Purpose
In case of an out-of-hospital cardiac arrest (OHCA), 30-40% of patients have return of spontaneous circulation (ROSC) on scene. It is important to determine the relation between time to ROSC and survival to decide when transport should start without ROSC.

Methods
Data of OHCA patients with suspected cardiac origin, transported with any ROSC between 2014 and 2016 in the Amsterdam Resuscitation Study (ARREST) database were analysed. Patient, process and time characteristics were collected. Any ROSC includes those patients whose ROSC was intermittent or transient before or during transport. The association between the time of EMS arrival until first ROSC (time-to-ROSC) and 30-day survival was analysed.

Results
Of 2636 OHCA patients with attempted resuscitation, 1025 (39%) had any ROSC and 451 (18%) survived 30-days. Transport started without ROSC in 40/1025 (4%) after median 21 min (IQR 15,27). Survivors had a significant shorter time-to-ROSC of median 5 min; IQR 2,9) vs. non-survivors of median 12 min (IQR 8,17) (p<0.001), 90% of survivors achieve ROSC within 14 minutes compared to 23 minutes of non-survivors (figure). In a multivariable model time-to-ROSC per minute adjusted for known system determinants was significantly associated with 30-day survival (OR 0.89; 95%CI 0.87-0.91).

Conclusion
In OHCA patients transported with any ROSC survival significantly decreases with increasing time-to-ROSC. After 14 minutes of EMS resuscitation the chances of achieving ROSC and survive are less than 10%.

2 - Time to return of spontaneous circulation (ROSC) and survival in out-of-hospital cardiac arrest (OHCA) patients in the Netherlands