Moving diagnostics upstream: prehospital blood gas analysis is associated with safe community care and improved patient selection for hospital admission

Background Emergency departments (EDs) in high-income countries face rising demand, workforce shortages and crowding. We investigated whether prehospital point-of-care blood gas analysis (BGA), used by emergency physicians, is associated with higher ambulatory treatment rates and improved patient selection for hospital admission. Methods We retrospectively analysed routinely collected data from a pilot implementation of a mobile blood gas analyser in physician-staffed emergency medical services (EMS) in Jena, Germany (July 2023 to May 2024). Adult emergency patients receiving prehospital BGA were compared with propensity score-matched EMS controls without BGA. Primary outcomes were the proportion treated on scene and, among transported patients, the hospital admission rate. Secondary outcomes were 30-day safety among ambulatory patients and associations between BGA parameters and disposition. We used standardised mean differences to assess balance and receiver operating characteristic analysis for lactate thresholds. Results Of 109 patients receiving prehospital BGA, 98 met inclusion criteria after excluding 9 patients with missing NACA scores, 1 on-scene death and 1 invalid age record; these were matched to 390 controls (total n = 488). Baseline demographics, severity and vital signs were well balanced. Ambulatory treatment was markedly higher in the BGA cohort compared with matched controls (27.6% vs 8.7%; OR 3.98, 95% CI 2.26 to 7.01; p<0.001). No ambulatory BGA patient required ED re-attendance or repeat EMS contact within 30 days. Among transported patients, 58% in the BGA cohort were admitted to hospital, compared with an overall regional ED conversion rate of approximately 30%. Lactate [&ge;]2.6 mmol/L was the most influential parameter for disposition decisions, with elevated lactate and acid-base disturbances strongly associated with transport and admission. Conclusion Prehospital BGA was associated with fourfold higher ambulatory treatment rates (27.6%) and a twofold higher ED conversion rate among the patients who were transported (58%), indicating improved risk stratification and resource allocation. These findings suggest that integrating objective biochemical data into prehospital assessment may enhance treat-and-refer decision-making and support more efficient use of limited emergency care capacity.