Hypernatremia

Description

• Mild hypernatremia: Serum sodium 146–155 mEq/L
• Severe hypernatremia: Serum sodium >155 mEq/L

Etiology

• Most common
• Loss or deficiency of water and sodium with water losses being greater than sodium losses
• Examples:
  • Renal failure
  • Medications (e.g., diuretics, lactulose)
  • Osmotic diuresis (mannitol, glucosuria, high-protein feedings)
  • Insensible losses (burns, sweating)
  • Respiratory loss
  • Defective thirst mechanism
  • Lack of access to water
  • Diarrhea/vomiting
  • Intubated patients

• Water deficiency without sodium loss; free water loss
• Examples:
  • Fever
  • Hypothalamic diabetes insipidus (DI):
    • Head trauma
    • Tumor
    • Congenital
    • Infection (TB, syphilis, mycoses, toxoplasmosis, encephalitis)
    • Granulomatous disease (sarcoid, Wegner)
    • Cerebrovascular accident
    • Aneurysm
  • Nephrogenic DI:
    • Congenital
    • Drugs (lithium, amphotericin B, foscarnet, demeclocycline)
    • Obstructive uropathy
    • Chronic tubulointerstitial disease (sickle cell nephropathy, multiple myeloma, amyloidosis, sarcoidosis, systemic lupus erythematosus, polycystic kidney)
    • Electrolyte disorders (hypercalcemia, potassium depletion)

• Gain of water and sodium, with sodium gain greater than water gain
• Examples:
  • Iatrogenic – most common cause:
    • Sodium bicarbonate administration
    • NaCl tablets
    • Hypertonic parenteral hyperaliment
    • Hypertonic IV fluid (IVF)
    • Hypertonic dialysis
  • Hypertonic medicine preparations such as ticarcillin and carbenicillin
  • Cushing disease
  • Adrenal hyperplasia
  • Primary aldosteronism
  • Sea water drownings

• More prone to iatrogenic causes
• More likely to die or to have permanent neurologic sequelae
• Morbidity ranges from 25–50% with mortality of 15%
• May present with high-pitched cry, lethargy, irritability, muscle weakness
• Poor breastfeeding and inappropriate formula preparations are a potential cause in neonates
• Breastfed infants among the highest risk groups to develop hypernatremia
• If hypernatremia is due to DKA, follow pediatric DKA protocols for fluid resuscitation
• DDAVP dose for 3 mo–12 yr is 5–30 mcg/d intranasally
• Consider NG hydration

• Most commonly affected group due to impaired renal concentrating ability and reduced thirst mechanism
• Consider neglect if underlying etiology is dehydration alone

• May encounter transient DI of pregnancy
• Vasopressin and desmopressin are category B drugs in pregnancy
• Hydration status much more difficult to evaluate accurately by exam