A RARE CASE OF DRUG-INDUCED METHEMOGLOBINEMIA

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SESSION TITLE: Wednesday Medical Student/Resident Case Report Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/23/2019 09:45 AM - 10:45 AM INTRODUCTION: Rasburicase is a recombinant urate oxidase approved for prevention and treatment of tumor lysis syndrome (TLS). TLS is an expected complication of chemotherapy, but rarely can occur spontaneously when there is increased tumor burden. Given the serious nature of this syndrome and high efficacy of rasburicase, it is not uncommon to prophylactically start therapy if high clinical suspicion exists. Rasburicase induced methemoglobinemia is very rare with an incidence of CASE PRESENTATION: A 56-year-old African American female with no known history of G6PD deficiency presented with tender left breast swelling. CT chest, abdomen and pelvis revealed multiple breast nodules with extensive metastatic disease. Labs revealed significant hyperuricemia and electrolyte disturbances. Rasburicase was administered to prevent spontaneous tumor lysis syndrome. Within 24 hours of rasburicase administration, her oxygen demands drastically increased, eventually requiring mechanical ventilation. Despite maximal oxygen support (FiO2 100%), pulse oximetry was persistently low (SpO2 of 85%) but arterial blood oxygen was high (PaO2 of 438). Co-oximetry revealed elevated methemoglobin levels. Immediate treatment with methylene blue and multiple blood transfusions was initiated which improved her oxygen saturation. DISCUSSION: Rasburicase converts uric acid to allantoin. Hydrogen peroxide is formed as a by-product leading to oxidative stress and formation of methemoglobin. Rasburicase induced methemoglobinemia has a higher incidence in African American males and glucose-6-phosphate dehydrogenase (G6PD) deficient individuals. Clinical presentation includes cyanosis and persistent hypoxia with normal arterial oxygen levels. Pulse oximetry measures relative light absorption at 2 wavelengths to differentiate oxyhemoglobin and deoxyhemoglobin. Methemoglobin increases absorption of light at both these wavelengths resulting in erroneous results. Diagnosis is commonly established by co-oximetry. Treatment recommendations include supplemental oxygen, blood transfusions, ascorbic acid or methylene blue. Methylene blue reduces methemoglobin to hemoglobin with the help of NADPH reductase. This enzyme is inactive in G6PD deficiency hence treatment with methylene blue is avoided. CONCLUSIONS: High level of suspicion should be maintained, if a saturation gap exists. Although methemoglobinemia is a rare side effect of rasburicase treatment, it can be potentially life threatening. Early recognition of this complication is crucial for timely management and to prevent serious outcomes. Reference #1: Alessa MA, Craig AK, Cunningham JM. Rasburicase-Induced Methemoglobinemia in a Patient with Aggressive Non-Hodgkin's Lymphoma. Am J Case Rep. 2015;16:590-3. Published 2015 Sep 3. https://doi.org/10.12659/AJCR.894088 Reference #2: Sherwood GB, Paschal RD, Adamski J. Rasburicase-induced methemoglobinemia: case report, literature review, and proposed treatment algorithm. Clin Case Rep. 2016;4(4):315-9. Published 2016 Feb 3. https://doi.org/10.1002/ccr3.495 DISCLOSURES: No relevant relationships by Kristin Fless, source=Web Response No relevant relationships by Aimen Liaqat, source=Web Response No relevant relationships by Nirav Mistry, source=Web Response No relevant relationships by Vagram Ovnanian, source=Web Response No relevant relationships by Fariborz Rezai, source=Web Response No relevant relationships by Sohaib Tariq, source=Web Response No relevant relationships by Lalithaa Thirunavukarasu Murugan, source=Web Response No relevant relationships by Paul Yodice, source=Web Response