Anaesthesia, 1979, Volume 34, pages 892-897

Forum Prernedication for elective Caesarean section

J . Selwyn C‘rawford F F A RCS, FRCOG, Consultant Anaesthetist, Birmingham Maternity Hospital, Birmingham B I S 2TC

It is likely that most patients who contemplate the approach of an operation are, to some degree, anxious. It is in part for that reason that, for decades, an intrinsic component of anaesthetic management has been the provision of a sedative or tranquillizer preparatory to the surgical procedure. Possibly the incidence or intensity of pre-operative anxiety is relatively lower among patients who are destined to undergo elective Caesarean section because in a sense the operation, rather than being curative or palliative, is productive. However, anxiety is a feature in many of these cases, and common humanity dictates that an attempt be made to relieve it, provided that such relief is not coincidentally detrimental to mother or infant. Several agents have been prescribed by the author during the past 25 years as premedicants for elective section, but none has proved on the basis of clinical impression alone to be convincingly worthy of advocacy. I t seemed therefore to be useful to conduct a controlled trial of a range of agents, and especially so as it appears that no such formal investigation has previously been reported.

Materials and methods

Four options were investigated, and were identified as A, B, C, and D. Each consisted of a bottle containing Mist. magnesium trisilicate BPC (that is, four bottles labelled appropriately A-D) and a capsule, of which there were four containers labelled A-D. Only senior members of the staff of the Pharmacy Department of the Queen Elizabeth Medical Centre knew the identity of each solution plus capsule, and only the writer and the pharmacists knew which drugs were being investigated. The choice of premedicant for a patient was determined by reference to a randomised series of the code letters.

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The study was confined to patients who were destined to undergo elective Caesarean section as a planned procedure. The premedication was prescribed to be given approximately one hour before the start of the procedure. On occasion, for reasons which will be well appreciated, the timing went awry, and only those patients who received the premedicants 45-120 min before the start of the operative procedure have been included in the reported study. Each patient received 30 ml of the antacid mixture and one capsule at the appropriate time. Subsequently she was transported to the anaesthetic room whilst lying laterally (‘journey tilt”) and then given 15 ml of the standard solution of Mist. mag. trisil. BPC. For those patients who were to be operated upon under general anaesthesia routine management was followed: the patient was placed on the operating table, with a lateral tilt provided by a wedge. After an intravenous infusion had been started, preoxygenation was provided for 3-4 min. Hysocine (0.6 mg) was injected intravenously, cricoid pressure applied, a sleep dose of thiopentone (usually 250300 mg) was administered, followed by suxamethonium (100 mg), and when relaxation had beenachieved an endotracheal tube was passed. Anaesthesia was maintained with a mixture of 8 litrelmin oxygen, 4 litrelmin nitrous oxide and 0.2% trichloroethylene until the end of the operation. Relaxation was sustained by the infusion of suxamethonium (1%). The time (in minutes) from induction to anaesthesia to complete delivery of the infant (I-D interval) was recorded, as was the time from initial incision into the myometrium to completion of delivery (U-D interval). Those of the patients who received lumbar extradural analgesia for the operation were also provided with a journey tilt and received a second dose of the antacid. The drug used was bupivacaine 0.5% plain

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0 1979 Blackwell Scientific Publication

Forum (the volume ranged from 20 to 3 0 ml). For these patients only the U-D interval was recorded. At the pre-operative visit on the evening before section the anaesthetist assessed the patient’s attitude to the coming operation. This was recorded as being either ‘no anxiety’, ‘anxious’ or ‘apprehension’ (in this context ‘apprehension’ indicated excessive anxiety). A similar assessment was made when the patient was seen in the anaesthetic room before induction. At the visit on the day after operation the patient was asked if the medication had calmed her, made her feel drowsy, increased her anxiety or had had no effect. She was also questioned about her recollection of the events immediately previous to induction of anaesthesia, and whether or not she had been aware or had had dreams (pleasant or unpleasant) during the operation. The questions were presented according to the protocol, and it is very doubtful that ‘leading questions’ introduced a bias. Note was made of the Apgar-minus-colour scores a t one and five minutes after delivery, of the time to sustained respiration (TSR) in minutes, and whether or not intubation had been a required part of neonatal resuscitation. Assessment of the condition of the infant later was derived by scrutiny of the paediatric and nursing notes. Five categories of condition were derived: trouble-free; sleepy; hypotonic; temperature instability; poor feedersome infants displayed more than one of these characteristics. I t would undoubtedly have been better to have subjected the infants to neurobehavioural assessment testing but this has to-date not proved to be feasible. All the mothers in the series as defined contributed to the evaluation of the medicants as pre-operative tranquillizers, although naturally consideration of ‘awareness’ and ‘dreams’ applied only to those who received general anaesthesia. Consideration of the possible effects upon the infant required that only patients in whoni there was no evidence of placental dysfunction (‘Group A elective section’) be included in the survey. I t was thought advisable also to distinguish between those who received general anaesthesia and those who received an extradural block. Furthermore, because of the influence exerted by the U-D interval upon the immediate condition of the infant2 i t was considered necessary to take this variable into account when making a comparative assessment.

Rcwrlfs

The entire series consisted of 219 patients, of whom 23 receivedextradural block. The distribution according to choice of premedicant was: A-48 general, 4 extradural block 8-53 general, 6 extradural block

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C 4 8 general, 10 extradural block D-47 general, 3 extradural block Of these, 76 ( 3 4 , 7 4 3 declared at the pre-operative visit that they were not anxious. Two patients in this group subsequently reported that they were anxious upon arrival in the anaesthetic room (one premedicant A (extradural block) one preniedicant B (general anaesthesia)). An appreciable percentage recounted that the premedicant made them feel more calm and/or drowsy (Table 1). Table 1 . Postoperative assessment of the ewects of the premedication as detailed by those patients who, at the pre-operative visit, declared theniselves to have ‘no anxiety’ Premedicant Number Calmed Drowsy Calmed and drowsy No difference

A

H

C

D

21 2 3 I I5

*77

-7

18 5 5

15

2

3

0

2 2 3

15

8

8

More detailed consideration is given to the 143 patients who had been either anxious or apprehensive on the day before operation. Twenty-five of these had been categorised as being apprehensive (seven each in series A, B and D, and four in C), but as maintaining the distinction made little difference to the outcome of the analysis the two categories have been amalgamated in the following account. The number of these patients who, at the time of transfer to the operating suite, appear t o have benefited from the premedication was small (Table 2). with mixtures C and D proving to be slightly Table 2. Number (and percentage) of patients who, having declared themslves to be anxious when seen preoperatively, appeared to be calm upon arrival in the anaesthetic room Premed ica t ion

n

No anxiety

A

31

B

31

C

40 35

6 (19) 8 (22) 10 (25) 10 (28)

D

better than the other two. Thedistinction between the two pairs of premedicar.ts is sustained when consideration is given to the postoperative assessment offered by these patients (Table 3). Consideration of the entire series, irrespective of the pre-operative emotional state of the patient, showed (Table 4)a considerably higher incidence of

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Forum Table 3. Patients’ estimate of the effect of the premedication, only those who expressed anxiety at the pre-operative visit are considered here

Premedication Number A

B C D

Calmed

Drowsy

9 I2 16 12

3 3 5 3

31 37 40 35

Calmed No and ditference drowsy

(x)

2 3 8

7

17 (55) 19 (51)

I 1 (27) 13 (37) ~

Table 4. Postoperative assessment of the premedication provided by the entire series of patients (percentage incidence in parentheses) Premedication n

No relief, more anxious or just drowsy Calmed or calmed and drowsy Drowsy or calmed and drowsy

drowsiness, with or without associated reduction of anxiety, and a considerably higher incidence of calming effect, with or without accompanying drowsiness, was associated with premedicants C and D than with the other two. Each patient in the entire series recalled her arrival in the anaesthetic room, the initiation of an intravenous infusion, the receipt of pre-oxygenation and the application of cricoid pressure. Eight patients reported that they had been aware, or had had unpleasant dreams, during the operation. Three of these had received prernedication A (6.2% of that group), four had received premedicant B (75%) and one had received D (2.1%). There was no case of painful awareness. Conclifion of /he infant. There were 151 patients who satisfied the criteria of the ‘clinically acceptable ideal case’3 and who received a general anaesthetic. The distribution according to premedication was: A-39; B-37; C-36; D-39. A previously reported study2 has shown that the immediate condition of infants delivered after a U-D interval which exceeds 90 s is very likely to be worse than that of suitably matched infants delivered after a shorter U-D interval. In this analysis, because of the formulation of our anaesthetic coding chart, the distinction has been drawn between U-D intervals of less than or more than 2 min. Most attention must be paid to the briefer interval, and there were 1 I3 patients in this category. Examination of the data referable to these patients (Table 5 ) revealed that there was little notable and consistent difference in the condition of the immediate newly born which

A

B

C

D

52 37 (71) 14 (27)

59 39 (66\ 20 (34) I I (19)

58 29 (50) 29 (50) 18 (31)

50 26 (52) 24 (48) I5 (30)

10 (19)

could be related to one or other of the premedications. The incidence of neonatal depression was more greatly influenced by the duration of the U-D interval than by the choice of premedication, being considerably greater in the series of cases in which the interval exceeded 2 min than in any of the previously described sub-divisions. Reference is also made in Table 5 to the neonatal outcome in the series of 18 sections conducted under extradural analgesia, (in two of these the U-D interval exceeded 2 min). Two of the latter infants (one each in group A and C) had a TSR longer than one min, the one whose mother had had premedication C required to be intubated. Consideration of the subsequent progress of the infants showed that the duration of the U-D interval played no consistent role in influencing this, and therefore data referable to the entire series of I5 1 infants of clinically acceptable ideal mothers who received general anaesthesia is presented here. A number of the infants exhibited more than one of the conditions under review. As the figures reveal (Table 6), there was a high incidence of infants who were reluctant to suck among those whose mothers had had premedication D,and infants in the premedication B series exhibited least recorded disabilities. There was otherwise, however, not a great deal of difference between the four groups of infants. Among the nineteen infants whose mothers had received an extradural block for section, fifteen (79%) were ‘trouble-free’ one was ‘sleepy’ (premedication D),one hypotonic (B) and two were ‘poor feeders’ (prernedications C and D).

Forum

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Table 5. Number of infants (and percentage incidence) who had a I-nlin Apgar-minuscolour score of less than 7, or a 5-min Apgdr-minus-colour score less than 8, or whose time to sustained respiration equalled or exceeded one minute or exceeded 5 min, or who required to be intubated for resuscitation. The groupings are of cases in which a general anaesthetic was administered-and classified according to whether the U-D interval was less than or more than 2 min-and of cases in which operation was con-

ducted under extradural analgesia

Table 6. Reported condition of the infants d u r i n g the first 2-3 days after delivery. Reference is made only to the infmts of mothers classified as clinically-acceptable ideal w h o received general anaesthesia for thc Caesarean section. Percentage incidence of each condition, in each series of premedicants, in parentheses

Premedication

A

B

C

D

~~

Number Trouble free Sleepy

39 29 (74) 4

is that the incidence of awareness plus unpleasant dreams was 6.394 among A plus B and 0.90,< among C plus D. If the distinctions between the groups of infants are indicative of differences relating to the character of the premedication (a postulate which is admittedly tenuous but which must be considered), then premedication D must be identified as one to be avoided. The conclusion is therefore that premedication C is marginally preferable to either A or B if the objective is to render the patient free from anxiety without concurrently complicating the neonatal condition.

(10)

Poor feeder

4

(10)

Hypotonic Hypothermic

0

2 (6)

Discussion

The effectiveness of each of the premedications was not very impressive. Only a third of the patients who received premedication A or B, and one half of those who received C or D, reported on the day after operation that they had felt calmer after taking the combined therapy. If drowsiness, unaccompanied by a feeling of calmness, is considered to be a worthwhile objective, then the advantage of C and D over A and B becomes rather clearer. An additional, and not unimportant distinction between the two pairs

The preceding account was written before the identity of the four individual premedications was known to the writer. Subsequently the following information was obtained from the Department of Pharmacy. Premedicant A : the placebo-the Mist. mag. trisil contained no additive and the cachet contained an inert substance. Premedicant B: each dose of the antacid mixture contained 10.6 ml 904< alcohol (the equivalent of a ‘double gin’, British measure) and the cachet contained an inert substance. Premedicant C: the antacid contained no additive, the cachet contained a tablet of diazepam, 5 mg. Premedicant D: the antacid contained n o additive, the cachet contained a tablet of lorazeparn, I mg.

It was comforting to discover that the placebo was less effective than was either benzdiazepine in reduc-

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Forum

ing anxiety, although i t was rather disappointing that alcohol exerted no notable action in this regard. Diazepam and lorazepani were equally effective in reducing the incidence of anxiety from that associated with the provision of a placebo, and were also associated with a much lower incidence of ‘awareness plus unpleasant dreams’. It is of some interest to note that in 1976, before this trial started, chlordiazepoxide (Librium) 20 mg was given orally as premedication to 88 patients who underwent elective Caesarean section, and five of these (5.7%) experienced either awareness or unpleasant dreams whilst receiving general anaesthesia precisely as described in this report. This suggests that as far as the mother is concerned diazepam (5 mg) and lorazepam (1 mg) are superior to chlordiazepoxide (20 mg). It is also noteworthy that every patient in the present series recalled the events leading up to induction of anaesthesia (arrival in the anaesthetic room, initiation of an intravenous infusion, pre-oxygenation and the application of cricoid pressure). Thus lorazepam did not induce anterograde amnesia. This is unsurprising in view of the report by Dundee et a/.4 that only 10% of patients given 1 mg of lorazepam orally are rendered amnesic. The distinction between diazepam and lorazepam in respect to the condition of the infants is salutory. The duration of action of lorazepam is very considerable and seems likely to be the reason for the relatively large number of infants in the lorazepam group who were poor feeders during the first couple of days after delivery. It appears that unless there is very strong justification for its use, lorazepam is a drug to be avoided in obstetric practice before the infant has been delivered. This requires especially to be emphasised in view of the fact that Dundee et a/.4 suggest that the optimum oral dose of lorazepam used for premedication is 4 mg.

experience which, it is worth noting, was reported by four of those patients in the ‘not anxious’ group (one placebo, two alcohol, and one lorazepam). This latter benefit is not applicable to patients who are operated on under extradural analgesia, and as yet we have insufficient data to determine whether or not the routine prescription of diazepam pre-operatively is of advantage intra-operatively to such patients.

Summary

Four coded, but otherwise unidentified, premedicants were prescribed in randomised order for 219 patients who were to undergo elective Caesarean section. Seventy-six (35%) of these patients affirmed at the pre-operative visit that they were not anxious. Diazepam 5 mg and lorazepam 1 mg appeared to be superior to the placebo and to 10.6 ml of 90% alcohol in inducing calmness and/or drowsiness, although the differences were not statistically significant. The incidence of awareness or unpleasant dreams was considerably higher in the placebo and alcohol series (6.2% and 7.5%) than in the diazepam and lorazepam series (nil and 2.1%). There was no remarkable difference in the condition of the immediate newly-born related to the premedicant recieved by the mother, any small differences being much less impressive than that related to the duration of the U-D interval. No notable differences were observed in the long term conditions between the infants in the placebo, alcohol and diazepam series but the infants in the lorazepam series displayed a high incidence of ‘reluctance to feed’. If relief from preoperative anxiety-and possibly a reduction in the likelihood of awareness-without undue effect upon the infant is considered desirable, diazepam 5 mg is the preferred choice from the four drugs investigated.

Conclusion

The results of this study suggest that if it is considered advisable to give a tranquillizer orally to a patient preparatory to elective Caesarean section, the choice of diazepam (5 mg) is to be preferred to that of either 90% alcohol (10.6 ml), or lorazepam ( I mg) or, probably, chlordiazepoxide (20 mg). It could reasonably be argued that a tranquillizer should not be prescribed for those mothers who, a t the preoperative visit, declare themselves not to be anxious (35% of this series). However, there are two counter arguments to this. More than half of the patients in this category who received either diazepam or lorazepam apparently benefitted from the medication (Table l). Secondly the results afford a suggestion that pre-operative medication with diazepam (or with lorazepam) is associated with a reduced incidence of awareness or unpleasant dreams-an

Key words

ANAESTHESIA; obstetric. PREMEDICATION; alcohol, diazepam, lorazepam.

Acknowledgments

The author is most grateful to the members of the Department of Pharmacy (Queen Elizabeth Hospital and Birmingham Maternity Hospital) for the preparation and sustained provision of the coded premedicants. Thanks are also due to the junior anaesthetists attached to this hospital during the period 1977/78, who gave most of the anaesthetics which comprised the series, and who concientiously maintained the records.

Forum References 1. CRAWFORD, J.S., BURTON, M. & DAVIES, P. (1973)

Anaesthesia for section: further refinements of a technique. British Journal of Anaesthesia, 45, 726732. 2. CRAWFORD, J.S., JAMES,F.M.,

DAVIES,P. & CRAWLEY, M. (1976) A further study of general anaesthesia for Caesarean section. British Journal o/

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3. CRAWFORD, J.S. (1965) Maternal and cord blood at delivery: vertex vaginal delivery of mature infant. Parameters of respiratory exchange. Biologia Neonatorurn, 8, I 3 1-1 72. J.W., LILBURN, J.K.,NAIH,S.G. &GEORGE, 4. DUNDEE, K.A. (1977) Studies of drugs given before anaesthesia. XXVI : Lorazepam. British Journal of Anaesthesia, 49. 1047-1056.

Anaesthesia, 48, 661-667.

Anaesthesia, 1979, Volume 34, pages 897-889

Hypercapnia and hyperkalaemia H . Hassan, MB, FFARCS, Consultant, J . Gjessing, M D , Director, Anaesthetic Department, Sundsvall Hospital, Sundsuall, Sweden, and P.J . Tomlin, MB, FFA RCS, Senior Lecturer, Uniuersity Department of Anaesthetics, Queen Elizabeth Hospital, Birminghatn, B15 2TH.

It has been suggested that acute hypocapnia may cause hypokalaemia.'. Experimental studies in rats3 and in dogs4. have shown an association between hypocapnia and hypokalaemia although the extent of the hypokalaemia varied. This variation was attributed to the residual effects of the drugs used to induce anaesthesia in these studies. Edwards et aL6 suggested that over a wide range of Pacol there is an association between the serum potassium levels and the arterial carbon dioxide tension. Peritoneoscopy using carbon dioxide as the insufflating gas is a well established clinical technique. To avoid serious hypercapnia during this procedure patients are often hyperventilated using thiopentone, nitrous oxide, relaxant anaesthesia. If, in spite of this technique, some elevation of Paco, does occur these patients would provide an opportunity to determine whether hypercapnia has any effects on the serum potassium levels.

Material and methods Twenty healthy females were studied. All were undergoing peritoneoscopy for a localised gynaecological condition. The mean age was 34 years, range 19-74 years. All freely gave their consent for arterial cannulation. Anaesthesia was induced using a small amount of thiopentone (200-300 mg) followed by nitrous oxide and oxygen. Intubation was performed with the aid of relaxation using pancuronium bromide in order to avoid changes in serum potassium levels that would otherwise have resulted if succinylcholine had been Artificial ventilation was provided using a Servo ventilator adjusted to provide a minute volume of 0003-2409/1000-0897$02.00

12-15 litres and a frequency of 16 breathslmin. Once anaesthesia had been stabilised, the peritoneoscopy was started and carbon dioxide was instilled into the peritoneal cavity until the intraperitoneal pressure was 5 cm H20.The carbon dioxide was delivered from a COIPNEU (Wisap West Germany) which also measured the volume of carbon dioxide supplied and this amounted to between 4 and 5 litres. At the end of the peritoneoscopy the abdomen was compressed and any residual gas within the peritoneal cavity was discharged freely into the room air. Arterial blood samples were taken before the induction of anaesthesia, after stabilising anaesthesia, but before the carbon dioxide was instilled (this was usually 10 min after induction of anaesthesia), then during instillation and 2 min after completion of the instillation and finally 10 min after the release of the residual carbon dioxide when the patient had had the relaxant reversed and was breathing room air spontaneously. Samples were analysed in duplicate for blood gases, using a n automatic blood gas analyser* and for serum potassium levels using the hospital's flame photometer auto-analyser.

Results The results showed that the technique of anaesthesia which was used prevented serious hypercapnia, given the volumes of carbon dioxide instilled, although the control of the hypercapnia was variable in efficiency. There was a small but statistic-

* Instrumentation 0 1979 Blackwell Scientific Publication

LaboraIories 61 3 Model.

Premedication for elective Caesarean section.

Anaesthesia, 1979, Volume 34, pages 892-897 Forum Prernedication for elective Caesarean section J . Selwyn C‘rawford F F A RCS, FRCOG, Consultant An...
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