Severe Hyponatremia Associated with the Use of Angiotensin II Receptor Blocker/thiazide Combinations
An 86-year-old Asian woman presented with general weakness which began on the day of presentation. She had been suffering from nausea while working in the fields in hot weather for 1 week prior to admission. The patient had been on losartan potassium/hydrochlorothiazide 50/12.5 mg qd, amlodipine 5mg qd, and aspirin 100 mg for hypertension which had been diagnosed 4 years before.\nOn arrival, the patient's vital signs were stable, and physical, neurological and radiological examinations were within normal limits. Initial laboratory results were as follows: WBC 8,240/mm3, Hb 12.4 g/dL, Hct 33.5%, and Platelet 488,000/mm3; Na 102 mmol/L, K 3.5 mmol/L, Cl 67 mmol/L, BUN 10 mg/dL, creatinine 0.4 mg/dL, and serum osmolality 223 mOsm/kg H2O; and urine creatinine 79 mg/dL, urine urea nitrogen 309 mg/dL, urine Na 79 mmol/L, and urine osmolality 398 mOsm/kg H2O. The patient's blood sugar was 142 mg/dL, and the HbA1c level was 5.6%. Thyroid function test and rapid ACTH stimulation test results were within normal range.\nInitial blood tests revealed the presence of hyponatremia with a Na level of 102 mmol/L, and serum osmolality was also low at 223 mOsm/kg H2O. Urine osmolality was 398 mOsm/kg H2O, upon which primary polydipsia was ruled out; the patient was hypovolemic, in combination with endocrine test results, implied that the possibility of hypothyroidism, adrenal cortex dysfunction, or SIADH was low. An increased urine Na level of 79 mmol/L and normal aldosterone levels, with no history of vomiting, led to the diagnosis of diuretic-induced hyponatremia.\nWe changed the patient's antihypertensive medication to a single-drug regimen of amlodipine 5mg qd. Hyponatremia was corrected with continuous intravenous infusion of 0.9% NaCl. On the following day, the serum Na level improved to 110 mmol/L; on the second day, it further improved to Na 121 mmol/L, at which point 0.9% NaCl infusion was discontinued.\nOn the fourth day of admission, the serum Na level and osmolality were substantially recovered to 130 mmol/L and 271 mOsm/kg H2O respectively, with urine osmolality of 207 mOsm/kg H2O and urine Na of 14 mmol/L. Blood pressure was stable at 120/80 mmHg. The patients' symptoms showed recovery and she was discharged.