Use of Epinephrine for Cardiac Arrest Prior to Hospital Arrival

To the Editor: An association between the use of epinephrine prior to hospital arrival in patients with out-of-hospital cardiac arrest and both a decreased chance of survival and poorer long-term functional outcomes was demonstrated by Dr Hagihara and colleagues.¹ We have several concerns about the statistical methods of the study.

First, their data show that the single most significant predictor of 1-month survival and good cerebral performance was the occurrence of ROSC (eTable 2 in article). The interval between the beginning of ventricular fibrillation and the occurrence of ROSC is a key predictor of these outcomes²; this time interval is not included in their analysis. Therefore, the use of epinephrine could be a surrogate marker of a more prolonged resuscitation and delayed ROSC in patients failing to respond to the initial defibrillation,³ and the time to ROSC a confounding factor for the effect of epinephrine. The time to ROSC is 1 of the core time events to be recorded in the Utstein template,⁴ allowing new analyses to be redone with the time from telephone call to ROSC as an additional factor.