A retrospective multi-centre cohort study: Pre-hospital survival factors of out-of-hospital cardiac arrest (OHCA) patients in Thailand

This study aimed to explore significant pre-hospital factors affecting the survivability of Out-of-Hospital Cardiac Arrest (OHCA) patients in countries with developing EMS systems.A retrospective cohort study was conducted examining data from January 1, 2017 to December 31, 2020 from Utstein Registry databases in Thailand, collected through Pan-Asian Resuscitation Outcomes Study (PAROS). Data were collected from three centres, including regional, suburban-capital, and urban-capital hospitals. The primary endpoint of this study was 30-day survival or discharged alive after an OHCA event. The multivariable risk regression was done by modified Poisson regression with robust error variance to explore the association between 30-day survival and pre-hospital factors with potential confounders adjustments.Of 1,240 OHCA cases transferred by Emergency Medical Services (EMS), 42 patients (3.4%) were discharged alive after 30 days, including 22 (8.6%), 8 (3.0%), and 12 (1.7%) from regional, suburban-capital, and urban-capital centres, respectively. The initial arrest rhythm was 89.7% unshockable, with no significant variations across the three centres. Overall, bystander Cardiopulmonary Resuscitation (CPR) was 40.4%. However, bystander CPR with Automated External Defibrillator (AED) application was 0.8%. Bystander CPR significantly increased 30-day survival probability (aRR 1.88, 95% CI 1.01 to 3.51; p 0.049). Additionally, reducing the EMS response time by one minute significantly increased OHCA survivability (aRR 1.12, 95% CI 1.04 to 1.20; p 0.001).Response time and bystander CPR are the factors that improve the 30-day survival outcomes of OHCA patients. In contrast, scene time, transport time, and pre-hospital advanced airway management didn't improve 30-day OHCA survival.