ECMO - Extracorporeal Membrane Oxygenation Complications and Troubleshooting Questions and Answers

Question 1

A patient on VV ECMO for ARDS secondary to an atypical pneumonia is noted to have persistently low pulse oximetry readings (SpO2 85-88%) despite an excellent post-oxygenator PaO2 of >400 mmHg on blood gas analysis.
The blood in the arterial line of the ECMO circuit appears unusually dark or 'chocolate brown.' This discrepancy is most suggestive of which complication?

Accepted Answer

Methemoglobinemia

Answer

Severe hemolysis

Answer

Significant recirculation

Answer

Carbon monoxide poisoning

Question 2

During management of a patient on VA ECMO with a centrifugal pump, you observe that the measured circuit blood flow has suddenly decreased from 4.5 LPM to 2.5 LPM, while the pump RPM has been increased from 3500 to 4000 in an attempt to compensate. Which of the following is the most likely cause for this change?

Accepted Answer

An obstruction in the arterial (return) line

Answer

Inadequate venous drainage due to hypovolemia

Answer

Sudden improvement in native cardiac function

Answer

Air embolism in the venous drainage line

Question 3

Which of the following clinical signs is the most specific indicator of an impending oxygenator failure due to plasma leak?

Accepted Answer

Frothy, pink-tinged fluid appearing in the oxygenator's gas exhaust port.

Answer

A progressive increase in the pressure gradient across the oxygenator.

Answer

A gradual decrease in the post-oxygenator PaO2.

Answer

A rapid increase in plasma-free hemoglobin levels.

Question 4

A patient on VV ECMO requires Continuous Renal Replacement Therapy (CRRT). The CRRT circuit is initiated, drawing blood from a pre-pump access port and returning it post-oxygenator. Shortly after initiation, the ECMO circuit's pre-membrane (access) pressure becomes significantly more negative, and the venous line begins to chatter. What is the most probable cause?

Accepted Answer

The CRRT machine's ultrafiltration rate is too high, causing patient hypovolemia.

Answer

The CRRT machine is adding excess volume to the circuit.

Answer

A large clot has formed in the ECMO oxygenator.

Answer

The sweep gas flow on the ECMO circuit was accidentally increased.

Question 5

While assessing a patient on VA ECMO, a large bolus of air is accidentally introduced into the venous drainage line just before the pump. What is the most critical and immediate sequence of actions?

Accepted Answer

Clamp the arterial and venous lines, and take the patient completely off ECMO support.

Answer

Place the patient in Trendelenburg and administer a fluid bolus.

Answer

Increase pump flow to push the air through the oxygenator quickly.

Answer

Decrease the sweep gas to zero and observe the circuit.

Question 6

A known complication of ECMO is acquired von Willebrand syndrome (AVWS), which can contribute significantly to bleeding. What is the primary mechanism by which the ECMO circuit leads to this coagulopathy?

Accepted Answer

Shear stress from the pump and circuit components causes unfolding and proteolytic cleavage of large von Willebrand factor multimers.

Answer

Continuous heparin infusion directly inhibits the function of von Willebrand factor.

Answer

Platelets adhere to the circuit surface, depleting the plasma of available von Willebrand factor.

Answer

The oxygenator membrane absorbs von Willebrand factor, removing it from circulation.