Isoflurane or halothane for cesarean section: comparative maternal and neonatal effects.

The maternal and neonatal effects of isoflurane and halothane combined with 50% N2O - 50% O2 were compared in 60 healthy parturients undergoing primary or repeat cesarean section. All patients had rapid sequence induction of anesthesia with sodium thiamylal 4 mg/kg followed by succinylcholine for tracheal intubation. Patients were randomly assigned to one of three groups of 20 each (inspired 0.5% isoflurane, 1% isoflurane or 0.5% halothane), combined with 50% N2O and O2. After delivery, 67% N2O in O2 was used, supplemented by butorphanol. Maternal blood loss did not differ significantly among the three groups and none of the patients developed intraoperative awareness. At the time of delivery, maternal plasma epinephrine levels were significantly above preinduction levels in the 0.5% isoflurane group but unchanged in the other two groups. Neonatal status as ascertained by Apgar scores, cord acid base status and the Neurologic and Adaptive Capacity Scores (NACS) was equally good in the three groups of patients. Serum inorganic fluoride concentrations in the mother after anesthesia were not significantly above preanesthetic levels in any of the groups and there was no biochemical evidence of renal toxicity. In all neonates fluoride ion concentrations in the first voided urine sample were less than 7 mumol/l, a value well below that associated with nephrotoxicity. It is concluded that isoflurane is a safe supplement to N2O - O2 mixture for cesarean section and is a safer alternative to halothane in situations when patients receiving beta-adrenergic therapy require cesarean section since halothane might potentiate arrhythmias caused by beta adrenergic agonists.