(1442) Methemoglobinemia in Renal Failure: A Case of Sustained and Refractory Hypoxia

Introduction: Methemoglobinemia (MetHb) is a rare but known adverse effect of rasburicase. Here we present a case in a patient with unexplained hypoxemia after receiving rasburicase to treat hyperuricemia.

Description: A healthy 14-year-old male presented with hypertension, proteinuria, and hematuria concerning for rapidly progressing glomerulonephritis. Evaluation revealed multiple electrolyte abnormalities, renal US suggesting kidney disease, low C3, and anemia. He was treated with pulse dose steroids and given rasburicase for hyperuricemia. Following administration, he developed persistent hypoxemia with SpO2 in the 60-70s despite lack of respiratory distress. VBG and chest x-ray were reassuring. Cooximetry obtained and revealed MetHb elevated to 17.9. He was transferred to the PICU for administration of methylene blue which decreased MetHb level to 14.1. Enteral ascorbic acid was started and levels quickly normalized. He continued to have unexpected, persistent hypoxemia for 48 hours after receiving methylene blue. This was thought to be secondary to oliguric AKI given methylene blue is renally excreted. During this time ABGs were used to monitor oxygenation. He was suspected to have underlying G6PD deficiency as the cause of MetHb. Renal biopsy revealed PIGN.

Discussion: MetHb is an uncommon condition that can be life-threatening if not recognized quickly. It decreases oxygen carrying capacity of hemoglobin due to conversion of the ferrous state of iron to the oxidized ferric state which is unable to bind to oxygen. Cyanosis can occur with MetHb levels as low as 10% and levels greater than 50% carry the risk of seizures, acidosis, and death. In this case the cause of MetHb was suspicious for G6PD, one of the most common human enzyme defects. Treatment with methylene blue is controversial with a diagnosis of G6PD given that it can precipitate hemolytic crisis via unreduced methylene blue causing further oxidative damage. However, it should not be withheld in severe cases. In this case there was concern for hemolysis but he stabilized with one transfusion of RBCs and was able to discharge home once his renal function improved and hypoxemia resolved. Clinicians should be mindful of the potential for sustained cyanosis following methylene blue administration in the setting of renal dysfunction.