Massive Transfusion Thresholds Associated with Combat Casualty Mortality during Operations in Afghanistan and Iraq: Implications for Role 1 Logistical Support Chains.

Limited literature exists examining outcomes associated with alternative thresholds for massive transfusion outside of the historical definition of 10 units of packed red blood cells (PRBC) in 24 hours. This study reports the predictive accuracy of alternative thresholds for 24-hour mortality and explores implications for Role 1 care supply requirements.We conducted a secondary analysis of data from the Department of Defense Trauma Registry (DODTR) spanning encounters from 1 January 2007 through 17 March 2020. We included all casualties who received at least 1 unit of either PRBC or whole blood. We calculated area under the receiver operator curve (AUROC) of blood product quantity received, including both PRBC and whole blood, as a predictor for mortality within 24 hours of arrival to a military treatment facility. We identified optimal predictive thresholds per Youden's index.We identified 28,950 encounters of which 2,608 (9.0%) entailed receipt of at least 1 unit of PRBC or whole blood. Most casualties sustained battle injuries (2,437, 93.4%) with explosives as the most common mechanism (1,900, 72.8%) followed by firearms (609, 23.3%). The AUROC for blood product received within 24 hours was 0.59. The optimal threshold for predicting 24-hour mortality per Youden's Index was 20 units (sensitivity of 34.9% and specificity of 78.6%). The threshold exceeding 90% sensitivity was 2 units; whereas, the threshold exceeding 90% specificity was 33 units.We identified a wide range of numbers of received blood products associated with short-term mortality based upon prioritization of sensitivity or specificity. This study found only 2 units of blood product received had a 90% sensitivity for predicting 24-hour mortality, highlighting the resource mobilization challenges that confront healthcare providers during resuscitation at the Role 1.