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Self-Assessment Questions

Nephrology

Hyponatremia: Review Questions

Anushree C. Shirali, MD, and Ursula C. Brewster, MD

Dr. Shirali is a fellow in nephrology, and Dr. Brewster is an assistant professor of medicine; both are at the Section of Nephrology, Yale University School of Medicine, New Haven, CT.



Choose the single best answer for each question.

Questions 1 and 2 refer to the following case.

An 80-year-old woman with a history of depression presents to the emergency department (ED) with weakness and dizziness. She takes furosemide 20 mg daily for lower extremity edema. She reports that her primary care physician prescribed hydrochlorothiazide for elevated blood pressure 1 week ago. The patient denies fevers, chills, nausea, or vomiting. She claims to be more thirsty than usual and has been drinking apple juice in response. Her blood pressure is 100/60 mm Hg lying down and 84/40 mm Hg sitting, and her weight is 60 kg. Lungs are clear with no lower extremity edema. Laboratory studies reveal a serum osmolality of 260 mOsm/kg, serum sodium of 125 mEq/L (normal, 135-154 mEq/L), serum potassium of 3.4 mEq/L (normal, 3.5-5.0 mEq/L), and serum creatinine level of 0.8 mg/dL (normal, 0.6-1.2 mg/dL). Urinalysis reveals a sodium level of 50 mEq/L (normal, 0-300 mEq/L) and urine osmolality of 200 mOsm/kg.

1. Which of the following is this patient’s most likely diagnosis?
  1. Adrenal insufficiency
  2. Furosemide-induced hyponatremia
  3. Hydrochlorothiazide-induced hyponatremia
  4. Syndrome of inappropriate antidiuretic hormone (SIADH)
  5. Thyroid disease
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2. How should this patient be managed?

  1. Give intravenous (IV) normal saline (0.9%) at 125 mL/hr
  2. Give IV 5% dextrose in half-strength normal saline at 50 mL/hr
  3. Restrict free water intake orally
  4. Provide salt tablets orally
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Questions 3 and 4 refer to the following case.

A 25-year-old woman with a history of frequent hospitalizations for alcohol intoxication is brought to the ED after a week of binge drinking. On physical examination, her blood pressure is 120/75 mm Hg, heart rate is 85 bpm, and weight is 70 kg. She is lethargic and mumbling incoherently. In the ED, the patient has a generalized tonic-clonic seizure, which resolves with IV diazepam. Laboratory results are significant for a serum sodium level of 110 mEq/L, serum potassium level of 3.8 mEq/L, alcohol level of 250 mg/dL, serum osmolality of 230 mOsm/kg, and serum glucose concentration of 92 mg/dL (normal, 70-115 mg/dL). Renal function is normal.

3.  How should this patient be managed at this time?

  1. IV hypertonic saline (3%) at 130 mL/hr
  2. IV hypertonic saline (3%) at 200 mL/hr
  3. IV normal saline (0.9%) at 100 mL/hr
  4. IV normal saline (0.9%) at 1000 mL/hr
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4. Eight hours after therapy is started, a serum chemistry profile reveals a sodium level of 120 mEq/L. The patient is now euvolemic and more responsive. What is the next step in this patient’s management?
  1. Continue current therapy, recheck sodium every 6 hours
  2. Start meningitic doses of IV ceftriaxone
  3. Stop IV fluids and administer a 1-time dose of IV furosemide 80 mg
  4. Stop IV fluids, restrict free water intake, and monitor serum sodium closely
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5. Serum chemistry results for a 50-year-old man admitted to the cardiac care unit with a myocardial infarction reveal a sodium level of 124 mEq/L. There are no other laboratory abnormalities; however, the sample is lipemic. The patient is resting comfortably and denies any symptoms. Which of the following is most likely to establish the diagnosis?

  1. Serum osmolality
  2. Serum uric acid
  3. Urine osmolality
  4. Urine sodium
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6. A 40-year-old man with a history of type 2 diabetes and end-stage renal disease on hemodialysis presents to the ED with weakness. He reports that he missed his regularly scheduled outpatient dialysis that day and ran out of his long-acting insulin 2 days ago. The patient has no other complaints. Physical examination is unremarkable, including a normal neurologic examination. Laboratory results reveal a serum sodium level of 125 mEq/L, serum potassium level of 5.2 mEq/L, serum chloride level of 104 mEq/L (normal, 96-106 mEq/L), and serum bicarbonate level of 19 mEq/L (normal, 21- 27 mEq/L). Serum glucose is 700 mg/dL and serum osmolality is 310 mOsm/kg. A chest radiograph reveals clear lungs, and an electrocardiogram shows normal sinus rhythm with no acute T-wave changes. Which of the following is the most appropriate next step in this patient’s management?

  1. Immediate hemodialysis
  2. Initiate IV short-acting insulin therapy
  3. Restart subcutaneous insulin therapy for dosing at home
  4. Restrict free water to correct hyponatremia
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