Objective: Obesity defined by a body mass index (BMI) >30 kg/m is associated with increased morbidity and mortality following trauma. Evidence suggests that obesity represents a state of chronic inflammation and that the adipose tissue content may affect the intensity and resolution of inflammatory response. We sought to avoid the confounding effects attributable to obesity and determine the association of BMI and outcomes following injury in nonobese patients.
Methods: Data were obtained from a multicenter prospective cohort study evaluating outcomes in blunt-injured adults with hemorrhagic shock. Only patients with a BMI≥18.5 and<30 were analyzed. Those with isolated traumatic brain injury and cervical cord injury and those who survived<24 hours were excluded. Logistic regression was used to evaluate the effects of BMI on mortality, multiple organ failure (MOF, multiple organs dysfunction score [MODS]>5), and nosocomial infection (NI) after adjusting for differences in demographics, injury severity, early resuscitation needs, shock parameters, and comorbidities.
Results: Overall mortality, MOF, and NI rates for the study cohort (n=820) were 13%, 37%, and 46%, respectively. Median Injury Severity Score was 33 (interquartile range, 22-41). Median BMI for the study cohort was 25 (interquartile range, 23-27). As BMI increased, maximum organ dysfunction scores also significantly increased for cardiac, respiratory, and renal systems. Logistic regression revealed no significant association with mortality (odds ratio [OR]=0.95; 95% confidence interval [CI], 0.9-1.0); however, BMI was independently associated with a higher risk of MOF (OR=1.09; 95% CI, 1.02-1.06) and NI (OR=1.07; 95% CI, 1.01-1.13). For every single-point increase in BMI, the risk of MOF and NI increase by 9% and 7%, respectively.
Conclusion: The risk of MOF and NI increases as BMI increases in the nonobese injured patient. These results suggest that body adipose content may be associated with the magnitude of or extent of the inflammatory response postinjury. Further studies are needed to elucidate the mechanism responsible for this association.