The third group will be patients undergoing elective surgical procedures that will likely require a post-operative admission to the SICU. This group will include patients undergoing open abdominal aortic aneurysm repair, esophagectomy, or other major abdominal or thoracic operation that will likely require a SICU stay of more than 24 hours. At least half of this group will consist of diabetic patients. These patients will be selected by one of the investigators based on their likelihood of requiring more than 24 hours of SICU care. Based on the experience of the investigators we believe we will be able to accurately predict which patients will require an ICU stay of at least 24 hours. Most commonly these patients will have significant co-morbid medical conditions including coronary artery disease, hypertension, hypercholesterolemia, obesity, etc. An attempt will be made to contact these patients pre-operatively by telephone within 1 week of their planned surgery at which time details of the research will be explained. Their willingness to participate will be ascertained and they will be formally enrolled and sign consent on the morning of surgery if possible. On some occasions patients will require ICU stays post-operatively that were not predicted pre-operatively. These patients and any patients that were not identified pre-operatively by the research team will be enrolled post-operatively often through their surrogate similar to the other study groups. Similarly if patient are enrolled pre-operatively and subsequently do not require SICU admission they will not undergo any of the study procedures and not be counted towards the total enrollment.