ECMO - Extracorporeal Membrane Oxygenation Weaning and Decannulation 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?

Accepted Answer

Systematically reduce the sweep gas flow to zero while maintaining ECMO blood flow.

Answer

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?

Accepted Answer

Increased preload and afterload.

Answer

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?

Accepted Answer

A rise in pulmonary capillary wedge pressure (PCWP) to >18 mmHg and a non-opening aortic valve on echocardiogram.

Answer

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?

Accepted Answer

pH 7.21, PaCO2 75 mmHg, PaO2 90 mmHg

Answer

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?

Accepted Answer

Acute arterial thrombosis or stenosis at the cannulation repair site.

Answer

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.

ECMO - Extracorporeal Membrane Oxygenation Practice Test

ECMO - Extracorporeal Membrane Oxygenation Practice Test

ECMO - Extracorporeal Membrane Oxygenation Weaning and Decannulation Questions and Answers