The objective of this study is to determine prevalence of postoperative delirium and confusion in patients undergoing cardiac surgery. This proposal is a pilot study designed to evaluate effect of cardiac surgery on prevalence of delirium and confusion.

The primary aim is to evaluate prevalence of delirium and confusion in patients undergoing cardiac surgery and to determine risk factors for this condition.

A secondary aim is to evaluate organic brain injury by early postoperative diffusion weighted magnetic resonance imaging (DW-MRI) in patients who develop delirium and confusion.

The hypothesis to be tested is that patients with postoperative delirium and confusion have high incidence of organic brain injury as detected by DW-MRI.

Inclusion criteria:

• All patients undergoing cardiac surgery in our institute in 2 year period
• Signed informed consent

Exclusion criteria:

• Past history of transient ischemic attacks, stroke, symptomatic carotid artery disease.
• Past history of psychiatric disorders
• History of alcohol and drug abuse
• History of severe kidney or liver disease (creatinine >2.5mg/dL and bilirubin > 2mg/dL)
• Known contraindications to MRI