Impact of Pre-Hospital Intravenous Infusion on Physiological Parameters in Severe Trauma Patients

Introduction The relationship between pre-hospital intravenous (IV) infusions administered by emergency life-saving technicians (ELSTs) to trauma patients in shock and the resulting variability in their vital signs before hospital arrival remains unclear. In 2014, Japan approved the use of lactated Ringer's solution via IV by ELSTs for patients aged 15 and older with non-cardiac arrest and shock symptoms not caused by cardiogenic factors. However, the impact of pre-hospital IV infusions on physiological parameters in severely injured trauma patients is still unknown. Aim The aim of this study is to investigate the impact of pre-hospital IV infusions administered by ELSTs on trauma patients with shock, focusing on the resulting variations in the shock index and other physiological parameters in the pre-hospital setting. Methods This retrospective cohort study included patients registered in the Japan Trauma Data Bank who were transported by ambulance from the pre-hospital to the hospital by ELST between 2019 and 2021. First, the data were categorized based on pre-hospital IV access as either IV (+) or IV (-). Propensity score matching was then performed to estimate the average treatment effect for patients receiving IV (+). The primary endpoint was the delta shock index (DSI), while secondary endpoints included systolic blood pressure (sBP), heart rate (HR), and respiratory rate (RR). Welch's t-test was used to estimate mean differences and 95% CIs, and Cohen's d was calculated to measure effect sizes. Results A total of 88,817 patients were enrolled in the study, with 19,793 included in the analysis. Of these, 778 patients were matched for comparison. IV access (+) was not significantly associated with changes in the DSI, showing a small effect size (-0.09 vs. -0.06; difference [95% CI]: -0.04 [-0.08 to 0.00]). Additionally, IV (+) was not significantly associated with differences in HR (-0.23 vs. 1.16; difference [95% CI]: -1.40 [-3.59 to 0.80]) or RR (-1.95 vs. -1.08; difference [95% CI]: -0.87 [-1.83 to 0.09]), both of which demonstrated small effect sizes. However, IV (+) was significantly associated with an increase in sBP difference, although the effect size remained small (13.22 vs. 8.73; difference [95% CI]: 4.49 [0.35 to 8.62]). Conclusions IV access was not directly associated with variations in the shock index in the pre-hospital setting; however, it significantly increased sBP. Future studies should include the volume of IV infusion to further elucidate these findings.