Normoxemic Versus Hyperoxemic Extracorporeal Oxygenation in Patients Supported by Veino-arterial ECMO for Cardiogenic Shock

Because of dual oxygenation and oxygenator performance (PO2 postoxygenator up to 500 mmHg), hyperoxemia (PaO2 \> 150 mmHg) is frequent in veino-arterial ECMO, especially in the lower part of the body, which is mainly oxygenated by ECMO. By enhancing oxygen free radicals' production, hyperoxemia might favor gut, kidney and liver dysfunction. We hypothesize that targeting an extracorporeal normoxemia (i.e. PO2 postoxygenator between 100 and 150 mmHg) will decrease gut, kidney and liver dysfunctions, compared to a liberal extracorporeal oxygenation.

Randomization: Patients will be randomized in the 6 hours following ECMO start in the normoxemia or in the hyperoxemia group. Randomization will be stratified on center, and medical or postcardiotomy indication for ECMO. Description of experimental arm (Normoxemia group): * After randomization, extracorporeal normoxemia is targeted by setting the ECMO membrane oxygen fraction (FmO2) at 60%. * The objective is to maintain oxygen partial pressure measured on the arterial cannula (PO2 postoxygenator) between 100 and 150 mmHg. * PO2 postoxygenator is monitored at least twice a day by the nurse. * If PO2 postoxygenator is less than 100 mmHg or more than 150 mmHg, FmO2 is modified by 10% and PO2 postoxygenator is monitored 10 minutes after. * Ventilator's settings at let to the clinician's discretion. However, PaO2 on right radial artery will be monitored to ensure that is more that 80 mmHg. * Intervention will be applied for 7 days after randomization. Description of the control arm (Hyperoxemia group): * After randomization, extracorporeal hyperoxemia is targeted by setting the ECMO membrane oxygen fraction (FmO2) at 100%. * The objective is to maintain PO2 postoxygenator higher than 300 mmHg. * PO2 postoxygenator is monitored at least twice a day by the nurse. * If PO2 postoxygenator is less than 300 mmHg, membrane change should be discussed. * Ventilator's setting at let to the clinician's discretion. However, PaO2 on right radial artery will be monitored to ensure that is more that 80 mmHg. * Intervention will be applied for 7 days after randomization.