Inadequate hypnosis in the absence of opioid analgesia may account for the increased incidence of awareness in caesarean section before delivery of the neonate. We investigated the concentration of sevoflurane and isoflurane required to maintain bispectral index (BIS) <60 unit1 delivery occurred. We enrolled 40 ASA physical status I, 11 parturients in an up-down sequential allocation study (group I (sevoflurane group) 20 patients and group 11 (tsoflurane group) 20 patients). The median effective end-tidal concentration (EC50) of sevoflurane and isoflurane was defined as that which maintain BIS<60 between skin incision and delivery in 50% of patients. The EC50 for sevoflw-ane and isoflurane was 1.2% (1.06-1.31) and 0.8% (0.64-0.92) respectively. There was no postoperative awareness in all patients in both groups. There were no differences regard haernodynamic parameters (HR-MAP) between both study groups. We conclude that sevarane concentration of at least 1.2-1.3% and isoflurane concentration of at least 0.8-0.9% should be administered during caesarean section to minimize the risk of awareness and recall |
