Temporal trends in Singapore for out-of-hospital cardiac arrest with an initial non-shockable rhythm

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Medical Research Council Singapore Background Out-of-hospital cardiac arrest (OHCA) with an initial non-shockable rhythm is the predominant form of OHCA in adults, yet outcomes are dismal. We evaluated its 10-year trends in epidemiology and management in Singapore. Methods Using the national OHCA registry we studied the trends of 20,844 Emergency Medical Services (EMS)-attended adult OHCA from April 2010 to December 2019. Survival to hospital discharge was the primary outcome. Analyses of the trends and outcomes were performed with linear regression and logistic regression, respectively. Results Incidence rates of EMS-attended adult OHCAs increased during the study period, with increasing proportion of adult OHCA being non-shockable OHCA (Figure 1). Compared to shockable OHCA, non-shockable OHCAs were significantly older (median age 71 vs 61 years), had more comorbidities (median Charlson Comorbidity Index 4 vs 3), more likely unwitnessed (46% vs 25%) and residential arrests (77% vs 53%) (all p<0.001); non-shockable OHCAs had longer no-flow time (median 16 vs 13 minutes), and received less bystander cardiopulmonary resuscitation (CPR) (49% vs 61%) and in-hospital interventions (coronary revascularization 1% vs 18%, targeted temperature management (TTM) 3% vs 14%) (all p<0.001). Amongst non-shockable OHCA, age, comorbidities, residential arrests, no-flow time and time to patient increased during the study period, while presumed cardiac etiology decreased; bystander CPR, epinephrine use and TTM increased (all p<0.05) (Figure 2). Survival for non-shockable OHCA did not improve (1% in 2010 to 1.3% in 2019, p=0.107), unlike shockable OHCA (10% to 26%, p<0.001). The likelihood of survival for non-shockable OHCA increased with witnessed arrest (adjusted odds ratio (aOR) 2.281) and bystander CPR (aOR 3.569), but decreased with presumed cardiac etiology (aOR 0.553), epinephrine administration (aOR 0.646), time to patient (aOR 0.938) and comorbidity burden (aOR 0.897). Significant two-way interactions were observed for no-flow time and arrest location with bystander CPR. Cardiac revascularization improved the odds of survival in patients who survived to admission (aOR 2.63). Conclusion Singapore saw increasing incidence and interventions for non-shockable OHCA between 2010 and 2019 but limited gains in survival, partly explained by ageing population with increasing comorbidity burden. This contrasts with the improvement in survival for shockable OHCA over the same period. The interactions of location and no-flow time with bystander CPR highlight opportunities to improve pre-hospital care for residential and non-shockable OHCA.