The Impact of Cardiopulmonary Resuscitation Guidelines Updates Against Out-of-Hospital Shockable Cardiac Arrest: A Population-Based Cohort Study

Background: International cardiopulmonary resuscitation (CPR) guidelines based on the best available evidence from resuscitation science have been updated since 2000. However, few nationwide population-based studies have been investigated comprehensive efficacy of those updates for out-of-hospital cardiac arrest (OHCA). Methods: From the All-Japan Utstein Registry between 2005 and 2015, we enrolled 73 578 adults who had witnessed shockable (ventricular fibrillation or pulseless ventricular tachycardia) OHCA. We examined temporal trends over eleven years (2005 on the Guidelines 2000 era, from 2006 to 2010 on the consensus on CPR and emergency cardiovascular care science with treatment recommendations [CoSTR] 2005 era, and from 2011 to 2015 on the CoSTR 2010 era). The primary end point was favorable neurological outcome (Cerebral Performance Category of 1 or 2) at 30 days after OHCA. Findings: Of 73 578 study patients, 61,080 (83%) were witnessed by bystander and 12 498 (17%) by emergency medical services (EMS) responder. After adjustment for Utstein variables, odds ratios for favorable 30-day neurological outcome increased year by year (reference, 2005): the bystander-witnessed group, 1∙19 (95% CI 1∙03-1∙37) in 2006, 2∙40 (95% CI 2∙10-2∙74) in 2010, 2∙45 (95% CI 2∙14-2∙80) in 2011 and 3∙02 (95% CI 2∙63-3∙46) in 2015; the EMS responder-witnessed group, 1∙27 (95% CI 1∙01-1∙60) in 2007, 1∙28 (95% CI 1∙02-1∙60) in 2010, 1∙54 (95% CI 1∙23-1∙94) in 2011 and 1∙58 (95% CI 1∙26-1∙99) in 2015. Similar results were seen in the subgroups receiving EMS-dispatcher CPR instruction, bystander chest compression-only CPR, early defibrillation, biphasic waveform defibrillators or advanced airway management. However, there was no evidence for any benefit from the addition of epinephrine. Interpretation: The international CPR guidelines updates for shockable OHCA had improved neurologically intact survival year by year. However, epinephrine is a topic for the future.  Clinical Trial Registration Details: This study is registered with the University Hospital Medical Information Network Clinical Trials Registry, UMIN000009918. Funding Information: None. Declaration of Interests: We declare no competing interests. Ethics Approval Statement: A subcommittee of resuscitation science in the Japanese Circulation Society conducted this study with approval from the ethics committee at Nihon University Hospital.