Conclusion. Among adults with out-of-hospital cardiac arrest, the use of epinephrine resulted in a higher rate of 30-day survival as compared with the use of placebo; however, there was no difference in the rate of a favorable neurologic outcome as more survivors in the epinephrine group had severe neurologic impairment.
Commentary
Epinephrine has been used as part of the resuscitation of patients with cardiac arrest since the 1960s. Epinephrine increases vasomotor tone during circulatory collapse, shunts more blood to the heart, and increases the likelihood of restoring spontaneous circulation.1 However, epinephrine also decreases microvascular blood flow and can result in long-term organ dysfunction or hypoperfusion of the heart and brain.2 The current study, the PARAMEDIC2 trial, by Perkins and colleagues is the largest randomized controlled trial to date to address the question of patient-centered benefit of the use of epinephrine during out-of-hospital cardiac arrest.
Similar to prior studies, patients who received epinephrine had a higher rate of 30-day survival than those who received placebo. However, there was no clear improvement in functional recovery among patients who survived, and the proportion of survivors with severe neurologic impairment was higher in the epinephrine group as compared to the placebo group. These results demonstrate that despite its ability to restore spontaneous circulation after out-of-hospital cardiac arrest, epinephrine produced only a small absolute increase in survival with worse functional recovery as compared with placebo.
One major limitation of this study is that the protocol did not control for or measure in-hospital treatments. In a prior study, the most common cause of in-hospital death was iatrogenic limitation of life support, which may result in the death of potentially viable patients.3 Another limitation of the study was the timing to administration of epinephrine. In the current study, paramedics administered the trial agent within a median of 21 minutes after the emergency call, which is a longer duration than previous out-of-hospital trials.4 In addition, this time to administration is much longer than that of in-hospital cardiac arrest, where epinephrine is administered a median of 3 minutes after resuscitation starts.5 Therefore, the results from this study cannot be extrapolated to patients with in-hospital cardiac arrest.
Applications for Clinical Practice
The current study by Perkins et al demonstrated the powerful effect of epinephrine in restoring spontaneous circulation after out-of-hospital cardiac arrest. However, epinephrine produced only a small absolute increase in survival with worse functional recovery, as compared to placebo. While further studies regarding dosage of epinephrine as well as administration based on the basis of cardiac rhythm are needed, we should question our tradition of using epinephrine in out-of-hospital cardiac arrest if meaningful neurological function is our priority.
—Ka Ming Gordon Ngai, MD, MPH, FACEP