Activation of electrocorticographic activity with remifentanil and alfentanil during neurosurgical excision of epileptogenic focus

Background. Opioids are known to stimulate surface electroencephalographicactivity in patients with temporal lobe epilepsy. The objectiveof the current study was to compare the electrocorticographicactivation effects of the newer short-acting opioid remifentanilwith those of alfentanil during epilepsy surgery under generalanaesthesia. Methods. Thirteen patients undergoing temporal lobe epilepsysurgery under general anaesthesia received alfentanil 30 µg kg^–1and remifentanil 1 µg kg^–1 as i.v. bolusesin sequence. The design was a randomized double-blind cross-overstudy. After opening the dura, electrocorticogram (ECoG) electrodecontact strips were placed over the temporal and supratemporalneocortex and depth electrodes were inserted in the amygdalaand hippocampus. Alfentanil 30 µg kg^–1or remifentanil 1 µg kg^–1 were administeredrandomly in a blinded fashion. The ECoG was recorded continuouslybefore and after the injection of each drug. The interictalepileptiform activity (spikes and sharp waves) above baselinewas analysed. Results. Both drugs increased epileptiform activity especiallythat recorded from depth electrodes in the temporal limbic structures.No epileptiform activity was recorded from the electrodes overlyingthe supratemporal neocortex before or after drug administration.The more potent activator was alfentanil, which caused an increasein activation from baseline of 99.8% compared with 67.4% forremifentanil. In addition, alfentanil activated the epileptiformactivity in 3 patients in which remifentanil had no effect.There were no changes in heart rate after the opioid boluses.Both remifentanil and alfentanil caused significant reductionsin blood pressure at 3 and 5 min after administration. Conclusion. We conclude that at the doses used in this study,alfentanil is the better opioid for intraoperative activationof the ECoG in neurosurgical patients undergoing resection ofa temporal lobe epileptic focus. This pharmacological activationof epileptiform activity assists in localizing and confirmingthe site of surgical excision. Neither alfentanil nor remifentanilactivated epileptiform activity in non-epileptic brain tissue. Br J Anaesth 2003; 91: 651–5