ECMO Anticoagulation and Hemostasis 2 — Questions and Answers
Question 1: Which coagulation factor is most significantly consumed during ECMO due to continuous contact with the circuit surface?
- Factor V
- Factor VIII
- Fibrinogen (Correct answer)
- Factor XIII
Correct answer: Fibrinogen
Fibrinogen is rapidly consumed during ECMO due to adsorption onto circuit surfaces and ongoing fibrinolysis, making it a critical monitoring parameter.
Question 2: A patient on ECMO has an ACT of 280 seconds and develops a new intracranial hemorrhage. What is the most appropriate immediate anticoagulation management?
- Increase heparin to maintain higher ACT
- Discontinue heparin entirely and monitor closely (Correct answer)
- Reduce heparin to maintain ACT 160-180 seconds
- Switch to bivalirudin immediately
Correct answer: Discontinue heparin entirely and monitor closely
Life-threatening intracranial hemorrhage on ECMO typically requires complete heparin discontinuation, accepting the risk of circuit thrombosis to prevent further bleeding.
Question 3: What is the primary mechanism by which bivalirudin anticoagulates ECMO patients?
- Activating antithrombin III to inhibit thrombin
- Directly and reversibly inhibiting free and clot-bound thrombin (Correct answer)
- Inhibiting vitamin K-dependent factor synthesis
- Blocking platelet ADP receptors
Correct answer: Directly and reversibly inhibiting free and clot-bound thrombin
Bivalirudin is a direct thrombin inhibitor that binds both free and fibrin-bound thrombin directly without requiring antithrombin as a cofactor.
Question 4: During ECMO, which laboratory test specifically assesses fibrinolytic activity and can detect hyperfibrinolysis?
- Thromboelastography (TEG) lysis index (Correct answer)
- Activated partial thromboplastin time (aPTT)
- Anti-Xa level
- Platelet aggregation study
Correct answer: Thromboelastography (TEG) lysis index
TEG/ROTEM provides a lysis index (LY30 or ML) that quantifies clot lysis over time, directly detecting hyperfibrinolysis in ECMO patients.
Question 5: A neonate on VA-ECMO has a platelet count of 65,000/μL. What is the standard transfusion threshold for neonates on ECMO?
- 50,000/μL
- 80,000/μL
- 100,000/μL (Correct answer)
- 150,000/μL
Correct answer: 100,000/μL
Most ECMO centers maintain platelet counts above 100,000/μL in neonates due to their higher hemorrhagic risk, particularly for intracranial hemorrhage.
Question 6: What is the most common cause of heparin resistance in ECMO patients?
- Elevated Factor VIII levels
- Antithrombin III deficiency (Correct answer)
- Protein C deficiency
- High fibrinogen levels
Correct answer: Antithrombin III deficiency
Antithrombin III (AT III) deficiency is the most common cause of heparin resistance in ECMO patients, as heparin requires AT III to exert its anticoagulant effect.
Question 7: Which hemostatic complication is uniquely associated with centrifugal pump ECMO circuits and involves destruction of von Willebrand factor multimers?
- Heparin-induced thrombocytopenia
- Acquired von Willebrand syndrome (Correct answer)
- Disseminated intravascular coagulation
- Thrombotic thrombocytopenic purpura
Correct answer: Acquired von Willebrand syndrome
Continuous shear stress from centrifugal pumps cleaves high-molecular-weight von Willebrand factor multimers, causing acquired von Willebrand syndrome and mucocutaneous bleeding.
ECMO Anticoagulation and Hemostasis 2
Which coagulation factor is most significantly consumed during ECMO due to continuous contact with the circuit surface?