CVP Cardiopulmonary Bypass (CPB) Management 2 — Questions and Answers
Question 1: During CPB, what is the primary purpose of the membrane oxygenator?
- To remove carbon dioxide only
- To add oxygen and remove carbon dioxide from blood (Correct answer)
- To filter cellular debris from the circuit
- To regulate systemic vascular resistance
Correct answer: To add oxygen and remove carbon dioxide from blood
The membrane oxygenator performs gas exchange by adding oxygen and removing carbon dioxide from venous blood, replacing lung function during CPB.
Question 2: What is the typical target activated clotting time (ACT) maintained during full cardiopulmonary bypass?
- 200–250 seconds
- 300–350 seconds
- 400–480 seconds (Correct answer)
- 550–600 seconds
Correct answer: 400–480 seconds
An ACT of 400–480 seconds is the standard target during full CPB to prevent thrombosis in the extracorporeal circuit.
Question 3: A patient on CPB develops sudden arterial line pressure drop with increased venous reservoir level. What is the most likely cause?
- Aortic dissection
- Venous air lock (Correct answer)
- Roller pump failure
- Oxygenator clotting
Correct answer: Venous air lock
Venous air lock impedes venous drainage, causing blood to accumulate in the venous reservoir while arterial pressure drops due to reduced pump output.
Question 4: Which parameter most directly reflects adequate systemic perfusion during CPB in an adult?
- Mean arterial pressure alone
- Mixed venous oxygen saturation (SvO2) (Correct answer)
- Pump flow rate alone
- Systemic temperature
Correct answer: Mixed venous oxygen saturation (SvO2)
SvO2 reflects the balance between oxygen delivery and consumption, providing the most direct indicator of systemic perfusion adequacy during CPB.
Question 5: During hypothermic CPB, what change in blood viscosity is expected and how is it typically managed?
- Decreased viscosity; no intervention needed
- Increased viscosity; managed with hemodilution (Correct answer)
- Decreased viscosity; managed with blood transfusion
- No change; managed with vasopressors
Correct answer: Increased viscosity; managed with hemodilution
Hypothermia increases blood viscosity, which is counteracted through hemodilution with crystalloid prime to maintain adequate microcirculatory flow.
Question 6: What is the recommended minimum pump flow rate (indexed to body surface area) during normothermic CPB in adults?
- 1.0 L/min/m²
- 1.6 L/min/m²
- 2.2–2.4 L/min/m² (Correct answer)
- 3.0 L/min/m²
Correct answer: 2.2–2.4 L/min/m²
A minimum cardiac index of 2.2–2.4 L/min/m² is recommended during normothermic CPB to ensure adequate organ perfusion.
Question 7: Which condition requires immediate circuit intervention when the perfusionist observes bright red blood in the venous line during CPB?
- Hemodilution artifact
- Arterial-venous line crossover or left heart venting anomaly (Correct answer)
- Oxygenator malfunction causing over-oxygenation
- Hypothermia-induced color change
Correct answer: Arterial-venous line crossover or left heart venting anomaly
Bright red (oxygenated) blood in the venous line indicates arterial-venous shunting or cross-connection, requiring immediate identification and correction.
CVP Cardiopulmonary Bypass (CPB) Management 2
During CPB, what is the primary purpose of the membrane oxygenator?