Relationship of pre- and postanesthetic EEG abnormalities to enflurane-induced seizure activity.

Abstract

In 12 subjects, serial electroencephalograms (EEGs) following a standard exposure to enflurane anesthesia were evaluated with respect to (1) preanesthetic baseline EEGs, and (2) the occurrence of clinical or electrographic epileptiform EEG activity during anesthesia. There were no consistent predictors of enflurane-induced seizure activity in the preanesthetic EEG recordings, although the one patient of the group with a marginal preanesthetic EEG abnormality manifested the largest number of seizures during anesthesia (but none subsequently). No specific relationship was found between the duration of postanesthetic EEG changes and the occurrence of a seizure during anesthesia. Postanesthetic EEGs from all subjects showed diffuse slowing. Three specific electrographic alterations were also found: (1) In all 12 subjects, the alpha frequency decreased by 1 to 4 Hz for 2 to 6 days after anesthesia. (2) In 8 subjects, posterior intermittent rhythmic delta activity persisted for 6 to more than 30 days after enflurane. (3) An increased amplitude and incidence of benign incidental preanesthetic focal EEG findings seen in 6 subjects could be demonstrated for 2 to 30 days after anesthesia. In general, EEG changes were seen for 6 to 30 days after anesthesia, but at no point did de-novo EEG epileptiform activity appear in any subject following anesthesia.