Platelets and Extracorporeal Membrane Oxygenation Veno-venous

Despite the frequency of thrombocytopenia in patients on VV-ECMO and its associated haemorrhagic consequences, its predictive factors are still poorly described. Furthermore, studies suggest the presence of thrombopathy in patients on ECMO, but they are scarce and based on a heterogeneous population with a small sample size, or with vent-arterial (VA) ECMO, mainly after cardiac surgery exposed to a different extracorporeal circulation. The factors responsible for this thrombopathy and its repercussions are currently unknown. In contrast to previous studies that focused on platelet functions in patients on ECMO, our study will be the first to analyse specialized platelet functions and thrombo-inflammation in a cohort only with VV-ECMO excluding cardiac surgery patients at risk of thrombopathy. This work will provide, for the first time, a comprehensive view of the patient on VV-ECMO, ranging from clinical characteristics to the study of platelet activation and functions and thrombo-inflammation analysis and also integrating biological data and ECMO characteristics, all over time. The procedure will involve collecting blood samples from the patient on VV-ECMO and platelet aggregation tests will be performed, along with measurements of platelet activation markers and a search for leuko-platelet aggregates. Investigators will evaluate the clinical-biological impact by searching for blood hemolysis, the level of inflammation, coagulopathy and hemorrhagic complications during VV-ECMO support. The patient's clinical characteristics will be analysed until their discharge from the intensive care unit. Clinical, biological, ECMO, and specialized haemostasis data will be studied to achieve the study objectives.

• blood draws (Other): Part of the biology data is used from the patient's routine blood tests. Additional blood samples are taken from an arterial catheter already in place. They are performed over 4 periods: one just before start ECMO and 3 under ECMO at 3-day intervals

Primary outcomes

• Platelet aggregation response over time during venovenous ECMO at baseline [T0: Baseline (before ECMO initiation)]: Platelet aggregation level (expressed as percentage intensity) during venovenous ECMO following stimulation with three platelet agonists (TRAP, CRP, and ADP).
• Platelet aggregation response over time during venovenous ECMO at Day 2 of ECMO [T1: Day 2 of ECMO]: Platelet aggregation level (expressed as percentage intensity) during venovenous ECMO following stimulation with three platelet agonists (TRAP, CRP, and ADP).
• Platelet aggregation response over time during venovenous ECMO at Day 5 of ECMO [T2: Day 5 of ECMO]: Platelet aggregation level (expressed as percentage intensity) during venovenous ECMO following stimulation with three platelet agonists (TRAP, CRP, and ADP).
• Platelet aggregation response over time during venovenous ECMO at Day 8 of ECMO [T3: Day 8 of ECMO]: Platelet aggregation level (expressed as percentage intensity) during venovenous ECMO following stimulation with three platelet agonists (TRAP, CRP, and ADP).

Secondary outcomes

• Number of bleeding event [Up to Day 10 of ECMO]: Numbers of Bleeding event occurring within the first 10 days of VV-ECMO: internal and/or external bleeding that, due to its severity, requires discontinuation of anticoagulation and/or a blood transfusion and/or a surgical or interventional procedure and/or results in a life-threatening condition
• Platelet activation marker [day 8]: Concentrations of platelet activation markers
• Platelet aggregation intensity [day 8]: Percentage of platelet aggregation intensity measured at the four sampling time points and following stimulation with three platelet agonists (TRAP, CRP, and ADP)
• Leukocyte-platelet aggregate percentage [day 8]: Percentage of leukocyte-platelet aggregates with leukocyte and platelet fluorescent labeling (flow cytometry)
• Systemic anticoagulation level (anti-Xa activity) [day 8]: The level of systemic anticoagulation will be assessed by anti-Xa activity (IU/mL)
• Markers of inflammation-leukocyte [day 8]: Serum concentrations of inflammatory markers including leukocyte count (/mm³)
• Markers of inflammation- CRP [day 8]: Serum concentrations of inflammatory markers including C-reactive protein (CRP, mg/L)
• Markers of inflammation_fibrinogen [day 8]: Serum concentrations of inflammatory markers including fibrinogen (g/L)
• Platelet activation and aggregation parameters [Day 8]: Platelet activation marker concentrations and platelet aggregation intensity percentage, including platelet-leukocyte aggregation percentage
• Hemolysis parameters-LDH [day 8]: Serum levels of lactate dehydrogenase (LDH, IU/L)
• Hemolysis parameters-free bilirubin [day 8]: Serum levels of and free bilirubin (µmol/L)

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Adults aged ≥ 18 years
* No objection to participation in the study, obtained from a relative or trusted person; if no relative is available, inclusion under emergency procedure (pending patient or relative non-opposition)
* Patients requiring admission to the general intensive care unit of Hôpital Rangueil for venovenous ECMO
* Equipped with an arterial catheter for blood sampling
* Ability to undergo the 4 blood draws relevant to the study
* Receiving therapeutic anticoagulation with unfractionated heparin
* Enrolled in a social security program or equivalent
* No measures for Limitation and Withdrawal of Therapy have been implemented

Exclusion Criteria:

* Minors
* Patients under court-appointed guardianship or conservatorship
* Pregnant or breastfeeding women
* Hematological disease (leukemia, lymphoma) or constitutional thrombocytopenia
* Platelet transfusion within 7 days prior to enrollment
* Indication for immediate emergency ECMO preventing blood sampling before placement
* Post-cardiotomy
* Patient on antiplatelet therapy
* Severe thrombocytopenia <50 G/L
* Other invasive mechanical support such as Impella®, intra-aortic balloon pump, or Left Ventricular Assist Device (LVAD)