• > 145 mmol\L.
  • High serum osmolality



(skin, GI, urine loss of fluids)

  • Simple dehydration: sweating, burns, fever, pneumonia (hyperventilation), diarrhea
  • Diabetes insipidus (DI): insufficient or ineffective ADH -> high-volume water loss
    • Central DI: failure to produce ADH in the brain -> give vasopressin\DDAVP
    • Nephrogenic DI: ADH insensitivity of the kidneys (caused by lithium, CKD, hypokalemia, hypercalcemia) -> correct K and Ca + give thiazides
    • Both result in: ↓ urine osmolality, ↓ urine sodium, ↑ urine volume



  • [CNS]: confusion, disorientation, seizures, coma

 Hypernatremia 1


  • General rule: give 2 cc\kg\h of free water to correct serum Na by about 0.5 mmol\L\h or 12 mm\L\d

Hypernatremia 2


Complications of therapy

  • If Na levels are brought down too rapidly -> cerebral edema (worsening confusion and seizure)


Download the PDF version: here


  • Step up to medicine
  • Toronto notes

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