Spreading Emergency Medicine Across the Globe ..
emmedonline
Dr. Ajith Kumar J MD
Dept. of Emergency Medicne
Travancore Medicity, Kollam
India
editor
Mercury occurs in both inorganic and organic forms.
Inorganic mercury exist as elemental mercury(quick silver) and mercurous salt (mercurous chloride or calomel) and mercuric salt (cinnabar or mercuric sulfide).
Organic mercury exist as short chain and long chained alkyl and aryl compounds.
Short chained alkyls such as methyl and ethyl mercuric are more toxic to human and must lethal been dimethyl mercury.
Pharmacology
Elemental mercury
Elemental mercury is absorbed primarily by inhalation of its vapor.
Vacuuming elemental mercury as from broken thermometer, increases volatility.
Absorption by GI tract is highly negligible and doesn't produce any adverse effects unless the tract is damaged.
IV injection of mercury produces pulmonary and systemic emboli. They can also cross BBB where it is ionized and trapped in the CNS.
IM injection can induce abcess and granuloma formation. Slow absorption and delayed toxicity has been reported.
Inorganic mercury salts
They are absorbed primarily through GI tract, may be absorbed from intact skin.
They are deposited in the ionised form primarily in the kidney, followed by liver and spleen.
Mercury salts do not enter CNS nor cross placenta.
Organic mercury
They absorbed primarily by GI tract .
They can cross membranes and accumulates in RBC, CNS, liver kidney and fetus.
Inorganic and aryl organic mercurials are eliminated in the urine and feces . Short chained alkyl compounds are excreted primarily in bile, where they undergo significant enterohepatic circulation.
Pathophysiology
Mercruy binds with sulfhydryl groups, affecting a diverse number of enzyme and protein systems.
Methyl mercury also inhibits choline acetyl transferase, which catalyses the final step in the production of acetylcholine and may produce symptoms of acetylcholine deficiency.
Clinical Features
Elemental mercury
Shortness of breath, fever, chills, cough, nausea, vomiting, diarrhea, metallic taste, headache, weakness and blurring vision.
Severe cases patients can develop acute lung injury and severe respiratory distress.
Inorganic mercury
Mercuric salts are caustic and an acute ingestion can produce severe hemorrhagic gastroenteritis with abdominal pain .
Graying of oral mucosa and metallic taste, excessive salivation, burning sensation in the mouth.
Shock and CVS collapse may ensue rapidly.
ARF results from both direct toxicity of the mercury ions and from decreased renal perfusion due to shock.
Chronic neurological toxicity includes tremors, neuroasthenia and erethism.
Neurasthenia is characterised by fatigue, depression, headaches and difficulty concentrating.
Erethism refers to easy blushing and extreme shyness; other symptoms include emotional liability, irritability, insomnia and delirium.
Acrodynia, also known as “pink disease” is an immune mediated reaction characterised by a generalized rash; edema and erythema of the palms, soles and face; excessive sweating, fever irritability , splenomegaly and generalised hypotonia.
Organic mercury
After a latent period of weeks to months, orofacial parasthesia develop.
Patients may develop headache, tremor and fatigue. Severe cases ataxia, muscle rigidity and spasticity, blindness, hearing deficits and dementia.
Diagnosis
For all forms of mercury poisoning except short chained alkyl 24 hr urinary measurement of mercury should be performed after a 5 days of seafood free diet.
A level 20>mcg/L indicates meaningful exposure.
Whole blood mercury levels are measured as these compounds concentrate in erythrocytes.
Blood mercury levels normally <5mcg/ml.
Short chained alkyl mercury compounds are excreted by bile and measuring urine mercury is invalid.
Treatment
For elemental mercury severe respiratory failure following inhalation or aspiration of volatilized elemental mercury may require positive pressure ventilation.
For ingestion of inorganic mercuric salt treat with aggressive IV hydration and GI decontamination, including gastric lavage and consider activated charcoal.
For organic mercury toxicity institute gastric decontamination. Neostigmine may improve motor function in methyl mercury poisoned patients by improving acteylcholine levels at NMJ.
Chelation
It is indicated only if there is history of significant mercury poisoning, elevated blood or urine mercury levels , signs and symptoms consistent with mercury poisoning.
Dimercarpol is contraindicated in methyl mercury poisoning as it can worsen neurological symptoms.
Adverse reaction includes nausea, vomiting,headache, paresthesia,diaphoresis. Fever in childrens.
Guidelines for chelation therapy | ||
| Inorganic mercury | Organic mercury |
Severe poisoning | Dimercaprol 5mg/kg IM q 4h for 2 days, followed by 2.5mg/kg IM every 6h for 2 days followed by 2.5 mg/kg IM 12 -24 h clinical improvement occurs or switch to succimer. | Succimer 10 mg/PO every 8h for 5d, then every 12h for 14 days |
Mild poisoning and chronic poisoning | Succimer, 10 mg/kg PO every 8h for 5d; then 12 h for 14 days. | No proven benefit |
Updated on 30/4/14
Reference
Tintinalli
Copyright 2020. emmedonline. All rights reserved.
Website is designed for desktop. Mobile user are advised use firefox for best results.
emmedonline
Dr. Ajith Kumar J MD
Dept. of Emergency Medicne
Travancore Medicity, Kollam
India
editor