Objective This study was performed to investigate the correlation among decreased regional cerebral oxygen saturation (rSO₂), blood levels of brain injury biomarkers, and postoperative cognitive disorder (POCD) after cardiac surgery with cardiopulmonary bypass (CPB). Methods This prospective observational study included 59 patients undergoing coronary artery bypass graft surgery with CPB. All patients underwent neuropsychological tests (Mini Mental State Evaluation, Rey Auditory Verbal Learning Test, digit span test, digit symbol substitution test, and Schulte table) the day before and 10 days after the surgery. The blood levels of two brain injury biomarkers, neuron-specific enolase (NSE) and glial fibrillary acidic protein (GFAP), were measured before and 1 day after the surgery. Results The rSO₂ decreased during surgery in 21 (35%) patients. POCD was detected in 22 (37%) patients. After the surgery, no significant changes in the GFAP blood level occurred in any patients. No significant correlations were found among the decreased rSO₂, increased NSE blood level, and rate of POCD. Conclusion These results suggest that a decrease in rSO₂ during cardiac surgery is not necessarily related to the development of POCD or an increased blood level of the brain injury biomarker NSE.

Keywords: Regional cerebral oxygen saturation; cardiac surgery; cardiopulmonary bypass; glial fibrillary acidic protein; neuron-specific enolase; postoperative cognitive dysfunction.