Intravenous Propofol during Cesarean Section

Abstract

Placental transfer and neonatal effects of propofol were investigated in 21 women undergoing elective cesarean section under general anesthesia. This study was conducted in two separate phases according to the use of propofol. In both phases, anesthesia was induced with an iv bolus of 2.5 mg/kg of propofol. In phase 1 (n = 10), anesthesia was maintained with 50% nitrous oxide in oxygen and halothane. In phase 2 (n = 11), a continuous infusion of propofol at a rate of 5 mg.cntdot.kg-1.cntdot.h-1 was started after the induction dose. Maternal venous and umbilical cord arterial and venous samples were obtained at delivery. The propofol concentration in whole blood was measured with a high performance liquid chromatography method. Where possible, breast milk/colostrum was expressed for both phases postoperatively and a sample of blood was collected during phase 2 from neonates via a heel prick 2 h after birth. Propofol crossed the placenta, as demonstrated by concentrations found in umbilical venous blood in phase 1 (0.13-0.75) .mu.g/ml) and in phase 2 (0.78-1.57 .mu.g/ml). At delivery, the ratio of the drug concentration in umbilical venous blood to that in natural blood was 0.70 .+-. 0.06 for phase 1 and 0.76 .+-. 0.10 for phase 2. The ratio of propofol concentration in the umbilical artery to that in the umbilical vein was 1.09 .+-. 0.04 for phase 1 and 0.70 .+-. 0.05 for phase 2. The mean propofol concentration in samples taken via a heel prick 2 h after birth in 8 neonates during phase 2 was low (0.078 .+-. 0.011 .mu.g/ml) and represented about 10% of the corresponding umbilical cord artery concentration at time of delivery. The very limited milk/colostrum data indicated that propofol concentrations were low (phase 1:0.089-0.24 .mu.g/ml; phase 2: 0.04-0.74 .mu.g/ml). Furthermore, propofol is cleared rapidly from the neonatal circulation and exposure of the neonate through breast milk/colostrum would be negligible compared to the placental transfer of the drug. In both phases, propofol seemed to have minimal efects on the healthy newborns. These results justify the performance of additional studies of propofol administration during general anesthesis for cesarean section, especially to compare propofol with thiopental and to evaluate the effect of this drug on the high risk fetus.