Evaluation of Intraoperative Cerebral Desaturation and Risk Factors Associated With Cognitive Dysfunction After Cardiac Surgery: A Prospective Observational Study

Background: Postoperative cognitive dysfunction (POCD) remains a common neurological complication after cardiac surgery, particularly among older patients. Intraoperative cerebral oxygen desaturation during cardiopulmonary bypass (CPB) may reflect impaired cerebral perfusion and is proposed as a contributing factor to postoperative cognitive impairment. This study aimed to evaluate the association between intraoperative cerebral oxygen desaturation and postoperative cognitive outcomes in patients undergoing cardiac CPB surgery. Methods: In this prospective observational study, 74 patients undergoing elective cardiac surgery with CPB between March 2023 and March 2024 were included. Cognitive function was assessed using the Mini-Mental State Examination (MMSE) preoperatively and on postoperative days (PODs) 4, 7, and 30. Bilateral frontal regional cerebral oxygen saturation (rSO2) was continuously monitored intraoperatively using near-infrared spectroscopy (NIRS). Cerebral desaturation was defined as a reduction of >20% in rSO2 from baseline. A standardized intervention protocol was applied when this threshold was exceeded. Results: The incidence of POCD was 32.4% during the first postoperative week and decreased to 20.2% by POD 30. Patients who developed POCD were significantly older than those without POCD (median (interquartile range [IQR]): 63 [58–68] vs. 59 [52–65] years; p = 0.026). Intensive care unit (ICU) and total hospital stays were significantly longer in the POCD group (median ICU stay: 74 [51.3–96] vs. 50 [46–60] hours; p < 0.001; median hospital stay: 9 [8–15.5] vs. 7 [7–9] days; p < 0.001). Intraoperative rSO2 values were significantly lower in the POCD group following the initiation of CPB, particularly during the hypothermic and rewarming phases (T2–T4). Percentage decreases in rSO2 at T2, T3, and T4 showed significant positive correlations with MMSE scores on POD 4 (r = 0.283, p = 0.014; r = 0.312, p = 0.007; r = 0.312, p = 0.007, respectively) and POD 30 (r = 0.314, p = 0.006; r = 0.270, p = 0.020; r = 0.349, p = 0.002, respectively). Conclusions: Intraoperative cerebral oxygen desaturation during CPB, particularly during the initiation, hypothermic, and rewarming phases, was associated with decreased early and late-postoperative cognitive performance after cardiac surgery. Continuous intraoperative cerebral oxygenation monitoring using NIRS may enable earlier identification of cerebral hypoperfusion and facilitate timely interventions in patients at increased risk of POCD. Clinical Trial Registration: NCT07361068. https://clinicaltrials.gov/search?term=NCT07361068.