Figure 2. Representative electroencephalograms at 1 and 4 h of anesthesia at 1.5 MAC. Electroencephalogram (EEG) recordings showed frequent burst (sharp or spike wave, 50–100 micro V) and suppression in the isoflurane group, whereas in the halothane and sevoflurane groups, 13–15-Hz (50–100 micro V) and 9–13-Hz activities (70–100 micro V) were predominant, respectively. There were no apparent changes in EEG pattern with time in all three groups.