Determination of the minimal alveolar concentration of sevoflurane associated with isoelectric electroencephalogram in children: A prospective, randomized, double‐blind study

OBJECTIVE: We investigated the minimal alveolar concentration (MAC) of sevoflurane associated with the occurrence of isoelectric electroencephalogram in 50% of children under steady-state conditions (MAC IE). The MAC IE was determined in 100% oxygen and with the addition of 50% nitrous oxide or after the injection of fentanyl. METHODS: Seventy-two children (ASA I or II, age 3-8 years) undergoing elective surgery were allocated to one of three groups: in 100% oxygen (group O2 ), in 50% oxygen and 50% nitrous oxide (group N2 O), or in 100% oxygen with a bolus of 3 μg/kg fentanyl (group FENTANYL). The state of isoelectric EEG was considered as significant when a burst suppression ratio of 100% lasted for >1 minute. The MAC IE was determined by the Dixon's up-and-down method after a 15-minute period with a stable endtidal concentration of sevoflurane. The concentration of sevoflurane was determined by the electroencephalogram of the previous patient: increase of 0.2% if isoelectric EEG were absent or decrease of 0.2% if isoelectric EEG were present. RESULTS: The MAC IE in group O2 (MAC IEO2 ) was 5.30 (5.12-5.48)% (median [95% CI]). The MAC IE in group N2 O (MAC IEN2O ) was 5.83 (5.67-5.99)%. The MAC IE in group FENTANYL (MAC IEFENTANYL ) was 5.37 (5.21-5.53)%, which was close to MAC IEO2 . CONCLUSION: The MAC IE of sevoflurane calculated in 100% O2 was 5.30% in children. Addition of 50% N2 O modestly increased MAC IE of sevoflurane, while 3 μg/kg fentanyl had no effect on MAC IE of sevoflurane.