b'Scientific Session Abstracts SUNDAY APRIL 21, 202441: INVESTIGATION OF THE OBESITY PARADOX WITH REGARDS TO PERIOPERATIVE COMPLICATIONS FOLLOWING LOWER EXTREMITY ARTERIAL BYPASSMohammed Hamouda, MD1, Mokhshan Ramachandran, BS1,Jonathan T. Unkart, MD, MPH2, Daniel Willie-Permor, MD, MPH, CPH1,Nadin Elsayed MD1, Mahmoud B. Malas MD, MHS, FACS, RPVI1.1 Center for Learning and Excellence in Vascular and Endovascular Research (CLEVER), Department of Surgery, Division of Vascular Surgery, UC San Diego, San Diego, California., 2 Department of Surgery, SUNY Downstate Medical Center, Brooklyn, NY.Background: The obesity paradox refers to a phenomenon by which obese individuals experience lower risk of mortality and even protective associations from chronic disease sequelae when compared to the non-obese and underweight population. Prior studies have demonstrated an obesity paradox after cardiac and other surgical procedures. However, the relationship between body mass index (BMI) and perioperative complications for patients undergoing infrainguinal bypass (IIB) remains unclear. Our study aimed to investigate if the obesity paradox exists for patients undergoing IIB with regards to 30-day mortality, surgical site infections (SSI) and adverse cardiovascular events.Methods: We queried the VQI for individuals undergoing IIB between 2003 and 2020. Chi- square and multivariable logistic regression analyzed the relationship of BMI categories [underweight (18.5), non-obese (18.5-24.9), Overweight (25-29.9), Class 1 obesity (30-34.9), Class 2 obesity (35-39.9) and Class 3 obesity (40)] with 30-day mortality, surgical site infection (SSI) and adverse cardiovascular events. To control for potential confounders, the logistic regression models were adjusted for patient demographics, comorbidities, ASA classification, preoperative medication use and technical aspects such as procedural length, preoperative hemoglobin, and estimated blood loss. Backward stepwise selection was implemented to identify significant variables for inclusion in the final model.Results: Our study included 60,588 IIB patients. Compared to non-obese and underweight individuals, obese patients were more likely to be male of white race, suffer from stable angina and diabetes, were on preoperative aspirin, ACE-inhibitor, beta blocker or statin therapy, and have a history of prior CABG (Table I). Upon multivariable logistic regression with the non-obese category as reference group, the odds of 30-day mortality were significantly decreased among the overweight/obese patients and increased in the underweight patient group [OR: 1.58, (95% CI: 1.16-2.13)] (Table II). Furthermore, a BMI-dependent positive association was present with SSI outcomes where patients in the Class 3 obesity category suffered the highest odds [OR: 2.10, (95% CI: 1.60-2.76)]. Finally, among the adverse cardiovascular event outcomes assessed, only MI demonstrated decreased odds among obese and overweight patient populations. (Table II).102SOUTHERN CALIFORNIA VASCULAR SURGICAL SOCIETY'