Risk factors for empyema after diaphragmatic injury: results of a National Trauma Databank analysis.

BACKGROUND: Empyema is a rare, but morbid complication of diaphragmatic injury. The purpose of this study was to use the National Trauma Databank of the American College of Surgeons to determine (1) the incidence of empyema after diaphragmatic injury, (2) risk factors for development of empyema after these injuries, and (3) the effect of empyema on mortality, hospital, and intensive care unit (ICU) length of stay (LOS) after diaphragm injury.

METHODS: The National Trauma Databank (v. 5.0) was used to identify adult patients sustaining diaphragmatic injury and surviving for greater than 48 hours. Demographics, injury characteristics, associated abdominal injuries, thoracic procedures, and outcomes data were abstracted for comparison of patients who did and did not develop empyema after these injuries. Stepwise logistic regression analysis was used to identify independent risk factors for the development of empyema. Subsequent adjusted analysis was used to determine the effect of empyema on outcomes (hospital LOS, ICU LOS, mortality).

RESULTS: Among 4,153 patients with diaphragmatic injury who survived more than 48 hours from admission, 57 (1.4%) developed empyema. Demographics did not differ significantly between the two groups. Empyema was associated with longer adjusted mean hospital (35.9 vs. 16.1, p < 0.001) and ICU (18.1 vs. 8.5, p < 0.001) LOS, but was not associated with increased mortality. Patients with empyema more commonly had associated hollow viscus (63.2% vs. 35.6%, p < 0.001), gastric (40.4% vs. 18.8%, p < 0.001), and splenic injuries (49.1% vs. 33.3%, p = 0.01). After multivariable analysis, two independent risk factors for the development of empyema after diaphragmatic injury were identified: gastric injury (adjusted odds ratio = 2.90; 95% confidence interval: 1.69-5.00; p < 0.001) and Injury Severity Score > or = 20 (adjusted odds ratio = 2.99; 95% confidence interval: 1.61-5.59; p = 0.001). Concomitant colonic injury did not significantly increase the risk of empyema in the study population.

CONCLUSIONS: Empyema is an uncommon sequela of diaphragm injury that contributes to the need for prolonged hospital and ICU LOSs. Associated gastric trauma and Injury Severity Score > or = 20 were independently associated with empyema development after diaphragmatic injury.