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

Summary 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 O 2 ), in 50% oxygen and 50% nitrous oxide (group N 2 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 O 2 ( MAC IE O 2 ) was 5.30 (5.12‐5.48)% (median [95% CI]). The MAC IE in group N 2 O ( MAC IE N 2O ) was 5.83 (5.67‐5.99)%. The MAC IE in group FENTANYL ( MAC IE FENTANYL ) was 5.37 (5.21‐5.53)%, which was close to MAC IE O 2 . Conclusion The MAC IE of sevoflurane calculated in 100% O 2 was 5.30% in children. Addition of 50% N 2 O modestly increased MAC IE of sevoflurane, while 3 μg/kg fentanyl had no effect on MAC IE of sevoflurane.