anti arrhytmics

Anti-Arrhythmics Pharmacology Unit II

Anti-Arrhythmics Overview

• Indication: Cardiac arrhythmias

  • Atrial Arrhythmias: Misfiring of the upper chambers.

  • Atrial Fibrillation: Irregular and often rapid heart rate leading to poor blood flow.

  • Atrial Flutter: Atria contract too quickly and regularly.

  • Multifocal Atrial Tachycardia: Multiple atrial ectopic foci causing tachycardia.

Ventricular Arrhythmias

• Indication: Misfiring of the lower chambers.

  • Ventricular Tachycardia (VT): Rapid heart rhythm originating from the ventricles.

  • Ventricular Fibrillation (VF): Very rapid heartbeat that results in ineffective quivering of the heart.

Anti-Arrhythmic Drug Classes

• Antiarrhythmic drugs are classified by their mechanism of action:

  • Class I: Sodium Channel Blockers

  • Class IA

  • Class IB

  • Class IC

  • Class II: Beta Blockers

  • Class III: Potassium Channel Blockers

  • Class IV: Calcium Channel Blockers

Class I: Sodium Channel Blockers

• Action: Blocks movement of sodium into myocardial cells.

• Indication: Ventricular tachyarrhythmia; applied when benefits outweigh risks.

Class IA: Quinidine

• Origin: Derived from cinchona bark.

• Action: Slows conduction and prolongs repolarization by blocking sodium channels.

• Indication: Effective for atrial and ventricular arrhythmias.

Nursing Implications for Quinidine

• Monitor: Take apical pulse before administration.

• Administration: Oral doses should be taken with food.

• Avoid: Grapefruit or grapefruit juice.

• Sustained Release: Note that the shell may appear in stool.

• Monitor K level for safety.

• Maintain Serum Levels: Between 2 - 6 mcg/ml.

Adverse Effects of Quinidine

• Gastrointestinal: Nausea & Vomiting (N&V), anorexia, diarrhea.

• Cardiac: Hypotension, ventricular tachycardia (V tach), ventricular fibrillation (V fib), embolism.

• Hypersensitivity: Reactions can range from mild to severe.

• Hepatotoxicity: Liver damage due to substances.

• Bone Marrow Suppression: Risk of reduced blood cell production.

• Cinchonism: Toxicity resulting from high levels of quinine, presenting as tinnitus, headache, etc.

Class IB: Lidocaine (Xylocaine)

• Action: Blocks Na⁺ channels to decrease automaticity and shortens the action potential duration.

• Indication: Ventricular arrhythmias, including ventricular tachycardia (VT) and premature ventricular contractions (PVCs) post-myocardial infarction; digoxin-induced tachyarrhythmia.

• Dosing for ACLS:

  • IV Bolus: 1–1.5 mg/kg.

  • Repeat Bolus: 0.5–0.75 mg/kg every 5–10 min (maximum total 3 mg/kg).

  • Maintenance Infusion: 1–4 mg/min (approximately 30–50 mcg/kg/min).

Adverse Effects of Lidocaine

• Central Nervous System (CNS): Dizziness, drowsiness, confusion, hallucinations, euphoria, blurred vision, tinnitus, convulsions.

• Cardiac: Bradycardia, hypotension, potential cardiac arrest.

• Respiratory Depression: Decreased breathing rate.

• Nursing Note: Do not use with epinephrine due to risk of enhanced cardiac effects.

Other Class IB Drugs

• Mexiletine: A lidocaine derivative for chronic ventricular arrhythmias.

• Phenytoin (Dilantin): Used for digoxin-induced ventricular tachyarrhythmia.

Adverse Effects of Mexiletine & Phenytoin

• Gastrointestinal: Nausea, vomiting, abdominal pain.

• Neurological: Dizziness, tremor, ataxia.

Class IC: Sodium Channel Blockers

• Action: Na⁺ channel blockers that markedly slow conduction and increase QRS duration.

• Indication: Life-threatening ventricular arrhythmias; occasionally for supraventricular tachycardia (SVT) with caution.

• Route: Oral administration.

• Drug Examples: Flecainide (Tambocor) and Propafenone (Rythmol).

Class II: Beta Blockers

• Action: Block beta-adrenergic receptors leading to decreased heart rate (HR), decreased myocardial contractility, and decreased conduction.

• Effect: Reduces sympathetic stimulation of the heart by antagonizing adrenergic receptors.

• Generations of Beta Blockers:

  • 1st Generation: Non-selective (β1 & β2).

  • 2nd Generation: Cardio-selective (β1).

Beta Blocker Drug Examples

• Non-Selective: Propranolol (Inderal).

• Cardio-Selective: Metoprolol (Lopressor), Atenolol (Tenormin).

Nursing Implications for Beta Blockers

• Monitoring: Measure HR and blood pressure (BP) before each dose; hold if HR < 60 bpm or systolic blood pressure (SBP) < 90 mmHg. Assess for peripheral circulation issues (e.g., cold extremities, cyanosis) and monitor blood glucose levels (BGL) as beta blockers can mask hypoglycemia symptoms.

• Signs of Congestive Heart Failure (CHF): Watch for shortness of breath (SOB), fatigue, edema, and weight gain.

• Caution: Do not stop abruptly due to potential rebound effects.

Adverse Effects of Beta Blockers

• Gastrointestinal: Nausea & vomiting, diarrhea.

• Respiratory: Bronchospasm, especially in asthmatic patients.

• Cardiac: Hypotension, bradycardia, AV block, potential worsening of CHF.

• Endocrine: Can mask hypoglycemia.

• Reproductive: Decreased libido and erectile dysfunction.

• Circulatory: Raynaud's phenomenon (coldness in extremities).

• Neurological: Fatigue, dizziness, sedation, vertigo, headache, visual disturbance, insomnia, confusion.

• Skin: Rash and pruritus (itching).

• Mood Effects: Depression.

Interactions and Contraindications

• Interactions: Caution with other drugs lowering BP or HR, such as calcium channel blockers and digoxin.

• Contraindications: Asthma, chronic obstructive pulmonary disease (COPD), peripheral vascular disease (PVD), heart block, and caution in diabetes patients.

Class III: Potassium Channel Blockers

• Action: Prolongs repolarization by blocking K⁺ channels leading to lengthened action potential and refractory period.

• Indication: Life-threatening ventricular arrhythmias (e.g., V-tach, V-fib), and sometimes used for atrial arrhythmias.

• Example Drug: Amiodarone (most common).

Amiodarone (Pacerone, Nexterone)

• Properties: Vasodilation, decreases HR and contractility of left ventricles.

• Use: First-line drug for ventricular fibrillation and pulseless ventricular tachycardia as per ACLS guidelines.

• Monitoring: Requires checks of ECG, BP, liver function, thyroid levels, and pulmonary function.

• Administration Routes: Available in both oral (PO) and intravenous (IV) routes.

Nursing Implications for Amiodarone

• Consistency: Taken at the same time daily as prescribed; may be taken with or without food.

• Avoid: Grapefruit, St. John's wort, excessive sunlight, or tanning beds.

• Monitoring: ECG, BP, liver function, thyroid function, and pulmonary status.

• Patient Education: Instruct to report vision changes, SOB, cough, or weight gain as signs of potential toxicity.

Adverse Effects of Amiodarone

• Ocular: Corneal micro-deposits (visual disturbances).

• Skin: Photosensitivity, blue-gray skin discoloration.

• Gastrointestinal: N&V, anorexia.

• Cardiac: Hypotension, bradycardia.

• Pulmonary: Risk of pulmonary toxicity (fibrosis).

• Hepatic: Potential hepatotoxicity.

• Endocrine: Can affect thyroid function (both hyperthyroidism and hypothyroidism).

Class IV: Calcium Channel Blockers

• Action: Blocks Ca²⁺ influx into myocardial cells, slowing conduction in the SA and AV nodes.

• Effects: Leads to decreased HR, decreased contractility, and prolonged refractory period.

• Indication: Effective for supraventricular tachycardia (SVT) and rate control in atrial fibrillation/flutter.

Calcium Channel Blocker Drug Examples

• Verapamil (Calan), Diltiazem (Cardizem), Amlodipine (Norvasc).

Nursing Implications for Calcium Channel Blockers

• Consistency: Taken at the same time daily as prescribed.

• Avoid: Grapefruit, which could increase drug levels and risk of toxicity.

• Monitoring: Measure HR and BP regularly; assess for signs and symptoms of CHF (e.g., peripheral edema, crackles, dyspnea, weight gain, jugular venous distention).

• Patient Education: Advise changing position slowly to prevent orthostatic hypotension.

Adverse Effects of Calcium Channel Blockers

• Cardiac: Hypotension, bradycardia, arrhythmias.

• Circulatory: Peripheral edema.

• Gastrointestinal: N&V, constipation, gingival hyperplasia (swollen gums).

• Neurological: Headache, dizziness, confusion.

• Skin: Rash and flushing.

• Other: Hepatotoxicity.

Class V: Other Anti-Arrhythmics

Atropine

• Action: An anticholinergic that increases HR by blocking vagal stimulation.

• Indication: Used for symptomatic bradycardia.

• Caution: Requires continuous ECG monitoring during administration.

• Doses:

  • Bradycardia: 0.5 mg IV every 3–5 min (maximum 3 mg).

  • Asystole: 1 mg IV; repeat every 3–5 min if needed (maximum 0.04 mg/kg).

  • Intratracheal: 2–2.5 times the IV dose diluted in 10 mL NS.

• Important Note: Doses < 0.5 mg may evoke paradoxical bradycardia.

Digitalis Glycoside: Digoxin (Lanoxin)

• Indication: Used primarily for rate control in atrial fibrillation and sometimes for heart failure.

• Action: Increases cardiac contractility (positive inotropic effect) and decreases HR by slowing AV nodal conduction.

Nursing Care for Anti-Arrhythmics

• Monitor: Always monitor the apical heart rate for a full minute.

• Patient Education: Instruct patients on self-pulse checks and the importance of assessing BP before each dose.

• Know Hold Parameters: Understand the guidelines for when to withhold medication.

• Administration:

  • Oral (PO): Take with a full glass of water.

  • IV: Require bed rest with continuous cardiac monitoring.

Electrolyte Monitoring

• Electrolytes: Regularly check for Na⁺, K⁺, Mg²⁺ imbalances that can increase arrhythmia risk.

• Liver Function Tests (LFTs) & Renal Function: Assess for drug clearance capabilities.

• Intake & Output (I&O): Track for fluid balance requirements.

• Dosing Regularity: Space doses at equal intervals for consistency.

Patient Education for Antiarrhythmics

• Self-Monitoring: Educate patients on taking their own pulse and BP (home monitoring machines recommended).

• Dry Mouth: Advise sips of water or chewing gum for relief.

• Position Changes: Encourage changing positions slowly to avoid dizziness.

• Weight Monitoring: Report weight gains exceeding 2 lbs per day.

• Edema Checks: Monitor for both seen (legs) and not seen (lungs) edema.

• Medication Habits: Do not omit doses or make changes without medical guidance; discourage OTC medications.

• Avoid: Grapefruit, alcohol, and smoking; caution against hazardous tasks if experiencing dizziness.

• Medic Alert: Advise wearing or carrying a medical alert for potential medication reactions.

Quick Guide for Antiarrhythmics

• Class I (Na⁺ Blockers): Administer IV for acute VT/VF, PO for chronic arrhythmias; Monitor ECG (QRS widening) and K⁺, Na⁺ levels; High proarrhythmic risk; avoid in structural heart disease.

• Class II (Beta Blockers): Administer PO or IV; hold if HR < 60 bpm or SBP < 90 mmHg; Monitor HR, BP, CHF signs; Bronchospasm risk with asthma/COPD; Masks hypoglycemia symptoms.

• Class III (K⁺ Blockers - Amiodarone): Administer PO or IV; first-line for V-fib/pulseless VT; Monitor ECG, BP, liver, thyroid, pulmonary function; Watch for pulmonary toxicity, hepatotoxicity, thyroid dysfunction; Avoid grapefruit.

• Class IV (Ca²⁺ Blockers): Administer PO or IV primarily for SVT/Afib rate control; Monitor HR, BP; hold if HR < 60 bpm or SBP < 90 mmHg; Severe bradycardia possible with concurrent beta blockers or digoxin.

• Class V (Digoxin, Atropine): Administer Digoxin PO; Atropine IV for bradycardia; Monitor apical HR for 1 minute; Digoxin levels between 0.8–2.0 ng/mL; Digoxin toxicity increases with hypokalemia; antidote = Digoxin immune Fab.

NCLEX PN High Priority Safety & Red Flags

• Safe Administration: Check apical HR for 1 full minute before administration; hold if HR < 60 bpm or SBP < 90 mmHg.

• Monitoring: Continuous ECG monitoring required for IV antiarrhythmics; electrolyte imbalances heighten arrhythmia risk; regularly check liver, renal, and thyroid function for amiodarone.

• CHF Symptoms: Look for edema, SOB, and significant weight gain during treatment.

• Patient Teaching: Instruct patients in self-monitoring of HR & BP; advise reporting dizziness, syncope, or irregular heart rhythms. Avoid grapefruit, OTC medications, and abrupt discontinuation of medications.

Critical Thinking Red Flags

• Amiodarone: Symptoms indicating potential pulmonary toxicity include cough or SOB.

• Digoxin: Watch for gastrointestinal symptoms and visual issues like yellow halos, indicating potential toxicity.

• Beta Blockers: Be cautious regarding bronchospasm in patients with asthma/COPD.

Study Smart for Antiarrhythmics

• Focus on Class Names & Purposes:

  • Class I: Na⁺ blockers → used for VT/VF.

  • Class II: Beta blockers → rate control in SVT, Afib.

  • Class III: K⁺ blockers → targeting life-threatening arrhythmias.

  • Class IV: Ca²⁺ blockers → SVT, Afib rate management.

  • Class V: Miscellaneous (Digoxin, Atropine).

• Administration Considerations: Always check HR/BP before dosing and hold as necessary; maintain ECG monitoring for IV drugs.

• Major Adverse Effects & Alerts:

  • Amiodarone: Watch for pulmonary fibrosis, thyroid dysfunction, and hepatotoxicity.

  • Digoxin: Monitor for toxicity particularly with low potassium levels; use Digoxin immune Fab as the antidote.

  • Beta Blockers: Be aware of bronchospasm and hypoglycemia masking.

  • Calcium Channel Blockers (CCBs): Understand the risk of severe bradycardia, particularly when combined with beta blockers or digoxin.

• NCLEX Traps: For quick recall:

  • Digoxin: Recognize hallmark toxicity signs (yellow halos).

  • Amiodarone: Be aware of the grapefruit interaction.

  • Beta Blockers: Recognize that they mask hypoglycemia symptoms.