Parathyroid surgery and methylene blue: a review with guidelines for safe intraoperative use.

Methylene blue has been used to help facilitate parathyroid surgery for over 30 years. Its use has been widely considered both safe and cost effective. Twenty-six cases of a toxic metabolic encephalopathy, however, have been reported with its use. As a result, some surgeons have stopped using this technique altogether. It is now known that methylene blue is a monoamine oxidase inhibitor. When combined with drugs that increase central serotonin neurotransmission, serotonin toxicity results. This is the cause of the encephalopathy described in the literature. A case report, review of the literature, and guidelines as to its proper use are presented so as to allow for safe parathyroid surgery.