Anaesthesia, 1976, Volume 31, pages 205-21 1

Anaesthetic induction for Caesarean section with propanidid

M. C. M A H O M E D Y , J. W. D O W N I N G , D. E. J E A L

A N D A.

J. C O L E M A N

Propanidid is a good anaesthetic and analgesic agent, and, unlike the ultra shortacting barbiturates, it is non-cumulative. After intravenous injection into the maternal circulation at Caesarean section, propanidid crosses the placental barrier. Despite rapid equilibration between mother and foetus, reports indicate that drug-induced neonatal depression occurs infrequently after propanidid admini~tration.’-~ In contrast, the biodegradation of thiopentone is slow, as recovery from anaesthesia occurs by redistribution. Depression of the newborn at birth by barbiturates has been described, particularly when large doses of the drug are The authors have previously detailed the use of propanidid as the sole anaesthetic agent for Caesarean ~ e c t i o nTheir . ~ results confirmed the relative lack of drug induced neonatal depression with propanidid but the infants exhibited an undesirable degree of metabolic acidaemia with the technique described-a finding possibly related to the assumption of the supine position by the mother during surgery.**’ This report describes the use of propanidid for the induction of anaesthesia at Caesarean section in the lateral tilt position. The results are compared with those of a previous similar series anaesthetised with thiopentone.’

Material and methods Fifty patients in the lower socio-economic group were included in this study. All the mothers, who gave their consent to the investigation, fulfilled the criteria of Crawford’s ‘clinically acceptable ideal case’. There was no evidence of placental insufficiency, and the parturients were clinically free of serious systemic disease. Gestational age was between 36 and 42 weeks; cases of multiple pregnancy were excluded. The patients were not in labour and their membranes were intact. The pre-operative management of the mothers has been described in previous communications.’*” An infusion of Ringer’s lactate solution was commenced in the M.C.Mahomedy, FFARCSI, Principal Anaesthetist, J.W.Downing, MB, BCh, FFA(SA), FFARCS, Professor & Head, D.E.Jeal, BM, BCh, FFARCS, DRCOG, Principal Anaesthetist, Department of Anaesthetics, University of Natal Medical School, P.O. Box 17039, Congella, Durban, South Africa, and A.J.Coleman, MB, BS, FFARCS, Consultant Anaesthetist, Department of Anaesthetics, Northwick Park Hospital, London.

205

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M . C. Mahomedy et al.

operating theatre. Atropine 0.6 mg and alcuronium 2.5 mg were administered intravenously, thereafter anaesthesia was induced by injecting into the infusion tubing, a mixture of propanidid (7 mg/kg) and suxamethonium (2 mg/kg). The doses of propanidid ranged from 400 to 600 mg, and suxamethonium from 100 to 150 mg. The rationale behind this induction sequence, and the precautions adopted to avoid accidental pulmonary aspiration of gastric contents, have been discussed A further dose of propanidid (1-2 mg/kg) was administered 3 minutes after the induction dose, in order to ensure anaesthesia during equilibration of the maternal blood with a narcotic tension of nitrous oxide. Ventilation of the lungs was controlled mechanically, using a Manley ventilator delivering an expired minute volume of 8-10 litres. Further muscle relaxation was obtained by giving ‘alloferin’ 10-1 5 mg. Anaesthesia was maintained using 60-65% nitrous oxide and oxygen prior to delivery of the foetus. Thereafter halothane 05% or enthrane 1% vapour was added to the inspired gases. Pethidine 50 mg was administered by intravenous injection after delivery. At the termination of surgery, the residual effects of alcuronium were reversed with intravenous atropine 1.2 mg and neostigmine 3.5 mg. Maternal arterial and foetal umbilical blood samples were obtained for blood-gas and acid-base analysis. Methods used have been described previously.’ The clinical assessment ofthe newborn was also similar to that in our earlier r e p ~ r t . ~ The measurement of arterialpH, carbon dioxide (Paco,), and oxygen (Pao,) levels in the mothers and infants, and the determination of base deficit values, including corrections for haemoglobin desaturation in the umbilical cord blood, have also been de~cribed.~ Post-operative care and assessment. The mothers were interviewed on the first postoperative day in an attempt to elicit the incidence of awareness and dreaming during anaesthesia. Enquiries were made regarding the occurrence of nausea, vomiting and productive coughing. The chest was examined clinically, and pyrexia not in keeping with the extent of surgery, noted.

Results Dosage and induction to delivery intervals The average maternal weight in this series was 71.2 kg (s.e.m. 1.4). The mean dosage of propanidid used for the induction of anaesthesia was 482 mg (s.e.m. 5 . 9 , and the average supplementary dose was 118.5 mg. (s.e.m. 7.0). The mean induction to delivery interval was 10.6 minutes (s.e.m. 0.48). This compares favourably with our previous thiopentone series where the mean induction to delivery interval was 9-8 minutes (s.e.m. 0.5).9

Apgar minus colour scores Five infants appeared mildly depressed at birth (Apgar minus colour score between 5 and 6). Severe neonatal depression (Apgar minus colour less than 5 ) was encountered in one infant. Mean Apgar minus colour score 2 minutes after delivery was 7.48 (s.e.m. 0.14). These results are comparable to those we reported after thiopentone anaesthe-

~ia.~

Induction with propanididfor Caesarean section

207

Blood-gas and acid-base studies Table 1 compares the blood-gas/acid-base status of the mothers before induction of anaesthesia, and at delivery in our present series with those following thiopentone induction of anae~thesia.~ Generally, a mild respiratory alkalosis with a compensatory metabolic acidosis was present in the mothers before induction of anaesthesia Table 1. Mean maternal blood-gas status before induction (FIo, 100%) and at delivery (FIOZ 3 5 4 % ) Group Propanidid

(s.e.m.)

PH 7.430 Pre-induction Pre-delivery 7.381 Pco2 (mmHg) Pre-induction 28.6 Pre-delivery 30.9 Po2 (mmHg) Pre-induction 460.0 Pre-delivery 132.9 Base deficit (mEq/litre) Pre-induction 48 Pre-delivery 5.7

Thiopentone

(0010) (0.007)

(s.e.m.)

Levels of significance

(0.007) (0.006)

NS* NS

7.41 1 7.383

NS NS

28.1 31.7 468.5 151.3

(11.7) (4.9)

NS

P< 0.025 NS NS

5.6 5.3

* NS,not significant. Table 2. Mean umbilical venous (Uv) and arterial (Ua) blood-gas status Group Propanidid

(s.e.m.)

Thiopentone

(s.e.m.)

Levels of significance

7.313 7.260

(0.006) (0.005)

P< 0~001 P< 0.001

PH

uv

7.259 (0.011) Ua 7.206 (0.012) Pco2 (mmHg) UV 46.3 Ua 54.3 Po2 (mmHg) uv 25.9 Ua 15.4 Oxygen saturation (%) UV 50.4 Ua 22.7 Base deficit (mEq/litre) uv 9.0 Ua 11.8

42.5 51.7

P< 0.05 NS*

33.9 18.9

P< 0.001 P< 0.025

71.7 34.9

P< 0~001 P< 0~005

5.9 7.9

P< oao1 P< 0.001

* NS,not significant.

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M.C. Mahomedy et al.

and at delivery in both series. The mean maternal arterial oxygen tension just before delivery of the foetus, however, was significantly lower in the propanidid series. Table 2 presents the umbilical venous and arterial blood-gas analysis; a degree of metabolic acidaemia is revealed which was markedly greater in the propanidid group than that seen previously in infants delivered following thiopentone anae~thesia.~ Umbilical venous carbon dioxide levels were also significantlyhigher, while both foetal venous and arterial oxygen tensions and oxygen contents were notably lower in the present propanidid series. The mean maternal arterial to umbilical cord blood blood-gas gradients can be seen in Table 3. Significantly greater pH and base deficit (Ma-Uv and Ma-Ua) gradients were apparent in the propanidid group. Mean carbon dioxide gradients between mother and foetus were also higher in the propanidid group but the difference was only significant regarding the (Ma-Uv) Pco, gradient. Mean umbilical venous to arterial blood-gas gradients are shown in Table 4. The base deficit (Uv-Ua) gradient was significantly greater after propanidid, whereas the oxygen (Uv-Ua) gradient was materially less. Table 3. Maternal to foetal blood-gas gradients Group Propanidid PH (Ma-Uv) 0122 (Ma-Ua) 0.175 Pcol (mmHg) (Ma-Uv) 16.7 (Ma-Ua) 23.4 Base deficit (mEq/litre) 41 (Ma-Uv) (Ma-Ua) 6.5

(s.e.m.)

Thiopentone

(0.009) (0010)

0.124

0.069

(1.5)

(s.e.m.)

Levels of significance

(0~004) (0,006)

P

Anaesthetic induction for Caesarean section with propanidid.

Anaesthesia, 1976, Volume 31, pages 205-21 1 Anaesthetic induction for Caesarean section with propanidid M. C. M A H O M E D Y , J. W. D O W N I N G...
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