PREOPERATIVE CEREBROVASCULAR SYMPTOMS AND ELECTROENCEPHALOGRAPHIC ABNORMALITIES DO NOT PREDICT CEREBRAL-ISCHEMIA DURING CAROTID ENDARTERECTOMY

Background and Purpose The purpose of this prospective study was to es tablish (1) whether patients with neurological symptoms scheduled for carotid endarterectomy had an increased incidence of electroencephalog raphic (EEG) abnormalities during awake baseline recordings, (2) wheth er these symptoms and EEG abnormalities predicted ischemic EEG pattern changes at carotid artery cross-clamp, and (3) whether there was an a ssociation between age, presence of EEG baseline abnormalities, and is chemic pattern changes at carotid artery cross-clamp. Methods We revie wed the medical record of each patient scheduled to undergo carotid en darterectomy and recorded the patient's age and history of previous ne urological symptoms. We then continuously monitored and analyzed 16 ch annels of anteroposterior bipolar EEG and two of referential derivatio ns from at least 5 minutes before induction of anesthesia and througho ut the operation. Results We completed 394 consecutive studies. Preope rative neurological symptoms were related to EEG abnormalities in awak e patients (P<.001) and to EEG asymmetries in anesthetized patients (P <.001). Abnormal awake EEG findings were associated with asymmetries a fter anesthesia (P<.0001). Twenty-eight percent of both symptomatic (7 0/249) and asymptomatic (41/145) patients had EEG ischemic pattern cha nges at carotid artery cross-clamp. Neither neurological symptoms nor EEG abnormalities were associated with age or the development of EEG i schemic pattern changes at carotid artery cross-clamp. Conclusions Des pite the strong association between a history of cerebral ischemic sym ptoms and preoperative EEG abnormalities in patients undergoing caroti d endarterectomy, patients who have suffered strokes or transient isch emic events are at no greater risk of having EEG evidence of cerebral ischemia during carotid artery cross-clamp than patients without sympt oms and with normal baseline EEGs. We conclude that preoperative EEG a bnormalities in symptomatic patients are not due to age or to insuffic iency of regional cerebral blood flow.