Methylene blue (MB) has been applied clinically as blue dye since introduced by Keaveny in 1968 for identification of parathyroid adenoma as it can be uptake by endocrine tissues easily. From then on, MB was widely used to aid naked eyes to identify parathyroid glands or insulinomas which was coloured blue in thyroid/parathyroid surgery or pancreatic surgery , but after a high-dose intravenous injection (3-7.5mg/kg). High-dose MB not only stains the operative field, but also brings a substantial risk of serious adverse events, such as toxic metabolic encephalopathy and exerting neurotoxic effects on the central nervous system .