Paediatric out-of-hospital cardiac arrest occurring before and after emergency medical service arrival: a retrospective study.

AIM: To examine the association between witness status and the incidence, characteristics, and survival outcomes of paediatric out-of-hospital cardiac arrest (OHCA) attended by emergency medical services (EMS). METHODS: We conducted a retrospective cohort study of paediatric (<18 years) OHCA cases attended by EMS between 1 January 2000 and 31 December 2024. Cases were identified from the Victorian Ambulance Cardiac Arrest Registry (VACAR). Witness status was categorised as unwitnessed, bystander witnessed, or EMS witnessed. Multivariable logistic regression was used to evaluate the association between witness status and outcomes, adjusting for age, sex, arrest location, region, aetiology, initial rhythm and year. RESULTS: A total of 2,645 paediatric OHCAs were attended by EMS, of which 1,891 (71.5%) received a resuscitation attempt. Among EMS-treated cases, 59.8% were unwitnessed, 32.0% were bystander witnessed, and 8.1% were EMS witnessed. The incidence of unwitnessed and bystander witnessed OHCA declined over the 25-year period (p<0.001), whereas EMS witnessed incidence remained stable. After adjustment, EMS witnessed arrests were associated with significantly higher odds of survival to hospital discharge (AOR 1.91, 95% CI 1.04-3.52) and prehospital ROSC (AOR 1.83, 95% CI 1.20-2.77) compared with bystander witnessed arrests, while unwitnessed arrests had substantially lower survival across all outcomes. CONCLUSION: Paediatric OHCA witnessed by EMS is associated with significantly higher adjusted odds of survival compared with bystander witnessed events. These findings highlight the importance of early professional intervention and support the need for paediatric-specific strategies to improve recognition and response to these events.