Abstract Body: Introduction
Epinephrine administration and advanced airway management (AAM) (i.e., supraglottic airway insertion or endotracheal intubation) are commonly performed prehospital interventions for out-of-hospital cardiac arrest (OHCA). The optimal sequence of these two interventions remains unclear.

Research Question
Is the sequence of epinephrine administration and AAM associated with patient outcomes after OHCA?

Methods
We conducted a retrospective cohort study of adults (aged≥18 years) with nontraumatic OHCA who received prehospital epinephrine and/or AAM during cardiac arrest in the Resuscitation Outcomes Consortium Registry, a prospective OHCA registry at 10 sites in the US and Canada from 2011 to 2015. The main exposure was the sequence of intravenous or intraosseous epinephrine administration and AAM (epinephrine-first vs. AAM-first). The outcome was survival to hospital discharge. We used propensity scores and inverse probability of treatment weighting (IPTW) to address imbalances in patient demographics, arrest characteristics, and bystander interventions for each sub-cohort of initial shockable and nonshockable rhythms.

Results
Of 41,659 eligible patients (median [IQR] age, 67 [55-80] years), 26,535 (63.7%) were male. 8,431 patients (20.2%) had an initial shockable rhythm, and 33,228 (79.8%) had an initial nonshockable rhythm. Among patients with a shockable rhythm, 5,846 received epinephrine first, 2,272 received AAM first, and 313 received epinephrine and AAM concurrently. In patients with a nonshockable rhythm, 21,519 received epinephrine first, 10,365 received AAM first, and 1,344 received epinephrine and AAM concurrently. Using IPTW, all covariates between the epinephrine-first and AAM-first groups were well balanced (standardized mean differences <0.1). Compared with the AAM-first group, in the weighted population, the epinephrine-first group was not associated with survival to hospital discharge in the shockable rhythm (OR 1.00, 95% CI 0.92-1.08), but had a lower likelihood of survival to hospital discharge in the nonshockable rhythm (OR 0.80, 95% CI 0.74-0.87).

Conclusion
In the shockable rhythm, the epinephrine-first approach was not associated with survival to hospital discharge. In the nonshockable rhythm, the epinephrine-first approach was associated with a lower likelihood of survival to hospital discharge, suggesting that the AAM-first approach might be the optimal strategy in the initial nonshockable rhythm.