Morning Report: Digoxin Toxicity

Thanks to Dr. Freedman for today’s Morning Report!

Digoxin Toxicity

Background:

• Naturally occurring chemical compounds
• Na+/ATPase Channel blockers
• Prone to poisoning
  • Large volume of distribution
  • Long half-life, ~36 hours
  • Narrow therapeutic window, 0.6 – 1.3 ng/mL

Digoxin:

• An Old Drug: CHF, A fib
  • ~2% of all international patients.
  • One of the 50 most commonly prescribed in U.S.
  • 1,601 acute ingestions in U.S. in 2011
  • In U.S., 1% of outpatients and ~18% of NH patients will develop toxicity
  • 0.4% of all U.S hospital admissions

Plant Cardiac Glycosides:

• Many different flowering plants
  • Foxglove, oleander, lily of the valley et al.

• 2.6% of all toxic plant exposures
• 1,336 in U.S. in 2011

Acute Ingestions

Epidemiology: the young (one pill kill)

• Adults: LD50 10mg
• Pediatrics: LD 50 0.3mgkg

Presentation: Cardiac symptoms

• Bradycardia +/- hypotension
• Dysrhythmias
  • Sinus
  • Junctional
  • AV block
  • Slow a fib/flutter
  • Bidirectional V tach

Chronic Toxicity

Epidemiology: Elderly, chronically ill

• Normal or sub-therapeutic levels
• Triggered by:
  • Electrolyte disturbance
  • Hypovolemia
  • Drug-drug interactions

Presentation: Often non-specific

• Altered mental status, weakness, fatigue
• Nausea/vomiting, abdominal pain
• Visual complaints

ECG findings:

• “Scooped” ST segment, Digitalis Effect
• Any of the acute dysrhythmias

ED Management

• ABCs
  • Supportive care
  • Correction of electrolyte disturbance

• H+P
  • Acute?
    • When, how much?

• • Chronic?
    • Index of suspicion
    • Trigger?

• Lab Studies
  • Digoxin Level
    • 6 hour level
    • Earlier levels don’t reflect steady state
  • Potassium
    • Marker of acute toxicity
    • Prognostic value

• Interventions
  • Bowel decontamination
    • Consider if <1-2 hours
  • Atropine
    • Not contra-indicated….
  • Pacing
    • Not recommended
  • Dialysis
    • Not plausible
  • Digi-Fab
    • Ingestion of 10 mg in adults, or 0.3 mg/kg in children
    • Acute ingestion with steady-state level > 10ng/mL
    • Chronic ingestion with steady-state level > 6ng/mL
    • Any dysrhythmia, irrespective of level
    • Serum potassium > 5.5 in acute ingestion
    • Any plant toxicity

Emergency Medicine Mythology:

Intravenous calcium is contraindicated in digoxin toxicity. “Stone Heart” Syndrome. Based on case studies. No data to support theory. Weak data exist to suggest calcium is safe in dig-toxic. Bottom-line: Give IV calcium if you suspect hyperkalemia.

Bidirectional V tach

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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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