Hypernatremia

Descriptive text is not available for this imageBASICS

DESCRIPTION

  • Formally defined as a serum sodium (Na) concentration of >145 mEq/L but generally considered at concentrations ≥150 mEq/L
  • Results from an imbalance between total body Na and water, most commonly due to excess water loss in relation to Na, but can also occur in settings of excess Na administration

EPIDEMIOLOGY

  • Typically seen in patients who are unable to access water freely, due to age or physical or mental status
  • Congenital nephrogenic diabetes insipidus (DI) is X-linked, so generally occurs in males.
  • Breastfed infants have a higher risk of hypernatremia as compared to formula fed infants.
  • Children with neurologic impairment are at higher risk.

ETIOLOGY

  • Plasma osmolality (osm) is a function of antidiuretic hormone (ADH) release from the posterior pituitary and thirst mechanisms that drive water ingestion.
  • Occurs in the setting of excess water loss or excess Na administration
  • Causes of excess Na administration:
    • Often iatrogenic (IV fluids, Na-containing medications, improper formula mixing); can also be due to intentional salt ingestion or poisoning
  • Causes of excess water loss in relation to Na:
    • Nephrogenic DI (abnormal renal tubular response to ADH secretion)
    • Central DI (abnormal ADH production)
    • Diarrhea/GI illness
    • Burns
    • Thirst mechanism disorders
    • Renal tubular disease can cause hyponatremia or hypernatremia.
    • Osmotic diuresis can result in hypernatremia.
    • Hypercalcemia and hypokalemia can cause reversible hypernatremia.

RISK FACTORS

  • Extremes of age
  • Hospitalized patients without free access to water
  • Patients fed via g-tube (GT), total parenteral nutrition (TPN)
  • Lithium use
  • Diuretic use has variable effects on Na, and it may cause hypernatremia or hyponatremia.

GENERAL PREVENTION

  • Ensure adequate hydration (balance of I/Os) in patients with underlying water loss and/or diminished thirst mechanisms.
  • Avoid unnecessary PO fluid restriction in hospitalized patients.
  • Monitor serum electrolytes in patients receiving IV fluids.

COMMONLY ASSOCIATED CONDITIONS

  • DI (nephrogenic or central)
  • Medications: lithium, amphotericin, ifosfamide, foscarnet (high doses), and cidofovir; these medications can cause nephrogenic DI.
  • Hypercalcemia and hypokalemia can cause an acquired nephrogenic DI.
  • Several antibiotics and other medicines may contain high Na content.

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