Methemoglobinemia is a condition in which the iron within the hemoglobin is oxidized from the ferrous (Fe2+) state to the ferric (Fe3+) state, resulting in an inability to transport oxygen to the tissues. Acquired methemoglobinemia, more common than the congenital forms, has been reported following exposure to a number of medications and oxidizing substances. Presentation may vary from cyanosis to frank seizures, coma and death depending on the levels of methemoglobin (MetHb) in blood. MetHb levels more than 70% have almost always reported to have been fatal. However, the level of MetHb may not always correlate with severity of illness or predict outcomes in these cases as was seen in the two cases reported here. While a 6 year old boy with thinner ingestion and MetHb levels of 85% survived, an adolescent girl with levels of 28.5% succumbed to her injuries. Both the children presented with severe respiratory distress and cyanosis that persisted despite 100% oxygen and positive pressure mechanical ventilation. Methemoglobinemia was suspected in both cases due to the presence of ‘oxygen saturation gap’ and confirmed by estimating the blood MetHb levels. Despite an alarmingly high MetHb level the boy survived probably due to early presentation and aggressive goal directed resuscitation. On the other hand, the girl with levels of only 28.5% succumbed to her injuries probably due to delayed presentation and prolonged cerebral anoxia prior to presentation.

Key words: Methemoglobinemia; Methylene blue; Oxygen saturation gap.