CCP Mechanical Circulatory Support & ECMO Management 2 — Questions and Answers
Question 1: The intraaortic balloon pump (IABP) improves coronary artery perfusion through which mechanism?
- Inflating during systole to augment stroke volume
- Deflating during diastole to reduce venous return
- Inflating during diastole to increase diastolic aortic pressure (Correct answer)
- Deflating during systole to decrease left ventricular preload
Correct answer: Inflating during diastole to increase diastolic aortic pressure
The IABP inflates at the onset of diastole, raising diastolic aortic pressure and thereby increasing coronary perfusion pressure, since coronary filling primarily occurs during diastole.
Question 2: What is the standard first-line anticoagulant used during ECMO support?
- Warfarin
- Bivalirudin
- Unfractionated heparin (Correct answer)
- Fondaparinux
Correct answer: Unfractionated heparin
Unfractionated heparin is the preferred anticoagulant for ECMO because it can be rapidly titrated, monitored with ACT or aPTT, and reversed with protamine if needed.
Question 3: A patient on peripheral VA-ECMO develops 'Harlequin syndrome.' What pathophysiology does this describe?
- Lower extremity ischemia from femoral arterial cannulation
- Upper body hypoxia when poorly oxygenated native cardiac output mixes with ECMO-oxygenated return before reaching the cerebral circulation (Correct answer)
- Cerebral hyperperfusion caused by excessive ECMO flow rates
- Differential cyanosis between upper extremities due to subclavian steal
Correct answer: Upper body hypoxia when poorly oxygenated native cardiac output mixes with ECMO-oxygenated return before reaching the cerebral circulation
Harlequin (north-south) syndrome occurs when a recovering native heart ejects deoxygenated blood that perfuses the upper body before retrograde femoral ECMO-oxygenated blood can reach it, causing upper body hypoxia.
Question 4: Which parameter best reflects the adequacy of systemic oxygen delivery during ECMO support?
- Peripheral oxygen saturation (SpO2)
- Mixed venous oxygen saturation (SvO2) (Correct answer)
- End-tidal CO2 (EtCO2)
- Pulmonary capillary wedge pressure (PCWP)
Correct answer: Mixed venous oxygen saturation (SvO2)
Mixed venous oxygen saturation reflects the balance between oxygen delivery and tissue consumption; a declining SvO2 indicates that tissues are extracting more oxygen because delivery is insufficient.
Question 5: What is the typical ECMO circuit flow rate range required to provide adequate cardiac output support in an adult on VA-ECMO?
- 0.5–1.0 L/min
- 1.0–2.0 L/min
- 2.5–4.5 L/min (Correct answer)
- 6.0–8.0 L/min
Correct answer: 2.5–4.5 L/min
Adult VA-ECMO typically targets flows of 2.5–4.5 L/min to approximate normal resting cardiac output and maintain adequate systemic perfusion.
Question 6: Which condition is a contraindication to intraaortic balloon pump (IABP) insertion?
- Cardiogenic shock post-myocardial infarction
- Moderate aortic regurgitation (Correct answer)
- Refractory unstable angina
- Post-CABG low cardiac output syndrome
Correct answer: Moderate aortic regurgitation
Aortic regurgitation is a contraindication because IABP inflation during diastole raises aortic root pressure, worsening regurgitant volume back into the already failing left ventricle.
Question 7: In ECMO circuit management, what is the primary function of the sweep gas flowing through the oxygenator?
- To regulate circuit blood temperature
- To remove carbon dioxide from the blood (Correct answer)
- To maintain circuit prime volume
- To prevent fibrin deposition on the membrane
Correct answer: To remove carbon dioxide from the blood
Sweep gas (typically oxygen or an oxygen/air blend) flows countercurrent across the oxygenator membrane to remove carbon dioxide; increasing sweep flow lowers PaCO2.
CCP Mechanical Circulatory Support & ECMO Management 2
The intraaortic balloon pump (IABP) improves coronary artery perfusion through which mechanism?