VALUE OF PREOPERATIVE EEG FOR CAROTID ENDARTERECTOMY

Purpose: This study was designed to determine whether the preoperative , baseline electroencephalogram (EEC) can be used for intraoperative d ecision making during carotid endarterectomy, and to identify circumst ances where the EEG can be eliminated. Methods: The charts of all pati ents undergoing carotid endartectomy at the authors' institution from June 1991 to May 1995 were reviewed to identify those patients that ha d adequate pre- and intraoperative EEG monitoring. EEGs during 331 car otid endartectomies in 303 patients were coded without knowledge of ou tcome; primary and secondary endpoints were EEG changes with clamping and clinical outcome, respectively. Results: The incidence of mortalit y and major neurological morbidity was 1.8%. Baseline-EEGs were abnorm al in 105 patients (32%). Whereas baseline-EEG changes were highly pre dictive of EEG changes after anesthetic induction (P < .0001), they we re not predictive of EEG changes with clamping or of clinical outcome, Prior stroke (CVA) predicted abnormal baseline-EEGs (P < .0001) and a bnormal post-anesthetic EEGs (P < .0001) but did not predict changes w ith clamping or perioperative CVA. EEG changes with clamping occurred during 18% of operations: such changes were predicted only by contrala teral occlusion (P < .0016) and EEG changes during a prior contralater al carotid endartectomy (P < .0001). The only variable that predicted an adverse neurological outcome was the presence of contralateral occl usion, which increased the likelihood of a perioperative neurological event seven-fold (P = .0038). Clinical outcomes in the 57 of 105 patie nts with abnormal baseline-EEGs and the 49 of 83 with prior CVA who we re shunted were not different from those who were not. Conclusions: ba seline-EEG is not of value for the prediction of adverse events during carotid endartectomy and can be eliminated. Because contralateral occ lusion is highly predictive of changes with clamping, and patients und ergoing a second carotid endartectomy will usually manifest EEG change s identical to those at the first, operative EEG monitoring can also b e eliminated from both these circumstances. Finally, prior stroke does not lead to a higher incidence of clamp-induced EEG changes, and thus is not an indication for shunting in and of itself. (C) 1998 The Inte rnational Society for Cardiovascular Surgery. Published by Elsevier Sc ience Ltd. All rights reserved.