RESUMO
Methemoglobinemia is a condition in which the iron portion of hemoglobin, which binds to oxygen, is oxidized to produce methemoglobin, which increases blood concentration. There are many causes of methemoglobinemia, the most common being food, drugs, and chemicals. A 75-year-old male patient who had taken an herbicide did not notice any nonspecific symptoms. However, after 4 hours, his methemoglobin levels increased to 17.1%, while after 7 hours it increased to 26.5%, at which time intravenous administration of methylene blue 1 mg/kg (an antidote) was started. After a total of five doses of methylene blue at 1 mg/kg due to reactive methemoglobinemia for about 36 hours, the methemoglobin levels increased to 23.7%. Because no more methylene blue could be administered, 10 g of ascorbic acid (vitamin C) was administered intravenously. After 82 hours, ascorbic acid 10 g was administered six times for repeated reactive methemoglobinemia. No additional reactive methemoglobinemia was observed. The ventilator and endotracheal tube were successfully removed on day 5 after admission.