Antidysrhythmic DrugsAntidysrhythmics- Dysrhythmia – Any deviation from the normal rhythm of the heart- Antidysrhythmics – Used for the treatment and prevention of disturbances in cardiac rhythmCardiac Cell- Inside the resting cardiac cell there is a net negative charge relative to the outside of the cell- This difference in electronegative charge results from an uneven distribution of ions (sodium, potassium, calcium) across the cell membraneo Resting membrane potential (RMP)Resting Membrane Potential (RMP)- An energy-requiring pump is needed to maintain this uneven distribution of ionso Sodium-potassium ATPase pumpAction 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- Four phases – The SA node and the Purkinje cells each have separate action potentialsAction Potential Duration- Absolute or effective refractory period- Relative refractory period- Threshold potential – Automaticity (dependent on the distribution of ions) or pacemaker activityElectrocardiography- ECG or EKG- P wave, PR interval, QRS complex, ST segment, and T waveCommon Dysrhythmias- Supraventricular dysrhythmias- Ventricular dysrhythmias- Ectopic foci – pacemaker is coming from somewhere else in the heart muscle - Conduction blocks – results in an abnormal rhythm or abnormal pulse Vaughan Williams Classification- System commonly used to classify antidysrhythmic drugs- Based on the electrophysiologic effect of particular drugs on the action potential- Normal digoxin level 0.5-2 ng/mL- Normal K+ 3.5-5 mg/dL- Class I (Class Ia, Class Ib, and Class Ic), Class II, Class III, and Class IV- Mechanism of Action – Class Io Membrane-stabilizing drugso Fast sodium channel blockerso Divided into Ia, Ib, and Ic drugs, according to effects- Class Ia: quinidine, procainamide (pronestol), disopyramideo Block sodium (fast) channels Using this to slow down the heart o Delay repolarizationo Increase APDo Used for atrial fibrillation, premature atrial contractions, premature ventricular contractions, ventricular tachycardia, Wolff-Parkinson-White syndromeo Diarreha - Class Ib: phenytoin (antiseizure), lidocaine o Block sodium channels Can further liver damage Can become toxico Accelerate repolarizationo Increase or decrease APDo Lidocaine is used for ventricular dysrhythmias onlyo Phenytoin is used for atrial and ventricular tachydysrhythmias caused by digitalis toxicity,long QT syndromeo *****Too much lidocaine leads to toxicity then convulsions - Class II: beta blockers: atenolol, esmolol, metaprololo Reduce or block sympathetic nervous system stimulation, thus reducing transmission of impulses in the heart’s conduction systemo Depress phase 4 depolarizationo General myocardial depressants for both supraventricular and ventricular dysrhythmiaso Also used as antianginal and antihypertensive drugs- Class III: amiodarone (Last drug of choice), dronedarone, dofetilide, sotalol*(most potent, only used here), ibutilide o Increase APD (action potential duration)o Prolong repolarization in phase 3o Used for dysrhythmias that are difficult to treat Life-threatening ventricular tachycardia or fibrillation, atrial fibrillation or flutter that is resistant to other drugo Amiodarone can cause skin to slough off, cause dysrhythmia - very hard medicine- Class IV: verapamil, diltiazem o Antidysrhythmics, reduce AV node conduction – tachycardia o Calcium channel blockers Inhibit slow-channel (calcium-dependent) pathwayso Depress phase 4 depolarizationo Reduce AV node conductiono Used for paroxysmal supraventricular tachycardia; rate control for atrial fibrillation and flutterUnclassified 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- Used instead of dyfibrilator to cure Antidysrhythmics: Adverse Effects- ALL antidysrhythmics can cause dysrhythmias!o Hypersensitivity reactionso Nauseao Vomitingo Diarrhea ***Increase fiber unless on digoxin – then it is contraindicated!!o Dizzinesso Blurred visiono HeadacheNursing Implications- Obtain a thorough drug and medical history- Measure baseline BP, P, I&O, and cardiac rhythm- Measure serum potassium levels before initiating therapy- Assess for conditions that may be contraindications for use of specific drugs- Assess for potential drug interactions- Instruct patients to report dosing schedules and adverse effects to physician- 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- Instruct patients to take medications as scheduled and not to skip doses or double up for missed doses- Instruct patients to contact their physician for instructions if a dose is missed- Instruct patients not to crush or chew oral sustained-release preparations- Monitor ECG for prolonged QT interval with use of antidysrhythmics, including amiodarone, procainamide, quinidine, dofetilide, bepridil, sotalol, flecainide- Administer IV infusions with an IV pump- Solutions of lidocaine that contain epinephrine should not be given IV—they are to be used ONLY as local anesthetics- Ensure that the patient knows to notify health care provider of any worsening of dysrhythmia ortoxic effectso Shortness of breath, Edema, Dizziness, Syncope, Chest pain, GI distress, Blurred vision- Teach patients taking beta blockers, digoxin, and other drugs 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- Monitor for therapeutic responseo Decreased BP in hypertensive patientso Decreased edemao Decreased fatigueo Regular pulse rate o Pulse rate without major irregularitieso Improved regularity of rhythmo Improved cardiac outputQuestions1. A patient has received an IV dose of adenosine, and almost immediately the heart monitor shows asystole. What should the nurse do next?A. Check the patient’s pulse.B. Prepare to administer CPR.C. Set up for defibrillation.D. Continue to monitor the