Estimating the Need for Prehospital Blood Transfusion in Trauma: Insights from the German Trauma Registry and HEMS Data

Background: Hemorrhagic shock remains a leading cause of preventable death after major trauma. Prehospital blood transfusion (PHBT) has been introduced in several trauma systems but is rarely used in Germany. The target population for PHBT is not well defined. Patients requiring early blood transfusion likely represent the most relevant group for this intervention. This study estimated the number of trauma patients within German Helicopter Emergency Medical Services (HEMS) likely to require early relevant transfusion. A simple prehospital risk score based on routinely collected mission data was developed to identify these patients. Methods: We conducted a retrospective cohort study using anonymized data from ADAC Luftrettung (2018–2022). Early relevant transfusion (ERT) was defined as the administration of ≥5 units of packed red blood cells (PRBC) prior to ICU admission, based on TraumaRegister DGU® documentation. As no existing score met the operational requirements for prehospital use, we developed a new logistic regression model using 46,807 trauma cases. The resulting Luftrettung (LRG) Score was based exclusively on prehospital variables and applied to 28,990 ADAC trauma patients to estimate transfusion probability. Results: The LRG Score demonstrated good discriminatory ability (Area under the curve AUC 0.86; 95% CI: 0.85–0.87) for predicting early relevant transfusion. In the ADAC cohort, 954 patients (3.3%) were estimated to require ≥5 units of PRBC. Transfusion risk exceeded 10% from a score of 7 and peaked at 56% for scores ≥13. Conclusion: This study provides a nationwide, registry-based estimate of prehospital blood transfusion eligibility in Germany. The LRG Score enables identification of trauma patients at risk for early relevant transfusion (≥5 PRBC prior to ICU admission) using only prehospital data, ensuring methodological consistency and operational feasibility. These findings support future observational research, inform strategic planning, and lay the groundwork for pilot implementation of PHBT in civilian trauma systems.