CVP Cardiopulmonary Bypass (CPB) Management 3 — Questions and Answers
Question 1: During CPB, the perfusionist notices the arterial line pressure is rising while pump flow remains constant. What is the most likely explanation?
- Vasodilation from anesthetic agents
- Aortic cannula malposition or partial obstruction (Correct answer)
- Venous reservoir overfill
- Oxygenator membrane rupture
Correct answer: Aortic cannula malposition or partial obstruction
Rising arterial line pressure at constant flow suggests increased resistance, most commonly due to aortic cannula malposition, kinking, or partial obstruction.
Question 2: Which type of CPB circuit component is most responsible for hemolysis due to mechanical shear stress?
- Membrane oxygenator
- Roller pump (Correct answer)
- Arterial filter
- Heat exchanger
Correct answer: Roller pump
Roller pumps generate the highest mechanical shear stress on red blood cells, making them the primary source of pump-related hemolysis in the CPB circuit.
Question 3: A perfusionist is managing a patient with known heparin-induced thrombocytopenia (HIT). Which anticoagulant is most appropriate for CPB?
- Increased heparin dose
- Bivalirudin (Correct answer)
- Warfarin
- Low-molecular-weight heparin
Correct answer: Bivalirudin
Bivalirudin is the preferred direct thrombin inhibitor for CPB anticoagulation in patients with confirmed HIT, as heparin is contraindicated.
Question 4: What is the purpose of retrograde autologous priming (RAP) in CPB circuits?
- To warm the circuit before initiation of bypass
- To reduce hemodilution by displacing crystalloid prime with patient's blood (Correct answer)
- To flush air from the oxygenator
- To increase oncotic pressure in the reservoir
Correct answer: To reduce hemodilution by displacing crystalloid prime with patient's blood
RAP replaces crystalloid prime in the circuit with the patient's own blood before bypass, reducing hemodilution and transfusion requirements.
Question 5: During rewarming on CPB, what is the recommended maximum temperature gradient between the water heater and the patient's blood to prevent gas emboli?
- 5°C
- 10°C
- 14°C (Correct answer)
- 20°C
Correct answer: 14°C
A maximum gradient of 10–14°C between the heat exchanger water temperature and blood temperature is recommended to prevent gas supersaturation and bubble formation.
Question 6: Which of the following best describes the role of the arterial line filter during CPB?
- Removes gaseous and particulate microemboli from blood returning to the patient (Correct answer)
- Filters venous blood before entering the oxygenator
- Regulates arterial line pressure by throttling flow
- Separates plasma from cellular components
Correct answer: Removes gaseous and particulate microemboli from blood returning to the patient
The arterial line filter (typically 20–40 microns) captures gaseous and particulate microemboli before blood is delivered to the patient's arterial circulation.
Question 7: Cardioplegia delivery pressure for antegrade infusion into the aortic root should generally be maintained below which threshold to avoid coronary injury?
- 50 mmHg
- 100 mmHg (Correct answer)
- 150 mmHg
- 200 mmHg
Correct answer: 100 mmHg
Antegrade cardioplegia should be delivered at pressures below 100 mmHg (aortic root) to prevent coronary endothelial injury and ensure even distribution.
CVP Cardiopulmonary Bypass (CPB) Management 3
During CPB, the perfusionist notices the arterial line pressure is rising while pump flow remains constant.
What is the most likely explanation?