Comparison of simultaneous electroencephalographic and mental status monitoring during carotid endarterectomy with regional anesthesia

Purpose: This study examines the accuracy of intraoperative electro encepha lographic (EEG) monitoring for the detection of cerebral ischemia by compar ing EEG with simultaneous mental status evaluation (MSE) during carotid end arterectomy in awake patients. Methods: Between 1994 and 1997, 208 consecutive carotid endarterectomies we re prospectively evaluated for cerebral function during surgery with simult aneous MSE and EEG monitoring. Regional anesthesia (RA), which consisted of superficial cervical block, was chosen preferentially in 75% of the cases, with general anesthesia (GA) reserved for the patients who did not fulfill the criteria for RA. When available, 8-channel EEG monitoring was performe d (59% with RA and 55% with GA). Results: The EEG was a reliable predictor in comparison with MSE in most bu t not ail cases of cerebral ischemia. Significant neurologic changes were n oted using MSE in 4 of 89 patients (4.5%) that were not detected using EEG (false negative results). Conversely, 6 of 89 cases (6.7%) showed unilatera l slowing without associated changes in MSE (false positive results). For t he awake patients, 21 of 150 cases (14%) showed MSE changes that required a shunt. By contrast, 9 of 32 GA cases (28%) shorted EEG changes that would have led to shunting (P = NS). In the RA group, there were no strokes versu s 3 of 58 cases (5.2%) with strokes in the GA group. Two of 150 cases (0.1% ) had transient ischemic attacks in the RA group. There was 1 myocardial in farction in the GA group; no deaths occurred in this series. Conclusion: EEG monitoring yielded a significant number of false positive ( 6.7%) and false negative (4.5%) results in the detection of neurologic defi cits when compared with MSE in the awake patients. In this series, the pref erential use of RA resulted in less shunt use and was possibly associated w ith a lower stroke rate.