Comparison of the placental transfer of halothane, enflurane, sevoflurane, and isoflurane during cesarean section.

The concentrations of placental transfer of halothane (H), enflurane (E), sevoflurane (S), and isoflurane (I) were measured in 46 patients during cesarean section. The mean inhalation times of H (0.5%), E (1%), S (0.8%), and I (0.6%) were 13 min 27 s, 13 min 49s, 13 min 20s, and 8 min 8s, respectively. The mean concentrations in the maternal artery (MA) were 5.2mg·dl-1 in H, 12.3 mg·dl-1 in E, 5.2mg·dl-1 in S, and 2.4mg·dl-1 in I. The concentration ratio between the MA and the fetal umbilical vein (UV) was 0.44 for H, 0.49 for E, and 0.38 for S, and these ratios were not significantly different for these anesthetics. Although the concentration ratio for I (0.27) was significantly lower than those of the other three anesthetics, the UV:MA ratio was calculated to be 0.4 for an inhalation time 13 min. Our result, therefore, suggests that if the inhalation times were equal, the ratios of placental transfer would not differ among these four inhalational anesthetics. The Apgar scores in these four groups were not different from that in the group given only 66% nitrous oxide in oxygen as anesthetic (N2O group). The cardiovascular changes induced by skin incision were bigger in the N2O group than in the other groups. The use of a low concentration of H, E, S, or I is, therefore, suggested to be a useful and acceptable anesthetic method for cesarean section.