Body mass index and outcomes in critically injured blunt trauma patients: weighing the impact.

Background: The influence of increased body mass index (BMI) on morbidity and mortality in critically injured trauma patients has been studied, with conflicting results. The objective of this study was to investigate the relationship between stratified BMI and outcomes in blunt injured patients.

Study Design: Consecutive adult trauma patients from July 2001 to November 2005 with Injury Severity Score (ISS) > or = 16 and blunt mechanism were evaluated using the National Trauma Registry of the American College of Surgeons. Demographics, injury severity, hospital course, complications, and mortality were compared among standard BMI strata. Logistic regression was used to determine odds ratios (OR) with 95% confidence intervals and evaluate BMI as an independent risk factor for morbidity and mortality. Statistical significance was set at p < 0.05.

Results: The study group consisted of 1,543 patients. Controlling for age, gender, Injury Severity Score, and Revised Trauma Score, and using BMI 18.5 to 24.9 kg/m(2) as the reference category, morbid obesity (BMI> or =40 kg/m(2)) was associated with acute respiratory distress syndrome (OR 3.675, 95% CI, 1.237 to 10.916), acute respiratory failure (OR 2.793, 95% CI, 1.633 to 4.778), acute renal failure (OR 13.506, 2.388 to 76.385), multisystem organ failure (OR 2.639, 95% CI, 1.085 to 6.421), pneumonia (OR 2.487, 95% CI, 1.483 to 4.302), urinary tract infection (OR 2.332, 95% CI, 1.229 to 4.427), deep venous thrombosis (OR 4.112, 95% CI, 1.253 to 13.496), and decubitus ulcer (OR 2.841, 95% CI, 1.382 to 5.841). Morbid obesity was not associated with increased mortality (OR 0.810, 95% CI, 0.353 to 1.856).

Conclusions: This is the largest study to date evaluating the relationship between BMI and outcomes in critically injured trauma patients. Increasing BMI increases morbidity while having no proved influence on mortality.