Author:
Denise A.Whitfield
David A.Tanen
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, ceramics, antibacterial agents, pesticides, thermometers, batteries, fossil fuels, plastics, paints, jewelry, lamps, explosives, fireworks, vinyl chloride, and dyes
- Exposure through taxidermy, photography, mercury mining, and embalming
- Contaminated seafood and grains
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, acute respiratory distress syndrome and respiratory failure
- Metallic taste, salivation
- Weakness, nausea, vomiting, 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, rash
- Pink discoloration with desquamation
- Organic mercury ingestion:
- Historically, infants exposed in womb are most severely affected (e.g., Minamata Bay, Japan)
- Exposure often from seafood consumption
- 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 occupational, environmental, or accidental exposure to mercurial products
- Document the patient's 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
Diagnostic Tests & Interpretation
Lab
- Inorganic mercury exposure:
- CBC
- Electrolytes, BUN, creatinine, glucose
- 24-hr urine mercury collection:
- Normal urine levels <0.5 μg/L
- Whole-blood mercury level:
- Organic mercury exposure:
- CBC with peripheral smear
- Electrolytes, BUN, creatinine, glucose
- Whole-blood mercury level:
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
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
- Pneumonia
- Pulmonary embolism
Prehospital
- Remove from toxin exposure
- Decontamination:
Initial Stabilization/Therapy
- Secure ABCs and monitoring
- 0.9% NS
- IV fluid resuscitation for hypotension:
- Blood transfusion for significant gastrointestinal hemorrhage
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/hr).
- 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 if acute ingestion suspected
- Chelate with oral DMSA
Medication
First Line
- Succimer (DMSA): 10 mg/kg PO tid for 5 d, then b.i.d for 2 wk for mild to moderate intoxication
- Dimercaprol (BAL): 5 mg/kg IM once, then 2.5 mg/kg IM q 12-24h beginning on day 2 and continue for 10 d
Second Line
- D-penicillamine:
- Adult: 250 mg PO q.i.d for 7-14 d
- Peds: 5-7 mg/kg PO q.i.d for 7-14 d
- N-acetyl-DL-penicillamine (NAP) is an investigational analog with fewer side effects
- 2,3-Dimercapto-1-propanesulfonate:
- IV or PO formulations. Contact your poison center at 1-800-222-1222 for availability
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
- ClarksonTW, MagosL, MyersGJ. The toxicology of mercury—current exposures and clinical manifestations . N Engl J Med. 2003;349(18):1731-1737.
- RochaJB, AschnerM, DóreaJG, et al. Mercury toxicity . J Biomed Biotechnol. 2012;2012:831890.
- TheobaldJL, MycykMB. Iron and heavy metals. In: Rosen's Emergency Medicine: Concepts and Clinical Practice. 9th ed.Philadelphia, PA: Elsevier; 2018.
- Young-JinS. Mercury. In: FlomenbaumNE, GoldfrankLR, HoffmanRS, et al., eds. Goldfrank's Toxicologic Emergencies. 10th ed.New York: McGraw-Hill; 2015.
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