BACKGROUND The benefits of physician-staffed emergency medical services (EMS) for trauma patients remain unclear because of the conflicting results on survival. Some studies suggested potential delays in definitive hemostasis due to prolonged prehospital stay when physicians are dispatched to the scene. We examined hypotensive trauma patients who were transported by ambulance, with the hypothesis that physician-staffed ambulances would be associated with increased in-hospital mortality, compared with EMS personnel-staffed ambulances. METHODS A retrospective cohort study that included hypotensive trauma patients (systolic blood pressure ≤ 90 mm Hg at the scene) transported by ambulance was conducted using the Japan Trauma Data Bank (2004-2019). Physician-staffed ambulances are capable of resuscitative procedures, such as thoracotomy and surgical airway management, while EMS personnel-staffed ambulances could only provide advanced life support. In-hospital mortality and prehospital time until the hospital arrival were compared between patients who were classified based on the type of ambulance. Inverse probability weighting was conducted to adjust baseline characteristics including age, sex, comorbidities, mechanism of injury, vital signs at the scene, injury severity, and ambulance dispatch time. RESULTS Among 14,652 patients eligible for the study, 738 were transported by a physician-staffed ambulance. In-hospital mortality was higher in the physician-staffed ambulance than in the EMS personnel-staffed ambulance (201/699 [28.8%] vs. 2287/13,090 [17.5%]; odds ratio, 1.90 [1.61-2.26]; adjusted odds ratio, 1.22 [1.14-1.30]; p < 0.01), and the physician-staffed ambulance showed longer prehospital time (50 [36-66] vs. 37 [29-48] min, difference = 12 [11-12] min, p < 0.01). Such potential harm of the physician-staffed ambulance was only observed among patients who arrived at the hospital with persistent hypotension (systolic blood pressure < 90 mm Hg on hospital arrival) in subgroup analyses. CONCLUSION Physician-staffed ambulances were associated with prolonged prehospital stay and increased in-hospital mortality among hypotensive trauma patients compared with EMS personnel-staffed ambulance. LEVEL OF EVIDENCE Therapeutic, level IV.
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