Improving Outcomes of Witnessed Out‐of‐Hospital Cardiac Arrest After Implementation of International Liaison Committee on Resuscitation 2010 Consensus: A Nationwide Prospective Observational Population‐Based Study

BACKGROUND: The International Liaison Committee on Resuscitation (ILCOR) periodically updates the consensus recommendations for cardiopulmonary resuscitation to improve the outcomes of out‐of‐hospital cardiac arrest (OHCA). However, little is known about the differences in outcomes of witnessed OHCA following the publication of the ILCOR 2010 and the ILCOR 2005 recommendations. METHODS AND RESULTS: We enrolled 241 990 adults who experienced witnessed OHCA between 2007 and 2013 from a prospective, nation‐wide, population‐based cohort database in Japan. We compared neurologically favorable 1‐month survival and 1‐month survival rates post‐OHCA by dividing the study period into 2 categories: the ILCOR 2005 period and ILCOR 2010 period. The associations between guideline periods and outcomes were estimated using multivariable logistic regression analysis and reported as adjusted odds ratio and 95% CI. Among 241 990 patients examined in this study, OHCA was witnessed in 44 706 patients (18%) by emergency medical service personnel and in 197 284 patients (82%) by citizens. Compared with the ILCOR 2005 period, the neurologically favorable 1‐month survival rate improved from 4.6% to 5.2% (adjusted odds ratio, 1.54; 95% CI, 1.42–1.67; P<0.001), and the 1‐month survival rate improved from 9.0% to 9.7% (adjusted odds ratio, 1.34; 95% CI, 1.27–1.42; P<0.001) in the ILCOR 2010 period. These improvements were also shown in patients receiving conventional versus compression‐only cardiopulmonary resuscitation. CONCLUSIONS: Outcomes of witnessed OHCA were better in the ILCOR 2010 period than those in the ILCOR 2005 period. Our results can provide baseline data for many future prospective studies.