Comparison of out-of-hospital cardiac arrest occurring before and after paramedic arrival: epidemiology, survival to hospital discharge and 12-month functional recovery

Background: Despite immediate resuscitation, survival rates following out-of-hospital cardiac arrests (OHCA) witnessed by emergency medical service (EMS) are reportedly low. We sought to compare survival and 12-month functional recovery outcomes for OHCA occurring before and after EMS arrival.

Methods: Between 1st July 2008 and 30th June 2013, we included 8648 adult OHCA cases receiving an EMS attempted resuscitation from the Victorian Ambulance Cardiac Arrest Registry, and categorised them into five groups: bystander witnessed cases±bystander CPR, unwitnessed cases±bystander CPR, and EMS witnessed cases. The main outcomes were survival to hospital and survival to hospital discharge. Twelve-month survival with good functional recovery was measured in a sub-group of patients using the Extended Glasgow Outcome Scale (GOSE).

Results: Baseline and arrest characteristics differed significantly across groups. Unadjusted survival outcomes were highest among bystander witnessed cases receiving bystander CPR and EMS witnessed cases, however outcomes differed significantly between these groups: survival to hospital (46.0% vs. 53.4% respectively, p<0.001); survival to hospital discharge (21.1% vs. 34.9% respectively, p<0.001). When compared to bystander witnessed cases receiving bystander CPR, EMS witnessed cases were associated with a significant improvement in the risk adjusted odds of survival to hospital (OR 2.02, 95% CI: 1.75-2.35), survival to hospital discharge (OR 6.16, 95% CI: 5.04-7.52) and survival to 12 months with good functional recovery (OR 5.56, 95% CI: 4.18-7.40).

Conclusion: When compared to OHCA occurring prior to EMS arrival, EMS witnessed arrests were associated with significantly higher survival to hospital discharge rates and favourable neurological recovery at 12-month post-arrest.