ECMO - Extracorporeal Membrane Oxygenation Weaning and Decannulation Questions and Answers — Questions and Answers
Question 1: A 55-year-old patient on Veno-Venous (VV) ECMO for severe ARDS has shown significant improvement in lung compliance and chest X-ray findings. The clinical team decides to perform a liberation trial. What is the most appropriate initial step in this process?
- Gradually decrease ECMO blood flow to a minimal level (e.g., 1 L/min).
- Systematically reduce the sweep gas flow to zero while maintaining ECMO blood flow. (Correct answer)
- Discontinue all sedation to assess neurological readiness.
- Increase the PEEP on the mechanical ventilator to 20 cm H2O.
Correct answer: Systematically reduce the sweep gas flow to zero while maintaining ECMO blood flow.
Weaning from VV ECMO primarily assesses the native lung's ability to perform gas exchange, specifically carbon dioxide removal. This is achieved by reducing and then stopping the sweep gas flow through the oxygenator. ECMO blood flow is typically maintained to prevent thrombosis within the circuit.
Question 2: During a weaning trial from Veno-Arterial (VA) ECMO, the primary goal of reducing circuit blood flow is to assess the native heart's ability to handle what physiological change?
- Increased preload and afterload. (Correct answer)
- Decreased systemic vascular resistance.
- Reduced coronary artery perfusion.
- Improved oxygenator efficiency.
Correct answer: Increased preload and afterload.
Reducing VA ECMO flow decreases the amount of blood being drained from the venous circulation and pumped into the arterial system. This forces the native heart to handle a higher volume of blood returning to it (increased preload) and to pump against greater resistance (increased afterload), directly challenging myocardial contractility and function.
Question 3: Which of the following is the most definitive sign that a patient is failing a VA ECMO weaning trial after ECMO flows have been reduced?
- A slight increase in the patient's heart rate from 80 to 95 bpm.
- A decrease in central venous pressure (CVP) from 12 to 8 mmHg.
- An increase in the patient's native cardiac output by 1 L/min.
- A rise in pulmonary capillary wedge pressure (PCWP) to >18 mmHg and a non-opening aortic valve on echocardiogram. (Correct answer)
Correct answer: A rise in pulmonary capillary wedge pressure (PCWP) to >18 mmHg and a non-opening aortic valve on echocardiogram.
A rising PCWP indicates increasing left ventricular end-diastolic pressure and pulmonary congestion, while a non-opening aortic valve demonstrates the left ventricle is unable to generate enough pressure to overcome afterload and eject blood. These are clear signs of severe left ventricular failure and an inability to tolerate the reduced ECMO support.
Question 4: A patient on VV ECMO is undergoing an "off-sweep" trial. After 30 minutes with the sweep gas turned off, an arterial blood gas (ABG) is drawn. Which of the following ABG results would indicate the patient has failed the trial and is not ready for decannulation?
- pH 7.38, PaCO2 42 mmHg, PaO2 85 mmHg
- pH 7.45, PaCO2 35 mmHg, PaO2 150 mmHg
- pH 7.21, PaCO2 75 mmHg, PaO2 90 mmHg (Correct answer)
- pH 7.35, PaCO2 45 mmHg, PaO2 78 mmHg
Correct answer: pH 7.21, PaCO2 75 mmHg, PaO2 90 mmHg
The primary purpose of the off-sweep trial is to assess the native lungs' ability to clear carbon dioxide. A PaCO2 of 75 mmHg leading to significant respiratory acidosis (pH 7.21) is a clear indication that the patient's lungs are not yet capable of adequate independent gas exchange, thus signifying a failed trial.
Question 5: A 60-year-old male is decannulated after 10 days of femoral Veno-Arterial (VA) ECMO. The arterial cannulation site was repaired surgically. Four hours post-procedure, the patient's right foot becomes cool and pale, with non-palpable pedal pulses confirmed by Doppler silence. What is the most likely cause of these findings?
- Venous air embolism from the decannulation site.
- Phlegmasia cerulea dolens due to a massive deep vein thrombosis.
- Systemic inflammatory response syndrome from the ECMO run.
- Acute arterial thrombosis or stenosis at the cannulation repair site. (Correct answer)
Correct answer: Acute arterial thrombosis or stenosis at the cannulation repair site.
The classic signs of acute limb ischemia (pain, pallor, pulselessness, poikilothermia) point directly to an obstruction of arterial blood flow. Following femoral arterial decannulation, the most probable cause for these acute signs is the formation of a thrombus or the development of stenosis at the arteriotomy repair site, impeding distal perfusion.
Question 6: A patient has been successfully weaned from peripheral Veno-Venous (VV) ECMO. The team is preparing for decannulation at the bedside. Which of the following is a critical preparatory step to minimize the risk of bleeding complications?
- Ensuring anticoagulation has been held and coagulation parameters are in a safe range. (Correct answer)
- Administering a bolus of unfractionated heparin to prevent thrombus dislodgement.
- Maximizing ECMO blood flow just prior to cannula removal.
- Placing the patient in a steep Trendelenburg position to prevent air embolism.
Correct answer: Ensuring anticoagulation has been held and coagulation parameters are in a safe range.
Decannulation involves removing large-bore cannulas from major vessels, posing a significant risk of hemorrhage. To ensure effective hemostasis via manual pressure or surgical repair, systemic anticoagulation must be discontinued and its effects must be verified to have diminished (e.g., via aPTT or ACT) before proceeding with cannula removal.
ECMO - Extracorporeal Membrane Oxygenation Weaning and Decannulation Questions and Answers
A 55-year-old patient on Veno-Venous (VV) ECMO for severe ARDS has shown significant improvement in lung compliance and chest X-ray findings.
The clinical team decides to perform a liberation trial.
What is the most appropriate initial step in this process?