Drugs Used to Treat Dysrhythmias

Chapter 23: Drugs Used to Treat Dysrhythmias

Overview of Dysrhythmias

  • Definition: Dysrhythmias refer to irregularities in the heart's electrical conduction system, impacting the pumping efficiency.
  • Causes:
  • Firing of abnormal pacemaker cells.
  • Blockage in the normal conduction pathway.
  • Factors such as stress, ischemia, and heart failure can aggravate irregular muscular contractions.
  • Normal Conduction Pathway: Begins with the sinoatrial (SA) node, followed by the atrioventricular (AV) node and the bundle of His.

Classification of Dysrhythmias

  • Supraventricular Dysrhythmias:

  • Occur above the bundle of His.

  • Includes:

    • Atrial flutter
    • Atrial fibrillation
    • Premature atrial contractions
    • Sinus tachycardia & bradycardia
    • Paroxysmal supraventricular tachycardia

  • Ventricular Dysrhythmias:

  • Occur below the bundle of His.

  • Includes:

    • Premature ventricular contractions
    • Ventricular tachycardia
    • Ventricular fibrillation

Drug Therapy for Dysrhythmias

  • Class I: Myocardial depressants inhibiting sodium ion movement.
  • Class Ia: Prolong duration of electrical stimulation (e.g., Quinidine).
  • Class Ib: Shorten duration (e.g., Lidocaine).
  • Class Ic: Potent myocardial depressants, slow conduction.
  • Class II: Beta-adrenergic blocking agents.
  • Class III: Slow rate of electrical conduction (e.g., Amiodarone).
  • Class IV: Block calcium ion flow (e.g., Verapamil, Diltiazem).

Assessment of Patients with Dysrhythmias

  • Baseline Assessments:
  • Initial monitoring with ECG.
  • Review medical history and presence of cardiovascular disease signs:
    • Chest pain
    • Dyspnea
    • Fatigue
    • Edema
    • Syncope
    • Palpitations
  • Monitor vital signs: BP, pulse, respirations, and oxygen saturation.
  • Laboratory tests: Electrolytes and blood gases.

Antidysrhythmic Agents

Class Ia: Quinidine
  • Action: Prolongs electrical stimulation duration.
  • Uses: Treats atrial fibrillation, WPW syndrome, premature ventricular contractions.
  • Adverse Effects: Dry mouth, myocardial toxicity, urinary hesitancy.
Class Ib: Lidocaine (Xylocaine)
  • Action: Shortens electrical stimulation duration.
  • Uses: Treats premature ventricular contractions and VT.
  • Adverse Effects: Lightheadedness, muscle twitching, seizures.
  • Note: Different preparation for prophylaxis of dysrhythmias vs. local anesthesia.
Class Ic: Potent Myocardial Depressants
  • Uses: Treats ventricular tachycardia and frequent PACs.
  • Adverse Effects: Dizziness, visual disturbances, exercise intolerance.
Class II: Beta Blockers (Esmolol, Metoprolol)
  • Action: Reduces heart rate and cardiac output.
  • Uses: Treats various forms of ventricular dysrhythmias.
Class III: Amiodarone
  • Action: Prolongs action potential duration; increases refractory period.
  • Uses: Treats life-threatening dysrhythmias.
  • Adverse Effects: CNS symptoms, pulmonary issues, GI discomfort, thyroid dysfunction.
Class IV: Calcium Channel Blockers (Verapamil, Diltiazem)
  • Action: Block calcium channels; slow AV node conduction.
  • Uses: Manage tachycardias.
Miscellaneous Agents
  • Adenosine: Converts supraventricular tachycardia to normal sinus rhythm; common effects include flushing and chest pressure.
  • Digoxin: Slows AV node conduction; increases cardiac output.

Conclusion

  • Critical Nursing Actions: Understanding drug classifications, side effects, and patient assessments are essential for managing dysrhythmias effectively. Regular monitoring and appropriate medication management are key to ensuring patient stability and efficacy of treatment.