This study will enroll people undergoing heart surgery. On the day before surgery, participants will undergo a blood collection and neuropsychological testing. They will then be randomly assigned to either a traditional method of blood glucose control or an intensive, tailored method of blood glucose control. Participants following the traditional method of blood glucose control may receive insulin several times a day, based on the results of glucose monitoring. Participants following the intensive, tailored method of blood glucose control will undergo hourly measurements of their glucose levels and receive insulin adjustments as needed to maintain a glucose level of 100-140 mg/dL. During surgery, all participants will undergo an ultrasound of their neck to monitor blood vessel activity. Additional blood samples will be collected during surgery, 6 hours after surgery, 24 hours after surgery, and upon hospital discharge or 5 days after surgery.