20 - Arsenic Poisoning

MAIN SOURCES :

Smelting and microelectronics industries; wood preservatives, pesticides, herbicides, fungicides; contaminant of deep-water wells; folk remedies; and coal; incineration of these products

METABOLISM :

Organic arsenic (arsenobentaine, arsenocholine) is ingested in seafood and fish, but is nontoxic; inorganic arsenic is readily absorbed (lung and GI); sequesters in liver, spleen, kidneys, lungs, and GI tract; residues persist in skin, hair, and nails; biomethylation results in detoxification, but this process saturates.

TOXICITY :

Acute arsenic poisoning results in necrosis of intestinal mucosa with hemorrhagic gastroenteritis, fluid loss, hypotension, delayed cardiomyopathy, acute tubular necrosis, and hemolysis.

Chronic arsenic exposure causes diabetes, vasospasm, peripheral vascular insufficiency and gangrene, peripheral neuropathy, and cancer of skin, lung, liver (angiosarcoma), bladder, kidney.

Lethal dose: 120–200 mg (adults); 2 mg/kg (children).

DIAGNOSIS :

Nausea, vomiting, diarrhea, abdominal pain, delirium, coma, seizures; garlicky odor on breath; hyperkeratosis, hyperpigmentation, exfoliative dermatitis, and Mees' lines (transverse white striae of the fingernails); sensory and motor polyneuritis, distal weakness. Radiopaque sign on abdominal x-ray; ECG–QRS broadening, QT prolongation, ST depression, T-wave flattening; 24-h urinary arsenic >67 micromoles/day; (no seafood x 24 h); if recent exposure, serum arsenic >0.9 micromoles/L ( 7 micrograms/dL) . High arsenic in hair or nails .

TREATMENT :

If acute ingestion, ipecac to induce vomiting, gastric lavage, activated charcoal with a cathartic. Supportive care in ICU.

Dimercaprol 3–5 mg/kg IM q4h x 2 days; q6h x 1 day, then q12h x 10 days; alternative: oral succimer.

19 - organophosphorous poisoning mcqs

1q: a 5 year old child presents with confusion, increased salivation, lacrimation, fasciculations, miosis, tachycardia and hypertension. Which of the following poisons can cause these manifestations ?

a. opium
b. organophosphorous insecticide
c. dhatura
d. organochlorine pesticide

answer b. organophosphorous insecticide

explanation : only opium and organophosphorous insecticides out of the above 4 options cause miosis . it is to be noted that dhatura ( atropine ) and organochlorine cause mydriasis .

organsophosphate poisoning : organophosphate poisons irreversibly inhibit acetylcholinesterase and cause accumulation of acetylcholine at muscarinic and nicotinic receptors .

Muscarinic effects of organosphosphorous poisons are :

1. miosis and blurred vision
2. increased sweating, salivation, lacrimation
3. increased bronchial secretions, bronchoconstriction
4. abdominal cramps, diarrhea, nausea, vomiting
5. urinary frequency and incontinence

Nicotinic effects of organophosphorous poisons are :

1. on striated muscles – twitching, fasciculations, cramps and muscle paralysis
2. on sympathetic ganglia – hypertension and tachycardia

CNS effects of organophosphorous poisons are :

1. anxiety , restlessness and confusion
2. seizures and coma

- this child presents with tachycardia and hypertension which are nicotinic manifestations. Sometimes the presentation can vary due to the muscarinic effect on cardiovascular system which causes bradycardia and hypotension , but this occurs due to severe organosphosphorous poisoning .

This question was asked in the november 2002 AIIMS question paper .