II. Pathophysiology

  1. Increased Total Body Water (TBW)
  2. Increased Total Body Sodium
  3. Increased Extracellular Fluid

III. Causes

  1. Hemodialysis
  2. Excessive intravenous Sodium administration
    1. Hypertonic Saline administration (3% saline)
    2. Sodium Bicarbonate infusions
    3. Replacing hypotonic insensible loss with 0.9% saline
  3. Mineralocorticoid excess
    1. Cushing Syndrome
      1. Consider 24-hour Urinary free cortisol level, Serum ACTH, Dexamethasone Suppression Test
    2. Hyperaldosteronism
      1. Presents with Hypertension and Hypokalemia
      2. Consider serum aldosterone to plasma renin activity ratio
  4. Excessive Salt intake
    1. Ingestion of salt tablets or salt water
    2. Saline enemas
    3. Enteral feeding

IV. Management

  1. Discontinue hypertonic Sodium administration or other causative agents
  2. Consider evaluation for primary Hyperaldosteronism (if Hypokalemia, Hypertension)
  3. Administer Diuretics
    1. Furosemide AND high dose Thiazide Diuretics
      1. Indapamide 2.5 to 5 mg orally daily OR Chlorothiazide 500 mg IV every 12 hours
    2. Monitor electrolytes with diuresis (Serum Potassium and Serum Magnesium)
  4. Free water replacement
    1. See Isovolemic Hypernatremia for protocol
    2. Calculate free water requirements
      1. See Free Water Deficit
      2. See Hypernatremia
    3. Chronic Hypernatremia (>48 hours) should be replaced slowly (esp. in under age 30-40 years)
      1. Limit Serum Sodium reduction to 12 mEq/L per day
    4. Delivery
      1. Enteral water sources are preferred (e.g. Feeding Tube)
      2. D5W is an alternative (avoid 1/2NS due to risk of volume overload)

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