Inclusion Criteria:  Patient receiving V-V ECMO Patient is located in a participating unit of the Vanderbilt University Medical Center (VUMC) adult hospital.  Exclusion Criteria:  Patient is pregnant Patient is a prisoner Patient is < 18 years old Patient underwent ECMO cannulation greater than 24 hours prior to screening  Presence of an indication for systemic anticoagulation:  Ongoing receipt of systemic anticoagulation Planned administration of anticoagulation for an indication other than ECMO Presence of or plan to insert an arterial ECMO cannula  Presence of a contraindication to anticoagulation:  Active bleeding determined by treating clinicians to make anticoagulation unsafe Major surgery or trauma less than 72 hours prior to randomization Known history of a bleeding diathesis Ongoing severe thrombocytopenia (platelet count < 30,000) History of heparin-induced thrombocytopenia (HIT) Heparin allergy Positive SARS-CoV-2 test within prior 21 days or high clinical suspicion for COVID-19 The treating clinician determines that the patient's risks of thromboembolism or bleeding necessitate a specific approach to anticoagulation management during V-V ECMO