CVP Physiological and Pathophysiological Concepts 3 — Questions and Answers
Question 1: During CPB, a patient with a known left ventricular aneurysm is at greatest risk for which perfusion-related complication?
- Paradoxical air embolism through the aneurysm wall
- Inadequate LV venting leading to ventricular distension (Correct answer)
- Spontaneous coronary artery dissection
- Aortic root over-pressurization
Correct answer: Inadequate LV venting leading to ventricular distension
LV aneurysms impair contractility and ventricular ejection, increasing risk of inadequate venting and distension during CPB.
Question 2: The oxygen-hemoglobin dissociation curve shifts to the right in the presence of:
- Alkalosis and hypothermia
- Acidosis, hyperthermia, and elevated 2,3-DPG (Correct answer)
- Low CO2 partial pressure
- Fetal hemoglobin
Correct answer: Acidosis, hyperthermia, and elevated 2,3-DPG
Acidosis, hyperthermia, and elevated 2,3-DPG all decrease hemoglobin's affinity for oxygen, shifting the dissociation curve rightward (Bohr effect).
Question 3: Which pathophysiologic mechanism underlies the phenomenon of 'coronary steal' in patients with coronary artery disease during CPB?
- Vasodilators preferentially dilate non-stenotic vessels, diverting flow from ischemic territories (Correct answer)
- Hypothermia causes coronary vasospasm in diseased segments
- Hemodilution reduces oxygen-carrying capacity beyond compensatory limits
- Elevated perfusion pressure forces flow into non-ischemic regions
Correct answer: Vasodilators preferentially dilate non-stenotic vessels, diverting flow from ischemic territories
Coronary steal occurs when vasodilators dilate normal vessels, reducing perfusion pressure distal to stenoses and diverting blood away from ischemic myocardium.
Question 4: In the context of cardiopulmonary bypass, which statement about the systemic inflammatory response syndrome (SIRS) is most accurate?
- SIRS is caused exclusively by protamine administration
- Contact of blood with the CPB circuit activates complement, cytokines, and neutrophils (Correct answer)
- Hypothermia abolishes the inflammatory response during CPB
- SIRS only occurs in pediatric patients on CPB
Correct answer: Contact of blood with the CPB circuit activates complement, cytokines, and neutrophils
Blood contact with artificial surfaces activates complement cascades, releases cytokines, and primes neutrophils, generating a SIRS response during CPB.
Question 5: A patient's arterial blood gas on CPB shows pH 7.30, PaCO2 55 mmHg, PaO2 320 mmHg. The perfusionist should first:
- Decrease the oxygenator FiO2 to reduce PaO2
- Increase sweep gas flow rate to remove excess CO2 (Correct answer)
- Add sodium bicarbonate to correct the acidosis
- Reduce pump flow to lower metabolic CO2 production
Correct answer: Increase sweep gas flow rate to remove excess CO2
Increasing sweep gas flow through the oxygenator enhances CO2 elimination, directly correcting the respiratory acidosis.
Question 6: Which aspect of myocardial oxygen consumption (MVO2) is most significantly reduced by cardioplegic arrest?
- Basal cellular metabolism
- Wall stress component from pressure work
- Electromechanical activity (Correct answer)
- Fatty acid oxidation substrate utilization
Correct answer: Electromechanical activity
Cardioplegic arrest eliminates electromechanical activity, which accounts for the majority of MVO2 during normal cardiac function.
Question 7: During reperfusion after global myocardial ischemia, calcium overload of myocytes is primarily mediated by:
- Reversal of the sodium-calcium exchanger due to intracellular sodium accumulation (Correct answer)
- Direct membrane rupture from ischemic injury
- Increased L-type calcium channel expression
- Mitochondrial calcium release triggered by ATP restoration
Correct answer: Reversal of the sodium-calcium exchanger due to intracellular sodium accumulation
Ischemia-induced intracellular sodium accumulation causes the Na⁺/Ca²⁺ exchanger to run in reverse during reperfusion, flooding myocytes with calcium.
CVP Physiological and Pathophysiological Concepts 3
During CPB, a patient with a known left ventricular aneurysm is at greatest risk for which perfusion-related complication?