Arsenic toxicity

Background

• infamous historical poison
• heavy metal
• sources of exposure: poisoning, contaminated drinking water, eruptions, metal and semiconductor industry, wood preservatives
• seafood arsenic felt to be organic form which is NONTOXIC and cleared from body in few days
• readily absorbed via GI tract and inhalation, poorly via skin
• organic trioxide form used as chemotherapeutic agent
• trivalent form, As3+, is toxic to over 200 intracellular enzymes
• known carcinogen: skin, lung, other
• ingestion fatal dose: 100-200mg

Clinical Features

1. Acute ingestion

• GI symptoms
• pulmonary edema
• shock
• rhabdomyolysis
• sz
• coma
• death
• cardiovascular instability
• Arsine gas exposure: hemolysis causing abdominal pain, hematuria, jaundice

    2. Subacute or chronic poisoning

• anemia
• sensory motor neuropathy
• skin changes
• ataxia
• CNS depression

Workup

• urine arsenic level (usual normal level is <50mcg/L); both urine spot test and 24h urine collection
• blood arsenic level not helpful (cleared within 2 hrs of exposure)
• ECG to eval for QT prolongation in acute exposure
• CBC to eval for hemolysis
• BMP, Mg, phos, Ca, LFTs, CK, type and screen
• CXR if respiratory symptoms 

Treatment

• supportive care, ABCs, IV, O2, monitor
• removal from exposure
• NO charcoal- adsorbs poorly to arsenic
• consider whole bowel irrigation if large radiopaque material in GI tract on xray 
• airway management and mechanical ventilation if acute inhalation of arsine gas and resp distress
• IV fluids
• CHELATION therapy: if severe symptoms present.

1. Dimercaprol (BAL). 3-5 mg/kg IM Q4-6h

Disposition

• admit pt's with significant symptoms
• ED observation and discharge with follow-up for mildly symptomatic pts

Sources

Harwood-Nuss, EMedicine