Neurophysiological Correlates of Post-Operative Cognitive Disorders

Objectives. To study post-operative cognitive dysfunction (POCD)-associated parameters of high-frequency β activity in patients who have undergone coronary bypass (CB) with on-pump circulation. Materials and methods. A total of 60 patients were investigated 3–5 days before operation and on day 7–10 after CB using neuropsychological testing and recording of the resting EEG in 62 standard leads with the eyes closed. Study results were processed statistically in Statistica 10 and a data clustering method was developed; optimum solutions were sought using software implementation of a binary clipping and branching algorithm. Results. Patients with POCD were found to have greater pre- and post-operative levels of power of biopotentials in the high-frequency (20–30 Hz) β2 range as compared with patients without post-operative cognitive decline. A regression model demonstrated that the post-operative cognitive decline corresponded to high pre-operative β2 activity indicators in the right frontal areas of the cortex and lower levels in the left parietal areas after CB. Clustering of β2 power measures before and after CB showed that the best measures of cognitive status corresponded to stable assignation of patients to the clusters identifi ed. Conclusions. Specifi c correlates of POCD were identifi ed in CB patients characterized by pre-operative increases in β2 activity in the frontal areas of the right hemisphere and post-operative decreases in the left parietal areas of the cortex. The method of classifying patients in terms of levels of the pre- and post-operative β2 rhythm has good discriminating ability. Stable assignment of patients to clusters based on β2 activity was characterized by higher levels of cognitive status.