The Blue Coma: The Role of Methylene Blue in Unexplained Coma After Cardiac Surgery

Objectives: Methylene blue commonly is used as a dye or an antidote, but also can be used off label as a vasopressor. Serotonin toxicity is a potentially lethal and often misdiagnosed condition that can result from drug interaction. Mild serotonin toxicity previously was reported in settings in which methylene blue was used as a dye. The authors report 3 cases of life-threatening serotonin toxicity in patients undergoing chronic selective serotonin reuptake inhibitor (SSRI) therapy who also underwent cardiac surgery and received methylene blue to treat vasoplegic syndrome.

Design: An observational study.

Setting: A cardiothoracic intensive care unit (ICU) in a teaching hospital.

Participants: Three patients who received methylene blue after cardiac surgery, later discovered to be undergoing chronic SSRI therapy.

Interventions: None.

Measurements and main results: All 3 patients received high doses of fentanyl during general anesthesia. They all developed vasoplegic syndrome and consequently were given methylene blue in the ICU. All 3 patients developed serotonin toxicity, including coma, after this administration and diagnostic tests were negative for acute intracranial pathology. Coma lasted between 1 and 5 days. Two patients were discharged from the ICU shortly after awakening, whereas the third patient experienced a complicated postoperative course for concomitant refractory low-cardiac-output syndrome.

Conclusions: Patients undergoing chronic SSRI therapy should not be administered methylene blue to treat vasoplegic syndrome.