Case:
A 73-year-old woman with medical problems of hypertension, hyperlipidemia, and coronary artery disease underwent left CEA for asymptomatic carotid artery stenosis. Preoperative computed tomography (CT) angiogram showed severe calcification of the aortic arch and the proximal left common carotid artery. Her preoperative laboratory workup was unremarkable with a baseline sodium of 139 mmol/L (Table 1).  The operation was performed under regional anesthesia with sedation and there were no intraoperative complications. The patient was discharged on postoperative day (POD) one in a stable condition.
On POD four, the patient presented to the emergency room with a three-day history of lethargy, confusion, nausea, and emesis. Given the patient’s altered mentation, the initial history was provided by her family. On examination, the patient was somnolent and lacked orientation to person, place or time. No other focal neurological deficits were appreciated. There was no peripheral edema, and the skin turgor was normal. Initial laboratory evaluation showed severe hyponatremia (109 mmol/L), hypokalemia, and normal renal function (Table 2).