The influence of intravenous anaesthetics on enflurane-induced central nervous system seizure activity

This study assesses the effects of agents commonly used in anaesthesia on enflurane-induced seizure threshold and on established seizure activity, during steady state enflurane anaesthesia. EEG seizure activity was monitored in cats from chronic cortical and subcortical recording sites. Diazepam, thiopentone, methohexitone and ketamine all enhanced established EEG seizure challenge. This latter effect was most evident under conditions of lowered PaCO2. The effects of these intravenous agents on established enflurane seizure patterns exceeded in duration the expected EEG effect of the agent when used alone. The limited number of experiments, however, precluded statistical verification of our findings. The similarities between centrencephalic minor motor seizures and enflurane seizure pattern in terms of EEG and convulsive expression, including drug response, are noted.