Patient demographic variables included age (>70 years [defined as elderly] vs ≤70 years), sex, and race. General preoperative variables included body mass index, whether the patient was a current cigarette smoker (within 1 year of operation), alcohol use of more than 2 drinks per day, and functional health status (independent, partially dependent, or totally dependent). Preoperative comorbid conditions included the presence of diabetes mellitus, dyspnea (with moderate exertion or at rest), history of chronic obstructive pulmonary disease, ascites, previous percutaneous cardiac intervention, previous cardiac surgery, hypertension requiring medication, history of revascularization procedure or amputation for peripheral vascular disease, history of rest pain or gangrene, and history of transient ischemic attack or stroke. Other preoperative variables included preexisting open wound, steroid use for chronic condition, weight loss of more than 10% in the preceding 6 months, bleeding disorders, prior operation within 30 days, and preoperative systemic sepsis within 48 hours before operation. Finally, the most recent preoperative laboratory values were collected within 90 days before the operation: sodium, creatinine, albumin, bilirubin, alkaline phosphatase, aspartate aminotransferase, white blood cells, hematocrit, platelets, and international normalized ratio. All laboratory results were categorized into values below, above, or within the normal range. Intraoperative factors included American Society of Anesthesiologists physical status class (1, 2, or 3), type of pancreaticoduodenectomy, histologic diagnosis (neoplasm of duodenum, pancreas, or bile duct vs other), the number of packed red blood cell units transfused intraoperatively (0, 1, 2, or ≥3), and the duration of operation (≤6 hours vs >6 hours).