Background:
Despite advances in cardiopulmonary resuscitation (CPR), survival after out-of-hospital cardiac arrest (OHCA) remains low. Use of veno-arterial extracorporeal membrane oxygenation (VA ECMO) as extracorporeal CPR (ECPR) may improve outcomes in refractory OHCA. We evaluated the effect on hospital discharge rate and neurological function of integrating on-scene ECPR into routine emergency care for refractory OHCA. Besides that we assessed predictors of unfavorable outcomes.

Methods:
A prospective observational study was conducted from October 2013 to September 2023 in Regensburg, Germany. A dedicated ECMO team was alerted 24/7 in parallel with standard emergency medical services for suspected OHCA. On-scene VA ECMO was initiated based on predefined inclusion/exclusion criteria. Patients were transported to a university medical center for guideline-based post-resuscitation care. Clinical data, including CPR parameters, initial physiology, and outcomes, were recorded and analyzed.

Results:
Over ten years, 11,235 alerts resulted in 2,655 (23.6%) on-scene evaluations of OHCA. VA ECMO was initiated in 213 patients with refractory OHCA (8.0% of on-scene CPR evaluations). The median time between beginning of CPR and start of VA ECMO was 45 min (IQR: 35–63). Median ECMO duration was 2 days (IQR 1–4). Survival to hospital discharge was 34.7% (74/213), with 89.2% (66/74) achieving a good neurological outcome and an independent daily living. In multivariable analysis restricted to on-scene variables, independently associated with unfavorable outcomes were: bilaterally dilated pupils (OR 5.79 [1.85–19.8]; p = 0.003), absence of bystander CPR (OR 4.38 [1.23–18.2]; p = 0.029), use of mechanical CPR devices (OR 5.53 [2.09–15.9]; p < 0.001), initial asystole (OR 35.0 [5.24–731]; p = 0.002), and CPR-to-ECMO interval > 45 min (OR 3.07 [1.09–9.14]; p = 0.037).

Conclusions:
Prehospital ECPR is feasible and can be integrated into a regional emergency medical system when performed by a highly experienced team. Survival rates in this selected cohort exceeded typical OHCA outcomes, with a high proportion of patients achieving favorable neurological recovery. Early VA ECMO initiation and several on-scene factors are key determinants of prognosis.