An 80-year-old woman presents to the clinic with increasing fatigue, dizzy spells, and nausea. She has been followed for several years for osteoporosis, type 2 diabetes mellitus, depression, and mild cognitive impairment. She was recently started on treatment for systolic hypertension. She lives independently with support provided by a visiting nurse three times weekly. She performs all of her own activities of daily living.
Her current medications include alendronate, sertraline, metformin, and hydrochlorothiazide.
Her temperature is 36.7 C (98.1 F) , blood pressure is 146/70 mm Hg supine and 139/75 mm Hg standing (160/75 mmHg during the previous visit) , pulse is 84/min, and respirations are 14/min. She is 5' 5" (165 cm) and her BMI is 19 kg/m². There is 2/6 ejection-type systolic murmur at the right upper sternal border without radiation to the carotids. Her lungs are clear. Muscle strength is preserved and deep tendon reflexes are symmetrical bilaterally. Her gait is mildly unsteady. Her mini-mental status exam score is 22/30 (1 year ago 27/30) . Fingerstick glucose level is 220 mg/dL.
Which of the following is most likely responsible for this patient's current symptoms?

Question

Quizplus · Accepted Answer

This patient's symptoms are most likely due to hyponatremia; an occasional, but possibly fatal complication of thiazide diuretics. Thiazide-induced hyponatremia usually occurs within 1-2 weeks after starting the drug, more commonly in older woman with low body mass index. One study showed that 36% of patients had a plasma sodium < 130 mEq/L and patients > age 70 had a 3.9 times higher risk of developing hyponatremia. Thiazide diuretics cause hyponatremia by increasing sodium and potassium excretion in the cortical distal tubule and increasing medullary water reabsorption. The concentrated urine leads to ADH-induced water retention, which further dilutes the serum and worsens the hyponatremia. Although they work in the loop of Henle to decrease sodium reabsorption and increase excretion, loop diuretics have a lower incidence of hyponatremia because they impair medullary water reabsorption and make the medulla less responsive to ADH-induced water retention. Patients with thiazide-induced hyponatremia usually appear clinically euvolemic but can present with dizzy spells, lethargy, malaise, vomiting, associated significant hypokalemia, and metabolic alkalosis. Treatment involves stopping the diuretic, replacing potassium, and giving normal saline for evidence of volume depletion. Hypertonic saline is reserved for patients with marked symptomatic hyponatremia. (Choice A) This patient's symptoms and signs suggest global central nervous system dysfunction rather than a focal cerebellar stoke. (Choice B) Hypercalcemia can result in fatigue, nausea, constipation, and impaired cognition. Although thiazide diuretics can mildly increase the serum calcium, they usually do not cause significant symptomatic hypercalcemia unless another cause for hypercalcemia is present. (Choice C) The osmotic force of hyperglycemia results in water movement out of cells to decrease cell volume, but this effect would be very small in this patient and less likely to cause her symptoms. (Choice E) Volume depletion is less likely in this patient without clinical findings such as orthostatic changes, tachycardia, or decreased skin turgor. Educational objective: Thiazide diuretics can lead to hyponatremia (more commonly than loop diuretics), especially in frail and elderly women with a low body mass index. Patients with nonspecific symptoms after starting thiazide diuretics should have laboratory evaluation of their electrolytes. Treatment consists of stopping the diuretic and fluid repletion in symptomatic patients. __________ References: Thiazide diuretic prescription and electrolyte abnormalities in primary care. (http://www.ncbi.nlm.nih.gov/pubmed/16390355) Risk factors for thiazide-induced hyponatremia. (http://www.ncbi.nlm.nih.gov/pubmed/14631057)

An 80-Year-Old Woman Presents to the Clinic with Increasing Fatigue