Relationship between prehospital time and 24-hour mortality following injury in patients with major trauma in New Zealand

Abstract

Aim: To explore the relationship between time spent in the prehospital phase and 24-hour mortality following injury in patients with major trauma in New Zealand (NZ). Methods: Following a systematic review to describe the incidence and characteristics of major trauma in NZ, analysis of routinely collected data from a retrospectively designed prospective cohort study was undertaken. Individuals of any age attended by an Emergency Medical Services (EMS) provider in NZ immediately following major trauma between 1 December 2016 and 30 November 2018 were included. Factors predictive of prehospital mortality were explored using modified Poisson regression. Models were built for total prehospital time and EMS time intervals, and were adjusted by patient sociodemographic, triage and injury characteristics. Results: A total of 3,334 patients met the eligibility criteria, of which 105 (3.1%) died prehospital and 111 (3.4%) died 24 hours following injury. Median total prehospital time was 74.6 minutes (IQR: 50.6–104.8). Response and transport times were significantly lower for those patients who died 24 hours following` injury (p<0.05). In the univariate analysis, total prehospital time greater than 60 minutes was a predictor of survival, reducing the risk of death in 49% (RR: 0.51; 95%CI: 0.35-0.76). Response time greater than 14 minutes, on-scene time between 30- 45 minutes and transport times of 10 minutes or more were predictive of less risk of death (p<0.001). In the multivariable analysis response time between 5-10 minutes (adjusted RR (aRR): 0.39; 95%CI: 0.18-0.84) or greater than 14 minutes (aRR: 0.37; 95%CI: 0.18-0.80) predicted survival. Other factors increasing the risk of 24-hour mortality in this cohort included age (80-84 years), triage (purple/red), having one or two previous hospital admissions, experiencing non-blunt trauma, and having an injury severity score greater than 24. Conclusion: Although longer total prehospital times were found to predict reduced 24-hour mortality, analysis of the components of prehospital time was less conclusive and highlighted the importance of factors such as age, triage, and other related-injury factors, namely the severity of trauma. Studies considering 30-day mortality as an outcome and exploring reasons for onscene and transport delays would be useful extensions to this research.