Aim 1a. Test the hypothesis that endothelial injury is associated with delirium. The investigators hypothesize that endothelial dysfunction is associated with an increased incidence of delirium after cardiac surgery. To test this hypothesis, the investigators will measure biomarkers from subjects undergoing cardiac surgery. Blood samples from three time points [baseline, upon arrival to the intensive care unit (ICU), and postoperative day 1 (POD1)] will be analyzed and compared between patients that did and did not develop postoperative delirium.