Determination of nitrites
Last reviewed: 23.04.2024
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Poisoning with nitrites, sodium nitroprusside, nitroglycerin, as well as chlorates, sulfonamides, aniline dyes, nitrobenzene, antimalarial drugs, butyl nitrite or amylnitrite can cause methemoglobinemia. In methemoglobin (MetHb), iron is oxidized to a form of ferric iron, which is incapable of binding and carrying oxygen. Symptoms of intoxication include headache, fatigue, dyspnoea, palpitations, dizziness and generalized cyanosis (indicating MetHb concentrations in the blood above 15%). Cyanosis does not decrease with inhalation of oxygen and is combined with normal p a O 2.
The diagnosis of nitrite poisoning is confirmed by the determination of the level of MetHb in the blood. The content above 50% indicates severe intoxication, which is usually accompanied by CNS depression, convulsions, coma, and heart rhythm disturbances; the level above 75% is fatal. In some cases of toxic methemoglobinemia, the Heinz-Erlich body (rounded eosinophilic or dark violet inclusions consisting of defective hemoglobins) is revealed in the blood test. Hospitalization is indicated for all patients with clinical manifestations of methemoglobinemia and a MetHb level above 20%.