Anesth Analg 2005;101:608-609
© 2005 International Anesthesia Research Society
doi: 10.1213/01.ANE.0000159003.49024.F5
LETTER TO THE EDITOR
Prolonged Postoperative Disorientation After Methylene Blue Infusion During Parathyroidectomy
Christian Siebert, MD,
Stefanie Kroeber, MD, and
Norbert Lutter, MD
Department of Anesthesiology; University of Erlangen-Nuremberg; Erlangen, Germany; christian.siebert{at}kfa.imed.uni-erlangen.de
To the Editor:
Bach et al. (1) report a patient with intraoperative administration of the serotonin antagonist ondansetron who had been chronically treated for depression with the selective serotonin reuptake inhibitor paroxetine. Paroxetine is known to inhibit CYP2D6 (cytochrome P450 system), which vice versa provides for the ondansetron degradation. A similar case was published by Stanford (2) of postoperative disorientation in a patient who had received paroxetine preoperatively and ondansetron, but not methylene blue, intraoperatively. This patient’s postoperative disorientation may have been induced subsequent to a significant impairment of serotonin regulation, including a history of other serotonin-associated mental disorders (e.g., anxiety, depression).
Hypovolemia may have eventually contributed to an impaired mental state despite adequate sodium levels as reported. Because of arterial hypertension and chronic diuretic use and considering the patient’s body mass of 115 kg, an IV infusion of 1500 mL of lactated Ringer’s solution during a 2-h procedure might not have compensated sufficiently for the fluid deficit.
Moreover, as a large dose of methylene blue produces a significant methemoglobinemia, thereby decreasing oxygen delivery, neither pulse oximetry nor co-oximetry are capable of reliably estimating the arterial saturation if methylene blue is present. Therefore, as methylene blue is rapidly excreted in urine, repeated postoperative co-oximetry would have allowed for exact determination of an increased methemoglobin fraction.
The obvious lack of sufficient information (e.g., preoperative liver function, co-oximetry, fluid balance) prevents a more detailed consideration of the transient postoperative neurological symptoms as described.
References
- Bach KK, Lindsay FW, Berg LS, Howard RS. Prolonged postoperative disorientation after MB infusion during parathyroidectomy. Anesth Analg 2004;99:1573–4.[Abstract/Free Full Text]
- Stanford BJ, Stanford SC. Postoperative delirium indicating an adverse drug interaction involving the selective serotonin reuptake inhibitor, paroxetine? J Psychopharmacol 1999;13:313–7.[Abstract/Free Full Text]
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