ACLS Emergency Pharmacology 4 — Questions and Answers
Question 1: For a stable narrow-complex tachycardia that does not respond to vagal maneuvers, what is the first drug of choice?
- Diltiazem 20 mg IV over 2 min
- Adenosine 6 mg rapid IV push (Correct answer)
- Metoprolol 5 mg IV over 5 min
- Verapamil 2.5–5 mg IV over 2 min
Correct answer: Adenosine 6 mg rapid IV push
Adenosine 6 mg rapid IV push is the first pharmacological treatment for stable regular narrow-complex SVT.
Question 2: Procainamide is preferred over amiodarone for stable wide-complex tachycardia in which clinical scenario?
- Known severe LV dysfunction
- Pre-excitation syndrome (WPW) with AF (Correct answer)
- Polymorphic VT with long QT
- RBBB with normal LV function
Correct answer: Pre-excitation syndrome (WPW) with AF
Procainamide is preferred over amiodarone for WPW with AF because it does not slow AV nodal conduction preferentially.
Question 3: What is the primary mechanism of action of adenosine in terminating SVT?
- Sodium channel blockade slowing conduction
- Temporary AV nodal blockade interrupting reentry (Correct answer)
- Beta-adrenergic blockade reducing heart rate
- Calcium channel blockade in accessory pathways
Correct answer: Temporary AV nodal blockade interrupting reentry
Adenosine transiently blocks AV nodal conduction, interrupting the reentrant circuit responsible for most SVTs.
Question 4: A patient in third-degree AV block is awaiting transcutaneous pacing. Which drug can be used as a temporizing measure?
- Atropine 0.5 mg IV (Correct answer)
- Digoxin 0.5 mg IV
- Adenosine 6 mg IV
- Diltiazem 15 mg IV
Correct answer: Atropine 0.5 mg IV
Atropine 0.5 mg IV can increase heart rate temporarily while preparing for transcutaneous pacing in symptomatic bradycardia.
Question 5: Dopamine infusion is used for post-resuscitation hypotension. At what dose range does it primarily act as a vasopressor?
- 1–3 mcg/kg/min
- 3–5 mcg/kg/min
- 5–10 mcg/kg/min
- 10–20 mcg/kg/min (Correct answer)
Correct answer: 10–20 mcg/kg/min
At 10–20 mcg/kg/min, dopamine primarily stimulates alpha-1 receptors causing vasoconstriction and increased blood pressure.
Question 6: Which electrolyte abnormality does magnesium sulfate treat beyond Torsades de Pointes in ACLS?
- Hypokalemia from diuretics
- Hypomagnesemia-induced refractory VF (Correct answer)
- Hypocalcemia from blood transfusion
- Hypernatremia from saline infusion
Correct answer: Hypomagnesemia-induced refractory VF
Magnesium sulfate 1–2 g IV is indicated for VF/pulseless VT associated with hypomagnesemia.
Question 7: What is the primary reason atropine is NOT recommended for Mobitz type II second-degree AV block?
- It causes paradoxical slowing of the ventricular rate (Correct answer)
- It is metabolized too slowly to be effective
- It only works on the SA node and not the AV node
- It increases myocardial oxygen demand dangerously
Correct answer: It causes paradoxical slowing of the ventricular rate
In Mobitz II, atropine can increase atrial rate without improving ventricular conduction, potentially worsening the block and slowing ventricular rate.
ACLS Emergency Pharmacology 4
For a stable narrow-complex tachycardia that does not respond to vagal maneuvers, what is the first drug of choice?