Anuesthesiu, 1982, Volume 37, pages 748-753

Forum Anaesthesia for Caesarean section. The potential for regional block

A.G. Davis, MB. ChB, FFARCS, Consultant Anaesthetist, Southern General Hospital, Glasgow G51 4TF

Summary

Thi.r .study of the obstetric und anaesrhetir circumstances relating to 100 con.recutive Caerurew sections under general anaesthesia .sug,qests thal the general anaesthesia rate for Caesarean section could he reducedfrom the present 37 to 220,; hj, niuking tncrsinium use of epidural block and to 164;, by using subarachnoid block in addition. The need,for generul anaesthesia on account of'urgenry ro deliver can he grea f l y reduced by the administration of epidural analgesia during luhour in patients identified as being more likely than uveruge to require Caesarean section, and hv the use of suhuruchnoid block when the need for section arises unexpectedly. Patients' objections to undergoing Cuesurean .section while corwious were analjsed, and suggestions are made .for minimising the number of patients who derline. Ttvhnicul problems with blocks may sometimes be overcome without resort to generul anaesthesia, while patients ut risk .from haemorrhugr or coaguloputhy will continue to require general anaesrhesiu.

Key words

Anaevthesia; obstetric. Annesthetic techniques: balanced. regional

Both of the recent reports of enquiries into niaternal mortality',' show that general anaesthesia remains a prominent caiicc of maternal deaths. Thc almost univer- sal association with avoidable factors makes these deaths particularly regrettable. Most of the deaths due to anaesthesia have been caused by acid aspiration syndrome or hypoxic cardiac arrest associated with difficult or failed tracheal intubation. and it is now well recognised that the avoidance of general anaes- thesia whercver possiblc must be a major part of the strategy in preventing further such tragic deaths in young women.

The reduction in thc incidence of general anaesthesia in parturients over the years 1976 80 in the obstetric unit of the Southern General IIospital. Glasgow. is shown in Table I. The increasing use of epidural analgesia is also evident. although the epidural service is still restricted to certain days on account of shortage of anaesthetists. Cacsarean section is thc commonest indication for general anaesthesia, and Table 2 shows how the increasing use of regional block for Caesarean

Table 1. General anaesthesia and epidural anaesthesia in parturients

1976 1977 197X 1979 19x0 1981*

Deliberies 2320 2341 2816 3053 2957 1435

General

~~ ~~~~ -~

anaesthesia 306 267 289 258 ?I4 57 I.?? 11.4 10.3 8 5 7 2 4.0

Epiduriil anae\ lhrva Y4 I 0 1 316 340 506 272

4.1 4.3 11.2 1 1 . 1 17.1 19.0

sectioii has hecn the major factor in lowering the total incidence of general anaesthesia.

Properly administered regional block not only avoids problems of failcd tracheal intubation. acid aspiration syndrome and awareness during general anaesthesia, hut also carries thc advantages of greater maternal

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0003-2409i82i070748 + 24 $03.00/0 0 1982 The Association of Anaesthetists of Gt Britain and Ireland 748

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decision4elivery interval. In order to obtain a measure of the total time required to achieve delivery under regional block when epidural block was not already established. the preparation time, i s . from the start of scrub-up until the administration of the epidural or subarachnoid drug, must be taken into account. Preparation times were not recorded individually in all cases. but on the basis of times recorded by the author on his own cases, a standard allowance was made of 15 minutes for epidural and 10 minutes for subarach- noid block.

Table 2. Anaesthesia for Caesarean section

Year

1978 1979 1980 1981*

Caesarean section of deliveries

222 231 319 130 7.9 7.6 10.8 9 1

General anaesthesia 178 153 148 40 Yo of total number of Caesarean sections 80.2 66.2 46.4 30.8

Epidural anaesthesia 44 78 171 90 :< of total number of Caesarean sections 19.8 33.8 53.6 69.2

* January-June inclusive. The small number of subarachnoid blocks IS included under epidural analgesia.

satisfaction and postoperative well-being, and a more vigorous condition of the baby at birth. Against these advantages are drawbacks, namely the length of time taken to induce an epidural block, and the lack of universal acceptability. It is important to assess the incidence of these problems.

It was decided that it would be of interest to examine a sample of Caesarean sections with the aim of assessing the proportion of procedures in which indisputable indications for general anaesthesia exist, and conversely the maximum proportion which could reasonably bc performed under regional block. The actual incidence of gcneral anaesthesia in the unit over a period of time could then be compared with this ideal minimum.

Method7

Two hundred and seventy-three consecutive patients undergoing Caesarean section were studied prospec- tively. with particular reference to the 100 operations which were performed under general anaesthesia, but using, where relevant, certain observations from the 173 epidural and subarachnoid blocks.

The indications for Caesarean section and the rea- sons for the choice of general anaesthesia were re- corded. In emergency cases performed under general anaesthcsia the obstetric records werc reviewed post- operatively to determine whether or not the likelihood of Caesarean section as the mode of delivery could have been predicted. Patients who were given general anaesthesia because they refused to undergo Caesarean section while conscious were interviewed and their reasons for refusal analysed.

In order to relate thc time required to induce a block to that available for emergency delivery the following times were recorded: the time of the first epidural dose, or the subarachnoid injection, when a block was instituted just prior to surgery; the time of topping-up for abdominal delivery when an epidural block had been established earlier; and, in every case, time of delivery. In emergency cases in the general anaesthesia group, a record of the time of the decision to deliver by Caesarean section allowed calculation of the

Results

An analysis of Caesarean sections during the period of study is given in Table 3, grouped according to obstetric indication and method of anaesthesia. The indications for general anaesthesia are summarised in Tablc 4.

Timefactom. A study of the indications for emer- gency Caesarean section in Table 3 shows that, in gcneral, the greater the urgency to deliver the higher was the proportion of patients receiving general anaes- thesia. However, it can also he seen that general anaesthesia was used frequently even when urgency was less pressing.

The times taken to institute the various methods of analgesia or anaesthesia were used to define the suitability of each method in relation to the time available to achieve delivery, or the decision-delivery interval (Table 5).

The distribution of decision4elivery intervals of the patients given general anaesthesia because of time factors is given in column A, against the same time scalc. It can be seen that 39 of thc 54 patients had decision4elivery intervals of greater than 60 minutes; that is to say delivery would not have been delayed through the use of epidural block rather than general anaesthesia provided of course that epidural analgesia had already been established. In order to determine which patients would have merited earlier institution of epidural analgesia, the obstetric background and performance in labour of each patient was examined in relation to the list of factors given in Table 6. Column B in Table S shows the number of patients in column A who could thus have been considered genuine candidates for epidural analgesia at some point in time during labour well in advance of the decision to deliver by section.

The relationship between the time of day and the method of anaesthesia is shown in Table 7. It is seen that the likelihood of general anaesthesia being em- ployed is much greater during the 'night-time' third of the 24 hours.

Refusal. Of 192 patients who were offered regional analgesia for Caesarean section. 19 insisted upon general anaesthesia (10%). Six of the patients were elective cases and 13 were emergencies, of whom five already had epidural analgesia in progress.

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Table 3. Indications for Caesarean section I May 1980 t o 27 March 1981

~~ . ~

Elective Emergency

Mechanical problems of labour (with vertex presentation)

Stage of labour at delivery-First Second

First Second

Malpresentation and twins Stage of labour at delivery

Fetal dislress Cord prolapw Antepartum haemorrhiige Other

Rcgional block’ Gcneral anacsthesia Total _ _ _ _ - - . _ ~ ~ ~~~~

Primi Primi gravid Parous Total gravid Parous Toral

29 61 90 5 I I 16 106 ~. -

Tptal emergency 63 20 83(60) 54 30 X4(13) 167

I.01al 173 100 273 63.4 36.6

*Epidural block in 157 patients: subarachnoid block in 16 patients (10 elective, six emergency) Figures in brackets denote numbers of patients who had epidural block during labour.

Table 4. Indications for general anaesthesia

Emergency Elective Total

54 Time factors 54 ( 2 ) -

Patient refused block 13 ( 5 ) 6 19 Haemorrhage or coagulopathy 10 (--) 4 14 Technical problems with

epidural 6 (6) 2 8 Miscellaneous problems 1 (-) 4 5

Total 84(13) 16 100

Brackets indicate numbers within each group with epidural catheter in s i r u .

Group I (12 patients). These were patients whose attitudes were such that they would not accept surgery while conscious, even after the benefits had been explained and understood. A common thrcad ran through the objections of theae patients. typified by the statements ‘1 am just a coward’. and, more specifi- cally. ’I’m afraid of knowing of what’s going on even though I know that I won’t see the operation and I won’t feel pain’.

Group 2 (seven patients). Adverse circumstances were the prime reason for refusal by patients in this group, who often remarked when interviewed after- wards that an epidural would be acceptable in future in more favourable circumstances. One recognised pattern was the patient who, exhausted after a long and painful labour. just wanted to be put t o sleep. The other was the patient who had not heard of Caesarean section being done except under general anaesthesia, and for whom explanation had heen left too late for her to he receptive towards the idea of regional block.

Problems of huemorrhuge or cougulopathy. The 14 patients comprised 11 cases of placenta praevia: one of placental abruption. one of coagulopathy associated with severe pre-eclampsia and one of drug induced coagulopathy.

Subarachnoid or epidural block to the required lcvcl of Tb is contraindicated when major haemorrhage is anticipated, while a defect of coagulation also con- stitutes a contraindication.

Tdinical prohlrms (eight patimts). No attempt was made to perform cpidural block on one patient who had previous!y undergone spinal fusion surgery. Failure to locate the epidural space was the problem in another patient. The remaining six had epidural catheters in . d u . Of these, there was one unilateral block; one with an unblocked segment: three simply described as ‘not working’; and one in which, following a dural tap, the anaesthetist was reluctant to top-up for Caesarean section hccause there were features suggesting a degree of subarachnoid spread.

Miscelluneous problenzs (five paticnts). Language problems in three patients made communication diffi- cult or impossible; general anaesthesia was considered to be necessary in one patient on account of an eclamptic fit and in the other one because of the need for laparotomy for carcinoma of thc ovary at the same time as Caesarean section.

On the basis of these results. estimates were made of the number of cases in which general anaesthesia was indicated beyond doubt, and the number where it could arguably have been avoided. Table 8 shows two estimates: both allow for the fullcst possible use of epidural block: one excludes the use of subarachnoid block while the other allows for its selective use.

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Table 5. Degree of urgency of emergency Caesarean section and method of anaesthesia appropriate

Method of anaesthesia Time available from decision to ~-

section until delivery EDR EDB SAB GA (decision-delivery interval) de n m o in siru A B C

-

-

-

< 15 minutes 15-30 minutes 3 0 4 5 minutes -

45 60 minutes f + + 4 * 2 60-90 minutes * t t + 24 17 <90 minutes +

___ 54 33

EDB, epidural block; SAB, subarachnoid block; GA, general anaesthesia; + , approriate; +, may be achieved in some cases; -, inappropriate.

Column A: Distribution according to decision-delivery interval of patients given GA on account of time factors. ‘One patient in each of these groups had an epidural catheter in situ. Column B: Patients of Column A in whom need for Caesarean section was predictable. Column C: Column B as percentage of Column A.

Table 6. Factors associated with increased likelihood of Caesarean section

Obstetric background

Developments during labour

Short s ta turehge baby Unfavourable cervix Malpresentation Multiple pregnancy Primigravida over 30

More than 10 hours in labour Slow dilatation of cervix Failure of presenting part to descend Failure of conventional methods of

Warning signs of impaired fetal well- analgesia

being

Table 7. Number of Caesarean sections according to time of day, degree of urgency and method of anaesthesia

Elective Emergency Total ~-

0900-1700 b 1700-0100 h 01004l900 h Method (1900 1700 h ‘daytime’ ‘evening’ ‘night-time’ Total

Epidural 80 37 7 5 5 77 157 6 16 Subarachnoid 10 6

General anaesthesia I6 32 27 25 84 100 - -

section having been in receipt of epidural analgesia during labour, while Thorburn & MoirS implied that 27% of their elective sections were performed under general anaesthesia. In this unit, the general anaesthesia rate for Caesarean section is continuing to fall, having been 37% of all sections over the period of this investiga-

It is apparent that the commonest reason for the

Discussion

As the popularity of epidural analgesia for Caesarean section has grown very rapidly in the United Kingdom in the past 5 years, only the most recent figures of other authors are quoted in comparison with the present series. Milne ef reported a 23% general tion. anaesthesia rate among patients coming to Caesarean

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I'ablr 8. The potential for minimising the use of general anaesthesia (GA)

Indications for GA

Time factors Refusal of block Haemorrhage;

coagulopathy Technical Miscellaneous

Tcital

Total Caesarean secti~iis ",, incidence of GA

--

Kumbers of patients receiving CrA

A R c 54 I 4

14 8 5

I00

273 37

22 I7

14 X 5

61

271 22

I 1 12

14 3 5

45

273 16

Column A: Actual analysis of this aeries Column B: Estimate for maximum use of epidural block. Column C:: Estimate including selcctivc use of subarachnoid block in addition t o B.

choice of general anaesthesia is the rapidity with which it may be induced. allowing delivery to be completed promptly. It is true that the obstetric situation at times demands urgent delivery by Caesarean section. Yet in this series only some of the patients to whom general anaesthesia was given, allegedly on account of shortage of time, were in fact delivered in a shorter time than would have been possible under epidural block, especially if the latter had already been in progress. Sometimes the anaesthetist's involvement in other duties dictated the choice of time-saving general anaes- thesia, especially as at such times paticnts in labour coming to emergency Caesarean section did not have epidural catheters in place. Furthermore, at night there is an obvious attraction in a quick technique cvcn in the absence of either clinical urgency or a heavy work- load

It has been found in this unit that the greatest potential for furthcring the trend away from general anaesthesia towards epidural block for Caesarean section lies in the identification as early as possible in labour of potential candidatcs for emergency Caesarean section, with a view to instituting epidural analgesia with the dual aims of providing analgesia and ofmaking for quick and simple procedure to Caesarean section if and when this becomes necessary. These are often among the very patients for whom the obstetrician requesls epidural analgesia; indeed the need for epidural analgesia in labour, unfulfilled because of shortage of anaesthetists, was rccorded by the obstetrician in several of the patients in this series who were sub- scquently givcn gcncral anaesthcsia for Caesarean section. However, it is incumbent upon the anaesthetist. too, as a member of the obstetric team, to acquaint himself with the developmcnt of problems among the patients in labour (all of whom are potentially his patients) and so to make his own recommendations as to the institution ofepidural analgesia. This demands the active participation of anaesthetists who do not have duties elsewhere-a well established. if not widely

enough implemented. recommendation. The moreconi- monly induction of labour is practised (the current rate in this unit is 35-30'J the grcatcr is likely to be thc proportion of procedures taking place in normal waking hours ( i f not always normal working hours), but the use of general anaesthesia during the night merely for the sake of speed in the absence ofobstctric urgency i s not to he encouraged

The second most common reason for general anaes- thesia was the refusal of thc patient to undcrgo Caesarean section while conscious. While the anaes- thetist muqr accept and respect the feelings of the objectors classified in group 1 , there is much that can be done to reduce the numbers refusing because of adverse circumstances. Explanations about the practi- cality of Caesarean section under epidural block should not be lcft until thc last minute. In elective cases, the subject should be introduced (as it is by o u r obstetri- cians) at antenatal visits. Following admission. the patient's education should be reinforced by encourag- ing contact with other patients who have undergone the proccdurc. and, as early as possible. by the anaes- thctist's visit.

In the labour suite. early idcntitication of likcly candidates for emergency Caesarean section is again important. By starting epidural analgesia in labour the anaesthetist. as the bringer of pain relief, is in a most advantageous position to gain the patient's confidence. Provided that the epidural is conducted with meticulous attention to the maintenance of analgesia. with con- tinuity of care by one anaesthetist if possible. a bond of confidence with the patient is easily developed. Against this background. acceptance of Caesarean section under the epidural has, in the author's experi- ence. presented no problem, if the subject is explained to the patient at an opportune moment-neither un- necessarily early nor too late to gain the co-opcration of a nervous patient. N o patient declined on account of having heard accounts from other patients of inadequate blocks, which might seem surprising in view of the fact that in a recent qcrics in this unit 5" , of patients found their epidural blocks for Caesarean section lcss than entirely satisfactory, in addition to the _ _ 3 8"' ,/o in whom an obviously inadequate block neces- sitated induction of general anaesthesia (unpublished observations). There is scopc for further work such as that o l Crawford6 to identify factors affecting the quality of block. This would bcncfit the reputation of the technique among patients and allow anaesthetists to be more confident when predicting pain-free pro- cedures for their patients

Technical problems with epidurals will always occur. some of which may be overcome, given sufficient time. skill and determination. Some of these problems may also occiir with subarachnoid block; in other cases the author has found subarachnoid block useful in avoiding general anaesthesia when a problcm has arisen with an epidural. for example when an epidural block has been

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persistently unilateral. General anaesthesia will remain the method of choice in the presence of problems of haemorrhage and coagulopathy, and a small percentage of miscellaneous indications for general anaesthesia will doubtless continue to occur.

The philosophy underlying the two sets of predictions in Table 8 is that, of the regional techniques, epidural block is preferable whenever a choice exists. Sub- arachnoid block has proved to be of value in avoiding general anaesthesia in a fairly narrow spectrum of cases where either lack of time or a technical problem precluded the use of epidural block: but difficulty in predicting the extent of the block, and unnecessarily profound motor block, and an incidence, albeit small, of post-spinal headache (even using 25-gauge needles) render the technique less satisfactory than epidural block.

If this is a representative sample of Caesarean sections, the results of the analysis would suggest that i t should be possible to employ regional block, usually epidural but occasionally subarachnoid, in about four out of five Caesarean sections. The recommendation of such a radical trend away from general anaesthesia is made, but is tempered with twowarnings. Oneis that, as extensive regional block carries its own dangers, its potential safety value will be realised only if it is employed by anaesthetists thoroughly familiar with the techniques. For example, a poor block may lead to the need for general anaesthesia to be induced during the operative procedure in circumstances considerably less favourable than would have pertained had general anaesthesia been chosen at the outset; whilst the prevention, detection and prompt treatment of hypo- tension and caval occlusion are vital considerations. There is force in the argument that a technique is only as safe as the anaesthetist administering it. Given

equal circumstances of proper administration, however, the belief is that the preservation of protective respira- tory tract reflexes renders regional techniques intrinsi- cally safer.

The other warning concerns the need to maintain the standard of general anaesthesia for the important minority who will continue to require it. If one Caesarean section patient in five in this unit were to receive general anaesthesia, there would be about one such case per week. Those responsible for training junior anaesthetists will have a duty to ensure that the diminished number of teaching opportunities are well utilised in order to secure the trainees’ competence in obstetric gencral anaesthesia.

Acknowledgments

The author wishes to thank Dr J.A. McGarry for constructive criticism from an obstetrician’s viewpoint; Dr Barbara Davis for reading the manuscript; and Mrs E.S. Bertram for secretarial assistance.

References

I .

2 .

3.

4.

5 .

6.

Report un an enquiry into nzaternal deaths in Scotland, 1972- 1975. London: Her Majesty’s Stalionery Ofice, 1978. Report on confidential enquiries inta maternal deaths in England and Wales 1973-197s. London: Her Majesty’s Stationery Ofice, 1979. MOIR DD. Anaesthesia and maternal deaths. Scottish Medico1 Journal 1979; 24: 187-9. MILNE MK, DALRYMPL~ DG, ALLISON R. LAWSON JIM. The extension of labour epidural analgesia for Caesarean section. Anuesrhrsiu 1979; 34: 992-5. THOREURN J, MOIR DD. Epidural analgesia for elective Caesarean section. Anaesthesia 1980; 3 5 3 4 . CRAWFORD JS. Experiences with lumbar extradural analge- sia for Caesarean section. British Journal of Anaesthesia 1980; 52: 8214.

Anaesthesia, 1982, Volume 37, pages 753-757

Carbon dioxide response after epidural morphine

R. B. Holland, MBBS, FFARACS, Director, Department of Anaesthetics, Westmead Centre, Westmead, NSW 2145, Australia, M. W. D. Levitt, MBBS (Syd.), Anaesthetic Regstrar, Western Metropolitan Regional Training Scheme, L. A. Whitton, MBBS, Intern, Concord Repatriation General

Hospital, N. Shadbolt, MBBS, Intern, Gosford District Hospital

Summary

The change in minute volume in response to a rising inspired carbon dioxide concentration was compared in 20patients who received epidural morphine for postoperative analgesiu (the test group), and 18 patients who did not (the control

Correspondence should be sent to Dr R.B. Holland, Director of Anaesthetlcs, Westmead Centre, Westmead. NSW 2145, Australia.