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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 <4%) was started thereafter. In 15 patients controlled hyperventilation was started immediately after loss of consciousness. EEG was recorded, and mean arterial pressure (MAP) and heart rate (HR) registered.

Results:

Epileptiform EEG patterns were seen in 13 patients in group I and in 9 patients in group D (n.s.). Periodic epileptiform discharges (PED) tended to occur more often in group I (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 ().

Keywords: EEG; Volatile anesthetics; epileptiform EEG; hyperventilation; sevoflurane

Document Type: Original Article

Affiliations: 1: Department of Anaesthesiology and Intensive Care Medicine, Helsinki University Hospital, Helsinki, 2: Department of Clinical Neurophysiology, Oulu University Central Hospital, Oulu, 3: Department of Anesthesia, Oulu University Central Hospital, Oulu, 4: Department of Anaesthesiology and Intensive Care Medicine, Helsinki University Hospital, Helsinki, Finland

Publication date: 2000-07-01

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