CCP CPB Circuit Assembly & Priming 3 — Questions and Answers
Question 1: Which centrifugal pump characteristic distinguishes it from a roller pump during CPB?
- It generates a fixed flow regardless of afterload
- Its flow is non-occlusive and afterload-dependent (Correct answer)
- It requires a larger priming volume
- It cannot be used with a membrane oxygenator
Correct answer: Its flow is non-occlusive and afterload-dependent
Centrifugal pumps are afterload-sensitive and will reduce flow if arterial resistance increases, unlike roller pumps which deliver a set volume per revolution.
Question 2: The standard pore size of an arterial line filter used in CPB circuits is:
- 10 microns
- 40 microns (Correct answer)
- 100 microns
- 200 microns
Correct answer: 40 microns
Most arterial line filters use a 40-micron screen to capture clinically significant gaseous and particulate microemboli while maintaining adequate flow.
Question 3: During CPB priming, adding mannitol (0.5 g/kg) to the prime solution is intended primarily to:
- Prevent systemic anticoagulation reversal
- Promote osmotic diuresis and reduce cerebral edema (Correct answer)
- Increase prime viscosity
- Chelate ionized calcium in the prime
Correct answer: Promote osmotic diuresis and reduce cerebral edema
Mannitol acts as an osmotic diuretic during CPB and may help reduce cellular swelling and free radical scavenging in ischemic tissues.
Question 4: A 'soft-shell' venous reservoir differs from a 'hard-shell' reservoir in that it:
- Contains an integrated membrane oxygenator
- Collapses as volume decreases, preventing air aspiration by the pump (Correct answer)
- Has a larger maximum volume capacity
- Incorporates an arterial line filter
Correct answer: Collapses as volume decreases, preventing air aspiration by the pump
Soft-shell (collapsible) reservoirs collapse when volume is low, providing a visual warning and preventing the pump from aspirating air.
Question 5: Which complication is most directly associated with roller pump tubing that is set too occlusively?
- Air entrainment into the circuit
- Excessive hemolysis and red blood cell destruction (Correct answer)
- Inadequate cardiac output during bypass
- Retrograde arterial blood flow
Correct answer: Excessive hemolysis and red blood cell destruction
Excessive roller pump occlusion increases shear stress on red blood cells as they pass through the compressed tubing segment, causing hemolysis.
Question 6: What is the recommended method to check roller pump occlusion before initiating CPB?
- Measure the pump flow at maximum RPM and compare to theoretical output
- Clamp the outlet tubing and observe the rate of retrograde fluid drop in a elevated segment (Correct answer)
- Run the pump and measure line pressure at the arterial cannula
- Perform a pressure-flow curve analysis
Correct answer: Clamp the outlet tubing and observe the rate of retrograde fluid drop in a elevated segment
The standard occlusion test involves clamping the outlet, elevating a tubing segment, and verifying the fluid falls no more than 1 cm/min, indicating appropriate but not excessive occlusion.
Question 7: During circuit priming, calcium chloride is sometimes added LAST because:
- It increases the viscosity of the prime, making mixing difficult
- It can precipitate with phosphate- or bicarbonate-containing solutions if mixed prematurely (Correct answer)
- It decreases the pH of the prime solution
- It reacts with heparin to cause coagulation
Correct answer: It can precipitate with phosphate- or bicarbonate-containing solutions if mixed prematurely
Calcium salts can form insoluble precipitates with phosphate or bicarbonate; adding calcium last after other additives are mixed prevents this chemical incompatibility.
CCP CPB Circuit Assembly & Priming 3
Which centrifugal pump characteristic distinguishes it from a roller pump during CPB?