Methaemoglobinaemia as a result of sodium nitrate poisoning.

Abstract

Sir We report a case of methaemoglobinaemia as a result of sodium nitrite poisoning. Early recognition and administration of the specific antidote methylene blue may lead to complete recovery. A 39-year-old man ingested 100 ml of a liquid he believed to be beer. On arrival in our department he was deeply cyanosed and unconcious with a pulse of 140 and a blood pressure of 70 systolic. Endotracheal intubation and ventilation with 100% oxygen failed to improve the cyanosis and a clinical diagnosis of methaemoglobinaemia was made. Despite intravenous methylene blue he developed an asystolic cardiac arrest from which he could not be resuscitated. Subsequent analysis of the ingested fluid showed it to contain 33.5% sodium nitrite. Sodium nitrite is used in industry during the manufacture of dyes and synthetics and is also used in low concentrations as a meat preservative. There are reports of nitrite poisoning due to' its excessive use a meat preservative (Walley et al., 1987) or as a result of mistaking sodium nitrite for table salt (McQuiston 1936). Abuse of organic nitrites by ingestion or inhalation for their psychodelic and stimulant properties may also lead to methaemoglobinaemia (Shesser et al., 1981). Small doses of sodium nitrite may produce headache, vomiting, diarrhoea, flushing and cyanosis. Ingestion of more than 1 g of sodium nitrite leads to rapid cardiovascular collapse and death (Polson et al., 1969). Typically, samples of the patients blood are dark brown and confirmation of the diagnosis is obtained by measuring serum methaemoglobin levels. Treatment of nitrite poisoning consists of the administration of high concentrations of oxygen and methylene blue intravenously in a dose of 1-2mgkg-1 body weight. Methylene blue acts by promoting reduction of the oxidized haem iron back to its ferrous state (Polson et al., 1969). Nitrite poisoning and methaemoglobinaemia are rare, however awareness of this condition in the cyanosed patient unresponsive to oxygenation and early administration of methylene blue may be life saving. It is recommended that methylene blue is available in Accident and Emergency A&E units for use in such cases.