Coagulopathy and Mortality in Combat Casualties: Do the Kidneys Play a Role?

Background: Acute traumatic coagulopathy (ATC) is a common condition after traumatic injury and is known to be associated with an increase in morbidity and mortality in trauma patients. ATC has been implicated as a causative factor in both early hemorrhage and late organ failure in this population, yet the pathophysiology remains largely unknown. Additionally, acute kidney injury (AKI) is a common condition among critically injured trauma patients. AKI has been associated with an elevated International Normalized Ratio (INR) and warfarin use, but its development has not been well studied in the setting of ATC. We hypothesized that the presence of ATC influences the development of AKI and may mediate mortality in combat casualties.
Methods: Data were obtained from the Department of Defense Trauma Registry, Medical Data Store and Composite Healthcare System, and the Armed Forces Medical Examiner System. A retrospective review was conducted of US service members injured in Iraq or Afghanistan between February 1, 2002 and February 1, 2011, who required ICU level care and survived evacuation out of theater. Exclusions were made for missing data. Cox proportional hazard regression was performed to determine the effect of ATC (a priori defined as first INR > 1.3) on the development of AKI. Further analysis was conducted to determine the influence of these variables on 30-d mortality, and multiple sensitivity analyses were performed to determine the effect of ATC on both AKI and mortality.
Results: A total of 1,288 patients were identified for analysis. ATC was a risk factor for subsequent AKI after adjustment (HR 1.67, 95% CI 1.28-2.18; p < 0.001). However, ATC was not a risk factor for mortality after adjustment in the full model (HR 1.87, 95% CI 0.95-3.65; p = 0.069). On sensitivity analyses exploring alternate definitions of ATC, an INR of 1.2 remained associated with AKI (HR 1.46, 95% CI 1.13-1.88; p = 0.004) and an INR of 1.5 became significant for mortality (HR 1.76, 95% CI 1.32-2.35; p < 0.001).
Conclusion: ATC is independently associated with the development of AKI. Although ATC is associated with mortality in the unadjusted model, it is not significant after adjustment for AKI. This implies that the kidneys may play a role in the adverse outcomes observed after ATC. Increased awareness and monitoring for coagulopathy and the subsequent development of AKI in combat casualty patients may lead to earlier diagnosis and treatment of these conditions, possibly decreasing morbidity and mortality.