The Acute Treatment of Methemoglobinemia in Pregnancy.

BACKGROUND: Methemoglobinemia can be a potentially lethal condition due to the hypoxic stress placed on the body. In pregnancy, the deleterious effects can be even more catastrophic. The benefits of treatment in all patients, especially in those who are pregnant, must outweigh the inherent risks of the therapies used to treat methemoglobinemia. CASE REPORT: We present a case of a 26-year-old Hispanic pregnant female at 30 weeks gestation presenting to the emergency department for chest pain, hypoxia, and cyanosis. She was subsequently diagnosed with methemoglobinemia, treated with methylene blue, and admitted to the intensive care unit with toxicology and obstetrics consultations. As an outpatient, the patient underwent genetic testing and was diagnosed with homozygous cytochrome b5 reductase deficiency as the etiology of the methemoglobinemia. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Methemoglobinemia is a rare, potentially lethal, but treatable condition. In the setting of pregnancy, methemoglobinemia can pose a significant risk to the mother and fetus by causing acute hypoxia. Because methemoglobinemia can be acquired or congenital, treatments vary based on the etiology. Methylene blue is the mainstay treatment for symptomatic methemoglobinemia of levels > 20%. The teratogenic risks of methylene blue require risk-benefit analysis and discussion with the patient before utilization. Systemic maternal administration is theorized to be of lowest risk to the fetus. In this case, methylene blue was used safely as an emergent therapy for congenital methemoglobinemia during pregnancy.