Background National data collection provides information on out-of-hospital cardiac arrest (OHCA) incidence, management and outcomes that may not be generalisable from smaller studies. This retrospective cohort study describes the first 2 years' results from the Irish National Out-of-Hospital Cardiac Arrest Register (OHCAR).

Methods Data on OHCAs attended by emergency medical services (EMS) where resuscitation was attempted (EMS-treated) were collected from ambulance services and entered onto OHCAR. Descriptive analysis of the study population was performed, and regression analysis was performed on the subgroup of adult patients with a bystander-witnessed event of presumed cardiac aetiology and an initial shockable rhythm (Utstein group).

Results 3701 EMS-treated OHCAs were recorded for the study period (1 January 2012–31 December 2013). Incidence was 39/100 000 population/year. In the Utstein group (n=577), compared with the overall group, there was a higher proportion of male patients, public event location, bystander cardiopulmonary resuscitation (CPR) and early defibrillation. Median EMS call–response interval was similar in both groups. A higher proportion of patients in the Utstein group achieved return of spontaneous circulation (35% vs 17%) and survival to hospital discharge (22% vs 6%). After multivariate adjustment for the Utstein group, the following variables were found to be independent predictors of the outcome survival to hospital discharge: public event location (OR 3.1 (95% CI 1.9 to 5.0)); bystander CPR (2.4 (95% CI 1.2 to 4.9)); EMS response of 8 min or less (2.2 (95% CI 1.3 to 3.6)).

Conclusions This study highlights the role of nationwide registries in quantifying, monitoring and benchmarking OHCA incidence and outcome, providing baseline data upon which service improvement effects can be measured.