Maximum FIO2 during caesarean section

Forty patients undergoing elective and emergency Caesarean section (excluding severe fetal distress) were divided into four groups to receive 50% oxygen, 50% nitrous oxide, and 0.5% halothane (group 1, controls) or 100% oxygen supplemented by 1.5 x MAC of halothane, enflurane or isoflurane (groups 2,3,4, respectively) reducing to 1.0 x MAC 5 min after induction. The umbilical venous PO2 in the oxygen-only groups was higher than in the oxygen-nitrous oxide groups, this difference reaching statistical significance when the patients in the oxygen-only groups were combined. Blood loss and uterine contractility were unaffected by the increased concentrations of volatile agents, and awareness did not occur. Improved cardiovascular stability was demonstrated in the elective high-oxygen groups. The technique is safe and warrants further study, since there are no important ethical objections.