COMPUTER-DERIVED DENSITY SPECTRAL ARRAY IN DETECTION OF MILD ANALOG ELECTROENCEPHALOGRAPHIC ISCHEMIC PATTERN CHANGES DURING CAROTID ENDARTERECTOMY

The purpose of this prospective study was twofold: 1) to determine the sensitivity and specificity of computer-derived density spectral arra y in detecting analog electroencephalographic (EEG) ischemic pattern c hanges during carotid artery cross-clamping in patients undergoing car otid endarterectomy; and 2) to assess the ability of density spectral array to identify such changes in comparison with the degree and type of change seen in the analog EEG ischemic pattern. Sixteen channels of anteroposterior bipolar and two to four channels of referential elect roencephalography with four channels of density spectral array were mo nitored simultaneously during carotid endarterectomy in 103 patients u nder general anesthesia. Two ''observers'' interpreted the density spe ctral array and the analog electroencephalograms, one during and immed iately after the operations and the other 6 months after completion of all surgery. Analyses were conducted to establish both the number of patients with analog EEG ischemic changes and the number of ischemia e vents during carotid artery cross-clamping. Observer A indicated that the density spectral array identified analog EEG ischemic changes in 2 1 of 29 patients, for a sensitivity of 72% (specificity 99%), whereas Observer B's results showed that the density spectral array identified analog EEG ischemic changes in 16 of 27 patients, for a sensitivity o f 59% (specificity 96%). Density spectral array detection of analog EE G ischemic changes based on severity classifications were 61% and 18% in the mild group, 70% and 71% in the moderate group, and 95% in the s evere group, indicating a relationship between density spectral array sensitivity and severity of analog EEG ischemic change, with p = 0.02 and p = 0.004 for the two observers. The kappa statistics for observer reproducibility were highly significant, with k = 0.95 for analog EEG ischemic changes and 0.85 for density spectral array changes. It is c oncluded that density spectral array does not reliably detect mild ana log EEG pattern changes of cerebral ischemia and is not a reliable sub stitute for 16-channel analog EEG monitoring of cerebral ischemia duri ng carotid endarterectomy.