HYPERNATREMIA
HYPERNATREMIA: Excerpt from Differential Diagnosis in Primary Care
If an electrolyte profile shows an elevated sodium level, the physiology model of intake, regulation and excretion may be applied to develop a list of possibilities. However, the focus should be on water intake, transport, regulation, and excretion because this will help recall most of the possibilities.
HYPERNATREMIA
Intake
When water intake is diminished in dehydration states, the sodium level increases.
Regulation
Antidiuretic hormone (ADH) allows for the retention of water by the distal tubule. When this hormone is reduced or absent as in pituitary diabetes insipidus, hypernatremia results. Furthermore, if the kidney does not respond to ADH as in renal diabetes insipidus, hypernatremia results. Aldosterone hormone promotes increased reabsorption of sodium in the distal tubule in primary aldosteronism causing hypernatremia. However, this may be counterbalanced by an increased ADH secretion and water retention causing the sodium to return to normal.
Excretion
Sodium excretion may be reduced in acute renal failure but since water is retained as well the plasma sodium is not usually increased. Other causes of hypernatremia include the administration of normal and hypertonic saline, prolonged vomiting, and heat exhaustion.
Approach to the Diagnosis
Dehydration can be diagnosed clinically by the tenting of the skin, mushy eyeballs, and concentrated urine. Laboratory work up includes serial electrolytes, chemistry panel, serum and urine osmolality, serum ADH, plasma renin, 24-hour urine aldosterone level, and consultation with an endocrinologist or a nephrologist. It is wise to withhold all noncritical drugs until a diagnosis is certain.
Book Source Details
- Book Title: Differential Diagnosis in Primary Care
- Author(s): R. Douglas Collins
- Year of Publication: 2007
- Copyright Details: Differential Diagnosis in Primary Care, Copyright © 2007 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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Hypernatremia (A Pocket Manual of Differential Diagnosis)
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