Hyperbaric oxygenation in the treatment of life-threatening isobutyl nitrite-induced methemoglobinemia--a case report.

Methemoglobinemia usually results from exposure to oxidizing substances such as nitrates or nitrites. Iron within hemoglobin is oxidized from the ferrous (Fe2+) state to the ferric (Fe3+) state, resulting in the inability to transport oxygen and carbon dioxide. Clinically, this condition causes functional cyanosis. As methemoglobin levels increase, patients show evidence of cellular hypoxia in all tissues. Death usually occurs when methemoglobin fractions approach 70% of total hemoglobin. We describe the case of a 35-year-old female patient with severe life-threatening isobutyl nitrite-induced methemoglobinemia of 75% of total hemoglobin. Toluidine-blue was administered as first-line antidotal therapy immediately, followed by hyperbaric oxygenation. The patient recovered uneventfully and could be discharged 3 days later.