POSTOPERATIVE NEUROPSYCHOLOGICAL DYSFUNCTION AND CEREBRAL OXYGENATION DURING CARDIAC-SURGERY

In 41 patients undergoing cardiac operations with extracorporeal circulation, oxidized cytochrome a,a3 (CtO(2)), deoxygenated hemoglobin (Hb), and oxygenated hemoglobin (HbO(2)) were measured in brain tissue by near-infrared spectrophotometry (NIRS) intraoperatively. Monitoring also included electroencephalography (EEG) and jugular-bulb venous saturation (SBJO2). All operations were performed using membrane oxygenators, moderate hypothermia (26-28 degrees C) and pH alpha-stat management. During cardiopulmonary bypass (CPB) CtO(2) and HbO(2) were reduced, reaching minimal values when rewarming was instituted. At the end of the operation CtO(2) and HbO(2) had regained initial levels. During CPB, arterial PCO2, pH, and temperature were closely related to CtO(2) (r = 1000, r = -0.964 and 0.929 respectively; p < 0.001, p < 0.001, and p < 0.003 respectively). Neuropsychological testing by the Mini-Mental-State Test indicated reversible postoperative neuropsychologicai deficits in four patients. These patients had a lower CtO(2) minimum compared to those without these deficits (-4.5 mu mol/L v. -0.7 mu mol/L; p = 0.036). These findings support the hypothesis that neuropsychological deficits in patients after cardiac surgery can be caused by intraoperative cerebral hypoxia.