We stratified all OHCA patients for

We stratified all OHCA patients for quartile of EMSs' CPR duration. Group 1 consisted of patients who fell under the 25th percentile of EMSs' CPR duration (under 15 min); group 2, patients who fell into the 25th to 50th percentile (between 15 and 19 min); group 3, patients who fell into the 50th to 75th percentile (between 20 and 26 min); and group 4, patients who fell at or above the 75th percentile (over 26 min). The primary endpoint was a favorable neurological outcome 1 month after cardiac arrest. The secondary endpoints were ROSC before arrival at the hospital and 1-month survival. RESULTS: A total of 383,811 patients aged over 18 years who had experienced OHCA between 2006 and 2010 in Japan, when stratified for quartile of EMSs' CPR duration, the epinephrine administration increased the rate of return of spontaneous circulation (ROSC) approximately tenfold in all groups. However, the beneficial effects of epinephrine administration on 1-month survival disappeared in patients on whom EMSs' CPR had been performed for more than 26 min, and the beneficial effects of epinephrine administration on neurological outcomes were observed only in patients on whom EMSs' CPR had been performed between 15 and 19 min (odds ratio, 1.327, 95 % confidence intervals, 1.017-1.733 P = 0.037). CONCLUSIONS: Epinephrine administration is associated with an increase of ROSC and with improvement in the neurological outcome on which EMSs' CPR duration is performed between 15 and 19 min.