EPILEPTIFORM ACTIVITY DURING OPIOID ANESTHESIA

The proconvulsant properties of exogenously administered opioids in ma n are not established. We prospectively evaluated relationships betwee n epileptiform activity and opioid dose in 20 patients undergoing coro nary artery revascularization. Baseline electroencephalograms were per formed before surgery. Ten subjects were given fentanyl and 10 sufenta nil, at 100 mu g/kg and 10 mu g/kg, respectively, in 4 divided doses, 3 min apart. Midazolam (4 mg) was given 3 min after the last dose of n arcotic. Serum opioid concentrations were measured by radioimmunoassay . Within 3 min of the first opioid dose, 19 of 20 patilnts developed e pileptiform activity, characterized by generalized single and multipha sic, low-to-moderate voltage spike discharges, similar in appearance t o benign epileptiform transients of sleep (BETS). Despite continuously increasing serum concentrations of opioid, the number of spike discha rges initially increased during the first and second dose intervals an d then declined during the third and fourth dose intervals. This disso ciation between epileptiform discharges and measured serum opioid conc entration was unexpected and remained unexplained. Spike activity was consistently attenuated (P = 0.000003) within 20 sec of midazolam admi nistration. Abrupt cessation of discharges after administration of the anticonvulsant, midazolam, suggests an epileptogenic mechanism for th e opioid-induced activity.