LAUSR

BACKGROUND Methylene blue (MB) has been used to treat methemoglobinemia. Recently, a fluorescence imaging technique using MB as a fluorophore was used in several region but still not in hepatobiliary and pancreatic surgery; thus, information on the safety of intraoperative fluorescence imaging using MB in a healthy Japanese population is lacking. We aimed to evaluate the usefulness of MB fluorescence imaging in patients undergoing hepatobiliary and pancreatic surgery and the safety of intraoperative administration of MB in patients without methemoglobinemia. METHODS Eighteen patients undergoing hepatobiliary and pancreatic surgery were enrolled. We developed and used a fluorescence imaging system to visualize MB as fluorescence. The fluorescence intensity of the blood vessels, tumors, liver, and intestine were measured. The primary endpoint was the ability of the MB fluorescence imaging to visualize vessels and tumors with fluorescence. The secondary endpoint was the safety of fluorescence imaging using MB in patients without methemoglobinemia. RESULTS For the 18 patients undergoing MB fluorescence imaging, no intraoperative and postoperative complications related to MB administration occurred. Seventeen patients (94%) successfully visualized the target object as fluorescence by MB fluorescence imaging, including 100% of neuroendocrine tumors (4 tumors) and peripancreatic vessels (n=13). CONCLUSION The administration of MB and application of fluorescence imaging using MB can visualize blood vessels and pancreatic neuroendocrine neoplasms. And it also showed the safety of using MB as a fluorophore in Japanese patients without methemoglobinemia.