The use of epinephrine during resuscitation for out-of-hospital cardiac arrest (OHCA) is ubiquitous. However, its value for increasing neurologically intact survival remains contested. Epinephrine is a strong catecholamine with alpha- and beta-adrenergic stimulating properties. Its alpha effects are believed to be beneficial and help increase coronary perfusion and increase vascular resistance during resuscitation. Epinephrine’s beta effects include increased cardiac rate, contractility, and automaticity which all increase myocardial oxygen demand and may be harmful to the OHCA patient. A variety of studies have been published indicating that increasing doses of epinephrine correlate to an increased likelihood of return of spontaneous circulation (ROSC) but are not associated with increased neurologically intact survival.
The Early Dose Gets the Worm
A new study published in JAMA on August 10, 2021, examined the relationship between the timing of the initial dose of epinephrine and functionally intact survival during OHCA.
This retrospective cohort study included more than 40,000 OHCA patients with both shockable and non-shockable rhythms from sites across the United States and Canada. While the authors were unable to establish causation, they identified a statistically significant increase in functionally intact survival associated with earlier administration of epinephrine. The most significant increases in survival were found among the patients that received the initial dose of epinephrine within the first 5 minutes after EMS contact when time was evaluated as a continuous variable (risk ratio (RR) decreased by 5.5% [95%CI 3.4-7.5%, p <0.001] per minute after EMS arrival).
-High performing EMS systems tend to have better outcomes overall and this study was unable to establish if early epinephrine administration was simply associated with overall system performance as opposed to a stand alone variable.
-The study was not adjusted for other confounders such as patient comorbidities, post-resuscitation care, and community factors.
-As an observational study causation cannot be established.
–Epinephrine remains a pillar of cardiac arrest resuscitation. However, the optimal timing and dosing of the medication have yet to be definitively established.
-The validated and most impactful prehospital interventions for prehospital resuscitation of OHCA are minimally interrupted high-performance CPR and early defibrillation.
-There appears to be a strong correlation between early administration of epinephrine during OHCA and neurologically intact survival.
-Upon arrival on the scene of an OHCA, rapidly establishing vascular access and administering the first dose of epinephrine is of primary importance for EMS clinicians within a high-performance resuscitation framework.