Pharmacology in Nursing Antidysrhythmic Drugs Mosby items and

Pharmacology in Nursing Antidysrhythmic Drugs Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Conditions Causing Dysrhythmias CAD MI Cardiac Surgery Valvular disease Hypoxia Electrolyte imbalance Acid/Base imbalance Hypovolemia External forces Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Antidysrhythmics Dysrhythmia Any deviation from the normal rhythm of the heart Antidysrhythmics Drugs used for the treatment and prevention of disturbances in cardiac rhythm Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Cardiac Cell Inside the resting cardiac cell there exists a net negative charge relative to the outside of the cell This difference in the electronegative charge results from an uneven distribution of ions (sodium, potassium, calcium) across the cell membrane Ø Resting membrane potential (RMP) Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Resting Membrane Potential (RMP) An energy-requiring pump is needed to maintain this uneven distribution of ions Ø Sodium-potassium ATPase pump Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Action Potential A change in the distribution of ions causes cardiac cells to become excited The movement of ions across the cardiac cell’s membrane results in an electrical impulse spreading across the cardiac cells This electrical impulse leads to contraction of the myocardial muscle Results in excitation of cardiac muscle fibers, weak electrical current Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Action Potential (cont’d) Four phases The SA node and the Purkinje cells each have separate action potentials Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

3 Types of Electrical Current Resting Membrane Potential: Sodium Potassium Pump activated, membrane is relatively permeable to K+, but much less to Na+ and Ca+ Depolarization: cell membrane suddenly becomes permeable to sodium, sodium enters cell, sharp increase in positivity, potassium migrates outside of cell Repolarization: re-establishment of resting membrane potential Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Four Phases to Action Potential Phase 1: Fast sodium channel closes ; period of repolarization begins Phase 2: Calcium ion influx occurs through slow channels Phase 3: Potassium ions flow outward, cell is repolarized to baseline Phase 4: Resting membrane potential Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Action Potential Duration Absolute or effective refractory period Relative refractory period Threshold potential Ø Automaticity or pacemaker activity Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Electrocardiography ECG or EKG P wave PR interval QRS complex ST segment T wave Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Common Dysrhythmias Atrial dysrhythmias Supraventricular dysrhythmias Ventricular dysrhythmias Ectopic foci Conduction blocks Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Supraventricular Dysrhythmias Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Ventricular Dysrhymias Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Ventricular Fibrillation Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Premature Ventricular Contractions Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Atrial Fibrillation Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Atrial Fibrillation with Rapid Ventricular Response Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Bradycardia & Heart Blocks Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Vaughan Williams Classification System commonly used to classify antidysrhythmic drugs Based on the electrophysiologic effect of particular drugs on the action potential Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Vaughan Williams Classification (cont’d) Class Ia Ø Class Ib Ø Class Ic Ø Class III Class IV Other Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Vaughan-Williams Classification Class Basic Mechanism Comments I Sodium-channel blockade Reduce phase 0 slope and peak of action potential IA -moderate Moderate reduction in phase 0 slope; increase APD, increade ERP IB -weak Small reduction in phase o slope IC -strong Pronounced reduction in phase 0 slope II Beta-blockade Block sympathetic activity, reduce rate and conduction III Potassium-channel blockade Delay repolarization, increase action potential IV Calcium-channel blockade Block L-type calcium channels, reduce rate and conduction, most Mosby items and derived items © 2007, 2005, 2002 byeffective Mosby, Inc. , an affiliate of Elsevier Inc. nodes at SA & AV

Vaughan Williams Classification: Mechanism of Action Class I Membrane-stabilizing drugs Sodium channel blockers Divided into Ia, Ib, and Ic drugs, according to effects (weak to strong) Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Vaughan Williams Classification: Mechanism of Action and Indications (cont’d) Class Ia: quinidine, procainamide, disopyramide Block sodium (fast) channels Delay repolarization Increase the APD Used for atrial fibrillation, premature atrial contractions, premature ventricular contractions, ventricular tachycardia, Wolff-Parkinson-White syndrome Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Vaughan Williams Classification: Mechanism of Action and Indications (cont’d) Class Ib: mexiletine, phenytoin, lidocaine, tocainide Block sodium channels Accelerate repolarization Increase or decrease the APD Used for ventricular tachyarrhythmias only Ø Premature ventricular contractions, ventricular tachycardia, ventricular fibrillation Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Vaughan Williams Classification: Mechanism of Action and Indications (cont’d) Class Ic: flecainide, propafenone , moricine Block sodium channels (more pronounced effect) Little effect on APD or repolarization Used for severe ventricular dysrhythmias May be used in atrial fibrillation/flutter, Wolff. Parkinson-White syndrome, supraventricular tachycardia dysrhythmias Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Vaughan Williams Classification: Mechanism of Action and Indications (cont’d) Class II: b-blockers: atenolol, esmolol, metoprolol, propranolol, nadolol, sotalol Reduce or block sympathetic nervous system stimulation, thus reducing transmission of impulses in the heart’s conduction system Depress phase 4 depolarization General myocardial depressants for both supraventricular and ventricular dysrhythmias Also used as antianginal & antihypertensive drugs Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Vaughan Williams Classification: Mechanism of Action and Indications (cont’d) Class III: amiodarone, sotalol, * ibutilide, bretylium Increases action potential Prolong repolarization in phase 3 Used for dysrhythmias that are difficult to treat Life-threatening ventricular tachycardia or fibrillation, atrial fibrillation or flutter—resistant to other drugs Ø Sustained ventricular tachycardia Ø *Sotalol also exhibits Class II properties Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Drug to Know: Amiodarone (Cordarone) Classification: Antiarrhythmics (class III) Indication: Life-threatening ventricular arrhythmias , part of ACLS protocol Action: Prolongs action potential, slows sinus rate, prolongs QT interval, suppresses arrhythmias Side Effects: Dizziness, fatigue, pulmonary fibrosis, CHF, bradycardia, hypotension, hypo or hyperthyroidism, nausea, vomiting, constipation, anorexia, corneal microdeposits, photosensitivity Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Amiodarone Nursing Assessment Monitor ECG continuously during IV therapy Monitor for QT prolongation Assess for signs of pulmonary toxicity Assess for signs of thyroid dysfunction Monitor BP for hypotension Regular ophthalmic exams for oral route Monitor for neurotoxicity Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Vaughan Williams Classification: Mechanism of Action and Indications (cont’d) Class IV: verapamil, diltiazem Calcium channel blockers Ø Inhibit slow-channel (calcium-dependent) pathways Depress phase 4 depolarization Reduce AV node conduction Used for paroxysmal supraventricular tachycardia; rate control for atrial fibrillation and flutter Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

3 Classes of Calcium Channel Blockers Dihydropyridines amlodipine (Norvasc) nicardipine (Cardene) nimodipine (Nimotop) Non-dihydropyridines Verapamil (Calan) Diltiazem (Cardizem) Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Vaughan Williams Classification: Other Antidysrhythmics digoxin, adenosine Have properties of several classes and are not placed into one particular class Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Unclassified Antidysrhythmic adenosine (Adenocard) Slows conduction through the AV node Used to convert paroxysmal supraventricular tachycardia to sinus rhythm Very short half-life—less than 10 seconds Only administered as fast IV push May cause asystole for a few seconds Other adverse effects minimal Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Adenosine Injection Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Antidysrhythmics: Adverse Effects ALL antidysrhythmics can cause dysrhythmias! Ø Hypersensitivity reactions Ø Nausea Ø Vomiting Ø Diarrhea Ø Dizziness Ø Blurred vision Ø Headache Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Nursing Implications Obtain a thorough drug and medical history Measure baseline BP, P, I&O, and cardiac rhythm Measure serum potassium levels before initiating therapy Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Nursing Implications (cont’d) Assess for conditions that may be contraindications for use of specific drugs Assess for potential drug interactions Instruct patients regarding dosing schedules and adverse effects to report to physician Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Nursing Implications (cont’d) During therapy, monitor cardiac rhythm, heart rate, BP, general well-being, skin color, temperature, heart and lung sounds Assess plasma drug levels as indicated Monitor for toxic effects Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Nursing Implications (cont’d) Instruct patients to take medications as scheduled and not to skip doses or double up for missed doses Patients who miss a dose should contact their physician for instructions if a dose is missed Instruct patients not to crush or chew any oral sustained-release preparations Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Nursing Implications (cont’d) For class I drugs, monitor ECG for QT intervals prolonged more than 50% IV infusions should be administered with an IV pump Solutions of lidocaine that contain epinephrine should not be given IV—they are to be used ONLY as local anesthetics Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Nursing Implications (cont’d) Ensure that the patient knows to notify health care provider of any worsening of dysrhythmia or toxic effects Shortness of breath Ø Edema Ø Dizziness Ø Syncope Ø Chest pain Ø GI distress Ø Blurred vision Ø Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Nursing Implications (cont’d) Patients taking b-blockers, digoxin, and other drugs should be taught how to take their own radial pulse for 1 full minute, and to notify their physician if the pulse is less than 60 beats/minute before taking the next dose of medication Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Nursing Implications (cont’d) Monitor for therapeutic response Decreased BP in hypertensive patients Ø Decreased edema Ø Decreased fatigue Ø Regular pulse rate Ø Pulse rate without major irregularities Ø Improved regularity of rhythm Ø Improved cardiac output Ø Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Nonpharmacologic Treatment of Cardiac Dysrhythmias Pacemaker Catheter Ablation Direct current cardioversion Implantation of AICD Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.