F. C. Patel1, A. Gullick1, A. DeRussy1, D. I. Chu1, J. Grams1, M. Morris1 1University Of Alabama Birmingham,Department Of Surgery,Birmingham, Alabama, USA
Introduction: Obesity remains a growing epidemic in the United States. Studies have suggested that obesity may worsen post-operative outcomes such as surgical site infection (SSI), but many of these studies categorized patients only as obese or non-obese. By further stratifying the obese population, we aim to investigate the role of obesity classes in determining post-operative outcomes for patients undergoing elective colorectal surgery.
Methods: Patients who underwent elective colorectal surgery were queried from the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) 2011-2013 cohort and stratified by body mass index category into underweight (<18.5 kg/m2), normal weight (18.5-24.9 kg/m2), overweight (25-29.9 kg/m2), and class I (30-34.9 kg/m2), II (35-39.9 kg/m2), and III (>40 kg/m2) obesity. Univariate and bivariate comparisons were made with Chi-square and Wilcoxon Rank Sums tests to determine differences among categorical and continuous variables, respectively. Logistic regression analyses identified risk factors for 30-day mortality, 30-day readmission, and SSI (defined as superficial/deep SSI or wound disruption but excluding organ space infection).
Results: Of 74,891 patients who underwent elective colorectal surgery, 3,265 (4.4%) were underweight, 21,685 (29%) normal weight, 24,705 (33%) overweight, 14,797 (19.8%) class I obesity, 6,324 (8.4%) class II obesity, and 4,115 (5.5%) class III obesity. Comorbidities included non-insulin-dependent diabetes (10%), smoking (17.5%), and hypertension (49.2%). SSI rates in the overall cohort were 8.7% and ranged from the highest in class III obesity to the lowest in normal weight patients (15% vs. 6.5%, p<0.001). Fully adjusted modelling showed an increased risk of post-operative SSI with increased obesity class: Overweight (OR 1.34, CI 1.24-1.44), Class I (OR 1.68, CI 1.55-1.82), Class II (OR 2.32 CI 2.10-2.55), and Class III (OR 2.56 CI 2.20-2.74). Underweight patients were at increased risk of 30-day mortality (OR 1.34 CI 1.01-1.79), but obesity did not predict mortality. No weight categories were associated with an increased risk of readmission.
Conclusion: Obesity has a dose dependent association with SSI following elective colorectal surgery, but is not associated with readmission or 30-day mortality. BMI may account for some of the variation in post-operative outcomes such as SSI. In order to improve post-operative outcomes, pre-habilitation including supervised weight loss may play an important role prior to elective surgery.