All trauma is not created equal: Redefining severe trauma for combat injuries

Area of Science:

• Trauma Surgery
• Emergency Medicine
• Military Medicine

Background:

• Injury Severity Score (ISS) and Shock Index (SI) are established trauma scoring systems.
• Their optimal cut-off values in combat trauma require specific evaluation for accurate patient assessment.

Purpose of the Study:

• To determine optimal cut-off values for ISS and SI in combat trauma.
• To assess the predictive accuracy of ISS and SI for mortality, massive volume transfusion (MVT), and emergent surgical procedures (ESP) in combat casualties.

Main Methods:

• Retrospective analysis of the Department of Defense Trauma Registry (2008-2016).
• Calculation of Areas Under Receiver Operating Characteristic Curves (AUROCs) for ISS and SI.
• Determination of optimal cut-off values using the Youden Index (YI).

Main Results:

• Analysis included 22,218 combat trauma patients, predominantly male with penetrating injuries.
• ISS demonstrated higher AUROCs for mortality (0.882), MVT (0.898), and ESP (0.846) compared to SI.
• Optimal ISS cut-off was 12.5 for mortality, MVT, and ESP; optimal SI cut-offs were 0.94, 0.88, and 0.81 for mortality, MVT, and ESP, respectively.

Conclusions:

• The standard ISS threshold may not adequately represent severe combat injuries.
• The optimal SI cut-off values identified in this combat trauma cohort are comparable to those reported in civilian populations.
• These findings suggest a need to re-evaluate ISS interpretation in combat settings and highlight the utility of SI as a consistent predictor of trauma outcomes.