Appropriate timing and velocity of infusion for the selective staining of parathyroid glands by intravenous methylene blue

Background: Intraoperative parathyroid gland (PTG) identification by selective staining using methylene blue dye (MB) infusion has been shown effective but the degree of gland staining is inconsistent. Methods: The effect of timing and rate of MB infusion on gland uptake was investigated in a canine model by infusing MB either rapidly over 3 to 5 minutes (n = 8) or slowly over 30 minutes (n = 4). The pattern of dye uptake in an exposed PTG was determined by standardized serial photography. Results: Earliest uptake occurred between 10 and 20 minutes after infusion, and maximum uptake averaged 21 minutes, earlier than previously described. Rate of infusion did not affect staining. Conclusions: This rapid uptake of methylene blue by the parathyroid glands suggests that its selective intraoperative use when glands are difficult to locate intraoperatively, rather than a routine preoperative infusion, is possible without significant operative delay. Clinical experience has confirmed this impression