressed child (sconng say 5-7 points ), che administracon of oxygen at a flow-rate of about 2 l per minute via a soft tube placed in an unobstructed nostril will probably be adequate Frequent suction must be undertaken as these infants tend to froth a good deal having usually made considerable inspiratory efforts whulst in an environment of amniotic flud. Suction should be carned out as atraumatically as possible and should be performed infrequently enough to avoid the farce of aspirating directly from the mouth all the orygen entering through the nosc If depression is somewhat deeper oxygen must be administered under positive pressure In the presence of weak tespiratory activity this can be done by using a closely fitung face-mask and applying pressure from a small rebreathing-bag An oro-pharyngeal urway should always be inserted before the mask is applied. This measure is to be regarded as being sinctly short-term It provides no opportunity for aspiration of mouth and pharynx and, if conanued for longer than about one minute, is likely to lead to embarrassing gastric distension with possible regurgicagon After 60 seconds the mask should be removed. If the child s response has been good, its respiratory excursion increased and its oxygenation improved, then it is probable that under the influence of the blossoming pulmonary circulation progress will be maintained, and resort may be made to oxygen via a nasal catheter If there has been no improvement then treatment along the same lines as for a severely depressed infant must be instituted. A severely depressed child is a weak chuld, and this is of even greater moment in the premature. Mennon has already been made of the effort needed to overcome the resistance to the initial inspiration of air in the type of casc under review haste must be made to surmount this first obstacle on the child's behalf. Thus implies immediate scrupulously gentle endotracheal intubation and the momentary administration of oxygen under a pressure 40-60 mm. Hg Once the bronchioles and many of the alveoli have been inflated the resistance to subsequent inspirations is of a much lower order and the mechanical efficiency of any respiratory activity undertaken by the infant must be vastly increased There are workers who continue to advocate the giving of the method of gastric insufflation This regime should have no place in a oxygen by scheme of resuscitation of the newborn There is firstly some doubt as to its efficiency as a mode of oxygenation, and the view is held that inuch of the oxygen reaching the circulating blood does so from the ·PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA 104 'pharyngeal overflow', rather than by passing through the gastric mucosa The second objection to gastric insufflation is that if the method is used the child still has to take its first breath unarded and even if the orygenation is of temporary benefit the considerable and futile effort made to initiate respiration is likely on balance to lead the infant into an even more parlous condition There mught be a place for gastric insufflation in supportive therapy as in the case of very small prematures once the fullest possible respiratory excursion has been established but even then naso-pharyngeal catheterization is probably of equal efficiency and is less dangerous The trachea of an infant is on the average 4 cm long and s-6 mm in diameter The distance from the gums to the cords is 5-6 cm and from the gums to the carina 9-10 cm Thus the endotracheal tube used should be no longer than 9 cm and no shorter than 7cm A Portex size o of size 00 is of satisfactory diameter The tube should be of the non-cuffed variety with a rounded bevel-end not rigid but firm enough to maintain a gentle curve After use it should be sterilized as in the general theatre and should be kept in its individual cellophane wrapper Oral intubation must be the rule for obvious reasons It should be performed under direct vision using the sort of laryngoscope blade with which the operator is most familiar The infant epiglottis is notoriously soft and tends to obstruct the view of the vocal cords It may be gently lifted out of the way with the tip of the laryngoscope blade (more easy when a straight blade is used) or with the end of the tube gripped by a short pair of Magill s forceps Except in the presence of disaster or of incompetent care of equpment blind intubation has no place in modern practice There are greater and lesser authorities who advocate this method and proudly demonstrate their aptness at it They tend to forget that their trail is littered with the excoriated mucosae of infants subjected to their early trials and errors The finger and finger-nail-clean or dirty-s no respecter of an infants mucous membrane Oxygen is administered from a simple system for whuch there are only three essentials a reducing valve on the cylinder a manometer and an efficient outlet Intermittency of positive pressure may be achieved by either the use of a bag in the familiar Magill system or the provision of a T-piece The latter should be sited fairly close to the infants end of the length of tubing which leads from the reducing valve to the endotracheal adapter Fingertip application to the open end of the T-piece allows the production of rapid changes of pressure within the system and this is probably the preferable method as the use of a bag for more than a few minutes invites carbon dioxide retention ·TUIE CINLD TOS The initial pressure as already explained, must be high of the order of 40-60 mm Hg Howeser of cqual importance is the fact that such pressures must be exerted for only a very short time otherwise there is considerable danger of pulmonary bullae formation with possible rupturc. Day and bus colleagues have indicated that such a range of pressure should be applied for about o 15 seconds and have stressed that there is a danger of producng structural lung damage of this period exceeds 0-2 seconds * As thus indication is of kotle significance in terms of human capaaty to perform, it is probably best to urge that the baby be subject to momentary bursts of pressure not exceeding 60 mm Hg Expansion of the thoracic cage must be taken as an indication that the cohesive effect of atelectasis has been overcome and thereafter the maumum pressure must be mamtained belon is mm Hg In all but the most hopeless cases inaal cxpansion of the lungs will be accompanied by a fushng of the pulmonary arculatory system, and this too will serve to diminish the resistance to orygen inflow Intermittent positive pressure should be continued at a rate of about 40 inflations per minute unol the infant appears to be capable of taking over on its own The endotracheal tube should be left in place for an appreciablc ame after the latter state has been rcached, to avoid the necessity of reintubation should a relapse occur Intermittent aspiraaon of Amd from the endotracheal tube is a necessary undertaking and after extubation the infant should always be * Since completing the text of the book, I have had the opportunity of personal discussion with members of the Neonatal Physiology Research Unit at the Sloane Hospital for Women, Presbyterian Medical Centre New York Regarding the scheme of conatal resuscitation, Dr V Apgar and Dr LS James have kindly permitted me to record an important new development es olving from a considerable quantity of data as yet impublished. It is now considered that whilst the figures quoted above-namely 40-60 mm Hg (55-80 cm H,O) for under o 2 seconds are applicable to the excised neonatal rat lung they must be modified to meet the Larger apaty presented by the lungs of human aconates Exerting a high pressure for such a short period will not roult in the introduction of a volume of a suffiacat to inflate the pulmonary tree to any significant degree The atelectatic neonatal lung will not begin to open until the applied pressure reaches - cm 40 the lungs will expand readily if a pressure within the range 35 35 CTIL. HO us repetitively maintained for 0 S-10 seconds with an interval of about 10 seconds beta een applications When such pressure us applied by the cruined resuscitator-using the mouth-to-airway technique currently advocated by this Unt characteristic sensation of give us appreciated as the respiratory tree expands and thereafter the pressure may be decreased as desenbed in the text At this los er pressure (js cm H2O) time does not appear to be quic as critical un relation to rupture or to bullae formation us with the higher pressures the margin of safety on the evidence of ammal copermenis being very considerable Above the level of 35-40 cm Ho the duration of application of pressttre assunes a significance which increases greatly with each successive rise in the pressure exerted provided that a volume sufficient to cause expansion of the lungs u moved into the chest ·106 PRL.ICIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA m the nursed in an oxyge-enriched atmosphere (for a review of the cqwpmot used for resuscitanon and supportive therapy see the following chapter) The pressures indicated above are to be taken as applymg also to the management of the premature infant, as the resistance due to cohesion and to elastiary are of the same ordy as those found in the infant at torm Various mechanical contraces have been introduced at times as ads to reusatation of the neu bom-intermittent positive pressure machines poriose/negasse phase respirators electro-phrenic stimula.ors and the like On the whole these hare not prosed to be of any great meat, and It is strongly felt that, though such machines will come to have an important place in the maintenance of respirason, ther use is not indicated cmergency of attempong to establish breathing It is not to bexpected that mechanical or clectrical equpment will surpass in efficacy the moety of hand and ge in providmg tha control and judgement erserial to the conduct of these cases It will be evident from the foregoing pages that assessment of the degree of depression of a neonate the choice of the therapeuoc measures to be taken, zad the application of those measures demand both common sense and experience The corollary holds true, and it must be emphasized that no one lacking in either common sense or appropriate experience should ever be allowed to assum- control over a depressed neonate All respons ible attendants ppon delser, -obstetnicians anaesthetists paediatricians and sendoz meduses-should be completely conversant with the scheme of resuscatation, and hould be adept at intubation Intubation of the premature mfant demands sery considerable skill and care, and should, if posible, be imdertaken only by a tramned anaesthetist. Though relapsely uncommon, gross anaemua, diaphragmatic hemma, port-choanal atresia and tracheo-oesophageal atresia and fistula arc Important causes of an infants failure to establish efficient respiradon. They must always be bome in mind and, should they be diagnosed, promptly dealt srhm an appropriate manner As Apgar has pointed out, it is $15 to remember that 20-30 per cent of cases of maternal hy dramnios are assocated with foetal abnormahnes Finally it must be remembered that if oxygen therapy is to be conmoed subsequently to the imbal period of resuscitation, the mfant must receive the gas in a concentradon no hizber than 40 per cent The associa- Don of retrolenscular fibroplasia with the administration of a high concentration of oxygen is box nelles.ablished. Of recent years the number of lse births anually in England and ·TIC CHILD 107 Wales has been approxmately 670 000 Notified stall-births amount to about. 3 per cent of the total inc births and of thesc, about half involve a foctus which has descloped normally and satisfactorily up to the onset of labour and which has been killed by asphyxia with or without significant intracranial hacmorrhage Thus cach year in England and Wales alone (a comparable figure is likely to apply to the whole of the United Kingdom) roughly 7,700 live-born viable infants die beforc the unutanon of respiration In addiuon the neonatal mortality ratc (that is the number of infants who, having once drawn brcath, dic within a month of birth) in England and Wales us about 11 000 per annumn Within this group the majority of deaths occur during the first week of life and the greatest single causative factor is asphyxa-even on the basis of certification 2300 of the 11 000 die of asphyxia and atelectasis. In the United States perinatal (including foctal) wastage is the thurd hughest cause of death, being exceeded only by cancer and heart disease Our relative failure to make satisfactory progress in this field is notably reflected in the well-recognized falure of the perinatal mortality rate to fall in parallel with the infant mortality rate during the past two or three generations Furthermore although It is obviously impossible to make an accurate estimate it is probably fair to say that for each viable child who fails to survive two or three will emerge from the struggle bearing wounds--probably of a neurological character Although there is yet no clear indication of a relationship between neonatal asphyxia and subsequent cerebral palsy or mental retardation vanous investigations of this question are in progress 25 and the general informed opinion appears to be that such a relatonship will be found It 15 surely not too farfetched to see a corollary between the acute hypoxic episode with its neurological sequelae in the adult recently so forcibly brought to the attention of anaesthetists and a state of sustained anoxia in a neonato To summanze in England and Wales alone a total infant mortality and morbidity rate of about 15-20 thousand per annum is entirely the result of inadequate attention to the danger of asphyxia Investigation and understanding of perinatal physiology is clearly of more than academic importance * REGRESSING PULMONARY EFFICIENCY OF THE NEWBORN There has come to be recognized during the past two or three decades a *For a very informative discourse on niconatal respiratory physiology the reader is referred to Cook C D Lucey J F Drorbaugh J'E Segal S Sutherland J M and Smith CA (1956) Apnea and respiratory distress in the newborn infant New Eng J Med 234 56 605 Ost ·108 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA syndrome in which the infant, within a short ame of attaining apparently adequate ventilation begins to suffer respiratory embarrassment, which is progressive and which almost invanably leads to death within 12-36 hours Outstandingly common is the association of this syndrome with prematunity maternal diabetes and Caesarean section At post-mortem examination, the primary pathology is found to be confined to the lungs with secondary changes following the usual pattern consequent upon anoxia. Microscopic examination reveals many of the terminal ar passages to be lined with an acellular cosmophilic membrane and surrounded by a large area of collapsed alveols. This picture is never seen in the stillbom mfant. In view of the histopathology the term “hyaline membrane disease' has been used to connote the syndrome but this does not find favour with all workers (P Gruciwaldo) as the membrane might be merely the terminal manifestation of a previously reversible process Application of the term 'pulmonary disease of the newbom is also not wholly in favour as it does not carry the implication of an initial institution of apparently satisfactory respiration. The clinical picture is well defined within a few minutes or at most an hour or two of birth, the infant who in only rare cases has required energetic resuscitation begins to exhibit inspiratory recession, first of the subcostal muscles later of the mtercostals In rapid sequence there follow the signs of progressive pulmonary inefficiency with an alert child, in possession of intact vital centres fighting with increasing desperation to draw breath Cyanosis is uncommon in the earlier stages but later in the course of the disease the infant suffers from cyanoac attacks which appear without warning and whuch consist of a period of apnoca lasting for one or two minutes Eventually one of these attacks proves to be terminal. It is of course impossible to know whether or not the infants who survive the initial stages of this syndrome of regression have at any time had hyalıne membrane formation within their lungs Donald! believes that radiological evidence of the membrane is demonstrable It must be remembered that initially it is difficult clinically to differentiate the syndrome under discussion from respiratory distress due to aspiration of gastric contents diaphragmatic hernia, pulmonary infoction or intracranial haemorrhage There are several disputed theories of the causation of regressing pulmonary efficiency The very fact of the relatively recent appreciation of the syndrome offers a challenge The considerable number of cases now seen 35 per cent of live births in one notable hospital (V Apgarº) ---mught be merely a reflection of the increased salvage rate of infants especially the prematures or those bom of diabetic mothers as compared ·THE CHILD 109 with that of earlier years On the other hand, the recent prominence of the syndrome mughe be indicative of a significant nitrogenic factor possibly concerned with the widespread use of narcode analgesics or of orygen therapy Although regwgitation and inhalagon by the infant of its highly sadic gastric contents has been implicated by some sorkers, most of the contemporary choones of the causaton of this disease are concerned with pulmonary haemodynamics As has been pomied out rapid filling of the capillary bed is strongly held to be a necessary requisite for prompt and effiamt lung acralon In the presence of hypovolaemia, as might be assoaited with siphonage of blood from the infant to its placenta, such wapıllary distension will tend not to be adequate However to postulate hypovolaemus as a cause of regressing pulmonary effiomncy on these grounds alone is surely inherently incorrect for in the final pathology the lungs are collapsed, not acelectaac (it is strongly fele chat the term atelectasis should be sinctly limited to the signifyng of lung zssue wach has never been acrated collapse' refers to lung assue bereft of its previously contaned 525 The terminological confusion can lead to unwitong discrepancies in theory and therapy) On the other hand, if adequatc vennlapon is attained, despite hypovolaemua, then the subu Otygenation attendant upon the relaave anacmua, together with a possible low level of plasma protein concentration, might promote some pulmonary crudate. More attracuve are the hypotheses which implicate hypervolacmua as one of the causative factors. It has been suggested to that ss per cent of che combined ventricular output of the foctus passes through the placenta. Upor occluding the umbilical cord cherefore, there is a sudden and sharp nise in systemic penpheral resistance. Opetung up of the vast pulmonary vascular network rapidly offsets this rise to a considerable extent Darres and his colleaguesto have claimed that there is an important intermediata stage in the change over from the focal to the adult arculanon (see Fig 2) The Oxford group his designared this stage as that of neonatal circuladon, and have indicated that during it the ductus arteriosus retrzains patent, but that a response to the increased penpheral rc sistance blood-flow within the vessel is reversed, leadsog now from aorta to pulmonary artery At the same time, the foramcn ovalc is shut off partly under the influeace of the increased pressure in the left atriun. Apparently this arrangement of Deonatal arculaton is winated normally within minutes of birth and remains effecove for two or three days after which ame che ductus attenosus becomes functionally closed. The effect of the open ductus plus chat of a considerable rise in peripheral ·ΙΙΟ PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTTIESIA FO havsuwz BODY L HEART R HEART azon DA G FOETAL BODY L HEART azer R HEART DA NEONATAL BODY L HEART R HEART ADULT FIG These figures illustrate n a simplified form, the changes in the arculation at birth. In the fetus both ventricles work in parallel to drive blood from the great veins to the arteries Tying the umbilical cord stops the placental circulation and the consequent reduction in inferior vena caval flow combued with a great mcrease in pulmonary blood flow causes closure of the forainen ovale (FO) These changes occur within a very few minutes of birth and give rise to the neonatal circulation, in which a large volume of blood flows through the lungs because the ductus artenosus (DA) is still open at the expense of a greater left ventncular output During the course of the next day or two the lungs become fully func tonal, and the ductus arteriosus which constructs considerably soon after birth, finally closes to produce the adult arculation, in wluch blood is pumped through the lungs and body by the two ventricles operating in series, (Reproduced from Bons, G V R., Dawes GS Mott J C. and Widdacombe J G (1954) Changes in the heart and lungs at birth Cold Sprug Harbor Symposium on the Mammalian Fetus 19 102 By kind PETITISSIOD of Dr Dawes and of the publishers ) ·TIT Tlir CIIILD) resistance is to increase thic pulmonary blood pressure if in addition hyper olaemia is present there is a strong suggestion that pulmonary cxudation will result This is cien more likely to occur in the case of a premature infant in whom the pulmonary capillaries are possibly more permeable, and whose vascular system immediately pnor to delivery contains a smaller proportion of the total circulating blood than docs that of a full-terın infint. Thus it is postulated, although respiration is satisfactorily initiated, a pulmonary crudate notably containing fibrinogen (C D Cook") is rapidly produced. It has been suggested that this is acted upon by thromboplasan from the amniotic flud to form hyaline membrane Apparently the amnyonic fund so ini oled need not be a residuc of that normally present in the lungs prior to delivery It has becn suggested by Dawes20 and by Jose that amnioac flud may be in part secreted from the trachcobronchial walls or filtered from the alveol in the foctus This process might well be perpetuated in the premature for many minutes following delivery It has been stated that at least in the newbom lamb the ductus arteriosus begins to constrict within 5-15 minutes of delivery the diameter being fairly rapidly reduced by half The velocity of blood-flow through the vessel is apparently greatly increased, and there is only a gradual decrease in the volume passing through it, considerable turbulence being promoted. A more marked contraction of the vessel is said to be provoked by relapve anoxaemia, ?? probably as the result of the release of pressor amines--and in this connection it will be recalled that in the premature infant the organ of Zuckerkandl is comparatively large and contains a considerable quanöity of noradrenaline Associated with thus response to anoxaemia there is of course a general systemic vaso-constriction leading to a further increase in peripheral resistance Now Gunther has observed that the umbilical vessels fail to contract in a normal manner when under the influence of pethidine even though the quantity of circulating drug is insufficient to produce obvious vital centre depression It is conceivable that a similar concentration of pethudine might result in an insufficient constructive response of the ductus arteriosus to sub-oxygenation or even to the normal determining factors with a resultant significant increase in pulmonary vascular pressure Central depression per se has been postulated as being a primary cause regressing pulmonary effiaency but this hardly seems to be likely the infant so obviously makes prodigious efforts to achieve satisfactory respiratory exchange The influences of a high concentration of oxygen in the child s environment increased or diminished humidification of the ·112 6 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA ambient air and raised or lowered body temperature are of doubtful importance in the production of thus syndrome (W A Silverman) Ignorance of the actiology of the condition means that treatment can be only symptomatic An attempt is made to augment the infants respiratory efforts by the use of ventilating devices and thereby not only to maintain its oxygenation but also to conserve its energy One such approach to this problem has been well outlined recently by Donald, and another involving routine tracheotomy by Benson and his colleagues 28 However the success of these methods seems at the present time to be so limited that a discussion of their application appears not to be indicated for a book of this type It will be observed that in the above rather disjointed presentation of aspects of the syndrome of regressing pulmonary efficency none of the notable workers in the field have been identified by name with any of the theones presented. This has been a deliberate policy for the subject is extremely complex and hypotheses and even observations appear to change radically from year to year Many factors remain to be elucidated, and their significance es aluated. To the anaesthetist those of more direct interest include the influence of narcotic analgesics the construction of efficient respirators the significance of the relapvely large size of the thymus (can this for instance be related to the anomalous response of infants to depolarızıng and non-depolanzing relaxants and is the progressive inefficiency of the respiratory muscles of some premature infants subsequent to an initial powerful contraction reflectve of a myasthenic state?) This entire section has been interpolated, not to give an accurate exposition of the views of advanced workers but in the hope of stimulating the interest of anaesthetists who are or who mtend to be especially concerned with obstetrics The problems are such as to requre for their solution the team work of informed obstetricians paediatricians anaesthetists and laboratory workers REFERENCES I Diamond, LK (1950) In Nelson s Textbook of Pediatrics sth cd p 1093 Philadelphia Saunders 2 Wintrobe MW (1956) Clinical Hematology 4th ed. p 105 Philadelphia Lea and Febiger 3 Sandford, H N (1957) In Brennemann and McQuame s Practice of Pediatrics 3 Chapter IS PI Hagerstown, Md. Prior 4. De Marsh QB Windle W F and Alt H L (194-) Blood volume of newbom infant in relation to early and later clamping of umbilical cord Amer J Dis Child 63 1123 ·TIE CIDLD 113 s Gunther M (1957) Transfer of blood between baby and placenta in the minutes after birth. Lancet I 1277 6 Special Committee on Infant Mortality (1958) Panel discussion on Respiratory difficulties of new bom infants NIS! Med 58 372 7 Mour C. (1936) Expulsise force of the uterus during labour Lancet 1 414 & Holland, W W and Young I M (1956) Neonatal blood pressure in relation to maturity mode of delivery and condition at birth Brit med J 3 1331 9 Wesbrot, I M James L. S Prince C E Holaday D A and Apgar V (1958) Aad base homeostasis of the new born infant during the first 24 hours of life J Pediat 52 395 10 Born, G VR Dawes GS Mott J Cand Widdicombe J G (1954) Changes in the heart and lungs at birth Cold Spring Harbor Symposium on the Mammalian Fetus, 19 102 It Eastman, NJ (1930) Foctal blood studies I Oxygen relationships of umbilical cord blood at birth Bull Johns Hop Hosp 47 221 12 Westin, B (1957) Technique and estimation of oxygenation of the human fetus in utero by means of hystero-photography Ana paediat, 46 117 13 James LS Weisbrot I M Prince C. E. Holaday D A and Apgar V (1958) Acid-base status of human infants in relation to birth asphyxia and the onset of respiration ) Pediat 52 379 14 Donald, L (1997) Neonatal respiration and hyaline membranc Brit Anaesth 29 553 15 Cross K. W Tizard, J P M and Trythall D A H (1957) Gascous metabolism of the newborn infant Ada pardial 46 265 16 Cook, C D Cherry R. B O Brien D Karlberg P and Smith C A (1955) Studies of respiratory physiology in the newbom infant I Observations on normal premature and full-term infants J Clin Invest 34 975 17 Bonham-Carter RE (1957) Architectural function of pulmonary capillaries Lancet I 1292 18 Apgar V (1953) Proposal for new method for evaluation of newborn infant Anesth & Analg 32 260 19 Apgar V Holaday D A James L S Prince C E and Weisbrot I M (1957) Comparison of regional and general anesthesia in obstetrics J Amer med Ass 165 2755 20 Potter E L (1955) State of the lungs at birth J Amer med Ass 15 1341 21 Freeman, L C and Scott RB (1954) Gastric suction in infants delivered by Cesarcan section. Amer J Dus Child 87 570 22 Apgar V (1956) In Hingson and Hellman s Anesthesia for Obstetrics Ist ed. P 310 Philadelphia Lippincott 23 Day R Goodfellow A M Apgar V and Beck G J (1982) Pressurs-tume relations in the safe correction of atclectasis in animal lungs Pediatrics 10 593 24 Donald, I and Lord J (1953) Augumented respiration studies in atelectasis nconatorum Lancet 19 25 Apgar V Girdany B R. McIntosh R. and Taylor H. C (1955) Neonatal I Study of relation of oxygenation at birth to intellectual develop- Pediatrics 15 653 26 Jost A in discussion following McCance R. A. and Widdowson, E. M. (1954) Water metabolism Cold Spnng Harbor Symposium on the Mammalian Fetus 19 164 2noxia ment ·114 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTILESIA 27 Bumard E. D (1958) Murmur from the ductus artenosus in the new bord baby Brit med J 1 806 28 Berison, F Celander O Haglund, G Nilsson, L Paulsen, L. and Renck, L. (1988) Positive-pressure respirator treatment of severe pulmonary insufficiency in the newbom infant. Ada anaesth scand : 37 1 ·CILAPTER VI EQUIPMENT AND ADMINISTRATION It is well enough recognized that, in this country the call for anacsthesia in the obstemic department is an emergency measure. It is therefore not unrcasonable to insist that a complete range of equipment for providing anaesthesia and resusatation be kept in a constant state of preparedness in the delivery room It is a duty of the anaestheac department that this equipment be frequently inspected, tested and, if necessary, replenished. The following observations apply to cqwpment which, from the point of view of the anaesthetist, must be maintained in each delivery room The obstetaan and the paediatrician will also have an interest in some of the articles discussed, and the joint concern should form part of the basis of co-operation between the three specialides The delery room bed or table in many hospitals is hopelessly obsolete not only hundering the rapid and efficient working of both obstetrician and anaesthetist, but also providing a potential threat of disaster for the patient. There is a variety of excellent beds now in production but it is not necessary to catalogue the various commercial products in thus book The essential features of such a bed are as follows ? It must be possible easily and rapidly to tilt it through 20 degrees in either direction. 2 By manupulatng a simple control it must be possible to cause the lower half of the bed to sink and then to slide beneath the upper part so that the patient may be put into the lithotomy position without having to be dragged and tugged down the table It must sall be possible to alt the table when thus manocuvre has been accomplished 3 Raising and lowering of the whole table must be attainable by the operation of a simple foot-control. 4 All the above-mentioned controls must be at the head-end of the table, and within easy reach of the anaesthetist $ The leg-supports of the Lithotomy poles should be of the moulded type allowing the waght of the patient s legs to be distributed over a considerablc arca. If stirrups must be used the supporting poles which its ·176 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA are so often seen to be diggug mto the patients calycs must be well padded. 6 Smooth-running casily secured, well-padded shoulder-rests must be held in readiness 7 It must be possible rapidly to screw a long dnp-poic wto position on other side of the table and the pole should be kept clipped to the table when not in use 8 It is preferable though not essential that there be an am-board attachment which can be apphed easily to either side of the cable 9 The mattress which should be of firm sorbo-like consistency should of course, be in two separate pieces the junction coinciding with the splt in the table. It should be of conductne materal and should not tend to slip over the polished metal surface of the table The disaesthetic machine will be of the type sa use in the general operating theatre and complete with closed-arcut equpment Whether the piping system as used or not gas and oxygen cybnders should be checked daily The usual range of face masks airways and endotracheal tubes--cuffed and plawa---with their respective connections should be kept with thic machine m a state of cleanliness and seadiness The point made by Par&ce? as well taken namely that ia the obstetric department face-masks should be transparent. Two adult-sized laryngoscopes should be kept on the anaesthouc machine, and their notonously fickle bulbs tested daily and also of every ataesthetic A special cupboard containing the following equipment should be situated within arm s length of the anaeschetst s station A range of autoclaved and easily identifiable syrmges and needles Several Ghordh-type cannulae Regularly autoclaved spinal and epidural packs Transfusion egwpment and cut-down sets (2 adult x anfane) Tracheotomy-set (1 adult 1 infant size) Cardiac massage set. Routinely tested bronchoscops preferably light-weight battery type, with appropriate sucker-end. Large-bore stomach tube (size 10 onophageal) Full complement of drugs needed to produce regional analgesia general anaesthesia, hypoaesthesia and relaxadon plus the pressor and hypotensive agezies apomorphone atropino and the vanous antagonists Full complemest of intravenous fluids other than blood. prior to induction ·EQUIPMENT AND ADMINISTRATION 117 Appropriate bottles for samples of blood to be used for typing and cross-matching together with the necessary laboratory forms Extra-long tubed stethoscope for taking blood pressure rcadings Blood-pressure should always be recorded before the start of anaesthesia, the sphygmomanometer auff being applied to the arm less likely to be used for transfusion Measurements should be continued and recorded, at intervals throughout the operation An electric suction apparatus tested for efficiency and reliability is essential for cach delivery room This must be reserved solely for use by the anaesthetist upon the mother and the appropnate tubing and sucker-end should be laid close to hand for the duration of the operation and the recovery phase Completely spark-proof models are now available and should be preferred The gas and air machines with their accompanying tubig and masks must be rouancly inspected and tested 2 The Trilene apparatus must by order be returned at six-monthly intervals to the National Physical Laboratory for testing The day-to-day care of the apparatus has been well detailed by Seward and Bryce-Smith. Intelligently formulated and well-kept record-cards are an essential part of good obstetric anaesthetic practice Not only do they permit of reliable reflection upon the course of a particular case but analysis of large numbers of such cards will and greatly the progress of understanding in the speciality Upon such cards should be recorded full details of the analgesia and anaesthesia used relevant aspects of the matemal signs and symptoms and pertinent data regarding the condition of the child before during and after delivery In parentheses it might here be noted that it is an excellent habit for the anaesthetist to insist that the foetal heart sounds be checked immediately prior to his starting work. The only obstetnc anaesthetic record card in use in England—and of which the author is aware—is that devised by Dr R J Hamer Hodges for use in the Portsmouth Hospital Group Details of thus are shortly to be published, and it is to be hoped that Dr Hodges example will rapidly be followed The resuscitation table should carry all the apparatus necessary for the treatment of a depressed infant An admirable example of such a table has been described by Secker 3 The table itself should be freely mobile light in weight able to be tilted from the horizontal through to is degrees head-down and of a height which permits the operator to work comfortably whilst sitting on an anaesthetist s stool. Au casily-washablc sponge nylon or soft sorbo mattress should cover ·1/8 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA the surface of the table and Secker makes the excellent suggestion that an oval hole (11 cm by 9 cm ) be made in the head-end of the mattress to allow the baby s head to be stabilized, especially during intubation A 66-gallon cylinder of oxygen with a reducing-valve and flowmeter should be attached to the lower end of the table and should be maintained in the customary fashion The tubing leading from the cylinder should be clipped along the side of the table the terminal sıx inches being allowed to hang freely at the head-end This arrangement helps to reduce the drag on the endotracheal tube A siction unit may be fed from the oxygen cylinder but it is probably more satisfactory to have a small electric sucker held on a shelf at the foot-end of the table The apparatus should be of low displacement and law maximum vacuum Secker suggests that a clock be incorporated into the table Whilst this might be considered as a rather refined luxury there is no doubt that a clock or watch with a prominent second-hand is a necessary arocle in the delivery room It should be kept well outside of the mother s field of vision for clock-gazıng alarms the nervous and depresses The following equipment should be neatly stored in a drawer of the infant-resuscitation table the wenry Moulded infant-sized face-masks made of transparent material Several Portex No o and No oo endotracheal mbes cut to length (see Chapter VI) and with connections attached Two or three Porter No ooo airit ays Two or three fine rubber nasal catheters with tapered plastic connectors attached Two or three rubber catheters (No 12 French) for oro-pharyngeal and gastric suction with tapered plastic connectors attached The latter should each have a hole about a quarter-inch diameter—along its length, to facilitate control of suction Two or three very fine suction catheters which may be threaded comfortably through the endotracheal tubes These too should have tapered perforated plastic connectors attached. Equipment--incorporating T-piece or rebreathing bag--for maintaining intermittent positive pressure It must be possible to apply the tubing casily but firmly to the endotracheal connection and to the lead from the oxygen cylinder A manometer must be included in the system and it is preferable that this be laud alongside the child s head so that manometer and infant thorax may be watched simultaneously ·EQUIPMENT AND ADMINISTRATION 119 Laryngoscope with 2 infant-sized blades-lested rouancly cach day and immediately beforc cach dehuery Alucus-catheter--this should liarc a 'body' (preferably transparent) of such a capaaty as to preclude the necessity of having to blow out the contents to leave room for further aspirations A number of simular catheters will of course be kept elsew here for uscat routine deluches but an advance will have been made when suction machines (offering a negaase pressure no greater than -0-40 mm Hs) entrely replace thesc rather dirty and often traumatic instruments Recent ---for water used to clear the suction catheters Two autoclaved 2 ml syringes with needles Supply of let allorphan Each piece of equipment intended for use within the infant s mouth or nosc should be stored within its individual plasac bag There is often considerable confusion and someames disagreement regarding the desirable location of the infant immediately it is separated from the placenta. There can be no doubt that the infant must be placed on the resuscitation table within arms length of the anacsthetist even if the latter takes no acave part in the treatment of the child. The anaesthetist should be considered as being the director of resusamoon and he should be in a position to observe and if necessary to control any measures taken whether by midwife pacdiatrician obstetraan or trainee anaesthetist If the anaesthetist is acang as demonstrator and instructor then the necessary arrangements for handing over the care of the mother at the appropriate time will already have been made If there is a serious shortage of attendants and the child is in urgent need of the anaestheasts attention then a common sense assessment of the situation must direct the course of action Having the child brought close to the head of the operating table obviously resolves much of the difficulty of the situaton under any arcumstances The simultancous appearance of a maternal crisis and neonatal aproca poses an invidious problem delberaton upon which us outside the scope of this book. However in general terms it might be suggested that, whilst inefficient resuscitanve measures of shortly succecded by adequate treatment might not cause very scnous harm to the neonate a simular course of events is likely to produce considerablc residual damage in the case of an adult In many hospitals in this country it is still the practice to perform all Cacsarcan sections in the general theatre This is to be strongly deprecated, as the two often long joumeys add greatly to the perils of both mother and child in many instances There seems little reason why in cach unit an ·120 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA cffort should not be made to equip one delivery room for the purpose of conducting Cassarean secaons A selection of all the apparatus mentioned in the foregoing pages, including the delivery table would be entirely applicable to the conduct of such cases Personnel As convention has it in this country at the moment anaestheasts appear in the labour ward only to attend operative deliveries and some mmes breech deliveries and extraction of retained placentae Aroches and comments humbatingly too numerous to detail make it obrows that even these meagre standards are barely upheld in many hospitals As stressed clsewhere in this book it is an urgent duty of the semor anzesthetist to ensure that his obstetric colleagues are able to obran without more than five minutes delay the services of a competent anaesthetist at any time It has previously been pomted out that obstetric anaesthesia is in the man emergency anaesthesia and this fact presents an obvious duty to the anaesthetic department At the same time the obstetrician es rarely caught unawates and in a well-integrated hospital the anaesthecast on duty can usually be given a prelimuary warning notice Wakun the limits of presene-day practice the responssbultes of the anaestheuc department 101 respect to obstetrics also mclude (6) Supervision of the training of pupil midwives in all aspects of analgesia for labour (h) Tke srestruction of concerned medical and sursing personnel in the theory and practice of neonatal resuscitation The anaesthetist should be the coordinator but not the inevitable star pict:apart in a team including obstetricians midwrtes paediatricians and funzor anaestheasts che aim of the team being to provide prompt, kanowledgeable and efficient relief of neonatal depression Domscılary Practice In this country 35-40 per cent of deliveries are conducted in the home The proportional occurrence of abnormalities is very much lower than is the comparable rate a hospital practice but forceps deliveries are all carried out (amounung to about 6 oco such operations annually) and the family doctor will on occasion be faced with a vorymgly depressed infant Some suggestons regarding donuciliary anaesthesia for delivery and for removal of a retained placenta, have been made in other chapters of thus book with some cmphasis on the possible scope of hypozesthesiz ·121 8 EQUIPMENT AND ADMINISTRATION The following suggestions are added in the hope that they mught prove useful to those general practitioners who have a special interest in obstetrics Use of the Western Reserse portable anaesthetic machine introduced by Hingson and reported upon in thus country by Mushın and Thompson scems to offer considerable advantage over most methods of general anaesthesia previously employed in the home Used in the manner suggested, the machunc can be niade to deliver a non-explosive mixture of oxygen cyclopropane and helium with wluch anaesthesia is induced within about 15-30 seconds and may be maintuned for 7-10 minutes without replenishing the gases A small soda-lime cannuster included in the apparatus prevents a clinically significant increase in carbon dioxide concentration within the system For full details of the construction and use of the machine the reader is referred to the relevant atacles. It must be remembered that explosion and firc cxcepted, the hazards of cyclopropane anaesthesia including vomiting and regurgitation are not obviated by this innovation It seems possible that a modification of the machine could be used for neonatal resuscitation. For this purpose Sparklet cylinders containing pure oxygen (as descnbed by Hingson) would be used and the adult-sized mask replaced by one suitable for an infant It must be very rarely that the innal hugh pressure referred to in the previous chapter necd be applied under condinons of domiciliary practice and the call is probably almost always for assisted respiration The Western Reserve machine is provided with a pressure-limiting safety valve which ensures an upper limit of 20 mm Hg when positive pressure is being applied Used in conjunction with an oral airway the apparatus should be of considerable service in aiding a mildly or moderately depressed infant As a means of coordinating ideas and experience between domuciliary and hospital practices it is suggested that the apparatus should also find a place in the delivery room scheme of neonatal resuscitation A much more simple and probably as effective piece of equipment for use in resuscitation is that based upon a suggestion by Safar This consists merely of two oro-pharyngeal airways-preferably Portexone infant size the other adult size which are taped together at their flanged ends so that there is conanuity between the interiors of the two To reduce the spread of droplet infection a few layers of gauze may be placed between the airways Both tape and gauze should of course be replaced after each case, the airways sterilized, and the whole stored in a plastic bag Short sharp puffs through this device appropriately placed, should provide a more comfortable and possibly a more efficient ·I 22 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA way of inflating the infant's lungs than that offered by the mouth tomouth method of Biblical fame REFERENCES i Parker R B (1984) Risk from the aspiration of vomit during general anaesthesia Brit med ) 2 65 2 Seward E H and Bryce Smith R (1957) Inhalational Analgesia in Childbirth Ist ed Oxford Blackwell 3 Secher O (1956) Resuscitation table for the newborn Lancet 2 341 4 HungSon R A (1958) The Western Reserve anesthesia machine oxygen Inhalator and resuscitator y Amer med Ass 167 1077 s Mushın W W and Thompson P W (1958) Cyclopropane in non-explosive mixture for out patient anaesthesia Brit med J 1 1376 6 Safar P and McMahon M (1958) Mouth to-airway emergency artificial respiration ] Amer med Ass 166 1459 ·EPILOGUE Enouck emphasis has already been laid in this book on the necessity of providing adequate anacsthetic cover for operative obstetrics in hospitals Attention has also been directed towards the need to encourage vigorous and co-ordinated investigations into the immediate and long-term effects of obstetric analgesia and anaesthesia upon the child together with complementary studies of normal perinatal physiology All thesc arc matters of urgent concern to the welfare of our patients and to the selfrespect of our speciality but what of the day after tomorrow? There appear to be two challenges which must faced within the next few years the delay bang enforced by lack of manpower in the one case and by lack of knowledge in the other At the present ame, of the 260 000 domualary deliveries occurring annually in England and Wales, about 6 000 are operative and require the aid of anaesthesia Comparable figures must apply to the whole of the United Kingdom Not much appears to be known about the infant mortality and morbidity rates in domiciliary obstetrics but there is some suggestion that maternal mortality and probably matemal morbidity-- is lower than in hospital practice. This has been referred to already in previous chapters and it has been proposed that the discrepancy is in part duc to the greater inadence of severc obstetric complications in hospital practice and in part to the extended experience of many general practitioners in their chosen methods of anaesthesia--an experience which in many cases is based upon that gained dunng medical training in the days before anaesthesia assumed its present highly specialized role whilst of is doubtful that the figure of 6 000 operative deliveries per year will be much reduced during the coming ten to fifteen years it is certain that there will in that period be many replacements in the ranks of general practitioners undertaking domualary obstetrics It has alrcady been suggested, in the Introduction that prospective general practitioners should have received appropriate training before becoming chgible to practice obstetnc anaesthesia under home conditions for though an outlet forceps operation mught almost always be a simple essay in obstetnes it can never be regarded as being child s play for the anaesthetist It is doubtful if a general practitioner anaesthetise service will ever 123 ·124 PRINCIPLES AND PRACTICE OF OBSTETRIC ANAESTHESIA achieve comprehensive coverage for all domiciliary obstetrics and it should be the aim of the local hospitals to provide one or two anaesthetists who will take part in a district duty rota—this of course being distinct from the obstetnc flying squad service It is easy to envisage a training programme involving both junior anaesthetists and interested general practitioners whuch would comcidentally lead to a more enlightened approach by specialist anaesthetists to the problems of domiciliary anaesthesia The second long-term issue is probably of even greater importance Related to the whole of medicine in more general terms it has been well presented by Dr Cicely Williams 2 Batish hospitals undertake the responsibilities of conducting undergraduate and post-graduate training for very many visitors from overseas who intend to practice in their respective homelands Increasing numbers of men and women are receiving their tuition from these British-trained doctors without themselves travelling to this country and thus the circle widens We must soon seriously begin to question the applicability to newly-developing countries of the methods of obstetric anaesthesia which we teach for home consumption Even in some highly industrialized states the challenge is immense A recent paper remarked upon the fact that in Japan before World War II neither analgesia nor anaesthesia was given for labour unless specifically indicated Now it seems the demand for relief from pain is growing steadily and in the face of a gross shortage of anaesthetists (and an absence even of US-style nurse anaesthetists) there must be considerable difficulty deciding upon a safe way of providing a satisfactory response to the demand In the underdeveloped countries especially those in which small communities are widely scattered and the doctor is likely to work in comparative isolation the problem is even greater * Many possibly most of the methods which we currently teach are obviously completely unrelated to the realities of overseas practice To retain our role as a university of the world we must accept in some measure a reversal of the teacher-student relationship and cagerly learn of the precise conditions under which many of our visitors will eventually work Only on such a basis will we be able to apply our special knowledge of the relevant physiology and pharmacology to the solving of many of these problems At the moment Hingson is engaged in an initial sortie into this field At the time of writing no report of his recently concluded Afro-Asian tour has been published no doubt he will be able to indicate many modifications which we must introduce into our curricula for students from overseas but there will certainly be a need for others not yet appreciated and his is only one of several niethods of investigation in ·EPILOGUE 125 The British Commonwealth cmbracos almost onc-third of the worlds population and most of its communities are included in the category under discussion. We in the United Kingdom havciong had the prvilege of culling sifting disalling and transmitang knowledge of the health and treatment of these variegated populations In matters of basic standards of health, sarutation response to drugs cmotional reactivity cultural standards domesac relatonships and the like, the norm of cach society differs widely from that of our own and those of others in the Commonwealth if we are to fulfil one of our major obligations accepted by our denaficagon with the Faculty of Anaesthetists of the Royal College of Surgeons then we must soon relate a part of the teaching of obstetric anaesthesiamas indeed, of all anaesthesia-to the specific problems of these more exouc environments REFERENCES 1 Parker R. B (1956) Maternal death from aspiranon asphyxia Brit med 2 16 2 Williams, C D (1958) Socul medicine in developing countries. Lancet 1 863 3 Yabuki, G and Hong S (1957) 'Pontoczıne saddle-block anesthesia in obstetrics for the general practioners in Japan. Far East Anesth 1 20 4 Malkoni, R P and Sikand S (1956) Forceps delivery under pudendal nerve block anaesthesia J Obstet Gynact India 27 193 ·INDEX Adrenaline placental transmission 23 Circulation, maternal 8 with epidural block 46 neonatal 43 95 109 Arway (oro-pharyngeal) for resusata neonatal pulmonary 99 IOS 109 tion, 121 uterine 8 in general anaesthesia 54 6. Curare see "Tubocuranine in hypoaesthesia 64 Cyclopropane in assisted breech dein neonatal resuscitation, 103 Insery 80 place in vomiting 73 in Caesarean section, 58 Amiphenazole in analgesia technique 41 in domualiary practice 1.I in neonatal resuscitation 1oz in forceps delivery 56 62 placental transmission, 27 in retained placenta 85 Anoxaemia sec Oxygen placental transmission, 24 Apgar scale 100 Apomorphine premedication, 72 Decamethonun iodide placental trans- Artificial respiration, see Respiration mission 28 Ataralgesia see Hypoaesthesia Digestion see Gastnc retention Dihydrocoderne placental transmission Blood, picture (maternal) 7 .6 picture (neonatal) 94 D-tubocurarine sec Tubocurarne reserve in placenta 95 Blood pressure in normal pregnancy 8 Epidural block in breech extraction 81 venous 9 8. neonatal 95 in diabetes 9- Buffer base change in pregnancy 10 in disordered uterine function, 18 89 m umbilical blood, 96 in heart disease go in labour 46 Carbon dioude dissociation curve 9 in operative obstetrics 68 during anaesthesia ss in pre-eclampsia 18 88 A neonatal resuscitation, 10. i prolapsed cord 84 in umbilical vessels, 2. 96 in prolonged labour 49 placental transmission, 22 in respiratory disease 92 Caudal block in disordered utenne Episiotomy indications in N Amenca function, 89 13 in labour 46 Ether in breech extraction 81 in prolonged labour 49 in Caesarean section, 56 Chloral hydrate in analgesia 4- in external version, 86 Chloroform in operative obstetrcs 59 in forceps delivery 52 placental transmission 23 in retained placenta, 85 Chloroprocaine for epidural block 47 placental transtussion 24 in disordered utenne function 90 in operative obstetncs, 69 Flaxedil in operative obstetrics 64 in pre-eclampsia, 88 placental transmission 8 Chlorpromazine in analgesia technique Fluothane in brecch extraction, 81 37 in external version, 87 in pre-eclampsia 88 u operative obstetrics 59 126 ·INDEX 127 Gastric retendon, assoxtition with Pethedusse analgesia 33 effect on foctal vessels 111 yoning 70 in Labour to in brorch extraction B3 in Cacsarean section, 63 Heroin, placental transmission, 26 u sridural technique 69 ua forceps delivery Oj Hyposestbesua m brecch deksery B2 on heart disease of in forces delistry 61 113 tetased placenta es in stained placenta 85 placental transmission 36 incomordinate uterine activity effect of Pharyngeal airway sec Airway Phenothiazine derivative cpidural block 18 89 sce under Chlorpromazine Promazine Levallorphan, un analgesu technique 40 Promethazine in hypoaesthesia 63 Pitressin, with cyclopropanie 59 in neonatal resuscitation, toz with succinylcholint 64 un premcdication, 56 Placental transmission cessabon of 19 placental transmission, 27 Post-maturity Promazine in anualgesia 40 Metabolic rate change in pregrizacy 9 Promethazine 11 gº511 37 Methylpentynol, an analgesia 41 in broech dchvery 82 placental transmission, 26 u epidural techniques 69 Matpaza, in analgesia, 42 un forceps delivery az in pzemedication, so placental transmission, 26 in pre-cclampsia 88 in sttaused placenta 8s Mortality rate national UK 2 placental transmission 26 naton2 US 3 preincdication so I Multiple pregnancy associated charac- Pudersdal block en breech delivery 80 teristics 14 82 delivery 83 w forceps debvery 64 in heart disease or Nallene in analgesia 40 in muluple pregnancy 83 placental transmison 26 Nitrous oxade i analgesia 33 un respiratory disease oz in retained placenta 86 in heart disease 90 placental transmission, 24 Nor-adrenaline placental transitussian Relaxants see individual drugs Renal disturbances in pregnancy and 23 Labour 10 Oro-pharyngeal airway sec Airway pain of 10 Oxygea, consumption of 21 Respiration, altered mechacus of 9 depnvation beanng-down, 13 aroficial sos dissociation curve 920 2. first breath 98 cffect on foctal vessels 111 neonatal 97 gastric insufflation, 103 in domualary practice 121 Scopolamine sanalgessa 41 in heart disease ol placental transmission 23 15 scopacal resuscitation, IOI Spinal block association with vomuong in umbilical vessels 20 g marcase is plasma 21 in diabetes 92 placental transmeton, 20 in operanve obstetrics 65 transport 57 protclampsia 14 prolapsed cod 84 retained placenta as Paraldehyde placerical transmission, 36 in transverse le 83 ·128 INDEX Trilene apparatus 117 in analgesia 34 39 in operative obstetrics 54 placental transmission 5 Tubo-curarine in operatie obstetrics 64 placental transmission 28 Succinylcholine in operative obstetrics 64 placental transmission 28 Thiopentone in breech delivery 80 in external version 86 in operative obstetrics 60 place in vomiting 73 placental transmission 27 Toxaema of pregnancy association with diabetes 92 association with multiple pregnancy 14 characteristics of 13 effect on placental function 17 cpidural block 18 87 Trachea neonatal 104 Valsalya s manoeuvre 13 Vomiting in breech delivery 82 in prolapsed cord 84 under anaesthesi3 70 Xylocaine an epidural block 46 in operative obstetrics 69 in pre-eclampsia 88

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