A 74-year-old female with major depressive disorder was started on sertraline 50 mg daily three weeks ago by her primary care provider. She presents to the psychiatric clinic with complaints of increased fatigue, nausea, mild confusion, and unsteady gait that developed gradually over the past week. Her daughter reports that the patient seems 'more confused than depressed now.' Her medical history includes hypertension managed with hydrochlorothiazide 25 mg daily and osteoarthritis for which she takes ibuprofen as needed. Laboratory results reveal sodium 126 mEq/L, serum osmolality 264 mOsm/kg, urine osmolality 480 mOsm/kg, and urine sodium 58 mEq/L. Her sodium level was 139 mEq/L on routine labs drawn one month ago. Which assessment finding pattern is most consistent with SSRI-induced syndrome of inappropriate antidiuretic hormone secretion?