Anticoagulation and Hemostasis Flashcards

Which ECMO configuration carries the highest risk of arterial thromboembolism due to retrograde aortic blood flow interactions?

Answer: VA-ECMO with femoral artery return cannula

Femoral VA-ECMO creates a watershed zone where oxygenated retrograde ECMO flow meets anterograde native cardiac output, increasing thrombus and watershed infarction risk.

In a patient on ECMO with suspected HIT, a 4T score of 6 is calculated. What is the appropriate next step?

Answer: Stop heparin immediately and start a direct thrombin inhibitor while confirmatory testing is sent

A 4T score of 6 represents high probability of HIT; heparin must be stopped immediately and an alternative anticoagulant started while awaiting confirmatory anti-PF4 antibody results.

What is the primary reason aPTT is considered an inferior monitoring tool compared to anti-Xa for heparin dosing in ECMO?

Answer: aPTT is affected by many non-heparin variables including factor deficiencies and acute phase reactants

aPTT is influenced by multiple variables common in ECMO patients — factor consumption, lupus anticoagulant, elevated factor VIII — making it an unreliable surrogate for heparin effect.

A patient on VV-ECMO for ARDS requires urgent surgical tracheostomy. How should anticoagulation be managed perioperatively?

Answer: Hold heparin 4–6 hours before and restart 2–4 hours post-procedure

For surgical procedures on ECMO, heparin is typically held 4–6 hours pre-procedure and restarted 2–4 hours post-procedure once hemostasis is achieved, balancing thrombotic and bleeding risk.

What is the clinical significance of detecting a rising D-dimer trend in an ECMO patient whose ACT is therapeutic?

Answer: It may indicate developing circuit thrombosis or DIC requiring circuit inspection

Rising D-dimer despite therapeutic ACT suggests active thrombus formation and fibrinolysis within the circuit or patient vasculature, warranting urgent circuit inspection.

Which pharmacokinetic property of bivalirudin makes it advantageous over argatroban in patients with hepatic failure on ECMO?

Answer: Bivalirudin is primarily metabolized by enzymatic cleavage in plasma, independent of liver function

Bivalirudin is metabolized primarily by thrombin-mediated proteolysis and non-specific plasma proteases, not by hepatic enzymes, making it predictable in liver failure.

During ECMO decannulation, protamine is administered to reverse heparin. What is the most feared complication of protamine administration?

Answer: Severe pulmonary hypertension and cardiovascular collapse

Protamine can trigger complement activation, thromboxane release, and pulmonary vasoconstriction, causing acute severe pulmonary hypertension and cardiovascular collapse, especially in right-heart-failure patients.