BACKGROUND: In cases that receive inhalation anesthesia for cesarean section, there is a high risk of recall. So the bispectral index (BIS) is useful for measuring the depth of anesthesia. This study was designed to determine optimal inspiratory sevoflurane concentrations and BIS index values during cesarean section.

METHODS: We randomized 30 patients scheduled for elective cesarean section to receive inspiratory sevoflurane 1.0 vol% (group 1, n = 10), inspiratory sevoflurane 1.5 vol% (group 2, n = 10), inspiratory sevoflurane 2.0 vol% (group 3, n = 10) in a 50% nitrous oxide oxygen mixture. Each group was assessed for BIS, blood pressure, heart rate, and end tidal sevoflurane concentration at the point of preinduction, skin incision, uterine incision, delivery, and at 1, 2, 3, 5 and 10 minutes after delivery. Responsiveness to verbal commands using the Tunstall isolated forearm technique, was detected throughout the study period. Neonatal effect was assessed using Apgar scores at 1 and 5 minutes.

RESULTS: The BIS index was lower in group 3 than in group 1 from the point of delivery (P<0.05) and the BIS index in group 2 was lower than in group 1 from 1 minute after delivery (P<0.05). However blood pressures, heart rates, and Apgar scores were not significantly different among the groups. No awareness was observed any subject.

CONCLUSIONS: We found that the use of inspiratory sevoflurane 2.0 vol% (endtidal 1.2 vol%) maintained a BIS index of under 60.