CVP CVP ECMO and Mechanical Circulatory Support 2 — Questions and Answers
Question 1: What is 'Harlequin syndrome' (North-South syndrome) in VA-ECMO?
- Differential oxygenation between upper and lower body due to competing native cardiac output and ECMO return (Correct answer)
- Pump thrombosis causing acute flow loss
- Air embolism entering the ECMO circuit
- Systemic hypertension from excessive ECMO flow
Correct answer: Differential oxygenation between upper and lower body due to competing native cardiac output and ECMO return
Harlequin syndrome occurs when the recovering native heart ejects poorly oxygenated blood to the upper body while ECMO returns well-oxygenated blood to the lower body via the femoral artery.
Question 2: What is the primary function of the oxygenator membrane in an ECMO circuit?
- To pump blood through the circuit at adequate flow rates
- To remove CO2 from and add O2 to blood across a hollow-fiber membrane (Correct answer)
- To filter microemboli and blood clots from the circuit
- To regulate blood temperature only
Correct answer: To remove CO2 from and add O2 to blood across a hollow-fiber membrane
The hollow-fiber membrane oxygenator allows gas exchange across a semi-permeable membrane: O2 diffuses in and CO2 diffuses out driven by concentration gradients.
Question 3: What serious vascular complication is associated with femoral arterial VA-ECMO cannulation?
- Hypothermia in the cannulated limb
- Limb ischemia distal to the arterial cannula (Correct answer)
- Systemic electrolyte imbalance
- Chronic hypertension in the cannulated leg
Correct answer: Limb ischemia distal to the arterial cannula
The large arterial cannula can obstruct femoral artery flow, causing acute limb ischemia distal to the insertion site, requiring vigilant monitoring and often a distal perfusion cannula.
Question 4: How is ECMO flow rate primarily managed by the perfusionist?
- By adjusting systemic blood pressure medications alone
- By adjusting pump speed (RPM) while monitoring flow, pressures, and patient hemodynamics (Correct answer)
- By changing membrane oxygenator size
- By adjusting only the sweep gas FiO2
Correct answer: By adjusting pump speed (RPM) while monitoring flow, pressures, and patient hemodynamics
The perfusionist titrates pump RPM to achieve target flow (typically 60–80 mL/kg/min for VA-ECMO) while monitoring circuit pressures, arterial saturation, and clinical perfusion markers.
Question 5: What is the purpose of a distal perfusion cannula (DPC) placed in the superficial femoral artery during VA-ECMO?
- To increase overall ECMO circuit flow capacity
- To perfuse the limb distal to the arterial cannula and prevent ischemia (Correct answer)
- To monitor continuous arterial pressure in the leg
- To deliver medications directly to the femoral circulation
Correct answer: To perfuse the limb distal to the arterial cannula and prevent ischemia
A DPC is a small-diameter side cannula placed distal to the main arterial cannula, connected to the ECMO circuit to maintain limb perfusion and prevent ischemic complications.
Question 6: ECMO support is generally considered contraindicated in which of the following situations?
- Post-cardiac arrest with presumed reversible cause
- Severe acute respiratory distress syndrome (ARDS)
- Irreversible organ failure with no candidacy for transplant or recovery (Correct answer)
- Cardiogenic shock following acute myocardial infarction
Correct answer: Irreversible organ failure with no candidacy for transplant or recovery
ECMO is a bridge — to recovery, to decision, or to transplant — and is not appropriate when there is no realistic chance of meaningful recovery or transplant eligibility.
CVP CVP ECMO and Mechanical Circulatory Support 2
What is 'Harlequin syndrome' (North-South syndrome) in VA-ECMO?