Cardiac: Antiarrythmics Flashcards
Lidocaine (Xylocaine)
Onset: less than 3 minutes
Peak effects: 5-7 minutes
Duration: 10-20 minutes
Half-life: 1.5-2 hours
ECG effects: widened QRS, prolonged QT
MOA: Depresses depolarization and automaticity in the ventricles. Has little effect on atrial tissues. In therapeutic doses, it does not slow AV conduction and does not depress myocardial contractility.
Class: sodium channel blocker; Class IB antiarrhythmic
Description: Is an amide-type local anesthetic that is used to treat life-threatening ventricular arrhythmias. Has been largely replaced with amiodarone.
Indications: ventricular tachycardia and ventricular fibrillation refractory to amiodarone
Contraindications: Type 2 second-degree heart block (Mobitz II), third-degree heart block. Note: Decreased ventricular rates may accompany high-grade heart block, resulting in escape beats that are PVCs. Whenever PVCs occur in conjunction with bradycardia, the bradycardia should be treated with atropine first.
Precautions: CNS depression may occur when the dose exceeds 300 mg/hr. Symptoms of CNS depression include decreased level of consciousness, irritability, confusion, muscle twitching, and seizures. Exceedingly high doses can result in coma and death.
Side effects: drowsiness, slurred speech, seizures, confusion, hypotension, bradycardia, heart blocks, N/V, respiratory and cardiac arrest
Interactions: should be used with caution when administered concomitantly with procainamide, amiodarone, phenytoin, quinidine, and beta-blockers, because medication toxicity may result
Route: IV, IO, ETT
Dosage: hemodynamically stable monomorphic ventricular tachycardia:
. Initial Dose: 1.0-1.5 mg/kg
. Subsequent doses: boluses of 0.5-0.75 mg/kg every 5-10 minutes with max dose of 3.0 mg/kg
. Once the arrhythmia has been suppressed, a lidocaine drip should be initiated at 2-4 mg/min.
Note: dosage should be reduced to 50% in pts over 70 years of age and in pts with liver disease, heart failure, bradycardias, or conduction disturbances.
Procainamide (Pronestyl)
ECG effects: widened QRS, prolonged QT
Class: Sodium Channel Blocker; Class IA antiarrhythmic
used to treat ventricular tachycardia with a pulse
Adenosine (Adenocard)
Onset: 20-30 seconds
Peak effects: 20-30 seconds
Duration: 30 seconds
Half-life: 10 seconds
ECG effects: prolonged PRI, bradycardias
MOA: a naturally occurring substance that is present in all body cells. Adenosine decreases conduction of the electrical impulse through the AV node, and interrupts AV reentry pathways in paroxysmal SVT.
Class: Class V antiarrhythmic
Description: slows AV conduction through the AV node
Indications: the preferred treatment of tachyarrhythmias refractory to vagal maneuvers, including SVT (narrow-complex tachycardia) and stable ventricular tachycardia (wide-complex tachycardia). Can be used as a diagnostic agent to determine whether the condition is narrow- or wide- complex tach.
Contraindications: Should not be administered in cases of irregular (atrial fibrillation) or polymorphic (torsades de pointes) tachycardia. It is contraindicated in pts with second- or third-degree heart block, sick sinus syndrome, asthma, Wolff-Parkinson-White Syndrome, or known hypersensitivity.
Precautions: Adenosine typically causes arrhythmias at time of cardioversion. These generally last a few seconds or less, and may cause PVCs, PACs, sinus bradycardia, sinus tachycardia, and various degrees of AV block. In extreme cases, transient asystole may occur. Use cautiously in pts with asthma.
Side effects: facial flushing, headache, shortness of breath, dizziness, nausea.
Interactions: Methylxanthines (aminophylline and theophylline) may decrease the effectiveness of adenosine, thus requiring larger doses. Dipyridamole (Persantine) can potentiate the effects of adenosine, and the dosage may need to be reduced.
Route: IV, IO RAPID IV PUSH
Dosage:
. initial 6mg
. second: 12mg
. third: 12mg
Verapamil (Isoptin, Calan)
Onset: 5 minutes (IV)
Peak effects: 5-15 minutes (IV)
Duration: 10-60 minutes (IV)
Half-life: 2-8 hours (IV)
ECG effects: prolonged PRI, bradycardias
MOA: causes vascular dilation and slows conduction through the AV node. First, verapamil inhibits arrhythmias caused by a reentry mechanism such as with PSVT. Second, it decreases the rapid ventricular response seen with atrial fibrillation and atrial flutter. It also reduces myocardial oxygen demand because it has negative inotropic effects and causes coronary and peripheral vasodilation
Calcium channel blocker (Class IV antiarrhythmic)
Description: Calcium ion antagonist. Calcium channel blockers cause a relaxation of vascular smooth muscle and slow conduction through the AV node. Verapamil has a greater effect on conduction and a lesser effect on vascular smooth muscle than do other agents in the same class
Indications: should only be given to narrow-complex tachycardias, including:
. stable, narrow-complex tachycardias if rhythm remains uncontrolled or unconverted by adenosine or vagal maneuvers if SVT is recurrent
. controlling ventricular rate in pts with atrial fibrillation or atrial flutter
Contraindications: severe hypotension, cardiogenic shock, ventricular tachycardia, Wolff-Parkinson-White Syndrome
Precautions: can cause systemic hypotension, and should be avoided in pts with heart failure. Calcium chloride can be used to prevent hypotensive effects or calcium channel blocker overdose
Side effects: N/V, dizziness, headache, bradycardia, heart block, hypotension, asystole
Interactions: should not be administered to patients receiving IV beta-blockers because of increased risk of CHF, bradycardia, and asystole
Route: IV, IO
Dosage: PSVT, 2.5-5mg over 2 minutes; repeated dose of 5-10mg after 15-30 minutes. Max dose 20-30mg.
Diltiazem (Cardizem)
Onset: 3 minutes
Peak effects: 7 minutes
Duration: 1-3 hours
Half-life: 2 hours
ECG effects: prolonged PRI, bradycardias
MOA: causes vascular dilation and slows conduction through the AV node. Slows the rapid ventricular rate associated with atrial fibrillation and atrial flutter. It is also used in the treatment of angina, because of its negative inotropic effect and because it dilates the coronary arteries
Class: Calcium channel blocker (Class IV antiarrhythmic)
Description: is a calcium-ion antagonist. Calcium channel blockers cause a relaxation of vascular smooth muscle, and slow conduction through the AV node. Diltiazem has a nearly equal effect on vascular smooth muscle and AV conduction
Indications: should ONLY be given to narrow-complex tachycardias, including:
. stable, narrow-complex tachycardias if rhythm remains uncontrolled or unconverted by adenosine or vagal maneuvers if SVT is recurrent
. controlling ventricular rate in pts with atrial fibrillation or atrial flutter
Contraindications: should not be administered to any pt with severe hypotension, CHF, or cardiogenic shock, ventricular tachycardia, ENSURE the pt does not have Wolff-Parkinson-White Syndrome
Precautions: can cause systemic hypotension. Calcium chloride can be used to prevent the hypotensive effects of calcium channel blockers, and in the management of calcium channel blocker overdose. Should be refrigerated.
Side effects: N/V, dizziness, headache, bradycardia, heart block, hypotension, and asystole
Interactions: should not be admin. to pts receiving IV beta-blockers because of an increased risk of CHF, bradycardia, and asystole
Route: IV, IV drip
Dosage: (0.25 mg/kg) 15-20mg over 2 minutes. Additional boluses: (0.35 mg/kg) 20-25mg 15 minutes after first bolus. A maintenance infusion of 5-15mg/hr should be admin for desired rate control
Amiodarone (Cordarone)
Onset: 1-3 minutes
Peak effects: 8-12 hours
Duration: varies
Half-life: 40-55 days
ECG effects: prolonged QT interval
MOA: prolongs the action potential duration in all cardiac tissues. Affects sodium, potassium, and calcium channels and has alpha and beta adrenergic blocking properties.
Class: Class III antiarrhythmic
Description: a potent antiarrhythmic agent and the first-line agent given during cardiac arrest. Can also be used in SVTs.
Indications: Used in life-threatening cardiac arrhythmias such as ventricular tachycardia and ventricular fibrillation. Can also be used for the following conditions:
. stable, irregular, narrow-complex tachycardia (atrial fibrillation)
. stable, regular, narrow-complex tachycardia
. controlling rapid ventricular rate due to accessory pathway
Contraindications: breast-feeding patients in cardiogenic shock and those with severe sinus node dysfunction in marked sinus bradycardia, second or third-degree AV block, symptomatic bradycardia, or a known hypersensitivity.
Precautions: should be used in caution in pts with latent or manifest heart failure because failure will worsen by its administration
Side effects: hypotension, bradycardia, increased ventricular beats, prolonged PRI, prolonged QRS complex, prolonged QT interval. Monitor pt for pulmonary toxicity for signs of dyspnea and cough
Interactions: may react with warfarin, digoxin, procainamide, quinidine, and phenytoin
Route: IV, IO
Dosage:
.ventricular fibrillation or pulseless ventricular tachycardia: 300 mg IV/IO. May be repeated at 150 mg for recurrent or refractory arrythmias
. ventricular tachycardia with a pulse: 150 mg in 100cc bag over 10 minutes
narrow-complex tachycardias: 150 mg over 10 minutes, repeated as necessary. This can be followed by a 1mg/min infusion over 6 hours, followed by a 0.5 mg/min infusion as needed.
Phenytoin (Dilantin)
Onset: 3-5 min
Peak effects: 1-2 hours
Duration: variable
Half-life: 22 hours
ECG effects: widened QRS, prolonged QT
MOA: used frequently in the treatment of epilepsy, but has antiarrhythmic properties. Is effective in managing arrhythmias caused by Digitalis toxicity or tricyclic antidepressant overdose. It depresses spontaneous depolarization of ventricular tissues, and appears to improve atrioventricular conduction. It can also be used in the management of status epilepticus.
Class: sodium channel blocker; Class IB antiarrhythmic; anticonvulsant
Description: an anticonvulsant and antiarrhythmic that depresses spontaneous ventricular depolarization
Indications: used in life-threatening arrhythmias resulting from digitalis toxicity or tricylic antidepressant overdose. NOTE: Ventricular arrhythmias in the setting of acute MI should first be treated with other agents
Contraindications: bradycardia, high-degree heart block. Should NOT be admin. to patients who take chronically for seizures, until blood level has been determined
Precautions: IV admin. should not exceed 50 mg/min. Signs of CNS depression or hypotension may occur. Elderly pts are at increased risk of developing side effects
Side effects: drowsiness, dizziness, headache, hypotension, arrhythmias, itching, rash, N/V
Interactions: must never be diluted in dextrose-containing solutions. Dilute in NS, or other non-glucose-containing crystalloids
Route: IV, IO
Dosage: 100mg over 5 min, max loading dose of 1,000mg, until the arrhythmia is suppressed, or until CNS depression appears
Magnesium Sulfate
Onset: immediate
Peak effects: variable
Duration: 1 hour
Half-life: N/A
MOA: Acts as a physiologic calcium channel blocker and blocks neuromuscular transmission. A decreased magnesium level (hypomagnesemia) is associated with cardiac arrhythmias, cardiac insufficiency, and sudden death. Hypomagnesemia can cause refractory ventricular fibrillation. Decreases complications associated with acute MI. Also used for eclampsia.
Class: Antiarrhythmic
Description: a salt that dissociates into the magnesium cation and the sulfate anion when admin. Magnesium is an essential body element in numerous biochemical reactions that occur within the body.
Indications: Torsades de Pointes (irregular, polymorphic ventricular tachycardia associated with QT interval prolongation)
Contraindications: shock, persistent severe hypotension, third-degree AV block, dialysis pts, decreased calcium levels (hypocalcemia)
Precautions: administer slowly. Check deep tendon reflexes frequently. Use caution in pts with renal insufficiency. Hypermagnesemia can occur. *Calcium salts (calcium chloride or calcium gluconate is the antidote.
Side Effects: flushing, sweating, bradycardia, decreased deep tendon reflexes, drowsiness, respiratory depression, arrhythmias, hypotension, hypothermia, itching, rash
Interactions: can cause cardiac conduction abnormalities if administered in conjunction with Digitalis
Route: IV, IM
Dosage: (1) Dilute in 10 ml of D5W
OR
(2) Dilute 1-2 grams in 100 ml of D5W or NS administered over 15 minutes as an IV/IO piggyback
Digoxin (Lanoxin)
Class: Cardiac Glycoside (Class V Antiarrhythmic)
Used for management of CHF and controlling HR in Atrial Fibrillation and Atrial Flutter
