[Neurophysiological correlates of postoperative cognitive disorders]

A special place among cognitive disorders in patients with cardiovascular diseases is given to postoperative cognitive dysfunction (POCD). The study aimed at investigating the patterns of beta-2 activity associated with postoperative cognitive dysfunction (POCD) in patients after coronary artery bypass grafting (CABG).

The study included 60 patients who underwent neuropsychological testing 3-5 days before surgery and on the 7-10^th day of CABG. A multichannel electroencephalogram of resting state with eyes closed in 62 standard leads was recorded. Statistical processing of the results was carried out using Statistica 10 (StatSoft Inc, USA) and the developed method of data clustering with a minimax criterion, a software implementation of the binary clipping and branching algorithm was used to find optimal solutions.

Patients with POCD had higher pre- and postoperative high-frequency beta-2 rhythm power (20-30 Hz) compared with patients without cognitive impairment. The regression model demonstrated that POCD was associated with high values of preoperative beta-2 activity in the right frontal cortex and with low values in the left parietal areas after CABG. The clustering of beta-2 rhythm power before and after CABG revealed that the best cognitive status corresponded to a stable affiliation of patients with the selected clusters.

The specific POCD correlates were established in patients after CABG. Low cognitive status was characterized by the preoperative beta-2 power increase in the right frontal areas and postoperative decrease in the left parietal cortex. The developed method for classifying patients according to the level of pre- and postoperative beta-2 rhythm power has a good discriminant ability. Stable patient affiliation with the selected clusters was associated with a higher level of cognitive status.