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Determination of nitrite
Medical expert of the article
Last reviewed: 05.07.2025
Poisoning with nitrites, sodium nitroprusside, nitroglycerin, as well as chlorates, sulfonamides, aniline dyes, nitrobenzene, antimalarials, butyl nitrite, or amyl nitrite can cause methemoglobinemia. In methemoglobin (MetHb), iron is oxidized to the ferric form, which is unable to bind and transport oxygen. Symptoms of intoxication include headache, fatigue, dyspnea, palpitations, dizziness, and generalized cyanosis (indicating a MetHb concentration in the blood above 15%). Cyanosis is not reduced by oxygen inhalation and is combined with a normal p a O 2.
The diagnosis of nitrite poisoning is confirmed by measuring the MetHb level in the blood. A level above 50% indicates severe intoxication, which is usually accompanied by CNS depression, seizures, coma, and cardiac arrhythmia; a level above 75% is fatal. In some cases of toxic methemoglobinemia, blood tests reveal Heinz-Ehrlich bodies (rounded eosinophilic or dark purple inclusions consisting of defective hemoglobins). Hospitalization is indicated for all patients with clinical manifestations of methemoglobinemia and a MetHb level above 20%.
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