Abstract
Introduction
Obesity affects over 40% of U.S. adults, with class IV (Body Mass Index (BMI) ≥ 50) rising substantially. The relationship between obesity and emergent trauma laparotomy outcomes is established, yet the literature collapses obesity class I–IV under a single category. However, physiology differs by obesity class, and no study has stratified morbidity and mortality across these classes. We aimed to characterize this relationship to more accurately represent each class. We hypothesized that as BMI increases, so do major adverse outcomes.
Methods
This was a retrospective cohort study using data from the American College of Surgeons (ACS) Trauma Quality Improvement Program (2017-2024). Inclusion criteria were age >18 years, BMI ≥30 kg/m2, abdominal AIS ≥3, and emergent laparotomy within 6 hours of ED arrival. Patients who died before or on ED arrival and those with non-blunt/penetrating mechanism were excluded. Groups for analysis were stratified by obesity class, I-II (BMI 30-39.9), III (BMI 40-49.9), and IV (BMI >= 50). Unweighted statistics characterized demographics and outcomes. Multivariate regression analyzed mortality, discharge disposition, LOS, infectious, and pulmonary complications.
Results
Of 18,583 patients included, there were 15,580 (83.8%) class I-II, 2,448 (13.2%) class III, and 555 (3.0%) class IV and above patients. Class III/IV patients were younger, more female, and more often black than class I-II (p 0.001), with higher rates of penetrating trauma (p = 0.041), and shock index ( p .001). After regression, class IV was the largest independent predictor of mortality (OR 2.78, 95% CI 2.04–3.79). Class III also predicted mortality (OR 1.41, 1.18–1.70). Class III and Class IV had higher odds of non-home discharge (OR 1.38,1.19-1.60), (OR 1.93, 1.46-2.56). Class III was associated with 1.5x odds of unplanned reoperation. Obesity class predicted pulmonary complications dose-dependently with (OR 1.27, 1.05-1.52) for Class III and (OR 1.55, 1.11-2.16) for Class IV. Although BMI class was not associated with surgical site infectious complications, class IV independently predicted severe sepsis (OR 1.68, 1.03–2.75).
CONCLUSIONS: Risk stratification in obese trauma patients undergoing laparotomy should extend beyond obese vs. non-obese. These findings highlight a dose-response relationship between escalating BMI class and mortality risk, unfavorable discharge disposition, and pulmonary complications. Contrary to current literature, surgical site infection was not associated with BMI class. BMI class carries independent prognostic significance and should not be treated as binary in trauma care.