Effect of fluid administration on scene to traffic accident patients by EMS personnel: a propensity score-matched study using population-based ambulance records and nationwide trauma registry in Japan

Death due to hemorrhage is an important issue in trauma care around the world. Indeed, it was reported that approximately 40% of trauma deaths occurring within 24 h were due to hemorrhage [1]. In the 1970s in the United States, fluid resuscitation prior to hospital arrival was considered an important component of prehospital care for trauma patients. In the Advanced Trauma Life Support guidelines from the American College of Surgeons, initial resuscitation with crystalloid fluid still begins with a 1-L bolus of warmed isotonic fluid [2]. Maintaining systolic blood pressure to stabilize tissue circulation and prevent acidosis is associated with a favorable prognosis for trauma patients. However, several observational studies and clinical trials have reported that aggressive fluid administration prior to definite care may actually increase mortality in trauma patients [3‐5]. Aggressive fluid administration to maintain blood pressure may contribute to bleeding due to pro-inflammatory effects and coagulopathy caused by hemodilution and hypothermia. In addition, several studies reported that patient transport from the scene to the hospital is delayed when paramedics secure intravenous lines in a prehospital setting [6‐8].

In Japan, the regulations for emergency life-saving technicians (ELST) were amended in 2014 to allow ELST to secure intravenous lines and administer lactated Ringer’s solution to patients in shock or with crush syndrome [9]. However, it is unknown whether fluid administration by ELST in Japan has contributed to the improvement of outcomes in trauma patients.

The emergency medical service (EMS) in Japan is a public service provided by the local government, and all ambulance records are reported to the Fire and Disaster Management Agency (FDMA). The Japanese Trauma Data Bank (JTDB) is the nationwide trauma registry in Japan, and about 300,000 trauma patients were registered by 2017. The aim of this study was to assess the effect of fluid administration by ELST on the prognosis of traffic accident patients by linking population-based ambulance records and the nationwide trauma registry in Japan based on a propensity score (PS)-matching method.

Figure 1 shows the patient flow in this study. From January 2016 to December 2017, 39,831 trauma patients were registered in the JTDB database, of whom 10,908 were traffic accident patients. Of these patients, 8519 were matched with ambulance records provided from the FDMA. We excluded the patients with an ISS of < 16 (n = 4579), patients in CPA at the time of ambulance arrival at the scene (n = 100), and patients with insufficient data (vital signs at hospital arrival, n = 127; date, n = 44; prognosis, n = 167) and thus included 3502 patients in this study. Of these patients, 142 patients were given fluid administration by ELST and 3360 patients were not given fluid administration by ELST.

Table 1 shows the clinical characteristics of the patients before and after PS matching. A higher population of males and more nighttime accidents were found in the fluid group than in the no fluid group, and the ISS was higher in the fluid group than that in the no fluid group before PS matching. In addition, there was a high percentage of shock and ungaugeable blood pressure or missing data at the scene in the fluid group and a high percentage of car drivers and patients with thorax injury and abdominal injury. After PS matching, 141 patients were selected from each group, and the area under the curve in the logistic regression model for PS calculation was 0.776. The covariates were improved among the groups after PS matching.

Table 2 shows the relationship between fluid administration by ELST at the scene and discharge to death. In the univariate regression analysis of the total cohort, the fluid group had a higher rate of discharge to death than the no fluid group (23.2% [33/142] vs 15.2% [512/3360], crude OR: 1.684, p = 0.011). In the multivariate logistic regression analysis, fluid administration by ELST at the scene was not associated with discharge to death (adjusted OR: 1.088 [95% CI, 0.658–1.798]; p = 0.743). In the PS-matched model, the proportions of discharge to death in the fluid group and the no fluid group were similar (23.4% [33/141] vs 26.2% [37/141]), and there was no significant relationship between fluid administration by ELST at the scene and discharge to death (crude OR: 0.859 [95% CI, 0.500–1.475]; p = 0.582). Fluid administration by ELST at the scene was also not associated with discharge to death in the multivariate logistic regression model (adjusted OR: 0.980 [95% CI, 0.443–1.986]; p = 0.955).

Table 3 shows the relationship between fluid administration by ELST at the scene and CPAOA. In the univariate regression analysis of the total cohort, there was little difference in the proportion of CPAOA in the fluid group compared with the no fluid group (5.6% [8/142] vs 4.0% [134/3360], crude OR: 1.134 [95% CI, 0.547–2.354]; p = 0.735). In the multivariate logistic regression model, the fluid group tended to have a better prognosis than the no fluid group, but the difference was not statistically significant (adjusted OR: 0.443 [95% CI, 0.185–1.060]; p = 0.067). However, in the PS-matched model, the fluid group had a smaller proportion of CPAOA than the no fluid group (5.7% [8/141] vs 12.1% [17/141], crude OR: 0.439 [95% CI, 0.183–1.053]; p = 0.064). The fluid group had a statistically better prognosis than the no fluid group in the multiple logistic regression model (adjusted OR: 0.231 [95% CI, 0.055–0.967]; p = 0.045).

Table 4 shows the results of subgroup analysis divided into patients with and without severe head injury. Fluid administration by ELST was not associated with discharge to death in either the patients with severe head injury (AOR: 1.081 [95%CI, 0.526–2.223], p = 0.832) or in those without severe head injury (AOR: 1.046 [95%CI, 0.481–2.271], p = 0.910). However, the proportion of CPAOA tended to be lower in the fluid group among patients without severe head injury, although this was not significant in the multivariate regression model (AOR: 0.231 [95% CI, 0.044–1.216], p = 0.084).

In this study, we found that fluid administration by ELST to traffic accident victims at the scene decreased the proportion of CPAOA but did not improve the mortality of these patients. In addition, both the time interval from ambulance call to hospital arrival and that between departure from the scene and hospital arrival were significantly longer in the group with fluid administration by ELST than those in the group without fluid administration by ELST. This study, which found that fluid administration by ELST improved the status of patients on hospital arrival, may be useful in examining the treatment for trauma patients by EMS personnel in the prehospital situation.

First, fluid administration by ELST was shown to be neither beneficial nor harmful to traffic accident patients in this study. In a subgroup analysis divided by severe head injury, fluid administration by ELST was neither beneficial nor harmful in either the patients with severe head injury or in those without severe head injury. There are several studies on intravenous access and fluid administration in prehospital settings. Some studies reported that fluid administration by EMS personnel to trauma patients had no effect on mortality [7, 23, 24], whereas other studies reported rather that it increased the mortality [6, 8]. Another report showed that the inability to obtain peripheral venous access is associated with the severity of injury [25]. As the present study included only traffic accident patients, all of the patients had suffered blunt trauma. This may be the reason why the present results differed from those of some of the previous studies.

Second, the proportion of CPAOA was lower in the group with fluid administration by ELST than that in the group without fluid administration in this study. In addition, fluid administration by ELST tended to be associated with a lower proportion of CPAOA among the patients without severe head injury. These results may be influenced by fluid administration by ELST and the maintenance of circulation in severe trauma patients. Seamon et al. reported that prehospital procedures were the only predictor of hospital mortality in a study of trauma patients undergoing emergency department thoracotomy, for which they compared ambulance versus non-ambulance transport methods such as a police car or private vehicle [6]. Although this previous study included trauma patients with emergency department thoracotomy, the present study included traffic accident patients, and not all of them underwent emergency department thoracotomy. Thus, it is possible that the urgency of the patients in the present study was less than that in the previous study, which may have led to a difference in these results. In a previous study by Sampalis et al., prehospital infusion provided no benefit when the prehospital time was < 30 min, and conversely, prehospital infusion increased the risk of mortality if prehospital time was longer than 30 min [8]. In that study, the mean ISS for patients with prehospital infusion was 15, and that for patients without prehospital infusion was 9. In contrast, among the PS-matched patients in the present study, the mean ISS was 31.3 for the patients in the fluid group and 30.3 for those in the no fluid group. Thus, because there were more severe trauma patients in this study than in the previous study, obtaining venous access in the prehospital setting may be useful for maintaining the circulatory system of severe trauma patients during their transport to the hospital. In addition, the prognosis of trauma patients is affected not only by prehospital care but also by surgical treatment and intensive care received in the hospital. Therefore, it may be difficult to assess the effect only of fluid administration by ELST or paramedics on hospital mortality. Indeed, other previous studies reported that prehospital time was longer in patients with versus without venous access obtained by paramedics and that mortality was same in the patients regardless of whether venous access was obtained by the paramedics [23, 24]. Therefore, in the present study, the proportion of patients with CPAOA was used as a measure to evaluate fluid administration by ELST because CPAOA is not affected by surgical treatment and intensive care. The results in the present study that fluid administration by ELST was associated with a lower proportion of CPAOA would suggest that fluid administration by ELST may contribute to the improved outcome of trauma patients. In addition, intraosseous infusion may improve the prognosis of trauma patients because it reduces the time interval to secure an infusion route. Furthermore, the method, dosage, and timing of administration of infusion products used in prehospital settings were evaluated in several studies [3, 7, 8, 23‐25]. Although the method and dosage of infusion products are determined by local medical controls in Japan, it is mentioned that a bolus dose of 250–500 mL of fluid should be administered to trauma patients with a systolic blood pressure of < 80 mmHg in the Japan Prehospital Trauma Evaluation and Care (JPTEC) program that most emergency care providers attend [26]. These differences between the method and timing of fluid administration in the prehospital setting may have influenced the difference in results between the present study and these previous studies.

In this study, we revealed that fluid administration by ELST to traffic accident patients at the scene was associated with a low proportion of CPAOA but was not associated with improved hospital mortality.