ECMO Complications and Troubleshooting 5 — Questions and Answers
Question 1: During VA-ECMO weaning, pump speed is reduced to minimum and the patient's mean arterial pressure drops to 50 mmHg with a CVP of 22 mmHg. This hemodynamic pattern suggests:
- Volume depletion requiring fluid resuscitation
- Cardiac recovery adequate for decannulation
- Inability to tolerate reduced ECMO support indicating failed wean (Correct answer)
- Vasodilatory shock requiring vasopressors only
Correct answer: Inability to tolerate reduced ECMO support indicating failed wean
Hypotension with elevated CVP during ECMO wean indicates the native heart cannot maintain adequate output independently, meaning the patient has failed the wean trial.
Question 2: Air is detected in the ECMO circuit approaching the patient. The immediate response is to:
- Increase pump speed to push the air through quickly
- Clamp the arterial limb and stop the pump immediately (Correct answer)
- Administer 100% FiO2 to absorb the air
- Tilt the patient into Trendelenburg position
Correct answer: Clamp the arterial limb and stop the pump immediately
Clamping the arterial limb and stopping the pump immediately prevents air from entering the patient's circulation and causing a fatal air embolism.
Question 3: A patient on ECMO develops a new right pleural effusion with progressive respiratory failure. The most appropriate diagnostic step is:
- Perform a contrast CT chest
- Thoracentesis with fluid sent for analysis including triglycerides (Correct answer)
- Increase ECMO flows and sweep gas
- Obtain a ventilation-perfusion scan
Correct answer: Thoracentesis with fluid sent for analysis including triglycerides
Thoracentesis both diagnoses and treats the effusion; triglyceride analysis helps identify chylothorax, a recognized ECMO complication from superior vena cava or thoracic duct involvement.
Question 4: A patient on ECMO receiving unfractionated heparin has an aPTT of 220 seconds. The appropriate intervention is:
- Continue current heparin dose and recheck in 4 hours
- Hold heparin infusion and recheck aPTT in 2 hours (Correct answer)
- Administer protamine sulfate to fully reverse anticoagulation
- Switch to bivalirudin immediately
Correct answer: Hold heparin infusion and recheck aPTT in 2 hours
A supratherapeutic aPTT of 220 seconds greatly increases bleeding risk; holding the heparin infusion temporarily allows levels to fall while avoiding full reversal that risks circuit thrombosis.
Question 5: A patient on neonatal ECMO has persistently low circuit flows despite normal volume status and cannula position. Inspection shows the tubing is not kinked. The next consideration is:
- Patient has outgrown the cannula size, requiring upsizing (Correct answer)
- Sweep gas flow is too high causing membrane back pressure
- Heparin dose is inadequate
- Cardiac tamponade is reducing venous return
Correct answer: Patient has outgrown the cannula size, requiring upsizing
Growing neonates can outpace the flow capacity of their original cannula size, necessitating cannula exchange to achieve adequate ECMO support.
Question 6: A team member notices the ECMO pump is running but there is no visible flow in the tubing and the flow meter reads zero. The MOST likely explanation is:
- Massive air lock in the circuit
- Centrifugal pump decoupling or mechanical failure (Correct answer)
- Oxygenator membrane rupture
- Extreme vasodilation reducing venous return
Correct answer: Centrifugal pump decoupling or mechanical failure
Centrifugal pumps can decouple or fail mechanically, causing the motor to spin without generating flow, which requires emergency pump head replacement.
Question 7: Following a circuit change for oxygenator failure, the ECMO specialist notes the new circuit's post-membrane pO2 is 500 mmHg on FiO2 1.0. This confirms:
- Recirculation is now occurring
- The new oxygenator is functioning appropriately (Correct answer)
- The patient has developed a pneumothorax
- Excessive sweep gas is causing hypocapnia
Correct answer: The new oxygenator is functioning appropriately
A post-membrane pO2 of approximately 500 mmHg on 100% FiO2 is the expected result of a fully functional oxygenator, confirming successful circuit exchange.
ECMO Complications and Troubleshooting 5
During VA-ECMO weaning, pump speed is reduced to minimum and the patient's mean arterial pressure drops to 50 mmHg with a CVP of 22 mmHg.
This hemodynamic pattern suggests: