Prehospital low‐titer group O whole blood in a multi‐agency civilian emergency medical system: Operational timelines, physiologic response, and stewardship across trauma and medical hemorrhage

BACKGROUND: Low-titer group O whole blood (LTOWB) is increasingly used for prehospital hemorrhagic shock, yet real-world data from multi-agency EMS systems, particularly in medical hemorrhage, remain limited. This evaluation describes the first 11 months of a regional LTOWB program, focusing on operational timelines, physiologic response, protocol adherence, and product stewardship. STUDY DESIGN AND METHODS: In this quality-improvement evaluation, all prehospital blood activations in the Pierce County EMS (PCEMS) region of Washington State were reviewed. Operational metrics included dispatch-to-blood time, scene time, transfusion location, and dispatch-to-ED interval. Physiologic response was assessed using systolic blood pressure (SBP), heart rate, and shock index (SI), with shock resolution defined as SI