Mercury Poisoning, Emergency Medicine

Basics

Description

Mercury: ‚

3 forms: Elemental, inorganic salts, and organic
Reacts with sulfhydryl groups, causing enzyme inhibition and alterations in cellular membranes
Binds to phosphoryl, carboxyl, amide, and amine groups of enzymes

Etiology

Exposure is usually through the GI tract and inhalation and less frequently dermal exposure.
Exposure through manufacturing of chlorine and caustic soda, diuretics, antibacterial agents, antiseptics, thermometers, batteries, fossil fuels, plastics, paints, jewelry, lamps, explosives, fireworks, vinyl chloride, and pigments
Exposure through taxidermy, photography, dentistry, mercury mining
Contaminated seafood

Diagnosis

Signs and Symptoms

Naturally occurring mercury is converted into 3 primary forms, each with its toxicologic effects:
Elemental mercury:
- Symptoms from inhalation occur within hours:
  - Cough and dyspnea, which may progress to pulmonary edema
  - Metallic taste, salivation
  - Weakness, nausea, diarrhea, fever, headaches, visual disturbances
- Subcutaneous deposits may present as granulomas or abscesses.
- IV exposure presents with symptoms consistent with pulmonary embolization.
- Relatively nontoxic from oral ingestion, although appendicitis has been reported
Inorganic mercurial salt ingestion:
- Caustic GI injury:
  - Abdominal pain with nausea, vomiting, and diarrhea
  - Metallic taste, sore throat
  - Hemorrhagic gastroenteritis with hematochezia and hematemesis
- Acute tubular necrosis
- Acrodynia (pink disease):
  - Idiosyncratic, occurs mainly in children
  - Painful extremities
- Pink discoloration with desquamation
Organic mercury ingestion:
- Historically, infants exposed in womb are most severely affected (e.g., Minamata Bay, Japan)
- May see GI symptoms acutely
- Delayed CNS toxicity predominates and may take weeks to months to manifest:
  - Paresthesias
  - Ataxia
  - Paralysis
  - Visual field constriction
  - Dysarthria
  - Hearing loss
  - Mental deterioration
  - Death

History

Ask about possible workplace, environmental, or accidental exposure to mercurial products.
Document the patients ingestion of seafood over the last few weeks.

Physical Exam

Elemental mercury:
- Cough progressing to respiratory distress if inhaled or intravenously injected
- Ataxia
- Subcutaneous nodules or granulomas if injected
Inorganic mercury:
- Oral burns
- Abdominal tenderness
- Heme-positive stools
Organic mercury:
- CNS abnormalities:
  - Progressive cognitive deterioration

Essential Workup

Good history for workplace or environmental exposure
Physical exam looking for:
- Respiratory distress
- Caustic GI injury
- Neuropsychiatric impairment
Lab tests:
- Renal failure
- Urine and blood mercury levels:
  - Not reliable with recent seafood ingestion

Diagnosis Tests & Interpretation

Lab

Inorganic mercury exposure:
- CBC
- Electrolytes, BUN, creatinine, glucose
- 24-hr urine mercury collection:
  - Normal urine levels <20 mg/dL
- Whole-blood mercury level:
  - Normal blood <10 mg/dL
Organic mercury exposure:
- CBC with peripheral smear
- Electrolytes, BUN, creatinine, glucose
- Whole-blood mercury level:
  - Normal blood <10 mg/dL

Imaging

Chest radiograph:
- For noncardiac pulmonary edema
- Evidence of IV mercury in pulmonary vascular tree
Abdominal radiograph:
- For presence of mercury with intentional oral ingestion
Head CT:
- May detect cerebellar atrophy

Diagnostic Procedures/Surgery
Lumbar puncture in the workup of altered mental status ‚

Differential Diagnosis

Multisystem involvement is often confused with other heavy-metal intoxications.
Cerebrovascular accident
Senile dementia, Alzheimer disease
Parkinson disease
Peptic ulcer disease
Gastrointestinal bleeding
Pancreatitis
Sepsis
Acute respiratory distress syndrome

Treatment

Pre-Hospital

Remove from toxin exposure.
Decontamination:
- Wash exposed skin.
For altered mental status:
- Dextrose
- Thiamine
- Naloxone (Narcan)
- Oxygen

Initial Stabilization/Therapy

Secure ABCs and monitoring.
0.9% NS
IV fluid resuscitation for hypotension:
- Blood transfusion for significant gastrointestinal hemorrhage
Naloxone, D50W, thiamine for altered mental status

Ed Treatment/Procedures

Elemental mercury:
- For inhalation exposure, observe closely for several hours for development of noncardiogenic pulmonary edema.
- Ingested elemental mercury passes through normal intestinal tract with minimal absorption.
- Consider chelation for symptomatic patients with oral dimercaptosuccinic acid (DMSA).
- For subcutaneous nodules/abscess, perform an incision and drainage.
Inorganic mercury salt ingestion:
- Administer activated charcoal.
- Aggressive 0.9% NS IV fluid resuscitation/blood products for hypovolemic shock:
  - Hydrate and maintain urine output (1 mL/kg/h).
- Chelate symptomatic patients:
  - IM dimercaprol (British anti-Lewisite [BAL])
  - Oral DMSA efficacy may be limited secondary to caustic GI injury.
Organic mercury:
- Administer activated charcoal.
- Chelate with oral DMSA.

Medication

First Line

Dextrose: D50W 1 amp: 50 mL or 25 g (peds: D25W 2 " “4 mL/kg) IV
Dimercaprol (BAL): 5 mg/kg IM q4h for 48 hr, then 2.5 mg/kg q6h for 48 hr, then 2.5 mg/kg q12h for 7 days
DMSA: 10 mg/kg PO q8h for 5 days, then q12h for 2 wk
Naloxone (Narcan): 2 mg (peds: 0.1 mg/kg) IV/IM initial dose
Thiamine (vitamin B1): 100 mg (peds: 50 mg) IV or IM

Second Line

D-penicillamine:
- Adult: 250 mg PO QID for 7 " “14 days
- Peds: 5 " “7 mg/kg PO QID for 7 " “14 days
2,3-Dimercapto-1-propanesulfonate:
- IV or PO formulations. Contact your poison center at 1-800-222-1222 for availability.

Follow-Up

Disposition

Admission Criteria
Acutely symptomatic patients: ‚

Any evidence of respiratory compromise
Ingestion of inorganic mercury salt that may lead to a caustic GI injury
Renal impairment
Any patient starting chelation therapy

Discharge Criteria

Asymptomatic patient with history of ingestion of elemental mercury and intact intestinal tract
Patient with history of inhalation exposure to elemental mercury who remain asymptomatic after 6 hr of observation

Issues for Referral

Medical toxicology referral for symptomatic patients or where chelation is considered
Gastroenterology for caustic GI injury
Pulmonary/ICU care for patients with symptomatic inhalational injury
Neurology in the evaluation of progressive cerebral deterioration
Poison center for all suspected exposures

Follow-Up Recommendations

For discharged patients with possible workplace or environmental exposures, follow up with their primary care provider for results of 24-hr urine or whole-blood mercury levels.
Outpatient referral to medical toxicology for suspected or confirmed cases
For the asymptomatic patient, have the patient refrain from eating seafood for 2 wk before repeating the 24-hr urine for mercury.

Pearls and Pitfalls

Obtain a good history for workplace, environmental or accidental exposure in patients with gastrointestinal and/or neuropsychiatric complaints.
Monitor patients for at least 6 hr if they were exposed to inhalational elemental mercury.
Ingestion of inorganic mercurial salts can lead to significant caustic GI injury.
Lab tests may yield false positives especially in patients who eat seafood.

Additional Reading

Clarkson ‚ TW, Magos ‚ L, Myers ‚ GJ. The toxicology of mercury " “current exposures and clinical manifestations. N Engl J Med. 2003;349:1731 " “1737.
Rocha ‚ JB, Aschner ‚ M, D ƒ ³rea ‚ JG, et al. Mercury toxicity. J Biomed Biotechnol. 2012;2012:831890.
Young-Jin ‚ S. Mercury. In: Flomenbaum ‚ NE, Goldfrank ‚ LR, Hoffman ‚ RS, et al., eds. Goldfranks Toxicologic Emergencies. 9th ed. New York, NY: McGraw-Hill; 2010.

Codes

ICD9

961.2 Poisoning by heavy metal anti-infectives
976.0 Poisoning by local anti-infectives and anti-inflammatory drugs
985.0 Toxic effect of mercury and its compounds
974.0 Poisoning by mercurial diuretics

ICD10

T37.8X1A Poisoning by oth systemic anti-infect/parasit, acc, init
T49.0X1A Poisoning by local antifung/infect/inflamm drugs, acc, init
T56.1X1A Toxic effect of mercury and its compounds, accidental (unintentional), initial encounter
T50.2X1A Poisn by crbnc-anhydr inhibtr, benzo/oth diuretc, acc, init

SNOMED

85180002 Toxic effect of mercury AND/OR its compounds (disorder)
22130008 Organic mercury poisoning (disorder)
47980004 Inorganic mercury poisoning (disorder)
212736008 Mercurial diuretic poisoning (disorder)

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