Okubo M, et al. - In this observational cohort study, researchers investigated the variation in survival following out-of-hospital cardiac arrest (OHCA) between emergency medical service (EMS) agencies. They found substantial unexplained variation in survival following OHCA across treating EMS agencies in North America, despite controlling for documented patient- and EMS agency-level variables.

Methods

• This study was conducted in the Resscitation Outcomes Consortium (ROC) Epistry—a prospective multicenter OHCA registry at 10 sites in North America—and included any adult with OHCA treated by an EMS agency from April 2011 through June 2015.
• The investigators performed data analysis from May 2017 to March 2018.
• Survival to hospital discharge was mainly assessed; return of spontaneous circulation at emergency department arrival and favorable functional outcome at hospital discharge (defined as a modified Rankin scale score ≤ 3) were also evaluated.
• For adjusting confounders and clustering of patients within EMS agencies, researchers used multivariable hierarchical logistic regression models.
• The quantification of the extent of residual variation in outcomes between EMS agencies was carried out by using calculated median odds ratios.

Results

• A total of 43,656 adults with OHCA treated by 112 EMS agencies were included in this analysis.
• Researchers found that, at the EMS agency level, survival to hospital discharge, return of spontaneous circulation on emergency department arrival, and favorable functional outcome varied largely.
• Even after adjustment for patient-level and EMS agency-level factors known to be related to outcomes, this variation persisted.
• The persistence of the variation continued even after restricting analysis to those who survived > 60 minutes after hospital arrival and including hospital treatment characteristics.