Abstract 107: Accelerated Intramuscular Epinephrine and Survival in Adult, Non-Traumatic Out-of-Hospital Cardiac Arrest: A Before-After Study

Introduction: Survival after out-of-hospital cardiac arrest is poor. Treatment with early epinephrine is associated with improved survival but delays in vascular access may impact its timely delivery. Outcomes may be improved by novel methods to administer epinephrine prior to vascular access. We previously established that intramuscular epinephrine reduced time from 911 call to drug administration.

Aim: To determine whether accelerated intramuscular epinephrine (IM-Epi) is associated with improved OHCA survival compared with standard IV/IO epinephrine.

Methods: We conducted a before-after analysis of the implementation of an IM-Epi EMS protocol. We included adult OHCAs treated by the Salt Lake City Fire Department. Interventions were: pre-IM Epi (Jan 2010-Nov 2019), standard care IV or IO epinephrine; post-IM Epi (Dec 2019-Mar 2023), a single dose of 5 mg IM epinephrine prior to the initiation of IV/IO access. All other care followed standard ACLS, including additional dosing of epinephrine via IV/IO. Using multivariable logistic regression, we determined the association between IM-Epi and hospital survival, ROSC, and good neurologic function adjusted for Utstein variables.

Results: Among 1,283 OHCAs, 307 (23.9%) received IM-Epi and 976 (76.1%) received usual care. Groups had similar sex, witnessed arrest, arrest location, initial rhythm, and response time, but younger age (57.3 vs. 59.5 years old; p=0.05) and higher bystander CPR (68.3% vs. 56.0%; <0.001) in the IM-Epi group. Time to epinephrine administration was faster for the IM-Epi group (12.0 vs. 15.3 min; <0.001). IM-Epi was associated with improved hospital survival (adjusted OR, 1.87; 95% CI, 1.12-3.10) and good neurologic outcome at discharge (adjusted OR, 1.76; 95% CI 1.02-3.01). IM-Epi first was not associated with differential rates of ROSC (adjusted OR, 1.02; 95% CI, 0.78-1.35) when compared to standard IV/IO first administration.

Conclusion: In this before-and-after analysis, IM-Epi was associated with increased survival to hospital discharge and favorable neurologic function compared to standard care IV and IO epinephrine. Prospective randomized trials are needed to determine whether the observed effects of IM-Epi in OHCA improves outcomes.