Normal Serum Level: 135-145 mEq/L
Daily Sodium requirement: 3- 5mEq/kg

Hypernatremia ( > 150mEq/L)

Causes : Loss of body water, inadequate intake of water, a lack of antidiuretic hormone (ADH), or excessive intake of sodium

Signs: Lethargy or mental status changes, which proceeds to coma and convulsions

Pathophysiology:

With acute and severe hypematremia, the osmotic shift of water from neurons leads to shrinkage of the brain and tearing of the meningeal vessels and intracranial hemorrhage; slowly developing hypematremia is generally well tolerated.

The latter adaptation occurs initially by movement of electrolytes into cells and later by intracellular generation of organic osmolytes, which counter plasma hyperosmolarity.

Note: Rapid correction causes cerebral edema.

  • < 48 hours: Can be corrected rapidly
  • >48 hours: Correct not more than 12 mEq/L/day

Treatment:

  • Restore intraavascular volume with 20 mL/kg normal saline , over 20 minutes (repeat until intravascular volume restored)
  • Time for correction on basis of initial sodium Concentration:
    145-157 mEq/L = 24hr
    158-170 mEq/L = 48 hr
    171- 183 mEq/L = 72 hr
    184-196 mEq/L = 84 hr
  • Fluid of choice and rate
    • ½ DNS ( + 1ml KCL in each 100ml fluid unlesscontraindicated i.e. no urine output)
    • Rate: 1.25- 1.5 times maintenance
    • Note: Hypotonic fluids should not be used as it causes rapid correction
  • Monitoring:
    • Check Na level every 4 hours (it should decrease by 2 mEq/L)
      • <2 mEq/L
        • Increase the fluid rate or reduce sodium content of fluid
      • >2mEq/L
        • Decrease the fluid rate or increase the sodium content of fluid
      • If patient develop seizure during treatment, it is due to rapid fall in sodium concentration
        • Give 3% NS Bolus at 4ml/kg over 30 minutes