['Previous studies have reported an 11% to 75% incidence of postoperative cognitive decline among cardiac surgery patients. The INVOS Cerebral Oximeter (Somanetics Corp, Troy, MI) is a Food and Drug Administration approved device that measures regional cerebral oxygen (rSo(2)) saturation. The purpose of this study is to examine whether decreased rSo(2) predicts cognitive decline and prolonged hospital stay after coronary artery bypass grafting (CABG).', 'The rSo(2) was monitored intraoperatively in a cohort of primary CABG patients. Patients were prospectively randomized to a blinded control group or an unblinded intervention group. Cognitive function was assessed preoperatively, postoperatively, and at 3 months using a battery of standardized neurocognitive tests. Cognitive decline was defined as a decrease of one standard deviation or more in performance on at least one neurocognitive measure. The rSo(2) desaturation score was calculated by multiplying rSo(2) below 50% by time (seconds). Multivariate logistic regression models were used to assess cognitive decline and hospital stay. The change in cognitive performance was also assessed using a multivariate linear regression model.', 'Patients with rSo(2) desaturation score greater than 3,000%-second had a significantly higher risk of early postoperative cognitive decline [p = 0.024]. Patients with rSo(2) desaturation score greater than 3,000%-second also had a near threefold increased risk of prolonged hospital stay (>6 days) [p = 0.007].'] Does cerebral oxygen desaturation predict cognitive decline and longer hospital stay after cardiac surgery?