Dr Ira Shah.
Medical Sciences Department, Pediatric Oncall, Mumbai, India.
ADDRESS FOR CORRESPONDENCE
Dr Ira Shah, 1/B Saguna, 271/B St. Francis Road, Vile Parle (W), Mumbai 400056. | | Abstract | | Methemoglobinemia is a condition in which ferrous iron within hemoglobin is oxidized to ferric iron resulting in impaired oxygen and carbon dioxide transport leading to cyanosis. It occurs as an acquired or congenital variant. Acquired methemoglobinemia occurs from exposure to oxidizing agents such as nitrates, nitrites, aniline dyes and medications such as lidocaine, prilocaine antimalarials. We report a 14 months old girl with acquired methemoglobinemia who developed cyanosis after ingestion of potato wafers consisting of monosodium glutamate. | | | | Introduction | | Methemoglobinemia is a condition in which ferrous iron within hemoglobin is oxidized to ferric iron resulting in impaired oxygen and carbon dioxide transport leading to cyanosis. This ferric state leads to the formation of methemoglobin that causes brownish discoloration of the blood. In healthy normal children, the ferric iron is reduced to ferrous state by the aid of cytochrome b5 oxidase (methemoglobin reductase) along with other systems such as NADH reductase, glutathione reductase and Glucose-6-phosphate dehydrogenase (G-6-PD). Normal concentration of methemoglobin is maintained below 1% in healthy individuals by these enzyme systems (1). Methemoglobinemia occurs as an acquired or congenital variant. Acquired methemoglobinemia is more common and occurs from exposure to oxidizing agents such as nitrates, nitrites, aniline dyes and medications such as lidocaine, prilocaine antimalarials. Pyridium etc (2). It is seen more commonly in premature infants and infants younger than 4 months of age due to presence of fetal hemoglobin and decreased levels of NADH reductase in that age group. Congenital methemoglobinemia is due to either presence of altered hemoglobin (Hemoglobin M) or NADH reductase deficiency. Patients with congenital methemoglobinemia are generally asymptomatic other than cyanosis from birth. Acquired methemoglobinemia is usually mild but can be severe depending upon the cause and can present with cyanosis, dyspnea, lethargy-headache, dizziness and deterioration of mental functioning. A history of exposure to a known toxin or drug may be elicited. (1) We report a child with acquired methemoglobinemia who developed cyanosis after ingestion of potato wafers consisting of monosodium glutamate. | | | | Case Report | | A 14 months old girl born of non-consanguineous marriage presented with cyanosis since 1 day. This was preceded by 4-5 episodes of vomiting after ingestion of Potato wafers containing monosodium glutamate. On examination, she had central and peripheral cyanosis without tachypnea or tachycardia. Other systemic examination was normal. Her pulse oximetry revealed an oxygen saturation of 86%. Investigations showed hemoglobin of 10.5 gm% with normal white cell and platelet count. ABG showed hypoxia with normal pH [pO2 = 55.8, O2 Saturation = 88.3%]. Her methemoglobin levels was 44.5% (Normal = 0-2%). Thus, she was diagnosed as a case of Methemoglobinemia due to ingestion of monosodium glutamate. She was treated with Methylene Blue and Ascorbic Acid following which her Methemoglobin level fell to 14% after 2 days and 2% after 14 days. | | | | Discussion | Methemoglobinemia can be easily diagnosed by pulse oximetry. The severity of cyanosis does not correspond to the pulse oximetry reading. The patient may appear extremely cyanotic but have a pulse oximetry reading in the high 80s. The arterial blood sample will show a normal PaO2 though the blood is chocolate brown. This blood when exposed to 100% oxygen continues to remain brown while deoxygenated blood changes to bright red. The diagnosis and severity of methemoglobinemia can be determined by methemoglobin levels. Methemoglobin levels greater than 1% are normal and symptomatic individuals usually have levels greater than 40-50%. (3)
Treatment consists of IV methylene blue (1-2 mg/kg) as a 1% solution over 5 minutes, repeated in our hour if necessary if methemoglobin levels are greater than 30%. Methylene blue is contraindicated in patients with G-6-PD deficiency as it can lead to severe hemolysis. Methylene blue is an oxidant at levels greater than 1 mg/kg and therefore can cause methemoglobinemia at higher doses. Ascorbic acid (200-500 mg) is found useful in congenital methemoglobinemia when methemoglobin level is above 30%. Rarely exchange transfusion may be required. Patients with acquired methemoglobinemia should avoid future exposure to precipitating agent. (4) | | | | Compliance with Ethical Standards | | Funding None | | | | Conflict of Interest None | | |
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- Herman MI, Chyka PA, Butler AY, Rieger SE. Methylene blue by intraosseous infusion for methemoglobinemia. Ann Emerg Med. 1999; 33: 111-113. [CrossRef]
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| Cite this article as: | | Shah I. METHEMOGLOBINEMIA. Pediatr Oncall J. 2005;2. |
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