Nationwide cohort study of independent risk factors for acute respiratory distress syndrome after trauma

BACKGROUND: The primary objective of this study was to evaluate the effect of specific direct and indirect factors that accounted, in trauma patients, for the development of acute respiratory distress syndrome (ARDS) and mortality in patients with ARDS. METHODS: We performed a retrospective cohort study of patients from the National Trauma Data Bank. Multilevel mixed-effects logistic regression was used with the development of ARDS as the primary and mortality in patients with ARDS as the secondary outcome measures. We compared trauma patients with versus without thoracic (direct) and extrathoracic (indirect) risk factors, using patient demographics, physiologic, and anatomic injury severity as covariates. Subset analysis was performed for patients with trauma-induced lung contusion (TILC) and for patients with minor (Injury Severity Score [ISS] ≤15) injury. RESULTS: A total of 2 998 964 patients were studied, of whom 28 597 developed ARDS. From 2011 to 2014, the incidence of ARDS decreased; however, mortality in patients with ARDS has increased. Predictors of ARDS included direct thoracic injury (TILC, multiple rib fractures, and flail chest), as well as indirect factors (increased age, male gender, higher ISS, lower Glasgow Coma Scale motor component score, history of cardiopulmonary or hematologic disease, and history of alcoholism or obesity). Patients with ARDS secondary to direct thoracic injury had a lower risk of mortality compared with patients with ARDS due to other mechanisms. DISCUSSION: Despite the decreasing incidence of trauma-induced ARDS, mortality in patients with ARDS has increased. Direct thoracic injury was the strongest predictor of ARDS. Knowing specific contributors to trauma-induced ARDS could help identify at-risk patients early in their hospitalization and mitigate the progression to ARDS and thereby mortality. LEVEL OF EVIDENCE: Prognostic study, level III.