The impact of prehospital time intervals on mortality in moderately and severely injured patients

BACKGROUND: Modern trauma systems and emergency medical services aim to reduce prehospital time intervals to achieve optimal outcomes. However, current literature remains inconclusive on the relationship between time to definitive treatment and mortality. The aim of this study was to investigate the association between prehospital time and mortality. METHODS: All moderately and severely injured trauma patients (i.e., patients with an Injury Severity Score of 9 or greater) who were transported from the scene of injury to a trauma center by ground ambulances of the participating emergency medical services between 2015 and 2017 were included. Exposures of interest were total prehospital time, on-scene time, and transport time. Outcomes were 24-hour and 30-day mortality. Generalized linear models including inverse probability weights for several potential confounders were constructed. A generalized additive model was constructed to enable visual inspection of the association. RESULTS: We included 22,525 moderately and severely injured patients. Twenty-four-hour and 30-day mortality were 1.3% and 7.3%, respectively. On-scene time per minute was significantly associated with 24-hour (relative risk RR, 1.029; 95% confidence interval, 1.018-1.040) and 30-day mortality (RR, 1.013; 1.008-1.017). We found that this association was also present in patients with severe injuries, traumatic brain injury, severe abdominal injury, and stab or gunshot wound. An on-scene time of 20 minutes or longer demonstrated a strong association with 24-hour (RR, 1.797; 1.406-2.296) and 30-day mortality (RR, 1.298; 1.180-1.428). Total prehospital (24-hour: RR, 0.998; 0.990-1.007; 30-day: RR, 1.000, 0.997-1.004) and transport (24-hour: RR, 0.996; 0.982-1.010; 30-day: RR, 0.995; 0.989-1.001) time were not associated with mortality. CONCLUSION: A prolonged on-scene time is associated with mortality in moderately and severely injured patients, which suggests that a reduced on-scene time may be favorable for these patients. In addition, transport time was found not to be associated with mortality. LEVEL OF EVIDENCE: Prognostic and Epidemiologic; level III.