Association between institutional volume of out-of-hospital cardiac arrest cases and short term outcomes

Abstract

BackgroundOut-of-hospital cardiac arrest (OHCA) is a serious condition. The volume-outcome relationship and various post–cardiac arrest care elements are believed to be associated with improved neurological outcomes. Although previous studies have investigated the volume–outcome relationship, adjusting for post-cardiac arrest care, intra-class correlation for each institution, and other covariates may have been insufficient. ObjectiveTo investigate the volume-outcome relationships and favorable neurological outcomes among OHCA cases in each institution. MethodsWe conducted a prospective observational study of adult patients with non-traumatic OHCA using the OHCA registry in Japan. The primary outcome was 30-day favorable neurological outcomes, and the secondary outcome was 30-day survival. We set the cutoff values to trisect the number of patients as equally as possible and classified institutions into high-, middle-, and low-volume. Generalized estimating equations (GEE) were performed to adjust for covariates and within-hospital clustering.1Department of Emergency Medicine, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8606, Japan ResultsAmong the 9909 registry patients, 7857 were included. These patients were transported to either low- (2679), middle- (2657), or high- (2521) volume institutions. The median number of eligible patients per institution in 19 months of study periods was 82 (range, 1–207), 252 (range, 210–353), and 463 (range, 390–701), respectively. After multivariable GEE using the low-volume institution as a reference, no significant difference in odds ratios and 95% confidence intervals were noted for 30-day favorable neurological outcomes for middle volume [1.22 (0.69–2.17)] and high volume [0.80 (0.47–1.37)] institutions. Moreover, there was no significant difference for 30-day survival for middle volume [1.02 (0.51–2.02)] and high volume [1.09 (0.53–2.23)] institutions. ConclusionThe patient volume of each institution was not associated with 30-day favorable neurological outcomes. Although this result needs to be evaluated more comprehensively, there may be no need to set strict requirements for the type of institution when selecting a destination for OHCA cases.