Development of posttraumatic empyema in patients with retained hemothorax: Results of a prospective, observational AAST study

Background: The natural history of retained hemothorax (RH), in particular factors contributing to the subsequent development of empyema, is not well known. The intent of our study was to establish the modern incidence of empyema among patients with trauma and RH and identify the independent predictors for development of this complication. Methods: An American Association for the Surgery of Trauma multicenter prospective observational trial was conducted, enrolling patients with placement of a thoracostomy tube within 24 hours of trauma admission, and subsequent development of RH was confirmed on computed tomography of the chest. Demographics, interventions, and outcomes were analyzed. Logistic regression analysis was used to identify the independent predictors for the development of empyema. Results: Among 328 patients with posttraumatic RH from the 20 participating centers, overall incidence of empyema was 26.8% (n = 88). On regression analysis, the presence of rib fractures (adjusted odds ratio [OR], 2.3; 95% confidence interval [CI], 1.3-4.1; p = 0.006), Injury Severity Score of 25 or higher (adjusted OR, 2.4; 95% CI, 1.3-4.4; p = 0.005), and the need for any additional therapeutic intervention (adjusted OR, 28.8; 95% CI, 6.6-125.5; p < 0.001) were found to be independent predictors for the development of empyema for patients with posttraumatic RH. Patients with empyema also had a significantly longer adjusted intensive care unit stay (adjusted mean difference, 4.1; 95% CI, 1.3-6.9; p = 0.008) and hospital stay (adjusted mean difference, -7.9; 95% CI, -12.7 to -3.2; p = 0.01). Conclusion: Among patients with trauma and posttraumatic RH, the incidence of empyema was 26.8%. Independent predictors of empyema development after posttraumatic RH included the presence of rib fractures, Injury Severity Score of 25 or higher, and the need for additional interventions to evacuate retained blood from the thorax. Our findings highlight the need to minimize the risk associated with subsequent thoracic procedures among patients with critical illness and RH, through selection of the most optimal procedure for initial evacuation. Level of Evidence: Prognostic study, level III.