Impact of preoperative cognitive impairment on changes in electrical activity of the brain in patients undergoing combined carotid endarterectomy and coronary artery bypass grafting

Abstract

HighlightsThe presence of preoperative mild cognitive impairment (MCI) in patients undergoing combined carotid endarterectomy and coronary artery bypass grafting is associated with an increased theta activity at the frontal and parieto-occipital regions of both hemispheres after surgery. AbstractAim. To study the impact of preoperative cognitive impairment on changes in electrical activity of the brain in patients undergoing combined carotid endarterectomy and coronary artery bypass grafting.Methods. Sixty-three patients undergoing combined carotid endarterectomy (CAE) and coronary artery bypass grafting (CABG) were included in the study. The patients were divided into three groups, depending on the preoperative cognitive functions: without cognitive impairment (n = 17), with MCI (n = 29), and with severe cognitive impairment (n = 17). High-resolution electroencephalography (EEG) (62 channels, bandpass filtered between 0.1–50.0 Hz, sampling rate of 1000 Hz) was performed 3–5 days before and 7–10 days after surgery.Results. Patients with severe cognitive impairment at baseline presented with higher theta activity at the frontal region of the left hemisphere compared to patients without cognitive impairment and patients with MCI (p = 0.048). At the same time, patients with MCI showed the most pronounced theta activity increase after surgery compared to preoperative levels at the frontal and parieto-occipital cortical regions of both the left and right hemispheres (p≤0.05). Postoperative changes of theta activity in patients with severe cognitive impairment were minimal and statistically insignificant.Conclusion. Patients without severe preoperative cognitive impairment presented with higher grade brain dysfunction in the form of increased theta activity at the frontal and parieto-occipital regions after combined CAE and CABG. A smaller decrease in theta power after surgery in patients with severe preoperative cognitive impairment, on the one hand, can indicate compensation after cerebral ischemia and resistance to hypoperfusion during on-pump cardiac surgery, and on the other, can be a manifestation of the ceiling effect and insufficiency of brain functional reserves.