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Chapter: Modern Medical Toxicology: Chemical Poisons: Heavy Metals

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Barium - Chemical Poisons

Important derivatives include barium sulfate, sulfide, chloride, and carbonate.


Barium

Important derivatives include barium sulfate, sulfide, chloride, and carbonate.

Uses

·              Rat poison—barium carbonate, hydroxide, or chloride.

·              Depilatory—barium sulfide.

·              Gastrointestinal x-ray—barium sulfate (the “barium meal”).

·              Golf balls—barium sulfate (along with calcium carbonate, zinc sulfide, castor oil, and fish oils).

·              All water or acid soluble barium salts are highly toxic. The most commonly involved in poisoning (accidental or intentional) are the following: barium carbonate (a white powder), barium fluoride, barium sulfide, barium oxide (a white to yellowish powder), barium chloride, barium acetate, and barium sulfate (water-insoluble, white or yellowish, odourless, tasteless, fine, heavy orthorhombic powder or crystalline solid).

Usual Fatal Dose

·               Barium carbonate—60 to 70 mg/kg

·              Barium chloride—12 to 20 mg/kg

·              It has been reported that the LD50 for barium ingestion is 1 gram.

Mode of Action

·      Hypokalaemia (Table 9.10), and neuromuscular blockade: The rapid onset of the marked hypokalaemia so charac-teristic of barium intoxication is due to sequestering of potassium by muscle cells. Barium clogs the exit channel for potassium ions in skeletal muscle cells.


·      Barium stimulates striated, smooth, and cardiac muscle resulting in violent peristalsis, arterial hypertension and arrhythmias.

Clinical Features

·      GIT—Salivation, vomiting, abdominal pain, diarrhoea.

·      CNS—Mydriasis, paraesthesias, depressed tendon reflexes,headache, confusion, convulsions.

·      CVS—Hypertension, cardiac arrhythmias (prematureventricular complexes, ventricular tachycardia, bradycardia and ventricular fibrillation asystole/fibrillation.

·      LMS—Myoclonus, myalgia, cramps, dysarthria, flaccidquadriplegia.

·      RS—Pulmonary oedema, respiratory failure.

·      Hypokalaemia, metabolic and respiratory acidosis, and renal failure are commonly reported. In fact, quadriplegia is usually the result of severe hypokalaemia.

·      Oral or rectal barium sulfate administration may cause constipation, impaction, obstruction, cramping, diarrhoea, and perforation of the bowel. Appendicitis, bowel perfo-ration, peritonitis and proctitis have been reported after oral or rectal barium sulfate use in radiologic procedures. ECG abnormalities have also been reported. Aspiration of barium sulfate may cause pneumonitis, granuloma forma-tion, severe dyspnoea, and hypoxaemia. Barium sulfate is almost insoluble and lacks the severe toxicity characteristic of ingestion of other salts.

·      Allergic reactions (including anaphylaxis) can occur following barium sulfate administration for radiologic purposes.

Diagnosis

·      X-ray of abdomen.

·      Blood barium level.

Treatment

·      Gastric decontamination (emesis, lavage). For lavage, 5 to 10 grams sodium sulfate can be added to the solution.

·              Monitor cardiac rhythm and serum potassium. Cardiac arrhythmias usually respond to potassium administration.

If not, consider lignocaine, amiodarone, or procainamide.

·      IV fluids (liberally, to flush out barium by diuresis). Administer 0.45% NaCl in D5W, and a diuretic such as intravenous furosemide (1 mg/kg to a maximum of 40 mg/ dose) to obtain a urine flow of 3 to 6 ml/kg/hr. Saline and furosemide forced diuresis has been reported to enhance barium elimination. If initial hydration is necessary, admin-ister 0.45% saline to which sodium bicarbonate has been added to bring to isotonic 80 mEq/L at 20 to 30 ml/kg/hr for the first few hours. 30 grams magnesium sulfate through a nasogastric tube (250 mg/kg for children). It precipitates the compound ingested into insoluble barium sulfate. In the past intrave-nous magnesium sulfate was recommended. This should be avoided because renal injury may result due to intrarenal precipitation of barium sulfate.

·      Treat hypokalaemia with potassium infusions (up to 250 mEq administered over 24 hours has been effective).

·      Haemodialysis.

·      Mild to moderate allergic reactions to barium sulfate administration can be managed with antihistamines, with or without inhaled beta agonists, corticosteroids or adrenaline. Treatment of severe anaphylaxis necessitates oxygen supplementation, aggressive airway management, adrenaline, ECG monitoring, and IV fluids.

Autopsy Features

·      Haemorrhagic gastritis and duodenitis.

·      Pulmonary oedema.

Forensic Issues

·              Most cases are accidental, usually the result of mistaken iden- tity, when a soluble barium salt is administered for a “barium meal” instead of the insoluble barium sulfate. Barium salts are sometimes also mistakenly ingested in place of Epsom salt, Glauber’s salt, or even common salt. Inhalation of a “barium meal” can produce granulomas in the lungs.

A few cases of mass poisonings have been reported, the most remakable being Pa Ping an endemic form of periodic paralysis which occurred in the early 1940s in the Szechuan province of China. This was due to massive contamination of table salt by barium chloride.

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