The hypothesis of this study is that intranasal insulin can prevent POD and POCD in elderly critically ill patients admitted to the intensive care unit after undergoing cardiac surgery. To test this hypothesis, this randomized, placebo-controlled, double-blinded Phase II study will enroll 60 patients >= 65 years old undergoing elective coronary artery bypass graft and/or valve surgery requiring cardiopulmonary bypass, and will treat them with either 40 IU of aspart insulin or placebo intranasally before surgery and then four times a day for 7 days or until hospital discharge (whichever occurs first).