ECMO Weaning and Decannulation 2 — Questions and Answers
Question 1: During VV-ECMO weaning, which parameter most reliably indicates adequate native lung recovery before a trial off?
- Static lung compliance > 20 mL/cmH2O
- SpO2 > 95% on FiO2 ≤ 0.4 with sweep gas off (Correct answer)
- PaO2/FiO2 ratio > 100 on full ECMO support
- Tidal volume > 8 mL/kg IBW on pressure support
Correct answer: SpO2 > 95% on FiO2 ≤ 0.4 with sweep gas off
SpO2 >95% with acceptable PaCO2 on room-air sweep-off conditions demonstrates that native lungs can sustain gas exchange independently.
Question 2: A patient on VA-ECMO for cardiogenic shock undergoes a 30-minute clamp trial. During the trial, the arterial pressure waveform becomes pulsatile with a pulse pressure of 40 mmHg. This finding indicates:
- Severe aortic regurgitation has developed
- Adequate left ventricular recovery to consider decannulation (Correct answer)
- Ventricular fibrillation has occurred
- The arterial line is dampened and needs troubleshooting
Correct answer: Adequate left ventricular recovery to consider decannulation
A robust pulsatile waveform during VA-ECMO clamping reflects meaningful left ventricular stroke volume, suggesting cardiac recovery.
Question 3: Which echocardiographic finding during a VA-ECMO weaning trial would most strongly support proceeding to decannulation?
- Left ventricular ejection fraction of 15%
- Severe mitral regurgitation with LA dilation
- LVEF ≥ 35% with no severe valvular abnormality (Correct answer)
- Right ventricular free wall akinesis
Correct answer: LVEF ≥ 35% with no severe valvular abnormality
LVEF ≥ 35% without severe valvular disease suggests sufficient cardiac reserve to sustain circulation without ECMO support.
Question 4: When weaning VV-ECMO, the sweep gas flow is progressively reduced. What physiologic effect does reducing sweep gas primarily alter?
- Oxygen delivery to the patient
- Carbon dioxide removal by the oxygenator (Correct answer)
- Blood flow rate through the circuit
- Venous return to the right heart
Correct answer: Carbon dioxide removal by the oxygenator
Sweep gas flow controls the rate of CO2 removal across the membrane; reducing it raises PaCO2 and stimulates native respiratory drive.
Question 5: After surgical decannulation of a femoral venous cannula, the preferred method for achieving hemostasis at the venous access site in a fully anticoagulated patient is:
- Immediate removal of anticoagulation and surgical cut-down closure
- Manual pressure for 30–45 minutes followed by a pressure dressing (Correct answer)
- Deployment of a vascular closure device
- Suture ligation of the femoral vein
Correct answer: Manual pressure for 30–45 minutes followed by a pressure dressing
Sustained manual compression for 30–45 minutes is standard practice for venous cannula sites, followed by a firm pressure dressing.
Question 6: During a VA-ECMO weaning trial at reduced flow (1 L/min), the patient develops hypotension (MAP 55 mmHg) and mottled extremities. The appropriate immediate action is:
- Administer a fluid bolus and continue the trial
- Return ECMO flow to full support and reassess in 24–48 hours (Correct answer)
- Proceed to decannulation with aggressive vasopressor support
- Increase the sweep gas flow to improve oxygenation
Correct answer: Return ECMO flow to full support and reassess in 24–48 hours
Hemodynamic deterioration during a weaning trial indicates the patient is not ready; restoring full flow and deferring decannulation is the safe response.
Question 7: A key advantage of a percutaneous 'Z-stitch' purse-string suture placed at the time of cannulation is that it:
- Prevents cannula migration during ECMO support
- Allows rapid hemostasis at decannulation without surgical exploration (Correct answer)
- Reduces the risk of cannula-related thrombosis
- Secures the cannula to the skin to prevent accidental dislodgement
Correct answer: Allows rapid hemostasis at decannulation without surgical exploration
The pre-placed purse-string suture can be tightened and tied at the moment the cannula is withdrawn, achieving immediate hemostasis percutaneously.
ECMO Weaning and Decannulation 2
During VV-ECMO weaning, which parameter most reliably indicates adequate native lung recovery before a trial off?