Methimazole overdosing and hypothyroidism treatment, an explanation for prolonged emergence from anesthesia

A 60-year-old woman with a past medical history of Graves’ disease, heart failure with reduced ejection fraction, and type 2 diabetes mellitus underwent an intramedullary fixation of the left hip. Postoperatively, the patient was transferred to the postoperative anesthesia care unit and later the surgical intensive care unit due to concern for hemodynamic instability. While in the SICU, the patient had altered mentation and continued to have altered mental status for the next six days. Neurologic etiologies were ruled out, and no other causes were identified. Her mentation only began to improve after withholding methimazole and starting levothyroxine. Days after her mentation returned to baseline, the patient was successfully discharged to an inpatient rehab facility. An explanation for her altered mental status due to hypothyroidism, induced by methimazole, is explored in this case report.