A 62 year- old woman, weighing 60 kg with ASA I was scheduled for sentinel lymph node biopsy. Her pulse oximetry values rapidly declined to a nadir of 88 % 30 min after subcutaneous injection of isosulfan blue. Arterial blood gas analysis revealed methemoglobinemia ([MetHb] = 5.2 %). Following 3 L/min O2 administration via nasal CPAP mask and 2x500 mg iv ascorbic acid treatment, methemoglobin levels dropped to 1.7 % after 15 hours. Although abnormal pulse oximetry has already been reported in association with isosulfan blue administration , methemoglobinemia due to isosulfan blue was reported just in a few cases.
Keywords: Methemoglobinemia, isosulfan