Morning Report: Digoxin Toxicity

Thanks to Dr. Kopping for presenting today’s Morning Report!

Digoxin Toxicity

• Digoxin falls under cardioactive steroids
  • Fox glove, oleander, dried toad secretions
• Na/K ATPase inhibition
  • Resting potential more positive, more likely to depolarize
  • Increases inotropy by preventing Ca leaving cell via Na/Ca channel
  • Increases automaticity
• Narrow therapeutic window
  • Poisoning carries with it high morbidity/mortality when left untreated
• Symptoms
  • GI (N/V/D), fatigue, vision changes, yellowing of vision, confusion, delirium, hallucinations, bradycardia, occasionally tachycardia
• Prior to advent of treatment, if K level is
  • <5 0% mortality
  • 5-5.5 50% mortality
  • >5.5 100% mortaility
  • Hypokalemia potentiates toxicity
• EKG findings
  • Just about anything accept for a supraventricular tachycardia with 1:1 conduction given AV nodal block
  • Specific- Bidirectional ventricular tachycardia (more than 1 ectopic foci)
  • Specific- accelerated junctional tachy
• Treatment
  • Supportive- Intubation, fluid status, etc
    • Potential for GI decontamination/gastric lavage/activated charcoal in acute ingestions
  • Hyper K
    • Stay away from calcium salts
    • Other typical treatments
  • Hypo K
    • Replete immediately, will only potentiate toxicity if not
  • Digibind/fab
    • Binds to intravascular digoxin which is then cleared via kidneys
    • Complex able to be removed using HD, although slow
    • Because volume of distribution is large, goes into tissues
      • Start removing complex, dig from tissues goes into intravascular space- “rebound toxicity”
    • How much?
      • Acute poisoning:
        • number of vials = Ingested dose (mg) x 0.8 (bioavailability) x 2 (note that 0.8 represents the 80% oral bioavailability of digoxin)
        • Unknown dose start with 5 vials if HD stable, 10 if HD unstable, 20 if in cardiac arrest. Re-dose every 30 minutes if still symptomatic
      • Chronic poisoning:
        • (serum digoxin concentration – ng/L) x (weight – kg) ÷ 100, round up
        • Many labs will give nM/L à divide by 1.28
        • Unknown level, start with 2 vials, re-dose in 30 minutes as needed
      • Initial response in 20-30 minutes, max at 90

References:

http://www.docstoc.com/docs/83478943/Digoxin-Toxicity-%28PowerPoint%29

http://www.nlm.nih.gov/medlineplus/ency/article/000165.htm

http://lifeinthefastlane.com/ccc/digoxin-toxicity/

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Jay Khadpe MD

• Editor in Chief of "The Original Kings of County"
• Assistant Professor of Emergency Medicine
• Assistant Residency Director
• SUNY Downstate / Kings County Hospital

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