CVP Pharmacology and Blood Management — Questions and Answers
Question 1: What is the mechanism of action of heparin in preventing clotting?
- Heparin binds to antithrombin III, dramatically accelerating its inhibition of thrombin and Factor Xa (Correct answer)
- It destroys existing blood clots
- It prevents platelet production
- It thins the blood by removing water
Correct answer: Heparin binds to antithrombin III, dramatically accelerating its inhibition of thrombin and Factor Xa
Heparin potentiates the natural anticoagulant antithrombin III, which then rapidly inhibits key clotting factors including thrombin and Factor Xa.
Question 2: What vasopressor is commonly used to maintain blood pressure during bypass?
- Phenylephrine (Correct answer)
- Aspirin
- Warfarin
- Digoxin
Correct answer: Phenylephrine
Phenylephrine is an alpha-adrenergic agonist commonly used during bypass to increase systemic vascular resistance and maintain adequate mean arterial pressure.
Question 3: What is the role of mannitol in cardiopulmonary bypass?
- It acts as an osmotic diuretic to maintain urine output and reduce cellular swelling (Correct answer)
- It prevents blood clotting
- It provides nutrition to the patient
- It regulates heart rhythm
Correct answer: It acts as an osmotic diuretic to maintain urine output and reduce cellular swelling
Mannitol is added to the bypass circuit as an osmotic diuretic that helps maintain kidney function and reduces tissue edema during the procedure.
Question 4: When is blood transfusion indicated during cardiopulmonary bypass?
- When hematocrit drops below a critical threshold, typically around 21-24% (Correct answer)
- At the beginning of every bypass procedure
- Only if the patient requests it
- Blood transfusion is never needed during bypass
Correct answer: When hematocrit drops below a critical threshold, typically around 21-24%
Transfusion is indicated when hemodilution reduces the hematocrit below the level needed to maintain adequate oxygen delivery, typically around 21-24%.
Question 5: What is the purpose of adding sodium bicarbonate during bypass?
- To correct metabolic acidosis by buffering excess acid in the blood (Correct answer)
- To prevent infection
- To thin the blood
- To increase blood flow
Correct answer: To correct metabolic acidosis by buffering excess acid in the blood
Sodium bicarbonate is used to correct metabolic acidosis, which can develop during bypass due to inadequate perfusion or hypothermia.
Question 6: What is epsilon-aminocaproic acid (Amicar) used for during cardiac surgery?
- To inhibit fibrinolysis and reduce bleeding (Correct answer)
- To increase blood clotting speed
- To prevent infection
- To maintain blood pressure
Correct answer: To inhibit fibrinolysis and reduce bleeding
Amicar inhibits the breakdown of blood clots (fibrinolysis), helping to reduce bleeding during and after cardiac surgery.
CVP Pharmacology and Blood Management
What is the mechanism of action of heparin in preventing clotting?