Severe decrease in SpO2 and methemoglobinemia following subareolar isosulfan blue administration and clinical relevance.

The level of axillary lymph node involvement in breast cancer is a critical decision factor for adjuvant therapy and the most important indicator of prognosis and survival. Sentinel lymph node biopsy is a minimally invasive technique with low morbidity in axillary staging of breast cancer. Radiocolloid substances (Technetium-99m) and/or blue dyes such as methylene blue or isosulfan blue are used during sentinel lymph node biopsy. Isosulfan blue stain is frequently used in sentinel lymph node biopsy and rarely causes complications. The present case report presents a severe decrease in SpO2 due to methemoglobinemia following isosulfan blue administration as well as skin and urine signs and inconsistency with clinical picture in a 67-year-old, 77 kg, ASA II female case who underwent sentinel lymph node biopsy under general anesthesia.