EEG changes during awake carotid endarterectomy

To determine the reason for differing shunt rates based on electroencephalographic (EEG) and neurologic changes during general and regional anesthetic, respectively, we compared simultaneous EEG tracings and neurologic status in 135 patients undergoing carotid endarterectomy (CEA) under cervical block over a 30-month period. The decision to shunt in these patients was made on the basis of neurologic changes only irrespective of EEG findings. This group was then compared to the 288 patients undergoing CEA under general anesthetic with EEG monitoring over the same period. EEG changes occurred in 7.4% of awake patients and 15.3% of asleep patients (p < 0.03). The rates of ipsilateral hemispheric changes were similar, but no awake patient manifested global EEG changes with clamping while 3.5% of patients under general anesthesia did (p < 0.04). Global, but not hemispheric, changes were correlated with systolic blood pressure variability during clamping. This implies that global EEG changes in anesthetized patients may be the result of the anesthetic technique itself, and that cervical block may in fact be cerebroprotective.