Assess whether elevated oxygen partial arterial pressure (PaO2) measured after the initiation of extra-corporeal cardiopulmonary resuscitation (eCPR), is associated with mortality in patients suffering from refractory out-of-hospital cardiac arrest (rOHCA).

Retrospective cohort study including rOHCA admitted to the ICU. Patients were divided into 3 groups, defined according to the PaO2 measured from arterial blood gas analysis 30 min after the initiation of eCPR. Hyperoxemia was defined as PaO2 ≥ 300 mmHg, hypoxemia as PaO2 ≤ 60 mmHg and normoxemia, as 60 < PaO2 < 300 mmHg.

The main outcome was the mortality rate on day 28 after hospital admission.

Sixty-six consecutive rOHCA, 77% male, with a mean age of 51 ± 14 years, were admitted to the ICU. rOHCA were mainly due to acute coronary syndrome (67%), hypertrophic cardiomyopathy (8%) and cardiotoxic overdose (8%). Mortality at day 28 reached 61%.

In the overall population, the mean PaO2 was 227 ± 124 mmHg.

An association between mortality and PaO2 was observed (OR = 1.01 [1.01–1.02]). The AUC for PaO2 after starting eCPR was 0.77 [0.65–0.89].

After adjustment for witnessed arrest, bystander's CPR, location, no-flow, low-flow, lactate and pH, age, and PaCO₂, hyperoxemia had an ORa of 1.89 (CI95 [1.74–2.07]).

We found an association between mortality and hyperoxemia in patients admitted to the ICU for rOHCA requiring eCPR. These data underline the potential toxicity of high dose of oxygen and suggest that controlled oxygen administration for these patients is crucial.