Selenium toxicity

Background

• Essential trace element
• Deficiency found to be the cause of Keshan disease and Kashin-beck disease
• Recommended daily dose is 5 μg/d
• Uses
  • Gun bluing solution
  • Dietary supplement
  • Antidandruff shampoo
  • Glass decolorizer and manufacturing
  • Insecticide
  • Vulcanization of rubber
  • Used in copper refineries

Toxicokinetics

• Cofactor in glutathione peroxidase
• Varied GI absorption
• Minimal dermal absorption
• Bioavailability (Lowest - Highest)
  • Elemental selenium
  • Inorganic selenite and selenate salt
  • Selenious acid
• Limited data on toxicokinetics as it varies amongst compounds

Clinical Features

• Acute
  • Oral exposure
    • Triphasic course
    • Rapid and fulminant
      • Symptoms can occur within minutes and death can occur with 1-4 hours
    • GI
      • Abdominal pain
      • Diarrhea
      • Nausea and vomiting
      • Caustic esophageal and gastric burns
      • Some patients have a garlic odor
    • Myopathic
      • Weakness
      • Hyporeflexia
      • Myoclonus
      • Fasciculations
      • Elevated CPK
      • Renal insufficiency
      • Delirium and coma
    • Circulatory symptoms
      • Dyspnea
      • Chest pain
      • Tachycardia
      • Hypotension
        • Toxic cardiomyopathy
      • EKG abnormalities
        • ST elevation
        • Prolonged QT
        • T wave inversions
      • Pulmonary edema
      • Ventricular dysrhythmias
      • Myocardial infarction
      • Mesenteric infarction
      • Metabolic acidosis
  • Inhalation
    • Hydrogen selenide
      • Throat and eye pain
      • Rhinorrhea
      • Wheezing
      • Pneumomediastium
      • Restrictive and obstructive pulmonary disease
    • Selenium dioxide and selenium oxide
      • Forms selenius acid in presence of water in respiratory tract
      • Bronchospasm
      • Hypotension
      • Tachycardia
      • Tachypnea
      • Chemical pneumonitis
      • Fevers
      • Vomiting and diarrhea
  • Dermal
    • Caustic burns
  • Ophthalmic
    • Corneal injuries
    • Lacrimation
    • Conjunctival edema
• Chronic or Selenosis
  • No deaths from chronic exposures
  • Seen in those taking nutritional supplements and in rural areas with farmland that has high selenium levels
  • Alopecia with brittle hair
  • Fatigue
  • Nail deformities
  • Pruritic scalp rash
  • Blistered skin with persistent red color
  • Neurologic
    • Hyperreflexia
    • Paresthesia
    • Anesthesia
    • Hemiplegia

Differential Diagnosis

Heavy metal toxicity

• Aluminum toxicity
• Antimony toxicity
• Arsenic toxicity
• Barium toxicity
• Bismuth toxicity
• Cadmium toxicity
• Chromium toxicity
• Cobalt toxicity
• Copper toxicity
• Gold toxicity
• Iron toxicity
• Lead toxicity
• Lithium toxicity
• Manganese toxicity
• Mercury toxicity
• Nickel toxicity
• Phosphorous toxicity
• Platinum toxicity
• Selenium toxicity
• Silver toxicity
• Thallium toxicity
• Tin toxicity
• Zinc toxicity

Evaluation

• BMP
• LFTs
• CBC
• CPK
• EKG
• Thyroid function tests

Management

• Supportive care
  • Mainstay of treatment
  • Acute toxicities usually require multi system support
• Pain management
  • 10% sodium thiosulfate solution/ointment to skin, nail, and eyes
    • Relief of pain by reduction of selenium dioxide to elemental selenium
  • Selenium hexafluoride gas exposures
    • Calcium gluconate gel
      • Same treatment as hydrofluoric acid exposures
• Decontamination
  • Irrigation for dermal exposures
  • Consider activated charcoal or oral gastric lavage in cases that could produce significant toxicity
  • Selenious acid
    • Judicious use of NG lavage (as will cause caustic burns) based on time of ingestion, amount and concentration due to potential for serious systemic poisoning
• Chelation
  • Dimercaprol, [[CaNa₂EDTA]], or Succimer may form nephrotoxic complexes and worsen toxicity

Disposition

• Consult Toxicology or Poison Control Center
• Acute toxicities will likely require ICU level of care
• Chronic exposures are likely safe for discharge and outpatient follow up

References

Calellor, D. Selenium. In: Goldfrank's Toxicologic Emergencies. 9th Ed. New York: McGraw-Hill; 2011: 1316-1320