The overall aim of the Obesity and Surgical Outcomes (OBSOS) study is to improve the outcomes of obese patients who must undergo general, orthopedic, vascular or urological surgery. Obesity has been implicated in predisposing patients to worse surgical outcomes (death and complications), however, the etiology of these outcome differences is not well understood or well defined, and hence approaches to improving outcomes in this population are challenging. The application has 3 aims: (1) Determine how obesity influences the post operative outcomes of death, complications, failure-to-rescue (the probability of death after complications), length of stay, readmission rates, and cost;(2) Identify potential risk factors that may be especially important in treating obese as compared to non-obese patients, such as: control of serum glucose, use of preoperative antibiotics, early ambulation, and epidural analgesia;and (3) Determine whether there are differences or disparities in the care of obese patients undergoing surgery as compared to normal weight patients, such as differences in the surgical procedures offered, anesthesia technique and postoperative pain control. The study will use an efficient design that incorporates: (1) a three state, 50 hospital, Medicare "augmented claims analysis" that includes height, weight, and serum albumin information from charts (N=20,000), and (2) a nested, detailed chart abstraction (N=4000) using a matched cohort design to answer questions that require clinical data not available from Medicare claims. The infrastructure for this study will be supported by Medicare's SCIP (Surgical Care Improvement Program) initiative. By using augmented claims data with a nested, matched cohort abstraction of detailed chart data, we will be able to address clinically important problems in the care of obese surgical patients that will have a significant impact on the surgical approach to, and perioperative care of, the elderly obese. RELEVANCE: The rates of surgery on the elderly have doubled over the past 20 years, while the obesity rate in this same population has reached over 33%. Although often considered a surgical risk factor, the impact of obesity on surgical outcomes is poorly understood;studies have generally been small and from single institutions. The multi-institutional OBSOS study will examine differences in outcomes and treatments between obese and normal weight patients, and in so doing, should make important contributions to the care of these patients.