The present study evaluated the independent effect of physician-led prehospital trauma care by including a larger number of patients than that included in previous studies and by considering prehospital time. The results demonstrated the independent survival benefit of physician-led prehospital trauma care. Furthermore, subgroup analysis revealed the specific subpopulations that might be likely to benefit from physician-led prehospital management. These findings could provide additional insights into the topic of prehospital trauma care, because some previous studies showing the superiority of physician-led prehospital trauma management would have been largely benefitted by the advantages of shortened prehospital transport time by HEMS[11, 12] in addition to the independent effect of physician-led prehospital care.
Several theoretical advantages of physician-led over paramedic-led prehospital management of severe trauma cases should be considered. First, physicians can provide a broader scope of surgical and medical interventions. Although medical interventions that paramedics are permitted vary depending on the country or area, the scope of their role tends to be limited compared to that of physicians. In Japan, paramedics responding to trauma patients without cardiac arrest are limited to performing spinal motion restriction, external fixation of bone fractures, oxygen administration using a mask, and administration of Ringer’s solution (only to patients with shock). Second, physicians’ interventions were reported to have a higher rate of success than those performed by paramedics; for example, a previous study showed a higher rate of achieving successful advanced airway management,[13–15] which prevents secondary brain injury, in physicians than in paramedics. Third, physicians can make precise and flexible clinical decisions following the latest trauma management strategy rather than uniform simplified management, such as introduction of restrictive fluid management based on strategic permissive hypotension.
Because the JTDB lacks detailed information on the treatments provided by physicians in prehospital settings, specific interventions contributing to survival benefit could not be mentioned in the present study. However, the results of the subgroup analysis in the present study suggested the candidates who were more likely to benefit from physician-led prehospital management. Patients younger than 65 years old were likely to receive survival benefit than patients aged ≥ 65 years. A previous study assessing the characteristics of geriatric trauma patients reported a positive linear relationship between age and mortality risk, suggesting that the effects of any treatment might be smaller in older patients. Furthermore, similar to the previous study showing the effectiveness of physician-led prehospital management especially in severe trauma patients,[19, 20] our data suggested that patients with ISS ≥ 25 were likely to benefit from physician-led prehospital management than patients with ISS < 25. Interestingly, patients who suffered severe injury in the pelvis or lower extremities were more likely to benefit from physician-led prehospital management than those without severe injury in these regions; however, such an association was not observed in the head, chest, and abdominal trauma. This could be partially explained by the nature of the procedures performed at the scene of injury or during transportation. Interventions that can be provided in the prehospital setting are generally limited to simple procedures; although physicians often can temporarily improve deteriorated vital signs by some effective procedures, including the use of a tourniquet or resuscitative endovascular balloon occlusion of the aorta, they cannot repair multiple and complicated organ injuries anatomically in the prehospital settings. Thus, treatments in prehospital settings might have been provided as bridging therapies until definitive care that can be provided after ED arrival. This hypothesis also could explain the result that total prehospital time had significant interaction in the effectiveness of physician-led prehospital management. That is, prolonged prehospital time might have reduced the effect of physician-led prehospital treatments because of the nature of the bridging therapy. These findings from subgroup analyses would serve as a basis for establishing optimal indication for dispatching physician-led teams to the scene of injury.
There were several limitations to this study that should be acknowledged. Because of the retrospective nature of this study, residual confounding was unavoidable. The number of patients with penetrating injury was limited. Physician dispatch criteria did not follow standardized protocols. Furthermore, detailed information on the treatments delivered by a physician was not available in the JTDB. As medical interventions that paramedics can provide vary depending on countries, the results are not always applicable in some countries. Despite these limitations, to the best of our knowledge, this was the first largescale retrospective cohort study that showed the independent survival benefit of physician-led prehospital trauma management. The results would serve as the basis for further developments to the effective prehospital trauma care system.