Effectiveness of Physician-Led Prehospital Management in Severe Trauma Patients: A Retrospective Analysis of the Japanese Nationwide Trauma Registry

Abstract

Background: The comparative effectiveness of physician-led over paramedic-led prehospital trauma management has been inconclusive. Regarding this topic, in some previous studies, the impacts of physician-led prehospital management were affected by the advantage of shortened prehospital time by helicopter transportation. This study aimed to evaluate the effect of physician-led prehospital management independent of prehospital time.

Methods: This retrospective cohort study analyzed the data of severe trauma patients who were transported directly to a hospital during 2009–2018 using Japan’s nationwide trauma registry. In-hospital mortality was compared between patients who received physician-led prehospital management and those who received paramedic-led management, using 1:4 propensity score-matched analysis. The propensity score was calculated using information on patient demographics, mechanism of injury, and vital signs at the scene of injury, as well as prehospital transport time. Subgroup analysis was performed to identify patients who were most likely to benefit from physician-led prehospital management.

Results: A total of 30,968 patients (physician-led: 3,032, paramedic-led: 27,936) were eligible for analysis, of whom 2,766 propensity score-matched pairs (i.e., physician-led: 2766, paramedic-led: 11,064) were generated and compared. Physician-led pre-hospital trauma management showed significant superiority over paramedic-led prehospital trauma management (in-hospital mortality: 395 [14.3%] and 1785 [16.1%], respectively; odds ratio [95% confidence interval] = 0.87 [0.77–0.97], p = 0.017). In subgroup analysis, cases characterized by patient age <65 years, Injury Severity Score ≥25, Abbreviated Injury Scale in pelvis and lower extremities ≥3, and prehospital transport time <60 min likely benefitted from physician-led prehospital management.

Conclusions: The result of a largescale registry-based cohort study showed that physician-led prehospital trauma management was significantly associated with survival benefit independent of prehospital transport time. The findings may provide a basis for future research to assess effective physician-provided treatments in prehospital-field.

Background

As the scope of medical interventions that paramedics can perform are generally limited compared to that of physicians, physician-led prehospital management is expected to improve survival outcomes in severe trauma patients. However, the effect of physician-led over paramedic-led prehospital management in severe trauma patients has been debatable. Although some randomized controlled trials[1, 2] and cohort studies[3–5] suggested beneficial effects of physician-led prehospital trauma management, a recent systematic review concluded that evidence of the superiority of physician-led over paramedic-led prehospital management in severe trauma patients is insufficient because of the limited number of studies with high methodological quality.[6] Notably, some studies evaluating this topic included helicopter emergency medical service (HEMS) with physicians, which had two major advantages: prehospital physician-led management itself and the shortened prehospital transport time. Another systematic review[7] reported that, although physician-led prehospital trauma management was associated with lower mortality, the benefit disappeared after excluding helicopter transport as a confounder.

As longer prehospital transport time has been reported to be associated with higher mortality rates,[8] it would be important to evaluate the benefit of physician-led trauma management independent of prehospital transport time for establishing optimal dispatch criteria for prehospital physician teams. However, studies evaluating the independent effect of physician-led trauma management, in which prehospital transport time was considered, have been scarce.

The aim of the present study was to evaluate the effect of physician-led prehospital trauma management on patient mortality considering the effect of time requiring patient transport. In addition, in subgroup analyses, we examined the characteristics of patients who were most likely to benefit from physician-led prehospital management itself.

Methods

Results

A flow diagram of the patient selection process is presented in Fig. 1. A total of 30,968 patients were eligible for analysis based on the inclusion and exclusion criteria. Of them, 3,032 patients (9.8%) received physician-led prehospital management. Physician-led prehospital management was more likely to be provided during daytime (between 6:00 and 17:59) than during nighttime. Median ISS (25th, 75th percentiles) was 25 (18, 32) in the physician-led group and 21 (17, 27) in the paramedic-led group, suggesting that patients in the physician-led group suffered more severe injuries than those in the paramedic-led group. The time lapse from the time of injury to physician contact was shorter in the physician-led group than in the paramedic-led group (median [25th, 75th percentiles] = 40 [30, 55] min and 46 [35, 61] min, respectively); however, the delay between the time of injury and hospital arrival was greater in the physician-led group than in the paramedic-led group (median [25th, 75th percentiles] = 56 [42, 73] min and 44 [34, 58] min, respectively). In-hospital mortality was observed in 460 (15.2%) patients in the physician-led group and in 3,417 (12.2%) patients in the paramedic-led group. Baseline characteristics of the overall study cohort are summarized in Table 1.

The variables used for propensity score estimation had high accuracy for predicting in-hospital mortality with C-statistics of 0.87. Via the matching process, a total of 2,766 propensity score-matched pairs (2,766 and 11,064 patients per physician-led group and paramedic-led group, respectively) were generated. All the ASMD values of the adjusted variables for the severity adjustment were < 0.1, indicating a well-matched balance (Table 2). Time lapse from the time of injury to physician contact was shorter in the physician-led group than in the paramedic-led group (median [25th, 75th percentiles] = 39 [30, 53] min and 53 [39, 73] min, respectively). In-hospital mortality was observed in 395 (14.3%) patients in the physician-led group and in 1,785 (16.1%) patients in the paramedic-led group. A significantly reduced in-hospital mortality rate was observed in the physician-led group in the propensity score-matched population (OR = 0.87, 95% CI, 0.77–0.97; p = 0.017). In the sensitivity analysis conducted with the overall study population using logistic regression analysis, the variance inflation factors for all the variables were less than 2, which eliminated the issue of multicollinearity in the model. The result also showed the significant association between physician-led prehospital treatment and reduced in-hospital mortality (adjusted OR = 0.86, 95% CI, 0.75–0.98; p = 0.021).

The results of subgroup analysis are summarized in Fig. 2. Patient who had age < 65 years, severe injuries with ISS ≥ 25, injury with AIS ≥ 3 in the pelvis or lower extremities, and total transportation time < 60 min likely benefited from physician-led prehospital management.

Discussion

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.[16] 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.[17]

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,[18] 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.

Conclusions

This large-scale retrospective cohort study showed a significant association between patient survival and physician-led prehospital trauma management independent of prehospital transport time. Further studies to identify effective interventions in prehospital-field care are necessary.

List Of Abbreviations

AIS, abbreviated injury scale

ASMD, absolute standardized mean difference

CI, confidence interval

ED, emergency department

HEMS, helicopter emergency medical service

ISS, injury severity score

JTDB, Japan Trauma Data Bank

OR, odds ratio

Declarations

Ethics approval and consent to participate

The Ethics Committee of Tokyo Medical and Dental University approved this study (#2192). The requirement for informed consent from each patient was waived because of the study’s retrospective design and the use of anonymized patient data.

Consent for publication

The manuscript does not include individual patient’s data. Therefore, consent is not applicable for this study.

Availability of data and materials

An overview of the Japan Trauma Data Bank (JTDB) is available at http://www.jtcr-jatec.org/traumabank/index.htm. The detailed data in the JTDB that support the findings of this study are available from Japan Trauma Care and Research but restrictions apply to the availability of these data, which were used under license for the current study, and hence are not publicly available.

Competing interests

The authors declare that they have no competing interests.

Funding

Not applicable

Authors’ contributions

AE drafted and revised the manuscript, prepared the study concept and design, and performed statistical analysis and data interpretation as well as accepts responsibility for conduct of research, final approval, and study supervision; MK revised the manuscript, prepared the study concept and design, and performed data interpretation as well as accepts responsibility for conduct of research and final approval; AS performed data acquisition and revised the manuscript as well as accepts responsibility for conduct of research and final approval; YO revised the manuscript and performed data interpretation as well as accepts responsibility for conduct of research and final approval.

Acknowledgements

The authors thank Editage (https://www.editage.jp) for assistance in English language editing.

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