DESCRIPTION

Selenium (Se) is found as elemental selenium, inorganic selenium salts (sodium selenite), organic selenium, hydrogen selenide (gaseous form), selenium oxychloride (liquid, vesicant), selenium dioxide, and selenious acid.

FORMS AND USES

Industrial Uses

• Selenium is used to imbue a red pigment to glass and plastic.
• It is used in the electronics, copper, photography, and rubber industries, as well as in photocopy machines.
• It is a component of various substances, including gun bluing solution, sheep and cattle drench, and paint, varnish, and glue remover.

Food Sources of Selenium

• Grains grown in soil high in selenium, garlic, nuts, sunflower seeds, brown sugar, mushrooms, and egg noodles
• Seafood, especially swordfish, tuna, and oysters; liver; kidney; skimmed milk; egg yolk; beef; and chicken

Other

Selenium also is used as an antibacterial and antiseborrheic agent in shampoo.

TOXIC DOSE

Chronic ingestion of 30 to 60 mg/day has produced toxicity.

PATHOPHYSIOLOGY

• Selenium in toxic doses is thought to bind and interfere with sulfhydryl groups on enzymes needed for protein synthesis.
• Elemental selenium is minimally toxic.
• Selenium salts may produce toxicity by ingestion, inhalation, and percutaneous absorption.

EPIDEMIOLOGY

Poisoning is uncommon.

CAUSES

• Poisoning is usually accidental.
• The possibility of child neglect or abuse should be considered in patients less than 1 year of age; suicide attempt in patients over 6 years of age.

PREGNANCY AND LACTATION

• Selenium crosses the placenta and is transmitted in breast milk.
• Selenium is teratogenic in animals.

WORKPLACE STANDARDS

• ACGIH. TLV TWA is 0.2 mg/m³.
• NIOSH. IDLH level is 1 mg/m³.
• OSHA. PEL TWA is 0.2 mg/m³.

Section Outline:

• DESCRIPTION
• FORMS AND USES
  • Industrial Uses
  • Food Sources of Selenium
  • Other
• TOXIC DOSE
• PATHOPHYSIOLOGY
• EPIDEMIOLOGY
• CAUSES
• PREGNANCY AND LACTATION
• WORKPLACE STANDARDS

DIFFERENTIAL DIAGNOSIS

Other causes of gastroenteritis include thallium toxicity, arsenic toxicity, and infectious gastroenteritis.

SIGNS AND SYMPTOMS

HEENT

Garlic or rotten horseradish breath, increased incidence of dental caries, chemosis, lacrimation, and "rose eye" (swelling and pink discoloration of the eyelids) may occur.

Dermatologic

• Dermatitis, alopecia, and brittle hair that breaks off at the scalp may occur.
• Selenious acid may cause chemical burn.

Cardiovascular

• Massive overdose causes hypotension, cardiomyopathy with ECG T-wave inversions, and elevated creatine kinase.
• Selenious acid may cause cardiomyopathy.

Pulmonary

• Inhalation of fumes or dust may cause respiratory mucosal irritation (sore throat, cough) that may last for 1 to 2 weeks after an acute exposure ("rose cold").
• High-dose exposure may cause pulmonary edema.

Gastrointestinal

• Gastrointestinal upset, abdominal pain, nausea, and vomiting may occur.
• Selenious acid may cause salivation and caustic gastrointestinal injury, hematemesis, and diarrhea.

Neurologic

• Dizziness, weakness, and peripheral painful paresthesia may occur.
• Hyperreflexia, convulsions, and motor disturbance can result.

Psychiatric

Languor, depression, and emotional instability can occur.

PROCEDURES AND LABORATORY TESTS

Essential Tests

No tests may be needed in asymptomatic patients.

Recommended Tests

• Complete blood count, arterial blood gas, serum electrolytes, BUN, creatinine, liver enzymes, and urinalysis should be obtained, especially after selenious acid ingestion.
• The selenium level in a 24-hour urine sample correlates well with dietary intake of selenium.
• Serum selenium levels also can be useful when renal dysfunction is present.
• Endoscopy may be needed for patients with caustic injury from ingestion of selenious acid.

Not Recommended Tests

Other body tissue levels (e.g., in hair or nails) are not useful.

Section Outline:

• DIFFERENTIAL DIAGNOSIS
• SIGNS AND SYMPTOMS
  • HEENT
  • Dermatologic
  • Cardiovascular
  • Pulmonary
  • Gastrointestinal
  • Neurologic
  • Psychiatric
• PROCEDURES AND LABORATORY TESTS
  • Essential Tests
  • Recommended Tests
  • Not Recommended Tests

• Therapy consists primarily of symptomatic and supportive care.
• Dose and time of exposure should be determined for all substances involved.

DIRECTING PATIENT COURSE

The health-care professional should call the poison control center when:

• Severe or persistent effects develop.
• Coingestant, drug interaction, or underlying disease presents an unusual problem.

The patient should be referred to a health-care facility when:

• Suicide or homicide attempt is possible.
• Toxic effects develop.
• Coingestant, drug interaction, or underlying disease presents an unusual problem.

Admission Considerations

Patients with serious end-organ injury (e.g., ECG changes, pulmonary edema) and patients with potential caustic injury from selenious acid should be admitted.

DECONTAMINATION

Out of Hospital

• The patient should be moved to fresh air following inhalation exposure.
• Skin exposures should be washed with copious amounts of water.

In Hospital

• Gastric emptying and activated charcoal are not recommended if caustic gastrointestinal injury has occurred.
• For acute ingestion, gastric lavage and activated charcoal are recommended.
  • Gastric lavage should be performed in pediatric (tube size 24-32 French) or adult (tube size 36-42 French) patients presenting within 1 hour of a large ingestion or if serious effects are present.
  • One dose of activated charcoal (1-2 g/kg) should be administered without a cathartic if a substantial ingestion has occurred within the previous few hours.

ANTIDOTE

There is no specific antidote for selenium poisoning.

ADJUNCTIVE TREATMENT

• Seizures, hypotension, bronchospasm, and pulmonary edema are treated in the usual manner.
• Not recommended treatments. Bromobenzene, British anti-Lewisite (BAL, dimercaprol), ethylenediaminetetraacetic acid (EDTA), and vitamin C have been tried and found to have inconsistent or harmful results.

Section Outline:

• DIRECTING PATIENT COURSE
  • Admission Considerations
• DECONTAMINATION
  • Out of Hospital
  • In Hospital
• ANTIDOTE
• ADJUNCTIVE TREATMENT

Future levels should be checked, especially if symptoms persist.

DISCHARGE CRITERIA/INSTRUCTIONS

Asymptomatic patients may be discharged from the emergency department or hospital following decontamination, 4 hours of observation, and psychiatric evaluation, if needed.

DIAGNOSIS

• Selenium toxicity must be suspected in order to be diagnosed.
• Doses recommended in multivitamin bottles may exceed a dose causing chronic toxicity.

FOLLOW-UP

It is important to identify the source of selenium toxicity and remove it to avoid further poisonings.

Section Outline:

• DIAGNOSIS
• FOLLOW-UP

Toxic effect of other substances, chiefly nonmedicinal as to source.

See Also: SECTION II, Seizures, Hypotension, and Pulmonary Edema chapters.

RECOMMENDED READING

Maejos MS, Romero CD. Urinary selenium concentrations. Clin Chem 1993;39:2040-2052.

Author: Gayle E. Long

Reviewer: Richard C. Dart