Potassium chlorate is a component of some match heads, barium chlorate (see also Barium) is used in the manufacture of fireworks and explosives, sodium chlorate is still a major ingredient in some weed killers used in commercial agriculture, and other chlorate salts are used in dye production. Safer and more effective compounds have replaced chlorate in toothpaste and antiseptic mouthwashes. Chlorate poisoning is similar to bromate intoxication (See Bromates), but chlorates are more likely to cause intravascular hemolysis and methemoglobinemia.
Mechanism of toxicity. Chlorates are potent oxidizing agents and also attack sulfhydryl groups, particularly in red blood cells and the kidneys. Chlorates cause methemoglobin formation as well as increased fragility of red blood cell membranes, which may result in intravascular hemolysis. Renal failure probably is caused by a combination of direct cellular toxicity and hemolysis.
Toxic dose. The minimum toxic dose in children is not established but is estimated to range from 1 g in infants to 5 g in older children. Children may ingest up to 1–2 matchbooks without toxic effect (each match head may contain 10–12 mg of chlorate). The adult lethal dose was estimated to be 7.5 g in one case but is probably closer to 20–35 g. A 26-year-old woman survived a 150- to 200-g ingestion.
Clinical presentation. Within a few minutes to hours after ingestion, abdominal pain, vomiting, and diarrhea may occur. Methemoglobinemia is common (See Methemoglobinemia). Massive hemolysis, hemoglobinuria, and acute tubular necrosis may occur over 1–2 days after ingestion. Coagulopathy and hepatic injury have been described.
Diagnosis usually is based on a history of exposure and the presence of methemoglobinemia (via co-oximetry) and hemolysis.
Specific levels. Blood levels are not available.
Other useful laboratory studies include CBC, haptoglobin, plasma free hemoglobin, electrolytes, glucose, BUN, creatinine, bilirubin, methemoglobin level, prothrombin time, liver aminotransferases, and urinalysis.
Emergency and supportive measures
Maintain an open airway and assist ventilation if necessary (See Airway and Breathing).
Treat coma (See Coma and stupor), hemolysis, hyperkalemia, and renal or hepatic failure (See Diagnosis of Poisoning) if they occur.
Massive hemolysis may require blood transfusions. To prevent renal failure resulting from deposition of free hemoglobin in the kidney tubules, administer IV fluids and sodium bicarbonate.
Specific drugs and antidotes
Treat methemoglobinemia with 1% solution of
(See Methylene Blue), 1–2 mg/kg (0.1–0.2 mL/kg). Methylene blue is reportedly most effective when used early in mild cases but has poor effectiveness in severe cases in which hemolysis has already occurred.
(See Thiosulfate, Sodium) may inactivate the chlorate ion and has been reported to be successful in anecdotal reports. However, this treatment has not been clinically tested. Administration as a lavage fluid may potentially produce some hydrogen sulfide, so it is contraindicated.
Decontamination (See Decontamination). Administer activated charcoal orally if conditions are appropriate (see Table I–38). Gastric lavage is not necessary after small to moderate ingestions if activated charcoal can be given promptly. ...