Epileptiform EEG during sevoflurane mask induction: Effect of delaying the onset of hyperventilation

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Abstract
Background: Hyperventilation during sevoflurane‐N2O‐O2 mask induction in adults is associated with a hyperdynamic circulatory response and epileptiform electroencephalogram (EEG). We tested the hypothesis that delaying onset of hyperventilation will prevent severe (periodic) epileptiform EEG and hyperdynamic response. Methods: Thirty patients were randomized to receive either delayed (group D, n=15) or immediate (group I, n=15) onset of hyperventilation during sevoflurane (8% in N2O 50%) mask inhalation induction with single‐breath method for unconsciousness. Fifteen patients were allowed to breathe spontaneously for 2 min after loss of consciousness and controlled hyperventilation (ETCO2 P=0.07). Heart rate and MAP were higher in group I than in group D from 2 min to 3 min (P<0.05), and both HR and MAP rose significantly from the baseline in group I. In group D, HR but not MAP rose significantly from baseline. Conclusion: Regardless of its timing, hyperventilation at a high sevoflurane concentration produced severe epileptiform EEG with a hyperdynamic response. PED tended to occur more often with immediate onset of hyperventilation ( 1).