The impact of pre-hospital time and Glasgow Coma Scale on drowning outcome: a linked data analysis from New South Wales

Drowning is a serious public health issue with more than 300,000 annual fatalities occurring globally. Within Australia, a leader in drowning prevention, the state of New South Wales (NSW) records the highest number of drownings, due in part to its large population and extensive waterways. The emergency medical services (EMS) system plays an important role in the survival chain; however, little is known about how EMS time intervals impact drowning outcome. The aim of this study was therefore to investigate how total prehospital time and its components affect drowning mortality in NSW, Australia. Individuals attended by NSW ambulance and transported to the Emergency Department (ED) for drowning between 1 January 2010 and 30 June 2022 were included. Age, sex, incident remoteness, Glasgow Coma Scale (GCS) score, and prehospital time intervals were analysed using a linked dataset comprising ambulance, emergency department, and death data. The primary outcome was 30-day mortality. Multivariable binary logistic regression identified predictors related to mortality. A total of 1686 patients were included, and 81 patients (4.8%) died at hospital within 30 days of the incident. Most incidents ( n = 1005, 59.6%) occurred in major cities. For patients with initial GCS of 3, each minute increment from emergency call receipt to ambulance arrival was associated with 5% increased odds of mortality (adjusted odds ratio; aOR 1.05, 95% confidence interval; CI 1.00–1.10). For patients with initial GCS greater than 3, each 5-year increase in age was associated with higher odds of mortality (aOR 1.23, 95% CI 1.04–1.45), but longer time to ambulance arrival was associated with lower odds of mortality (aOR 0.78, 95% CI 0.61-1.00). Time from scene departure to hospital was not associated with mortality. Patients with low initial GCS scores had higher mortality, and odds of survival were higher with faster ambulance response times. Patients with higher initial GCS had higher odds of survival with longer times to ambulance arrival, likely due to triage decisions. Further research is needed to elucidate interactions between factors.