Fast Five Quiz: Electrolyte Disorders

Vecihi Batuman, MD


March 23, 2021

Developing hypernatremia is virtually impossible if the thirst response is intact and water is available. Normally, an increase in osmolality of just 1%-2% stimulates thirst, as do hypovolemia and hypotension. Several risk factors exist for hypernatremia. The greatest risk factor is age older than 65 years. Other risk factors include:

  • Mental or physical impairment

  • Uncontrolled diabetes (solute diuresis)

  • Underlying polyuria disorders

  • Diuretic therapy

  • Residency in nursing home, inadequate nursing care

  • Hospitalization

Drugs that may cause hypernatremia include:

  • Diuretics

  • Sodium bicarbonate

  • Sodium chloride

  • Steroids (corticosteroids, anabolic, adrenocorticotrophic)

  • Hormones (androgens, estrogens)

Symptoms of hypernatremia include:

  • Cognitive: lethargy, obtundation, confusion, abnormal speech, irritability, seizures, nystagmus, myoclonic jerks

  • Dehydration or clinical signs of volume depletion: orthostatic blood pressure changes, tachycardia, oliguria, dry oral mucosa, abnormal skin turgor, dry axillae,

  • Other findings: weight loss, generalized weakness

The diagnosis of hypernatremia is based on an elevated serum sodium concentration (> 145 mEq/L). In addition, these lab studies are used to determine the etiology of hypernatremia:

  • Serum electrolytes (sodium, potassium, calcium)

  • Glucose level

  • Urea

  • Creatinine

  • Urine electrolytes (sodium, potassium)

  • Urine and plasma osmolality

  • 24-hour urine volume

  • Plasma arginine vasopressin level (if indicated)

The first step in the diagnostic approach is to estimate the volume status (intravascular volume) of the hypernatremic patient. The associated volume contraction may be mirrored in a low urine sodium level (usually < 20 mEq/L).

According to the Society for Endocrinology, overcorrection of hypernatremia should be avoided. For acute hypernatremia, serum sodium should be corrected at a rate of 5 mmol/L in the first hour (or until symptoms improve) and is limited to 10 mmol/L in a 24-hour period. For asymptomatic or mild hypernatremia, serum sodium corrections should not exceed 0.5 mmol/L/h and is limited to 10 mmol/L in a 24-hour period.

Read more about the treatment of hypernatremia.


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