Cardiac surgery is associated with multiple events and issues that increase risk for adverse postoperative neurological outcomes including postoperative cognitive dysfunction. The risk for postoperative delirium is generally thought to result from some previous health factors added to the susceptibility of the cardiac surgery process.

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

Inclusion Criteria:

• Patients in the study will be 50 or older undergoing elective cardiovascular surgery using cardiopulmonary bypass.
• Patients who can speak, read and understand the English language.
• Patients who understand the nature of the study and are willing to sign the consent form

Exclusion Criteria:

• Emergency surgery or patients intubated before surgery and, thus, cannot give informed consent.
• Patients diagnosed with neurocognitive disorders (e.g. Alzheimer's, Dementia)
• MMSE score greater than 21 Patients taking antipsychotic drugs A history of drug abuse
• Patients with an implant in the brain underneath the CerOx probes
• Women who are pregnant.
• History of significant, prohibitive skin allergies or reactions-

Subjects who are under going cardiac bypass surgery with the use of cardiac perfusion