C53-22 Rasburicase-Induced Methemoglobinemia in an Acutely Hypoxic Patient: A Case Report

Abstract Introduction Methemoglobinemia is an uncommon cause of hypoxia in critically ill patients. Here we present a case of suspected rasburicase-induced methemoglobinemia requiring intubation secondary to hypoxia. Case Presentation A 67-year-old female with a history of newly diagnosed high grade neuroendocrine carcinoma of the colon with liver metastasis presented to oncology clinic with worsening abdominal pain and nausea, and then admitted for inpatient chemotherapy. She was found to have tumor lysis syndrome with electrolyte abnormalities and an elevated uric acid level for which she received a dose of rasburicase with fluids. The following day, the patient became acutely hypoxic to 80% on room air. Oxygenation did not improve despite progressively increasing supplemental oxygen. An arterial blood gas (ABG) on high flow nasal cannula revealed pH 7.46, pO2 445, pCO2 31. The patient was transferred to the intensive care unit and intubated, however she remained hypoxemic with saturations as low as 40-60% despite maximal ventilator settings. Post-intubation ABG revealed significant discordance in oxygenation, with pH 7.44, pO2 447, pCO2 34. Initially, pulmonary embolism was initially highest on the differential given the patient’s acute decompensation and new cancer diagnosis, however the patient was too unstable for radiographic scan. Chest x-ray was negative for pulmonary edema, pneumothorax or other etiologies. Bedside echocardiogram was negative for pericardial effusion, cardiac tamponade, heart failure, evidence of right heart strain and intra-cardiac shunt. A methemoglobinemia level was checked and was elevated to 12.5%. Two doses of methylene blue were administered along with ascorbic acid and a unit of blood, with improvement in saturations to 80-90%. Methemoglobin levels improved to 9% and eventually 7.1%. Prior to administration of methylene blue, a glucose-6-phosphate dehydrogenase (G6PD) level was within normal limits. The patient recovered from the hypoxemia but later succumbed to multi-system organ failure related to sepsis. Discussion Rasburicase-induced methemoglobinemia is an extremely rare but documented complication. A recent systematic review found 43 published reports documenting this phenomenon. Notably, few of these cases progressed to requiring critical care time and intubation. Additionally, a diagnosis of G6PD deficiency alters management, as methylene blue is not recommended in these patients and exchange transfusion may instead be required. This patient’s G6PD screen was negative, however a follow-up level could not be obtained. This case highlights the diagnostic challenges of identifying methemoglobinemia early in hypoxic patients. Early consideration of this diagnosis and identifying potential triggers is important in the critical management of these patients. This abstract is funded by: n/a