Selenium toxicity

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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
  - Pulmonary edema
  - Ventricular dysrhythmias
  - Myocardial infarction
  - Mesenteric infarction
  - Metabolic acidosis
Inhalation
- Hydrogen selenide
  - Throat and eye pain
  - Rhinorrhea
  - Wheezing
  - Pneumomediastinum
  - 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

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

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
Consult Toxicology or poison control
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
Chelation
- Dimercaprol, CaNa₂EDTA, or Succimer may form nephrotoxic complexes and worsen toxicity

Disposition

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

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