Methylene blue-associated serotonin syndrome: a 'green' encephalopathy after parathyroidectomy.
BACKGROUND
Methylene blue (MB) infusion is frequently used to localize the parathyroid glands during parathyroidectomy and generally considered safe. Several recent reports suggest neurological toxicity and post-operative altered mental state typically after large dose infusions. The mechanism by which MB has neurotoxic effects in some patients remains uncertain.


RESULTS



METHODS
A 67-year-old male underwent lumbar laminectomy followed by parathyroidectomy. Postoperatively, he was comatose (Glasgow Coma Scale of 7) and underwent extensive neurological evaluation. Brain computed tomography (CT) imaging and CT angiography revealed no ischemia, vessel occlusion, or hemorrhage. Electroencephalogram (EEG) showed only slowing of cerebral hemispheric activity bilaterally. Over the next 48 h, his mental status slowly improved and the patient made a full neurological recovery (Glasgow Coma Scale 15).


CONCLUSIONS
Methylene blue, when used in patients on antidepressant drugs, may be associated with a transient encephalopathic state and serotonin syndrome. Patients on antidepressants undergoing parathyroidectomy who may receive MB infusion should be considered for alternative parathyroid gland identification or discontinuation of the antidepressants before surgery. MB-associated serotonin syndrome is an increasing and under recognized ('green') post-operative encephalopathy that warrants education to critical care neurologists and other physicians.
Rowley
Michael
M
Department of Anesthesiology, Mayo Clinic, Jacksonville, FL 32224, USA.
Riutort
Kevin
K
Shapiro
David
D
Casler
John
J
Festic
Emir
E
Freeman
William D
WD
D000368:Aged; D001927:Brain Diseases / Q000139:chemically induced / Q000000981:diagnostic imaging; D003128:Coma / Q000139:chemically induced* / Q000000981:diagnostic imaging; D003422:Critical Care; D004791:Enzyme Inhibitors / Q000009:adverse effects*; D015600:Glasgow Coma Scale; D006801:Humans; D008297:Male; D008751:Methylene Blue / Q000009:adverse effects*; D016105:Parathyroidectomy; D011183:Postoperative Complications / Q000139:chemically induced* / Q000000981:diagnostic imaging; D011859:Radiography; D020230:Serotonin Syndrome / Q000139:chemically induced* / Q000000981:diagnostic imaging; D014556:Urine
D004791:Enzyme Inhibitors; D008751:Methylene Blue