367 Red Blood Cell Exchange for Treatment of Acquired Methemoglobinemia in a Hospitalized Patient: A Case Report

Abstract

Most cases of methemoglobinemia are acquired, usually due to exposure to drugs/chemicals that cause increased formation of methemoglobin by directly oxidizing oxyhemoglobin to methemoglobin. We present a case of severe methemoglobinemia that resolved rapidly with red blood cell exchange (RBCX). The patient is a 57-year-old African-American woman with stage IV rectal adenocarcinoma, hepatitis C, arthritis, and bipolar disorder who was admitted to the hospital with a partial small bowel obstruction, for which she was treated conservatively. On hospital day five, the patient developed acute confusion and diaphoresis, and her oxygen saturation was noted to be 73%-75%. ABG was drawn, the blood was noted to be chocolate brown, and the methemoglobin level was too high to be quantitated (on three separate co-oximeters). The patient admitted to going through almost two bottles of HurriCaine spray (benzocaine) that morning for her sore throat. Methylene blue was considered for treatment, but the patient was on three different selective serotonin reuptake inhibitors at the time and there was concern for the precipitation of serotonin syndrome. Ascorbic acid was also considered, but the hospital did not have sufficient quantities on hand. The decision was made to proceed with RBCX. Using the Spectra Optia Apheresis system (Terumo BCT, Lakewood, CO), a 2.0 RBC volume RCBX was completed, using nine units of leukocyte-reduced type A positive packed red blood cells. Rinseback was not done. After the 108-minute uncomplicated procedure, the patient's methemoglobin level was 5.8%, and she subjectively felt much better and no longer had signs of cyanosis. Her O2 saturation was 97% on 2L nasal cannula, and the methemoglobin level was 1.7% 11.5 hours after the RBCX. Fewer than 10 cases of RBCX for methemoglobinemia have been published.