CCP Intraoperative Procedures & Patient Monitoring 2 — Questions and Answers
Question 1: During cardiopulmonary bypass, which parameter best reflects cerebral oxygen delivery adequacy when using near-infrared spectroscopy (NIRS)?
- Mixed venous oxygen saturation >70%
- Regional cerebral oxygen saturation (rSO2) >50% of baseline (Correct answer)
- Mean arterial pressure >60 mmHg
- Arterial PO2 >100 mmHg
Correct answer: Regional cerebral oxygen saturation (rSO2) >50% of baseline
NIRS-derived rSO2 dropping below 50% of the patient's baseline value is the accepted threshold indicating inadequate cerebral oxygen delivery.
Question 2: A patient on CPB develops sudden onset of bright red arterial line blood and a marked increase in arterial line pressure. The most likely cause is:
- Aortic dissection (Correct answer)
- Arterial cannula obstruction
- Oxygenator failure
- Venous air entrainment
Correct answer: Aortic dissection
Sudden bright red blood in the arterial line combined with a pressure spike suggests aortic dissection, where the cannula tip has entered the false lumen.
Question 3: Which of the following is the primary purpose of administering mannitol during cardiopulmonary bypass?
- Reduce heparin requirements
- Promote osmotic diuresis and free radical scavenging (Correct answer)
- Increase systemic vascular resistance
- Improve myocardial protection
Correct answer: Promote osmotic diuresis and free radical scavenging
Mannitol is used during CPB as an osmotic diuretic to maintain urine output and as a free radical scavenger to reduce reperfusion injury.
Question 4: During rewarming on CPB, the maximum recommended temperature gradient between the heat exchanger water and the patient's blood temperature is:
- 5°C
- 10°C (Correct answer)
- 15°C
- 20°C
Correct answer: 10°C
A water-to-blood temperature gradient exceeding 10°C risks gas coming out of solution and forming emboli in the blood.
Question 5: The activated clotting time (ACT) target for full heparinization during cardiopulmonary bypass is generally:
- >200 seconds
- >300 seconds
- >400 seconds (Correct answer)
- >480 seconds
Correct answer: >400 seconds
Most centers target an ACT greater than 400 seconds (some use 480 seconds) before initiating CPB to prevent clot formation in the circuit.
Question 6: Which physiologic change is expected when transitioning from normothermic to hypothermic CPB?
- Increased oxygen consumption and decreased CO2 production
- Decreased oxygen consumption and decreased CO2 production (Correct answer)
- No change in oxygen consumption but increased CO2 production
- Increased both oxygen consumption and CO2 production
Correct answer: Decreased oxygen consumption and decreased CO2 production
Hypothermia reduces cellular metabolic rate, decreasing both oxygen consumption (VO2) and carbon dioxide production (VCO2).
Question 7: A perfusionist notices increasing arterial line pressure with unchanged pump flow. The most appropriate initial response is to:
- Increase pump flow to maintain perfusion pressure
- Check for arterial cannula kinking or obstruction (Correct answer)
- Administer a vasodilator immediately
- Reduce pump speed and notify the surgeon
Correct answer: Check for arterial cannula kinking or obstruction
Rising arterial line pressure at constant flow suggests increased resistance in the arterial line, most commonly from cannula kinking, malpositioning, or aortic obstruction.
CCP Intraoperative Procedures & Patient Monitoring 2
During cardiopulmonary bypass, which parameter best reflects cerebral oxygen delivery adequacy when using near-infrared spectroscopy (NIRS)?