Anesthetic management of a patient with congenital methemoglobinemia

Methemoglobinemia occasionally causes cyanosis particularly in congenital methemoglobinemia. Avoidance of exposure to oxidizing agents is important for patients with congenital methemoglobinemia because of their deficient enzymatic pathways and decreased oxygen-carrying capacity. Here, we present a patient with preoperatively undiagnosed congenital methemoglobinemia who underwent uterine myomectomy under general anesthesia. The patient was a 35-year-old woman who displayed a low pulse oximetry reading of 91% prior to induction of anesthesia. Methemoglobinemia was first suspected intraoperatively because of a mismatch of SpO₂ of finger pulse oximetry and SaO₂ of arterial blood, and was later confirmed by multiple-wavelength CO-oximetry. The pathophysiology, etiology, clinical manifestations, anesthetic considerations, and treatment options of methemoglobinemia are discussed.