Impact of body mass index on perioperative outcomes in patients undergoing major intra-abdominal cancer surgery

Background: Obesity is an increasingly common serious chronic health condition. We sought to determine the impact of body mass index (BMI) on perioperative outcomes in patients undergoing major intra-abdominal cancer surgery. Methods: A prospective, multi-institutional, risk-adjusted cohort study of patients undergoing major intra-abdominal cancer surgery was performed from the 14 university hospitals participating in the Patient Safety in Surgery Study of the National Surgical Quality Improvement Program (NSQIP). Demographic, clinical, and intraoperative variables and 30-day morbidity and mortality were prospectively collected in standardized fashion. Analysis of variance, Bonferroni multiple comparisons of means tests, and multivariable logistic regression analysis were performed. Results: We identified 2258 patients who underwent esophagectomy (n = 29), gastrectomy (n = 223), hepatectomy (n = 554), pancreatectomy (n = 699), or low anterior resection/proctectomy (n = 753). Patients were stratified by National Institutes of Health (NIH)-defined BMI obesity class, with 573 (25.4%) patients classified as obese (BMI > 30 kg/m²). There were no differences in mean work relative value units, total time of operation, or length of stay amongst the BMI classes. After adjusting for other risk factors, obesity was not a risk factor for death or major complications but was a risk factor for wound complications. The risk of postoperative death was greatest in underweight patients (odds ratio [OR] 5.24; 95% confidence interval [CI] 1.7-16.2). Conclusion: In patients undergoing major intra-abdominal cancer surgery, obesity is not a risk factor for postoperative mortality or major complications. Importantly, underweight patients have a fivefold increased risk of postoperative mortality, perhaps a consequence of their underlying nutritional status.