Number Needed to Treat Analysis for Ground Prehospital Blood in Hemorrhagic Shock

BACKGROUND: Early hemorrhage control remains the cornerstone of trauma resuscitation, yet traditional ground emergency medical services (EMS) resuscitation relies predominantly on crystalloid fluids. We compared outcomes after prehospital crystalloid, packed red blood cells (pRBC), and whole blood (WB) resuscitation and quantified absolute risk reduction (ARR) and number needed to treat (NNT) for survival. STUDY DESIGN: Trauma patients with hemorrhagic shock (evidence of hemorrhage and shock index >1.0) enrolled in a prospective multicenter ground EMS registry who received crystalloid alone, pRBC, or WB during transport were evaluated. The primary outcome was in-hospital mortality. Secondary outcomes included change in shock index from the prehospital setting to emergency department arrival. ARR and NNT were calculated with 95% confidence intervals. RESULTS: Among 299 patients, mortality was highest after crystalloid resuscitation (13/84, 15.5%) compared with pRBC (9/168, 5.4%) and WB (2/47, 4.3%). Shock index improved in all groups, with the greatest reduction after pRBC (Δ-0.32 vs crystalloid Δ-0.14; p<0.001). Compared with crystalloid, ARR was 10.1% (95% CI, 2.5-19.7%) for pRBC (NNT≈10; p=0.02), 11.2% (95% CI, 1.5-20.9%) for WB (NNT≈9; p=0.03), and 10.4% (95% CI, 2.7-18.0%) for combined blood products (NNT≈10; p=0.006). Contextual comparison demonstrated favorable NNT estimates relative to established trauma interventions. CONCLUSIONS: In this prospective multicenter observational cohort, prehospital blood resuscitation was associated with lower in-hospital mortality than crystalloid alone, with a NNT of approximately 9-10. These findings support implementation research and systems-level evaluation of ground EMS prehospital blood programs for hemorrhagic shock.