ExtraCorporeal Membrane Oxygenation in the Therapy for REfractory Septic Shock With Cardiac Function Under Estimated

All patients in cohort 1 will initiate ECMO as fast as possible. A maximum of 6 hours is allowed between enrollment and the actual initiation of ECMO. ECMO catheterization and management will be operated by an experienced ECMO team and carried out at the bedside. VA or VAV mode will be chosen according to the patient's condition.