ECMO Complications and Troubleshooting 2 — Questions and Answers
Question 1: A patient on VA-ECMO develops a sudden drop in arterial line pressure with unchanged ECMO flows. What is the most likely cause?
- Oxygenator failure
- Cardiac tamponade (Correct answer)
- Pump thrombus
- Venous cannula migration
Correct answer: Cardiac tamponade
Cardiac tamponade reduces native cardiac output, causing a drop in arterial pulsatility and blood pressure despite maintained ECMO flow.
Question 2: During VV-ECMO, SpO2 remains persistently low at 78% despite flows at 5 L/min. The sweep gas is 10 L/min and FiO2 is 1.0. What should be evaluated first?
- Oxygenator membrane integrity
- Recirculation fraction (Correct answer)
- Venous cannula size
- Native lung function
Correct answer: Recirculation fraction
High recirculation means oxygenated blood is re-entering the drainage cannula before reaching the patient, causing persistent hypoxemia despite adequate flows.
Question 3: A visible clot is noted in the ECMO tubing near the pump head. The appropriate immediate action is to:
- Increase heparin infusion rate and continue monitoring
- Clamp the circuit and prepare for emergency circuit change (Correct answer)
- Increase pump speed to dislodge the clot
- Administer tPA through the circuit
Correct answer: Clamp the circuit and prepare for emergency circuit change
A visible thrombus in the circuit poses an immediate risk of systemic embolism or pump failure, requiring circuit change rather than acceleration.
Question 4: A patient on ECMO has a platelet count that drops from 180,000 to 30,000 over 48 hours. The MOST likely cause in this clinical context is:
- Heparin-induced thrombocytopenia (HIT)
- ECMO circuit consumption (Correct answer)
- Sepsis-related bone marrow suppression
- Dilutional thrombocytopenia from transfusions
Correct answer: ECMO circuit consumption
Platelet consumption due to contact activation within the ECMO circuit is the most common cause of thrombocytopenia in ECMO patients.
Question 5: The ECMO centrifugal pump is running at 3,000 RPM but flow has dropped from 4.5 to 2.0 L/min with no change in circuit resistance. What is the most concerning explanation?
- Air entrainment into the circuit
- Patient hypovolemia causing venous collapse
- Pump thrombus reducing pump efficiency (Correct answer)
- Oxygenator pressure drop
Correct answer: Pump thrombus reducing pump efficiency
Pump thrombus increases internal resistance and reduces the pump's hydraulic efficiency, causing decreased flow at the same RPM.
Question 6: A patient on peripheral VA-ECMO via femoral artery cannulation develops ipsilateral limb ischemia. The best intervention is to:
- Remove the arterial cannula immediately
- Place an antegrade perfusion cannula distal to the ECMO cannula (Correct answer)
- Increase ECMO flow to improve perfusion
- Administer systemic vasodilators
Correct answer: Place an antegrade perfusion cannula distal to the ECMO cannula
A distal perfusion cannula placed in the superficial femoral artery restores antegrade limb perfusion while maintaining ECMO support.
Question 7: Oxygenator post-membrane pO2 is measured at 85 mmHg with FiO2 of 1.0 and sweep at 10 L/min. This finding indicates:
- Adequate oxygenator function
- Oxygenator membrane failure (Correct answer)
- Excessive recirculation
- Inadequate sweep gas flow
Correct answer: Oxygenator membrane failure
A post-membrane pO2 of 85 mmHg with 100% FiO2 and high sweep indicates severely impaired membrane gas exchange, consistent with oxygenator failure.
ECMO Complications and Troubleshooting 2
A patient on VA-ECMO develops a sudden drop in arterial line pressure with unchanged ECMO flows.
What is the most likely cause?