Digitalis Overdose

First Things First (assess & treat for the following)

• Treat life-threatening conditions
• Begin with ABCs
  • Correct hypoxia, hypoglycemia, hypovolemia, and electrolyte abnormalities
  • Dysrhythmias
    • Bradydysrhythmias
      • Atropine
      • Cardiac pacing
      • Fab fragments
    • Ventricular dysrhythmias
      • Fosphenytoin or lidocaine
      • IV magnesium
      • Fab fragments
      • Cardioversion—last resort
  • Hyperkalemia
    • Glucose, insulin, sodium bicarbonate, enteral potassium binding resin
    • Fab fragments
• GI decontamination
  • Activated charcoal
• Pharmacology
  • Digoxin is the most common preparation of digitalis.
  • Found in foxglove, oleander, lily of the valley
  • Inhibits Na+- K+- ATPase pump
    • Normally this pump concentrates Na+ extracellularly and K+ intracellularly.
    • Provides the Na+ gradient that powers the Na+- Ca++ antiporter, which extrudes Ca++ from the cell
  • May also increase cytosolic Ca++ by interactions with the L-type calcium channels and interactions with the Ca++ triggered calcium release from the myocardial sarcoplasmic reticulum
  • Effects of increased Ca++ inside the cell are:
    • Increased inotropy
    • Increased automaticity
    • Shortening of atrial and ventricular repolarization
    • Decreased rate of conduction through the sinoatrial and atrioventricular nodes both directly and through increased vagal tone
    • Excessive increase in Ca++ by excessive digoxin results in transient late depolarizations that may initiate contractions.
• EKG
  • Decrease in ventricular response rate for SVT
  • QT segment shortening
  • ST segment and T-wave forces opposite in direction to the major QRS forces