Shock Index as a Predictor of Massive Transfusion and Emergency Surgery on the Modern Battlefield

Shock Index (SI) has been used to predict the need for massive transfusion (MT) and emergency surgical procedures (ESP) in civilian trauma. We hypothesize that SI can reliably identify combat trauma patients that will require MT and ESP when applied to the resource-constrained, combat environment.

A retrospective review was performed within the Department of Defense Trauma Registry (2008-2016). SI was calculated using heart rate and systolic blood pressure on arrival to the initial facility with surgical capabilities. A threshold value of 0.8 was used to stratify patients into two groups (Group I, SI < 0.8; and Group II, SI ≥ 0.8). The need for MT, ESP, and mortality was compared. Regression analyses were conducted to determine the independent association of SI with MT and ESP.

A total of 4008 patients were included. The mean age of the patients was 25.5 y, and the majority were predominately male (98%). Mechanisms of injury were blunt and blast injury (62%), penetrating injury (36.7%), and burn injury (0.5%). Overall, 77% of patients (n = 3070) were stratified to Group I, and 23% of patients (n = 938) were stratified to Group II, by SI. Group II patients had a significantly greater need for MT (8.4% versus 0.4%) and ESP (30.7% versus 6.5%), both P < 0.001. Regression analysis controlling for age, gender, Injury Severity Score, and Glasgow Coma Score confirmed that SI ≥ 0.8 was an independent risk factor for both MT and need for ESPs (P < 0.001).

SI is a significant predictor of the need for MT and ESPs in the military trauma population, representing a simple and potentially potent tool for triage and prediction of resource consumption in the resource-limited, austere setting.