ECMO Anticoagulation and Hemostasis 3 — Questions and Answers
Question 1: When monitoring anticoagulation with anti-Xa levels during ECMO, what is the generally accepted therapeutic range?
- 0.1–0.2 IU/mL
- 0.3–0.7 IU/mL (Correct answer)
- 0.8–1.2 IU/mL
- 1.5–2.0 IU/mL
Correct answer: 0.3–0.7 IU/mL
Most ECMO centers target anti-Xa levels of 0.3–0.7 IU/mL, which correlates with adequate anticoagulation while minimizing hemorrhagic complications.
Question 2: A patient on ECMO develops heparin-induced thrombocytopenia (HIT). Which anticoagulant is preferred as a replacement?
- Warfarin
- Low-molecular-weight heparin
- Argatroban or bivalirudin (Correct answer)
- Fondaparinux
Correct answer: Argatroban or bivalirudin
Direct thrombin inhibitors such as argatroban or bivalirudin are the preferred alternatives when HIT is confirmed during ECMO, as all heparin products must be avoided.
Question 3: What does the 'clot amplitude at 10 minutes' (CA10) on ROTEM primarily reflect in ECMO patients?
- Platelet function and fibrin polymerization (Correct answer)
- Fibrinolytic activity only
- Antithrombin levels
- Heparin concentration
Correct answer: Platelet function and fibrin polymerization
CA10 on ROTEM reflects the combined contribution of platelet function and fibrin polymerization to clot strength at 10 minutes after clotting begins.
Question 4: During prolonged ECMO, why does thrombocytopenia commonly develop even without active bleeding?
- Heparin directly suppresses megakaryocyte production
- Platelets are consumed by circuit surface activation and microthrombi (Correct answer)
- Hemolysis releases platelet-destructive enzymes
- Systemic anticoagulation prevents platelet release from the marrow
Correct answer: Platelets are consumed by circuit surface activation and microthrombi
Continuous platelet activation and adherence to circuit surfaces, along with microthrombus formation, consumes platelets faster than production can compensate.
Question 5: An adult VA-ECMO patient has a fibrinogen level of 98 mg/dL with ongoing oozing from cannula sites. What is the appropriate intervention?
- Administer protamine sulfate
- Transfuse cryoprecipitate or fibrinogen concentrate (Correct answer)
- Increase heparin infusion rate
- Administer fresh frozen plasma alone
Correct answer: Transfuse cryoprecipitate or fibrinogen concentrate
Cryoprecipitate or fibrinogen concentrate is the most efficient way to correct hypofibrinogenemia; fibrinogen levels below 150 mg/dL with bleeding warrant replacement.
Question 6: Which test best differentiates heparin resistance from disseminated intravascular coagulation (DIC) in ECMO patients?
- Anti-Xa level with concurrent AT III assay (Correct answer)
- Platelet count alone
- Prothrombin time (PT)
- D-dimer level alone
Correct answer: Anti-Xa level with concurrent AT III assay
Measuring anti-Xa activity alongside AT III levels distinguishes heparin resistance (low AT III, low anti-Xa despite adequate heparin dose) from DIC (multiple factor deficiencies).
Question 7: What is the significance of 'delta ACT' monitoring during ECMO circuit change-out?
- It measures the time to re-prime the new circuit with blood
- It detects the ACT drop when blood contacts the new uncoated circuit surface (Correct answer)
- It monitors heparin washout from the old circuit
- It guides protamine dosing after decannulation
Correct answer: It detects the ACT drop when blood contacts the new uncoated circuit surface
When blood contacts a new circuit surface, ACT drops as heparin is temporarily adsorbed and consumed, requiring a heparin bolus to re-establish therapeutic anticoagulation.
ECMO Anticoagulation and Hemostasis 3
When monitoring anticoagulation with anti-Xa levels during ECMO, what is the generally accepted therapeutic range?