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Hypernatremia

Definition: Serum Na >135 mmol/L. Hypernatremia is associated with hypertonicity, contributing to fluid shifts across cell membranes. 

Etiology: Hypernatremia represents a relative deficit of free water.

Renal water loss:

  • Central Diabetes Insipidus (DI): decreased ADH. Cause: trauma/post surgical, pituitary lesions, mass effect, sheehan’s syndrome. 
  • Nephrogenic DI: Decreased kidney responsiveness to ADH. Cause: 
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