An 80-year-old woman was admitted from a nursing home for progressive lethargy. She was in her usual state of health until she developed constipation three days ago. She was given several doses of lactulose and subsequently developed diarrhea that persisted for 24-48 hours. Since that time, she has refused to leave her bed and has become progressively less responsive.
She is known to have significant cognitive impairment, osteoporosis, hypertension, degenerative joint disease, and mild COPD. She has not taken any medications for two days.
Her temperature is 36.5 C (97.7 F), blood pressure is 90/45 mm Hg, pulse is 115/min, and respirations are 16/min. She appears lethargic but arousable. Her mucous membranes are dry and her skin turgor is markedly diminished. Her neck is supple. Cardiac, lung, and abdominal examinations reveal no significant findings. She moves all her extremities well and the deep tendon reflexes are 2+ and symmetric.
The patient's labs reveal:

Her EKG shows sinus tachycardia and tall T waves in anterior precordial leads.
Which of the following is the best initial therapy for this patient?

Question

An 80-year-old woman was admitted from a nursing home for progressive lethargy.  She was in her usual state of health until she developed constipation three days ago.  She was given several doses of lactulose and subsequently developed diarrhea that persisted for 24-48 hours.  Since that time, she has refused to leave her bed and has become progressively less responsive.
She is known to have significant cognitive impairment, osteoporosis, hypertension, degenerative joint disease, and mild COPD.  She has not taken any medications for two days.
Her temperature is 36.5 C (97.7 F), blood pressure is 90/45 mm Hg, pulse is 115/min, and respirations are 16/min.  She appears lethargic but arousable.  Her mucous membranes are dry and her skin turgor is markedly diminished.  Her neck is supple.  Cardiac, lung, and abdominal examinations reveal no significant findings.  She moves all her extremities well and the deep tendon reflexes are 2+ and symmetric.
The patient's labs reveal:

Her EKG shows sinus tachycardia and tall T waves in anterior precordial leads.
Which of the following is the best initial therapy for this patient?

Quizplus · Accepted Answer

11ec193a_98f2_8218_853d_b7e7c7c13d62_MD0002_00 This patient's clinical presentation is most consistent with hypovolemic hypernatremia, likely due to hypotonic fluid loss from the lactulose-induced diarrhea. Hypotonic fluid loss usually activates the thirst mechanism to increase one's water consumption and prevent the development of hypernatremia, provided that the ongoing fluid loss has stopped. Most individuals that develop hypernatremia have neurologic deficits, so they either do not sense or cannot express thirst. Elderly or disabled individuals are often unable to access water. The first step in treatment is to assess the volume status and treat symptomatic hypovolemic hypernatremia (as in this patient) with isotonic fluids (normal saline) to restore volume. Isotonic fluids are rarely used in hypernatremia except in patients with marked volume depletion and hemodynamic instability. Once the patient is euvolemic, the fluids can be switched to 5% dextrose for free water supplementation (Choice B). The goal is to replenish fluids to decrease the serum sodium by 0.5 mEq/dL/hr without exceeding12 mEq/dL/24 hours. Cerebral edema can occur if the sodium is corrected too quickly. (Choice A) Desmopressin is the treatment for central diabetes insipidus, which causes hypernatremia with polyuria and is less likely in this patient who appears volume depleted without polyuria. (Choice C) Intravenous antibiotics could be given for a possible urinary tract infection. However, the best initial step is volume resuscitation, given her significant hypotension. (Choice E) Hyperglycemia typically leads to an osmotic diuresis and dilutional hyponatremia, and is unlikely to explain this patient's hypernatremia. Educational objective: Hypernatremia is usually due to hypotonic fluid loss combined with defects in either cognition/thirst or ability to access water. Free water repletion (5% dextrose) is the preferred treatment in euvolemic patients. However, in patients with hypovolemic hypernatremia, correction of effective circulating volume deficit with isotonic fluids should be done before the replacement of water deficit. Sodium should be corrected at a rate of 0.5 mEq/dL/hr and should not exceed 12 mEq/dL/24 hours, since too rapid a correction results in cerebral edema. __________ References: Pathogenesis and treatment of hypernatremia. (http://www.ncbi.nlm.nih.gov/pubmed/12401933) Hypernatremia in elderly patients: A heterogenous, morbid and iatrogenic entity. (http://www.ncbi.nlm.nih.gov/pubmed/3619220)

An 80-Year-Old Woman Was Admitted from a Nursing Home for Progressive