Case 7

Simultaneous bleeding and thrombosis is a hallmark of ECMO because the circuit creates a consumptive coagulopathy. When blood contacts the foreign surface of the circuit, protein adsorption, platelet adhesion, and activation occur, with subsequent fibrin and thrombus formation. The artificial surface also activates inflammatory mediators including the complement, kinin, and coagulation systems, producing a DIC-like syndrome. This consumption of clotting factors (low fibrinogen, elevated INR) and platelets (thrombocytopenia) predisposes the patient to bleeding. Simultaneously, the ongoing activation of coagulation by the circuit surface promotes circuit thrombosis. The anticoagulation used to prevent circuit clotting further exacerbates bleeding risk—creating the central tension of ECMO management.

Answer: B. The most appropriate step is to hold heparin. The guiding principle is: if transfusion is required due to active bleeding, anticoagulation should be held. This patient is actively bleeding from the cannula site and requiring transfusion (3 units pRBCs in 6 hours). The anti-Xa is supratherapeutic at 0.55 IU/mL (target 0.3–0.5). While holding anticoagulation increases circuit thrombosis risk, the immediate threat of exsanguination takes priority. 

Increasing heparin (A) would worsen bleeding. While the falling platelets raise concern for HIT, this pattern is also consistent with consumption from the circuit; a formal HIT workup should be sent, but empirically switching to bivalirudin (C) should await serologic confirmation unless clinical suspicion is high. Protamine with aspirin (D) is not indicated.

The integrated approach to ECMO bleeding involves four pillars: 

(1) Source control is the first-line treatment. Bedside assessment of the cannula site to understand the amount of bleeding and degree of hemostasis is necessary. Direct pressure, topical hemostatic agents, or surgical intervention may be required. 

(2) Anticoagulation management: weigh the risks of holding anticoagulation (circuit thrombosis) against continued bleeding. If transfusion is required, hold anticoagulation. 

(3) Product replacement guided by laboratory assessment: replace platelets, fibrinogen (cryoprecipitate or fibrinogen concentrate), and clotting factors as needed. No single perfect test captures the entire coagulation system, so synthesis of data is required (CBC, coagulation studies, fibrinogen, TEG/ROTEM as needed). 

(4) In select cases, pharmacologic agents can be considered: antifibrinolytics (tranexamic acid), prothrombin complex concentrates, activated factor VII, and desmopressin if platelet dysfunction is contributing.

Routine screening for deep vein thrombosis (DVT) after decannulation is recommended. In one study of patients on VV ECMO with both femoral–femoral and femoral–jugular configurations, 70% of patients in each arm had DVT just two days after decannulation. DVT rates in ARDS patients on VV ECMO range from 18–85% across studies, and in COVID-19 patients on VV ECMO, the rate was 53%. If a clot is found, anticoagulation should be initiated once bleeding from the cannulation site is controlled.

Answer: D. Anti-Xa is a direct measure of heparin activity. It is based on the ability of heparin to catalyze antithrombin’s inhibition of factor Xa. The assay measures residual Xa activity through its action on an exogenous chromogenic substrate, producing a color change proportional to heparin activity. Because it uses an exogenous substrate, it is not affected by factor deficiencies or other coagulopathies. 

aPTT (A) is a plasma-based test that can be affected by factor deficiencies, lupus anticoagulant, and other variables beyond heparin activity. ACT (B) is a bedside test that does not linearly correlate with anticoagulant activity. TEG (C) evaluates global hemostasis including thrombotic and fibrinolytic activity and is useful in the bleeding patient, but its role in routine anticoagulation monitoring is not well-defined.