Relationship Between Institutional Volume of Out-of-Hospital Cardiac Arrest Cases and 1-Month Neurologic Outcomes: A Post Hoc Analysis of a Prospective Observational Study

Background: The influence of institutional volume of out-of-hospital cardiac arrest (OHCA) cases on outcomes remains unclear. Objectives: This study evaluated the relationship between institutional volume of adult, nontraumatic OHCA cases and 1-month favorable neurologic outcomes. Methods: This study retrospectively analyzed data between January 2012 and March 2013 from a prospective observational study in the Kanto area of Japan. We analyzed adult patients with nontraumatic OHCA who underwent cardiopulmonary resuscitation by emergency medical service personnel and in whom spontaneous circulation was restored. Based on the institutional volume of OHCA cases, we divided institutions into low-, middle-, or high-volume groups. The primary and secondary outcomes were 1-month favorable neurologic outcomes and 1-month survival, respectively. A multivariate logistic regression analysis adjusted for propensity score and in-hospital variables was performed. Results: Of 2699 eligible patients, 889, 898, and 912 patients were transported to low-volume (40 institutions), middle-volume (14 institutions), and high-volume (9 institutions) centers, respectively. Using low-volume centers as the reference, transport to a middle- or high-volume center was not significantly associated with a favorable 1-month neurologic outcome (adjusted odds ratio [OR] 1.21 [95% confidence interval {CI} 0.84–1.75] and adjusted OR 0.77 [95% CI 0.53–1.12], respectively) or 1-month survival (adjusted OR 1.10 [95% CI 0.82–1.47] and adjusted OR 0.76 [95% CI 0.56–1.02], respectively). Conclusions: Institutional volume was not significantly associated with favorable 1-month neurologic outcomes or 1-month survival in OHCA. Further investigation is needed to determine the association between hospital characteristics and outcomes in patients with OHCA.