We plan to assess the importance of tight glucose control during open-heart surgery. The prevalence of hyperglycemia (elevated blood glucose) during this operation is high. Hyperglycemia may be associated with increased vulnerability to surgical site infections, neurological damage, cardiac and renal injury. Conversely, tight glucose control may be associated with hypoglycemia (pathologically low glucose levels) that may results in neurological injury. We hypothesize that tight glucose control will improve patient outcomes following surgery.