CCP Vasoactive Drug Pharmacology 2 — Questions and Answers
Question 1: Which receptor subtype mediates the positive inotropic effect of dopamine at doses of 5–10 mcg/kg/min?
- Alpha-1
- Beta-1 (Correct answer)
- Dopamine-1
- Beta-2
Correct answer: Beta-1
At intermediate doses (5–10 mcg/kg/min), dopamine primarily stimulates beta-1 adrenergic receptors, increasing cardiac contractility and heart rate.
Question 2: Milrinone exerts its positive inotropic effect by inhibiting which enzyme?
- Adenylyl cyclase
- Phosphodiesterase III (Correct answer)
- Acetylcholinesterase
- Monoamine oxidase
Correct answer: Phosphodiesterase III
Milrinone inhibits phosphodiesterase III, preventing cAMP breakdown and increasing intracellular calcium availability for myocardial contraction.
Question 3: A patient on cardiopulmonary bypass develops hypotension with low SVR. Which vasopressor acts primarily on V1 receptors to increase SVR without affecting heart rate?
- Norepinephrine
- Phenylephrine
- Vasopressin (Correct answer)
- Epinephrine
Correct answer: Vasopressin
Vasopressin acts on V1 receptors in vascular smooth muscle to cause vasoconstriction independent of adrenergic pathways, with minimal chronotropic effect.
Question 4: During weaning from CPB, dobutamine is preferred over dopamine primarily because dobutamine:
- Has longer duration of action
- Causes less tachycardia and fewer dysrhythmias at equivalent inotropic doses (Correct answer)
- Is cheaper and more widely available
- Increases renal perfusion more effectively
Correct answer: Causes less tachycardia and fewer dysrhythmias at equivalent inotropic doses
Dobutamine produces strong beta-1 inotropic effects with less chronotropy and dysrhythmia risk compared to dopamine at comparable inotropic doses.
Question 5: Which pharmacologic property of nitroprusside requires co-administration of thiosulfate during prolonged infusions?
- Methemoglobin formation
- Cyanide ion accumulation (Correct answer)
- Metabolic alkalosis induction
- Tachyphylaxis development
Correct answer: Cyanide ion accumulation
Nitroprusside releases cyanide ions during metabolism; thiosulfate acts as a sulfur donor to convert cyanide to the less toxic thiocyanate.
Question 6: Levosimendan improves cardiac contractility by which mechanism of action?
- Inhibiting Na+/K+-ATPase
- Sensitizing troponin C to calcium (Correct answer)
- Activating beta-1 receptors
- Blocking phosphodiesterase V
Correct answer: Sensitizing troponin C to calcium
Levosimendan binds to troponin C and sensitizes the myofilament to calcium, enhancing contractility without increasing intracellular calcium levels.
Question 7: A perfusionist notes that a patient receiving high-dose norepinephrine develops cyanosis of the fingertips. This is most likely due to:
- Methemoglobinemia from the drug itself
- Excessive alpha-1 mediated peripheral vasoconstriction (Correct answer)
- Reflex bradycardia reducing cardiac output
- Histamine release causing cutaneous flushing
Correct answer: Excessive alpha-1 mediated peripheral vasoconstriction
High-dose norepinephrine causes intense alpha-1 adrenergic vasoconstriction in peripheral vessels, potentially leading to digital ischemia and cyanosis.
CCP Vasoactive Drug Pharmacology 2
Which receptor subtype mediates the positive inotropic effect of dopamine at doses of 5–10 mcg/kg/min?