EEG evidence for shunt requirement during carotid endarterectomy - OptimalEEG derivations with respect to frequency bands and anesthetic regimen

Currently there is no consensus on the derivations that should be used for EEG monitoring during carotid endarterectomy (CEA). The aim of this study w as to determine which derivations distinguish the best between patients req uiring a shunt and patients who do not need a shunt. Four predefined freque ncy bands and two regimens for general anesthesia (isoflurane versus propof ol) were used. EEG data (16 channels) were obtained from 152 EEGs recorded during carotid endarterectomy. Analog EEG signals of preclamp and clamp per iods of 100 seconds were digitized to compute power spectra. Changes in pow er during clamping were calculated for all possible derivations in four pre defined frequency bands and were expressed as Z-scores. For each derivation , the area under the receiver operating characteristics curve was calculate d. Derivations with the greatest area under the receiver operating characte ristics curve were considered to distinguish the best between the shunt and the nonshunt groups formed in retrospect on the basis of consensus between three independent and experienced board-certified electroencephalographers . The two different anesthetic regimens resulted in different patterns of E EG changes because of clamping. The optimal derivations to differentiate be tween the shunt and the nonshunt groups also differed for the two anestheti c regimens, although for both conditions, anterior head regions were especi ally preferred. The optimal derivations are given for each anesthetic regim en.