Presentation of dapsone-induced methemoglobinemia in a patient status post small bowel transplant

Methemoglobinemia, an uncommon hemoglobinopathy, affects oxygen transport, causing tissue hypoxia. In the perioperative period, methemoglobinemia is often overlooked as a cause of low oxygen saturation, often mistaken for the more common causes of hypoxia, such as atelectasis, pulmonary edema, or pulmonary embolus, among other causes of respiratory failure. Most cases of methemoglobinemia in the perioperative period are precipitated by local anesthetics, especially benzocaine. Dapsone, a sulfone antibiotic, is used for prophylaxis against Pneumocystis carinii pneumonia in immunosuppressed patients. It is commonly used in organ transplant patients, especially those intolerant to sulfa. With the expansion of organ transplantation and improved long-term survival of these patients, presentation of status post organ transplant patients for surgery will inevitably increase. We report a case of dapsone-induced methemoglobinemia observed in a status post small bowel transplant patient in the postanesthesia care unit.