Starting ECMO at the scene was linked to better survival in cardiac arrest

When someone's heart stops outside hospital and ordinary resuscitation is not restarting it, the odds are grim and they worsen with every passing minute. One response that some systems have adopted is extracorporeal cardiopulmonary resuscitation (ECPR): placing the patient on a venoarterial extracorporeal membrane oxygenation (ECMO) circuit — an external pump and oxygenator — to restore blood flow while the underlying problem is addressed. A study from the Netherlands, presented at the American Heart Association's 2026 Scientific Sessions and published in the New England Journal of Medicine on 7 November, asked whether starting that process at the scene, rather than waiting for hospital arrival, is associated with more survivors [s1].

The question

Most ECPR programmes begin the circuit in hospital. The delay matters, because the longer the brain and heart go without adequate circulation, the lower the chance of a good outcome. The OnScene study, registered as NCT04620070, examined whether equipping prehospital teams to begin ECMO at the scene was linked to better survival in a group with particularly high stakes and, often, a recoverable cause: young adults [s1][s2].

How the study was built

This was a nationwide, nonrandomised study [s1]. That design is the single most important thing to hold on to when reading the result. The investigators compared outcomes in patients aged 50 or younger with refractory out-of-hospital cardiac arrest who were attended by Helicopter Emergency Medical Services (HEMS) equipped to deliver prehospital ECPR — the intervention group — against those attended by HEMS without that capability — the conventional group [s1].

Because patients were not randomly assigned, the two groups could differ in ways other than access to on-scene ECMO — geography, timing, the teams dispatched — and such differences, not the intervention itself, could influence who survived. The primary outcome was survival until hospital discharge [s1].

A total of 144 patients were included in the intervention group and 87 in the conventional group [s1].

What it found

Survival to hospital discharge was twice as high where on-scene ECPR was available: 57 of 144 patients (40%) in the intervention group survived, compared with 17 of 87 patients (20%) in the conventional group [s1]. The odds ratio was 2.72, with a 95% confidence interval of 1.59 to 4.66 and a P value of 0.002 [s1].

Survival with brain function intact is the outcome that matters most after a cardiac arrest, and it moved in the same direction. At six months, a favourable neurologic outcome was reported in 51 of 141 patients (36%) in the intervention group and in 11 of 85 patients (13%) in the conventional group, with an odds ratio of 4.22 (95% CI 2.82 to 6.32) [s1].

The intervention was not without cost. There were 32 adverse events in the intervention group and 11 in the conventional group [s1] — unsurprising, given that ECMO is an invasive procedure involving large cannulas placed into major blood vessels under extreme time pressure.

What is, and is not, established

The honest summary is that incorporating ECPR into helicopter emergency services was associated with better survival and better neurologic outcomes in young people whose cardiac arrest did not respond to standard resuscitation [s1]. The authors frame it in exactly those associational terms [s1].

What the study cannot do, by its own design, is prove that on-scene ECMO caused the improvement. Without randomisation, the possibility remains that patients reached by ECPR-capable teams differed systematically from those who were not — and a nonrandomised comparison cannot fully rule that out. The adverse-event count is a reminder that this is a demanding, resource-intensive intervention, feasible only where the equipment, trained crews and systems already exist [s1]. The results apply to people aged 50 or younger; they say nothing about older patients, in whom refractory arrest is more common and recovery less likely [s1].

This article describes research and is not medical advice. How and when to deploy ECPR is a system-level and clinical decision made by emergency and critical-care teams.