An Uncommonly Low Sodium

ABSTRACT

A 60-year-old female contacted her doctor after being discharged from an inpatient mental health facility where a new medicine was introduced. Her chief complaint was falling at home several times. Her doctor had the laboratory perform a complete blood count and chemistry panel. The next day, the woman was informed by the doctor’s nurse that she had critically low sodium and was to go directly to the emergency department (ED). In the ED, her blood work was normal except for the sodium, which was 123 mmol/L (normal range = 137–145 mmol/L). She was admitted to the hospital for hyponatremia. The sodium level performed on her urine sample was 103 mmol/L (normal value for random urine sodium = 20 mmol/L). The urine osmolality was 762 mOsmol/kg (300–900). After starting salt tablets, the sodium steadily increased but was still low at 131 mmol/L upon discharge. The hospitalist told the woman she had inappropriate secretion of antidiuretic hormone, which can happen with some psychiatric medicines. The patient was taken off the medicine Trileptal, which is used off brand as a mood stabilizer. A subsequent sodium sample was within normal range.