Which clinical history findings are characteristic of hyponatremia?

Updated: Aug 24, 2020
  • Author: Kartik Shah, MD; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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The number and severity of symptoms increase with the degree of hyponatremia and the rapidity with which it develops. When the serum sodium level falls gradually, over a period of several days or weeks, sodium levels as low as 110 mEq/L may be reached with minimal symptomatology. In contrast, an equivalent fall in serum sodium level over 24-48 hours may overwhelm compensatory mechanisms, leading to severe cerebral edema, coma, or brainstem herniation.

Symptoms range from mild anorexia, headache, and muscle cramps, to significant alteration in mental status including confusion, obtundation, coma, or status epilepticus.

Hyponatremia is often seen in association with pulmonary/mediastinal disease or CNS disorders. Hyponatremia must be considered in patients with pneumonia, active tuberculosis, pulmonary abscess, neoplasm, or asthma, as well as in patients with CNS infection, trauma, or neoplasm. Patients with carcinoma of the nasopharynx, duodenum, stomach, pancreas, ureter, prostate, or uterus also have an increased risk.

Hyponatremia is associated with numerous medications. The patient's medication list should be examined for drugs known to cause hyponatremia.

Hyponatremia has been noted in patients with poor dietary intake who consume large amounts of beer (known as beer potomania) and after use of the recreational drug N- methyl-3,4-methylenedioxyamphetamine (ie, MDMA or ecstasy). MDMA-induced hyponatremia occurs via multiple mechanisms; these include the induction of syndrome of inappropriate antidiuretic hormone secretion (SIADH), the encouragement to drink large amounts of water to prevent unpleasant side effects of the drug, and the tendency among those intoxicated to be involved in vigorous physical activity that results in heavy sweating.

A history of hypothyroidism or adrenal insufficiency should be sought because each is associated with hyposmolar hyponatremia.

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