Cerebral Blood Flow During CPB During Cardiac Surgery and the Presence of Post op Delirium

Cardiac surgery is associated with multiple perturbations that increase risk for adverse postoperative neurological outcomes including postoperative cognitive dysfunction. These same perturbations likely also increase the risk for postoperative delirium although there are little data that have evaluated this hypothesis. As the subject is prepared for surgery 2 contact probes will be placed on the forehead to monitor the rSO2 and cerebral blood flow. This monitor can also measureblood flow velocity in blood vessels in the forehead. This will only be done while the subject is on the cardiac bypass machine during the surgery and end shortly after entering the intensive care unit.Prior to surgery and then once a day on three of the first four postoperative days, patients will be assessed for the presence and severity of delirium with brief standard psychological exams. We will compare rSO2 and CBF changes between patients with and without delirium