A 48-year-old man comes to the emergency department because of a 1-day history of weakness, shortness of breath, and blue discoloration of his lips. Medical history is remarkable for dermatitis herpetiformis, for which treatment with dapsone was started 10 days ago. He also has major depressive disorder treated with fluoxetine. He has smoked ten cigarettes daily for the past 32 years. His mother has celiac disease. The patient appears distressed. Temperature is 36.9°C (98.4°F) , pulse is 120/min, and respirations are 24/min. Pulse oximetry on room air shows an oxygen saturation of 85%. Cardiopulmonary examination discloses no abnormalities. Arterial blood gas analysis on room air shows:
PH 7.7
PCO₂ 17 mm Hg
PO₂ 99 mm Hg
Which of the following is the most appropriate next step in the treatment of this patient's current condition?

Question

Quizplus · Accepted Answer

Eductional Objective: Acquired methemoglobinemia is a rare blood disorder most commonly caused by exposure to exogenous substances that increase methemoglobin (MetHb) levels, such as dapsone, nitroglycerin, sulfonamides, and inhaled nitric oxide. Apart from discontinuing the offending medication, intravenous methylene blue is the first-line treatment for methemoglobinemia. However, it is contraindicated in patients with G6PD deficiency and those taking serotonergic drugs (e.g., fluoxetine), because it may precipitate hemolysis and/or serotonin syndrome. In those patients, ascorbic acid is the drug of choice. In patients who fail to respond to pharmacotherapy, exchange transfusion or hyperbaric oxygen therapy should be considered.

A 48-Year-Old Man Comes to the Emergency Department Because of a 1-Day