Effects of methylene blue on propofol requirement during anaesthesia induction and surgery

Abstract

SummaryDelayed emergence from anaesthesia and neurological disturbances have been reported in patients undergoing parathyroidectomy who received methylene blue (MB) pre-operatively. We hypothesised that MB would decrease propofol requirements. The Bispectral index (BIS) and a target-controlled infusion of propofol were used in two groups of 11 matched patients. Patients in one group were pretreated with MB. During induction, clinical sedation scores and BIS values were significantly lower at the predicted effect-site propofol concentration of 2 lg.ml )1 in the MB compared with the control group. Intra-operatively, although similar BIS values were achieved in the two groups, patients pretreated with MB required a mean 50% lower dose of propofol compared with controls. In view of these findings, care should be taken to ensure an adequate depth of anaesthesia by titrating the administration of anaesthetic agents whenever MB is infused peri-operatively. In addition to its use as an antidote for methaemoglobinaemia, the properties of methylthioninium chloride (methylene blue, MB) as a dye, antiseptic, vasopressor and psychotropic have extended its use for many medical applications [1,2]. In surgical practice, MB is often used for localisation of parathyroid adenoma, potentially preventing surgical nerve damage and reducing the operative time [3][4][5]. Moreover, by inhibiting the nitric oxide-cyclic guanylyl monophosphate (NO-cGMP) pathway, MB has also been advocated as a second line treatment for vasodilatory hypotension associated with cardiopulmonary bypass, liver transplantation, sepsis or the hepatopulmonary syndrome [6][7][8][9]. Although considered to be safe, numerous adverse effects including nausea and vomiting, chest pain, hypertension or hypotension, dyspnoea, haemolysis and neuropsychological disturbances have been described after intravenous administration of MB in the dose range of 1-10 mg.kg )1 [1,7]. Following parathyroidectomy, 22cases of transient neurological complications in relation to MB infusion have recently been reported in the medical literature [10][11][12][13][14][15][16][17][18]. Of note, no sensorimotor deficits have been reported and brain computed tomography (CT) scans were all unremarkable. The term 'MB-associated encephalopathy' has been coined to cover clinical manifestations, lasting from a few hours up to five days and ranging from disorientation to profound lethargy and coma with cardiorespiratory depression requiring tracheal re-intubation and resuscitation.In our clinical practice, we have witnessed several cases of delayed emergence from anaesthesia and prolonged confusional state after parathyroidectomy. We hypothesised that MB could potentiate the effects of general anaesthetic agents. Therefore, we compared propofol requirements during phases of anaesthesia induction and maintenance in two groups of patients, one of which received pretreatment with MB before undergoing parathyroid or thyroid surgery. In this case-controlled study general anaesthesia was conducted with a ta...

Cellular and molecular actions of Methylene Blue in the nervous system

“…In addition to its local analgesic actions, MB also decreases minimum alveolar concentration of general anesthetics such as sevoflurane (Masaki and Kondo, 1999), isoflurane (Vutskits et al, 2008), and the propofol (Licker et al, 2008). In fact, phenothiazine-class compounds were employed initially to potentiate the effects of anesthetics and sedatives (for reviews Kristiansen, 1989; Frankenburg and Baldessarini, 2008).…”

Intraoperative adjuncts in surgery for primary hyperparathyroidism

“…There is currently growing clinical and experimental evidence that MB can be associated with significant morbidity, in particular toxic encephalopathy [110][111][112][113][114][115][116][117][118][119][120][121][122][123]. MB appears to have additive or synergistic effects with anesthetic agents and may cause transient neurological dysfunction in the postoperative period [117], particularly in patients taking serotonin reuptake inhibitors (antidepressants) [107].…”

“…MB appears to have additive or synergistic effects with anesthetic agents and may cause transient neurological dysfunction in the postoperative period [117], particularly in patients taking serotonin reuptake inhibitors (antidepressants) [107].…”

Methylene blue treatment for vasoplegia and resultant isoelectric processed EEG (Bispectral Index)

“…Indeed, in human studies of patients undergoing general surgery, those who received 5 mg/kg of methylene blue require 50% less propofol to maintain equivalent BIS scores [24]. There is at least one report of a dramatic decrease in BIS score following methylene blue injection for the treatment of methemoglobinemia [25].…”