Ventricular Antidysrhythmics

Question 1

Amiodarone - 1st and 2nd dose during CPR

Answer 1

1st dose: 300mg IV/IO push 
2nd dose (if needed): 150mg IV/IO push

Question 2

Amiodarone - Indications

Answer 2

• VF/pulseless VT unresponsive to shock delivery, CPR, and a vasopressor
• Recurrent, hemodynamically unstable VT

Question 3

Amiodarone - infusion for stable Wide-QRS tachycardia

Answer 3

-1st dose: 150mg over 10min. Repeat as needed if VT recurs. Follow by maintenance infusion of 1mg/min for first 6hrs.

Question 4

Amiodarone - Precautions

Answer 4

• Rapid infusion may lead to hypotension
• Do not administer with other drugs that prolong QT interval (ie. Procainamide)
• Terminal elimination is extremely long - half life up to 40 days
• With multiple dosing, cumulative doses > 2.2g over 24hrs associated with significant hypotension
• Pregnancy Category D

Question 5

Amiodarone - Class

Answer 5

Class III antiarrhythmic agent

Question 6

Amiodarone - Mechanism of Action

Answer 6

Multiple:

• Beta-blocker-like and Potassium-channel-blocker-like actions on the SA and AV node.
• Na+/K+ pump blocker, prolonging the refractory period by increasing phase 3 of the cardiac action potential
• slows intra-cardiac conduction by affecting Na+ channels

Question 7

Procainamide - Doses

Answer 7

• 20mg/min IV infusion until one of the following occurs:
• > Arrhythmia suppression
• > Hypotension
• > QRS widens by 50%
• > Total dose of 17mg/kg is given

-50mg/min may be given in urgent situations to same total dose of 17mg/kg

Question 8

Procainamide - Maintenance Infusion

Answer 8

1 - 4mg/min (dilute in D5W or NS)

Reduce dose in presence of renal insufficiency

Question 9

Procainamide - Indications

Answer 9

• Treatment of stable monomorphic VT with normal QT interval and preserved LV function
• Reentry SVT uncontrolled by adenosine and vagal maneuvers if BP stable
• Stable wide-complex tachycardia of unknown origin
• A-fib with RVR in Wolff-Parkinson-White (WPW) syndrome

Question 10

Procainamide - Precautions

Answer 10

• If cardiac or renal dysfunction is present reduce Max total dose to 12mg/min and maintenance infusion to 1 - 2mg/min
• Proarrhythmic, especially in setting of AMI, hypokalemia, or hypomagnesemia
• May induce hypotension in patients with impaired LV function
• Use with caution with other drugs that prolog QT interval (ie. amiodarone)
• Pregnancy Category C

Question 11

Procainamide - Mechanism of Action

Answer 11

• Blocks Na+ channels, prolonging the cardiac action potential at Phase 4
• Ventricular excitability is depressed, reduces ectopic pacemaker’s automaticity
• Suppresses intraventricular conduction
• SA node is unaffected.

Question 12

Procainamide - Class

Answer 12

Antidysrrhythmic

Question 13

Procainamide - Contraindications

Answer 13

• Torsades de Pointes
• 2nd and 3rd degree AV blocks
• Pre-existing QT prolongation
• digitalis toxicity
• TCA overdose

Question 14

Amiodarone - Contraindications

Answer 14

• Cardiogenic shock
• Sinus bradycardia
• 2nd or 3rd degree AV block
• Severe Sinus node dysfunction