ECMO Veno-Venous (VV) ECMO Management 4 — Questions and Answers
Question 1: Which factor most reliably predicts the ability to successfully wean a patient from VV ECMO?
- Normalization of chest X-ray
- Maintenance of adequate SpO2 during a spontaneous breathing trial with sweep gas off (Correct answer)
- Resolution of systemic inflammatory markers
- Return of normal cardiac ejection fraction
Correct answer: Maintenance of adequate SpO2 during a spontaneous breathing trial with sweep gas off
A weaning trial with sweep gas reduced or off tests the native lung's ability to maintain gas exchange independently, which is the best predictor of successful decannulation.
Question 2: What ventilator strategy is recommended for native lung protection during VV ECMO support?
- High PEEP (18–22 cmH2O) with normal tidal volumes
- Ultra-protective ventilation: low Vt (2–4 mL/kg), low rate, permissive hypercapnia (Correct answer)
- High-frequency oscillatory ventilation as standard
- Pressure-controlled ventilation targeting PaCO2 of 35–45 mmHg
Correct answer: Ultra-protective ventilation: low Vt (2–4 mL/kg), low rate, permissive hypercapnia
ECMO allows ultra-protective ventilation with very low tidal volumes and rates, minimizing ventilator-induced lung injury while the circuit maintains gas exchange.
Question 3: During VV ECMO, a patient develops severe hypokalemia (K+ 2.8 mEq/L). Which factor unique to ECMO contributes to electrolyte depletion?
- ECMO pump-induced hemolysis releasing intracellular potassium
- High sweep gas flows causing transcutaneous electrolyte loss
- Continuous renal replacement therapy often co-administered (Correct answer)
- Plasma leakage through the membrane oxygenator
Correct answer: Continuous renal replacement therapy often co-administered
Many ECMO patients receive concurrent CRRT, which significantly increases electrolyte clearance and requires aggressive electrolyte replacement.
Question 4: A VV ECMO patient has a post-membrane pO2 of 500 mmHg but SvO2 measured from the drainage cannula is only 55%. What does this indicate?
- The oxygenator is failing
- High oxygen consumption relative to delivery (Correct answer)
- The patient is ready to wean from ECMO
- Adequate cardiac output with low recirculation
Correct answer: High oxygen consumption relative to delivery
Low drainage cannula SvO2 (which approximates true mixed venous oxygen saturation) indicates high oxygen extraction due to elevated consumption or insufficient delivery.
Question 5: Which intervention is indicated when a VV ECMO patient develops massive intracranial hemorrhage?
- Discontinue anticoagulation and consider urgent decannulation (Correct answer)
- Increase heparin dose to prevent catheter-related thrombosis
- Continue ECMO with no anticoagulation changes
- Switch to bivalirudin anticoagulation
Correct answer: Discontinue anticoagulation and consider urgent decannulation
Massive ICH on ECMO requires stopping anticoagulation immediately, and if the hemorrhage is life-threatening, urgent decannulation should be considered despite ECMO dependence.
Question 6: What is the primary purpose of the 'blender' on the sweep gas inlet of a VV ECMO oxygenator?
- To mix blood with anticoagulant before it enters the membrane
- To control the FiO2 of sweep gas for oxygenation regulation (Correct answer)
- To humidify sweep gas and prevent membrane desiccation
- To regulate sweep gas pressure to avoid barotrauma
Correct answer: To control the FiO2 of sweep gas for oxygenation regulation
The sweep gas blender adjusts oxygen concentration (FiO2) to regulate the amount of oxygen transferred across the membrane to the blood.
Question 7: A patient has been on VV ECMO for 14 days. Platelet count drops from 120,000 to 48,000 over 5 days despite no obvious bleeding. What is the most likely cause?
- Heparin-induced thrombocytopenia (HIT)
- Consumptive thrombocytopenia from circuit contact activation (Correct answer)
- Marrow suppression from prolonged critical illness
- Platelet sequestration in the spleen
Correct answer: Consumptive thrombocytopenia from circuit contact activation
Chronic contact of blood with artificial circuit surfaces activates platelets and causes ongoing consumption, making thrombocytopenia a common feature of prolonged ECMO.
ECMO Veno-Venous (VV) ECMO Management 4
Which factor most reliably predicts the ability to successfully wean a patient from VV ECMO?