The effects of remifentanil on epileptiform discharges during intraoperative electrocorticography in patients undergoing epilepsy surgery

Purpose: High-dose i.v. opioids (e.g., alfentanil, 50 mug/kg bolus) are kno wn to increase the intraoperative reading of epileptiform activity during e pilepsy surgery (ES), thereby facilitating localization of the epileptogeni c zone (i.e., the site of ictal onset and initial seizure propagation). How ever, this phenomenon has not been studied with remifentanil (i.e., a novel ultra-short acting opioid). The purpose of the present study was to evalua te the effect of remifentanil on electrocorticography (ECoG) during ES. Methods: After Institutional Review Board approval, 25 adult patients under going elective ECoG-guided anterior temporal corticectomy were enrolled. At the time of ECoG, anesthesia consisted of inhaled isoflurane less than or equal to0.1% (end-tidal) in 50% N2O, and i.v. fentanyl, 2 mug/kg/h and vecu ronium. Patients were maintained at normocapnia and normoxia during ECoG. A fter acquisition of baseline ECoG, bolus remifentanil, 2.5 mug/kg i.v., was administered. The number of epileptiform spikes occurring 5 min before and after this bolus were compared by using a one-sided sign test; p values le ss than or equal to0.05 were considered statistically significant, Results: When compared with baseline ECoG, bolus i.v. remifentanil signific antly increased the frequency of single spikes or repetitive spike bursts i n the epileptogenic zone while suppressing activity ill Surrounding normal brain. Conclusions: During ES, remifentanil enhanced epileptiform activity during intraoperative ECoG. Such observations facilitate localization of the epile ptogenic zone while minimizing resection of nonepileptogenic eloquent brain tissue. Although not specifically evaluated in this study, we speculate th at remifentanil's short elimination half-life will facilitate neurologic fu nction testing immediately after ES. Should this be the case, we envision r emifentanil has the potential to supplant other opioids (e.g., alfentanil) during ECoG-guided ES.