A Patient with "Rebound Methemoglobinemia" during Treatment of Methemoglobinemia Caused by Propanil Intoxication

ABSTRACT

Methemoglobinemia results from the oxidation of ferrous iron (Fe++) to ferric iron (Fe+++) within hemoglobin. It is caused by various etiologies, including the herbicide Propanil. Patients with low levels of methemoglobin (metHb) are asymptomatic but symptomatic patients and patients with high levels of metHb require treatment. Methylene blue is the first choice for the treatment of methemoblobinemia, but has some complications such as hemolytic anemia and rebound methemoglobinemia. We report the case of a 91-year-old woman who died of aniline herbicides poisoning. The level of metHb in her blood was initially 20.7% and her mental status was drowsy. She was intravenously treated with methylene blue within a therapeutic range for methemoglobinemia. After treatment with methylene blue, the level of metHb decreased but later increased above 20%. Methylene blue treatment was repeatedly attempted, but the patient suffered from hemolytic anemia and rebound methemoglobinemia. The patient finally died from renal failure and cardiopulmonary collapse. We must be careful because methemoglobinemia can occur even when treated pesticides such as propranil.