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
• Whole blood = 0.1–0.34 mg/L (1.27–4.32 μmol/L)
• Serum = 0.04–0.6 mg/L (0.51–7.6 μmol/L)
• Urine < 0.03 mg/L (<0.38 μmol/L)
• Hair < 0.4 μg/g (0.01 μmol/L)

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