3.3 Antidysrhythmic Medications Flashcards
Antidysrhythmic Medications
- Can be good and bad
- Treat with drugs if benefits outweigh the risks
Benefits
- Decrease in symptoms (palpitations, angina, faintness)
- Not a lot of evidence that these medications decrease mortality rates
Risks
- Making existing dysrhythmia worse and generating new dysrhythmias
USE ONLY IF..
- There is interference with ventricular pumping
- If patient is symptomatic and in great discomfort
- Risk of declined status
- ALL ANTIDYSRHYTHMIC MEDICATIONS CAN CAUSE DYSRHYTMIA
Holter Monitoring
- Outpatient monitoring system
- Worn by patient and records electrical activity of heart during normal life
- Patients should jot down symptoms they may experience throughout the day (dizzy, weak)
- Patient should also jot down the time it happened for clinicians to correlate causes of symptoms
Considerations of Medication Therapy
- Is the dysrhythmia sustained or non-sustained
- Is the patient having symptoms
- Is the dysrhythmia coming from above the ventricle (supraventricular) or does it involve the ventricle themselves. Ventricular dysrhythmias are more problematic than supraventricular dysrhythmias however supraventricular dysrhythmias can cause ventricles to not adequately fill.
- Does the doctor have an acute treatment. Drug therapy for long-term use is usually a lower dose
Non-Pharmacologic Therapies (preferred method)
- Implanted defibrillators
- Pacemakers
- Radiofrequency ablation
Action Potentials
Slow Action Potentials - SA node and AV node
Fast Action Potentials - His-Purkinje Fibers and Cardiac Muscle
Re-Entry Phenomenon
2 ways to get rid of reentry
- Remove the heart block
- Convert the heart block to a 2 way block
Anti-Dysrhythmics
Class 1 (Fast Channel Blockers)
- Blocks sodium channels (with some potassium blocking)
Class 2 (Beta-adrenergic Receptor Antagonist)
- Blocks effects of catecholamine on B-1 adrenergic receptors
Class 3 (Potassium Channel Blockers)
- Prolongs action potential and refractory period (suppressing re-entry rhythms)
Class 4 (Calcium Channel Antagonist)
- Impairs impulse propagation in nodal and damaged areas
Class 5 (Other)
- Work with unknown mechanisms
Medications
Class 1a - Sodium Channel Blockers
- Quinidine, Procainamide
Class 1b - Sodium Channel Blockers
- Lidocaine
Class 1c - Sodium Channel Blockers
- Flecanide
Class 2 - Beta-Adrenergic Antagonist (non-selective)
- Propranolol
Class 2 - Beta-Adrenoreceptor Antagonist (Cardioselective)
- Sotalol, Esmolol, Acebutolol
Class 3 - Potassium Channel Blockers
- Amiodarone, Dronedarone, Sotalol
Class 4 - Calcium Channel Antagonist
- Diltiazem, Verapamil
Antidysrhythmic
- Digoxin, Adenosine
Class 1A - Quinide
- Used for both atrial and ventricular dysrhythmias (SVT, A-Flutter, A-Fib, Sustained V-Tach)
- Also used for long-term suppression therapy after electrical conversion
- Suppresses phase 0 of action potential, decreases myocardial excitability, prevents re-entry phenomenon, delays repolarization.
- It is highly protein bound. Peaks in 3-4 hours and lasts 6-8 hours
ADVERSE EFFECTS
- GI symptoms (diarrhea, n/v most common)
- Cinchonas (tinnitus, vertigo, disturbed vision)
- Cardiotoxicity (sinus arrest and AV block)
Interactions
- Can double digoxin level
- Intensifies effects of warfarin
Nursing Interventions
- Monitor ECG, serum drug levels, liver/renal function, electrolytes (potassium)
- Watch for GI symptoms (most common side effect)
- Monitor hepatotoxicity and cardiac changes
Class 1B - Lidocaine
- Short-term treatment of ventricular dysrhythmias
- Depresses phase 0 (less than 1a) and suppresses automaticity
- IV bolus, short-term infusion
ADVERSE EFFECTS
- Most common is CV (dysrhythmias, hypotension) and CNS (dizziness, fatigue, drowsiness)
- Excessive levels include confusion, drowsiness, paresthesia
- Toxicity includes tinnitus, blurred vision, convulsions, respiratory arrest
Class 1C - Flecainide
- Used for life-threatening ventricular dysrhythmias if no safer drugs have worked
- Depresses phase 0 (depolarization) considerably and delays repolarization. Also decreases conduction
- Given IV bolus followed by short-term IV infusion
ADVERSE EFFECTS
- Dizzy, blurred vision, problems focusing, seeing spots, tremors
- Headache, nausea, fatigue
- MAY CAUSE QT PROLONGATION
INTERACTIONS
- Has interactions with antibiotics
- AVOID DRINKING MILK WITH ORAL MEDICATION
Nursing Responsibilities
- Monitor ECG (QT Intervals) and serum trough levels
Class 2- Betablockers
- Suppresses supraventricular tachycardias and re-entry
- Slows ventricular response for A-fib and A-flutter
- Depresses cardiac action potential to control arrhythmias, slows heart rate, decreases CO
MEDICATIONS - Used in acute situations
IV - esmolol, propranolol, metoprolol
Oral - Atenolol, Bisoprolol, Metoprolol, Sotalol
Class 3 - Amiodarone
- Used for life-threatening ventricular dysrhythmias that do not respond to other drugs
- Potassium channel blocker that prolongs refractory period, slows re-polarization and slows HR
ADVERSE EFFECTS
- Pulmonary Toxicity (most common)
- Hypotension, liver disease (rare), visual impairment, blue skin
NURSING RESPONSIBILITIES
- Regular follow-ups for 6 months (including x-ray)
- Pulmonary assessments and serum potassium
Class 4 - Calcium Channel Blockers
- Treats/prevents recurrence of paroxysmal supraventricular tachycardia. Reduces ventricular rate in a-fib and prevents re-entry.
- Inhibits movement of calcium across cardiac, slows AV node conduction, depresses SA node automaticity, depresses myocardial contractility, dilates coronary arteries and peripheral arteries
ADVERSE EFFECTS
- Lightheaded, hypotension, bradycardia, constipation, drowsiness
- Edema in feet and ankles
- GERD
Interactions
- Additive effects with anti-hypertensives and diuretics
- Grapefruit juice
- Verapamil may increase digoxin levels
Nurse Responsibilities
- Adequate fluid and fiber to prevent constipation
Class 5 - Adenosine (Unclassified)
- Used for supraventricular tachydysrhythmias
- Acts like a calcium channel blocker
HALF LIFE IS ONLY 1.5-10 SECONDS (give it as close to the entry of the IV into the patient as possible. No extra tubing)
- GIVEN VIA RAPID IV BOLUS (3-way IV)
- MUST BE ON CONTINOUS IV MONITORING
ADVERSE EFFECTS
- Short lived (1 minute)
- Sinus bradycardia (almost cardiac arrest)
- Dyspnea (bronchoconstriction)
- Hypotension (vasodilation)
Nursing Responsibilities
- Monitor 12-lead ECG
- Medications may make patients feel extremely apprehensive and light-headed
PROTOCOL - First give 6mg dose than 12mg dose
Class 5 - Digoxin (unclassified)
- Cardiac glycoside that manages HF and treats A-fib/flutter
- Positive Inotrope (contraction), negative dromotrope (conduction), negative chromotrope (HR)
- Net effect, it increases cardiac output and controls atrial rhythm
ADVERSE EFFECTS
- Toxicity caused by hypokalemia (GI disturbances, cardiotoxicity, CNS toxicity)
Antidote - Digifab (Digibind)
Nursing Responsibilities
- Monitor toxicity, electrolytes (potassium)
- Check apical pulse for 60 seconds before administering, hold if HR less than 60 in adults or 90 in pediatrics.
- Assess drug levels when starting therapy (therapeutic range - 0.5-2.0
Education
- Do not abruptly stop taking medication.
- Take pulse before each dose
- Weigh yourself every other day
- Medical alert bracelet required
