How is hyponatremic dehydration treated?

Updated: Dec 07, 2018
  • Author: Lennox H Huang, MD, FAAP; Chief Editor: Timothy E Corden, MD  more...
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Phase 1 management of hyponatremic dehydration is identical to that of isonatremic dehydration. Rapid volume expansion with 20 mL/kg of isotonic (0.9%) sodium chloride solution or lactated Ringer solution should be administered and repeated until perfusion is restored.

Severe hyponatremia (< 130 mEq/L) indicates additional sodium loss in excess of water loss. In phase 2 management, rehydration is calculated as for isonatremic dehydration. The additional sodium deficit must be calculated and added to the rehydration fluids. The deficit may be calculated to restore the sodium to 130 mEq/L and administered over 48 hours, as follows:

  • Sodium deficit = (sodium desired - sodium actual) X volume of distribution X weight (kg)

  • Example: Sodium = 123, weight = 10 kg, assumed volume of distribution of 0.6; Sodium deficit = (130-123) X 0.6 X 10 kg = 42 mEq sodium

A simplified approach is to use 5% dextrose in 0.9% sodium chloride as the replacement fluid. The sodium is closely monitored, and the amount of sodium in the fluid is adjusted to maintain a slow correction (about <0.5 mEq/L/h, with a correction goal of 8 mEq/L over 24 hours).

Frequently reassessing the serum sodium level during correction is imperative. Rapid correction of chronic hyponatremia (>2 mEq/L/h) has been associated with central pontine myelinolysis. Rapid partial correction of symptomatic hyponatremia has not been associated with adverse effects. Therefore, if the child is symptomatic (seizures), a more rapid partial correction is indicated. Hypertonic (3%) sodium chloride solution (0.5 mEq/mL) may be used for rapid partial correction of symptomatic hyponatremia. A bolus dose of 4 mL/kg raises the serum sodium by 3-4 mEq/L.

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