Comparison of the placental transfer of thiopental and diazepam in caesarean section.

Drug concentrations were measured in whole blood obtained from mother and child after induction of general anaesthesia with thiopental or diazepam and delivery by Caesarean section. In 27 cases given thiopental 3 mg/kg intravenously the 5-min child/mother concentration ratio rose with increasing injection-delivery (I-D) interval up to 8-10 min. The concentration in the newborn at 2 h showed a similar trend. In 30 cases given diazepam 0.3 mg/kg for sleep induction, there were some low values in cases delivered within 4 min after the injection. However, higher neonatal concentrations and child/mother ratios were observed when the operation lasted 4-5 min, and there was no further increase in cases with longer I-D intervals. There is evidence to suggest that net transfer to the fetus proceeds at a slower rate with thiopental than with diazepam. However, in the present series of low risk elective Caesarean sections, there was no appreciable difference between the induction agents with regard to their effect on the newborn infant.