11 Antidysrhythmics Upd

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11 Antidysrhythmics Upd

  1. 2. <ul><li>Dysrhythmia </li></ul><ul><li>Any deviation from the normal rhythm of the heart </li></ul><ul><li>Antidysrhythmics </li></ul><ul><li>Drugs used for the treatment and prevention of disturbances in cardiac rhythm </li></ul>
  2. 3. <ul><li>Inside the cardiac cell, there exists a net negative charge relative to the outside of the cell. </li></ul>
  3. 4. <ul><li>This difference in the electronegative charge. </li></ul><ul><li>Results from an uneven distribution of ions (sodium, potassium, calcium) across the cell membrane. </li></ul><ul><li>An energy-requiring pump is needed to maintain this uneven distribution of ions. </li></ul><ul><li>Sodium-potassium ATPase pump </li></ul>
  4. 6. <ul><li>A change in the distribution of ions causes cardiac cells to become excited. </li></ul><ul><li>The movement of ions across the cardiac cell’s membrane results in the propagation of an electrical impulse. </li></ul><ul><li>This electrical impulse leads to contraction of the myocardial muscle. </li></ul>
  5. 7. <ul><li>Four Phases </li></ul><ul><li>The SA node and the Purkinje cells each have separate action potentials. </li></ul>
  6. 9. <ul><li>System commonly used to classify antidysrhythmic drugs </li></ul>
  7. 10. <ul><li>Class 1 </li></ul><ul><ul><li>Class Ia </li></ul></ul><ul><ul><li>Class Ib </li></ul></ul><ul><ul><li>Class Ic </li></ul></ul><ul><li>Class II </li></ul><ul><li>Class III </li></ul><ul><li>Class IV </li></ul><ul><li>Other </li></ul>
  8. 11. <ul><li>Class I </li></ul><ul><li>Membrane-stabilizing agents </li></ul><ul><li>Fast sodium channel blockers </li></ul><ul><li>Divided into Ia, Ib, and Ic agents, according to effects </li></ul>
  9. 12. <ul><li>Class I </li></ul><ul><li>moricizine </li></ul><ul><li>General Class I agent </li></ul><ul><li>Has characteristics of all three subclasses </li></ul><ul><li>Used for symptomatic ventricular and life-threatening dysrhythmias </li></ul>
  10. 13. <ul><li>Class Ia </li></ul><ul><li>quinidine, procainamide, disopyramide </li></ul><ul><li>Block sodium channels </li></ul><ul><li>Delay repolarization </li></ul><ul><li>Increase the APD </li></ul><ul><li>Used for atrial fibrillation, premature atrial contractions, premature ventricular contractions, ventricular tachycardia, Wolff-Parkinson-White syndrome </li></ul>
  11. 14. <ul><li>Class Ib </li></ul><ul><li>tocainide, mexiletine, phenytoin, lidocaine </li></ul><ul><li>Block sodium channels </li></ul><ul><li>Accelerate repolarization </li></ul><ul><li>Decrease the APD </li></ul><ul><li>Used for ventricular dysrhythmias only (premature ventricular contractions, ventricular tachycardia, ventricular fibrillation) </li></ul>
  12. 15. <ul><li>Class Ic </li></ul><ul><li>encainide, flecainide, propafenone </li></ul><ul><li>Block sodium channels (more pronounced effect) </li></ul><ul><li>Little effect on APD or repolarization </li></ul><ul><li>Used for severe ventricular dysrhythmias </li></ul><ul><li>May be used in atrial fibrillation/flutter </li></ul>
  13. 16. <ul><li>Class II </li></ul><ul><li>Beta blockers: atenolol, esmolol, petaprolol, propranolol </li></ul><ul><li>Reduce or block sympathetic nervous system stimulation, thus reducing transmission of impulses in the heart’s conduction system </li></ul><ul><li>Depress phase 4 depolarization </li></ul><ul><li>General myocardial depressants for both supraventricular and ventricular dysrhythmias </li></ul>
  14. 17. <ul><li>Class III </li></ul><ul><li>amiodarone, bretylium, sotalol, ibutilide </li></ul><ul><li>Increase APD </li></ul><ul><li>Prolong repolarization in phase 3 </li></ul><ul><li>Used for dysrhythmias that are difficult to treat </li></ul><ul><li>Life-threatening ventricular tachycardia or fibrillation, atrial fibrillation or flutter—resistant to other drugs </li></ul><ul><li>Sustained ventricular tachycardia </li></ul>
  15. 18. <ul><li>Class IV </li></ul><ul><li>verapamil, diltiazem </li></ul><ul><li>Calcium channel blockers </li></ul><ul><li>Depress phase 4 depolarization </li></ul><ul><li>Used for paroxysmal supraventricular tachycardia; rate control for atrial fibrillation and flutter </li></ul>
  16. 19. <ul><li>Other Antidysrhythmics </li></ul><ul><li>digoxin, adenosine </li></ul><ul><li>Have properties of several classes and are not placed into one particular class </li></ul>
  17. 20. <ul><li>Digoxin </li></ul><ul><li>Cardiac glycoside </li></ul><ul><li>Inhibits the sodium-potassium ATPase pump </li></ul><ul><li>Positive inotrope—improves the strength of cardiac contraction </li></ul><ul><li>Allows more calcium to be available for contraction </li></ul><ul><li>Used for CHF and atrial dysrhythmias </li></ul><ul><li>Monitor potassium levels, drug levels, and for toxicity </li></ul>
  18. 21. <ul><li>adenosine (Adenocard) </li></ul><ul><li>Slows conduction through the AV node </li></ul><ul><li>Used to convert paroxysmal supraventricular tachycardia to sinus rhythm </li></ul><ul><li>Very short half-life </li></ul><ul><li>Only administered as fast IV push </li></ul><ul><li>May cause asystole for a few seconds </li></ul><ul><li>Other side effects minimal </li></ul>
  19. 22. <ul><li>ALL antidysrhythmics can cause dysrhythmias!! </li></ul><ul><li>Hypersensitivity reactions </li></ul><ul><ul><li>Nausea </li></ul></ul><ul><ul><li>Vomiting </li></ul></ul><ul><ul><li>Diarrhea </li></ul></ul><ul><ul><li>Dizziness </li></ul></ul><ul><ul><li>Blurred vision </li></ul></ul><ul><ul><li>Headache </li></ul></ul>
  20. 23. <ul><li>Obtain a thorough drug and medical history. </li></ul><ul><li>Measure baseline BP, P, I & O, and cardiac rhythm. </li></ul><ul><li>Measure serum potassium levels before initiating therapy. </li></ul>
  21. 24. <ul><li>Assess for conditions that may be contraindications for use of specific agents. </li></ul><ul><li>Assess for potential drug interactions. </li></ul><ul><li>Instruct patients regarding dosing schedules and side effects to report to physician. </li></ul>
  22. 25. <ul><li>During therapy, monitor cardiac rhythm, heart rate, BP, general well-being, skin color, temperature, heart and breath sounds. </li></ul><ul><li>Assess plasma drug levels as indicated. </li></ul><ul><li>Monitor for toxic effects. </li></ul>
  23. 26. <ul><li>Instruct patients to take medications as scheduled and not to skip doses or double up for missed doses. </li></ul><ul><li>Patients who miss a dose should contact their physician for instructions if a dose is missed. </li></ul><ul><li>Instruct patients not to crush or chew any oral sustained-release preparations. </li></ul>
  24. 27. <ul><li>For class I agents, monitor ECG for QT intervals prolonged more than 50%. </li></ul><ul><li>IV infusions should be administered with an IV pump. </li></ul>
  25. 28. <ul><li>Patients taking propranolol, digoxin, and other agents 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. </li></ul>
  26. 29. <ul><li>Monitor for therapeutic response: </li></ul><ul><ul><li>Decreased BP in hypertensive patients </li></ul></ul><ul><ul><li>Decreased edema </li></ul></ul><ul><ul><li>Regular pulse rate or </li></ul></ul><ul><ul><li>Pulse rate without major irregularities, or </li></ul></ul><ul><ul><li>Improved regularity of rhythm </li></ul></ul>

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