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


CONCLUSIONS
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.
Vakkuri
A
A
Department of Anaesthesiology and Intensive Care Medicine, Helsinki University Hospital, Finland. anne.vakkuri@hus.fi
Jantti
V
V
Särkelä
M
M
Lindgren
L
L
Korttila
K
K
Yli-Hankala
A
A
D000328:Adult; D000769:Anesthesia, Inhalation; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000009:adverse effects*; D001794:Blood Pressure / Q000187:drug effects; D004569:Electroencephalography / Q000187:drug effects*; D004827:Epilepsy / Q000139:chemically induced*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006985:Hyperventilation / Q000503:physiopathology*; D017214:Laryngeal Masks; D008297:Male; D008738:Methyl Ethers / Q000008:administration & dosage / Q000009:adverse effects*; D008875:Middle Aged; D000077149:Sevoflurane
D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane