Out of Hospital Cardiac Arrest Registry Review: Factors influencing decreased non-metropolitan out-of-hospital cardiac arrest survivability in New South Wales (NSW)

Renee Oldfield, Grace Higgins, Dr Alexa Seal

Background:

Out of Hospital Cardiac Arrest (OHCA) is a critical public health issue in Australia, with disparities in survival rates between metropolitan and rural areas. In 2020, New South Wales Ambulance (NSWA) attempted resuscitation in approximately 3000 OHCAs with a less than 11% survival rate to hospital admission. Since 2017, all cardiac arrests attended to by NSWA Paramedics has had data extrapolated to contribute to an OHCA registry. While much analysis has occurred of this data to determine survivability factors, the influence of paramedic skill level on survivability of cardiac arrest has not been widely investigated.

Aim:

Through collaboration with NSWA, this preliminary study aims to examine OHCA registry data to explore factors influencing survivability in NSW such as paramedic skill level, geographical isolation, patient age, and bystander interventions.

Methods:

A retrospective analysis was conducted on 5,147 adult OHCA cases from the NSWA 2023 OHCA data set. Patients under 18 years, or with unknown age were excluded. Cases with an outcome of “deceased on examination” were also excluded as these cases were disproportionately attended to by lower skilled paramedics and therefore could underestimate the impact of these skill levels on survivability. The primary outcome was “survival to ED”, meaning the patient was handed over either with return of spontaneous circulation (ROSC) or with resuscitation still in progress. Variables included Paramedic skill level, Modified Monash Model (MMM) remoteness category, age group and bystander intervention such as CPR and/or AED use. Data were analysed using chi-square testing for association and binary logistic regression to assess predictors of survival to ED.

Results:

Intensive Care Paramedics (ICPs) were associated with higher survivability in all ages of patients, particularly those aged 65 and older (p <0.001). Qualified Paramedics also show statistically significant survival rates in the greater than 65 population (p 0.022). With increasing rurality (MMM) survival declined, although this was not statistically significant. Bystander intervention positively influenced survivability, especially bystander AED use (p <0.001). Overall, younger patients aged 18-34 year's demonstrated the highest survival rates.

Conclusion:

This analysis suggests Paramedic clinical skill level, geographical remoteness, patient age, and bystander intervention play a crucial role in OHCA survivability in NSW. ICP involvement and bystander AED use positively influence survivability. While older age (>65 years) and increasing remoteness negatively impact patient outcomes. While some of these findings are supported by previous research, further research is required to confirm outcomes, particularly those related to Paramedic skill level. Findings from these types of studies support the need for workforce planning to improve cardiac arrest survivability, especially in rural NSW.