Assessment of Brain Oxygen Drops During Surgery and Related Risk Factors for Cognitive Problems After Heart Surgery

In this prospective study, the relationship between intraoperative cerebral oxygen saturation and postoperative cognitive dysfunction (POCD) was investigated in adult patients undergoing elective cardiac surgery with cardiopulmonary bypass (CPB). Patients with a preoperative Mini-Mental State Examination (MMSE) score ≥ 24, no history of cerebrovascular disease, and no conditions that could interfere with near-infrared spectroscopy (NIRS) monitoring were included. Measurements were recorded at the following time points: T0 (before induction), T1 (15 minutes after induction), T2 (5 minutes after initiation of CPB), T3 (during the hypothermic phase of CPB), T4 (rewarming phase of CPB, at 34 °C), T5 (termination of CPB), and T6 (upon admission to the intensive care unit). Patients were divided into two groups according to postoperative cognitive outcomes: those who developed POCD and those who did not. Cognitive function was assessed using the MMSE preoperatively and on postoperative days 4, 7, and 30. During surgery, cerebral oxygen saturation was measured at predefined time points using NIRS probes placed on the frontal region, and detailed intraoperative and perioperative data were recorded. Standardized interventions were implemented when a decrease of more than 20% in regional cerebral oxygen saturation (rSO₂) from baseline was detected in order to maintain adequate cerebral oxygenation.