Carotid endarterectomy monitoring: patterns of spectral EEG changes due tocarotid artery clamping

Objective: The purpose of the study was to make an objective and quantitati ve analysis of the EEG changes caused by carotid artery clamping during car otid endarterectomy (CEA) monitoring. Methods: Factor analysis was used to study the intraoperative spectral EEG changes in 94 patients during clamping of the carotid artery. In addition, the relation between the extracted factors and the changes in blood pressur e and blood flow velocity in the middle cerebral artery during clamping was studied. Results: Two factors were extracted with factor analysis. The first factor represented a change in power in the alpha and beta frequency ranges in com bination with a less pronounced opposite change in power in the delta frequ ency range. The second factor represented a change in power restricted to t he delta and theta frequencies. With the first factor, two types of spectra l EEG changes could be distinguished: changes indicative of cerebral ischem ia (decrease in fast activity and increase in slow activity) and the opposi te changes suggesting cerebral activation (arousal). With the two factors c ombined, the changes indicative of minor ischemia (decrease in fast activit y only) could also be distinguished. Conclusion: Further study is required to test whether patients showing the EEG changes indicative of activation or minor ischemia actually require shu nting. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.