(1658) Once in a Blue Moon: A Case of Acquired Methemoglobinemia in the Postoperative Period

Introduction: Methemoglobinemia is a rare blood disorder characterized by an elevated percentage of methemoglobin in the blood, which impairs oxygen delivery and can lead to hypoxemia. It can be congenital or acquired, and has multiple potential causes. Patients with conditions such as anemia, lung disease, sepsis, abnormal hemoglobin, sickle cell disease, and those at the extremes of age (less than 6 months and the elderly) are at higher risk for symptomatic methemoglobinemia at lower levels of methemoglobin compared to their healthy counterparts.

Description: We present the case of a 75-year-old male with an extensive medical history who developed acquired methemoglobinemia on postoperative day (POD) 18 while in the cardiovascular intensive care unit (CVICU). Although the exact cause is unknown, the patient had undergone fiberoptic bronchoscopy with exposure to topical lidocaine in the context of recent inhaled nitric oxide use. His methemoglobin level peaked at 13.5%. Upon identification, inhaled nitric oxide was discontinued, and the patient was treated with 200 mg of methylene blue, resulting in a reduction of methemoglobin levels to 4.2%.

Discussion: Treatment of methemoglobinemia involves first removing the precipitating agent and providing supportive care. In severe cases, methylene blue is the treatment of choice. In this patient, the etiology of methemoglobinemia is unclear, but a congenital variant is unlikely due to stable methemoglobin levels during a prolonged ICU stay and immediate stabilization following treatment. Contributing factors included untreated sepsis, multisystem organ failure (acute renal and liver failure, anemia), 17 hours of inhaled nitric oxide at 40 PPM, and topical lidocaine exposure during bronchoscopy.
While no specific inciting factor was definitively identified, this case highlights the complex interplay of multisystem organ failure, untreated sepsis, and therapeutic agents in the pathogenesis of methemoglobinemia. The clinical impact, though brief, underscores the importance of timely recognition and treatment of this rare metabolic condition.