What is hyponatremic volume depletion in pediatric dehydration?

Updated: Nov 12, 2018
  • Author: Alex Koyfman, MD; Chief Editor: Muhammad Waseem, MS, MBBS, FAAP, FACEP, FAHA  more...
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In hyponatremic volume depletion, the patient may appear more ill clinically than actual fluid losses would otherwise indicate. The degree of volume depletion may be clinically overestimated. Serum sodium levels less than 120 mEq/L may result in seizures—the risk of seizure is much higher in the setting of acute onset of hyponatremia, as opposed to gradual onset. If intravascular free water excess is not corrected during volume replenishment, the shift of free water to the intracellular fluid compartment may cause cerebral edema, especially in children. 

In hypernatremic volume depletion, plasma volume contracts with a disproportionately larger loss of free water. An example is the child with diarrhea whose fluid losses have been replenished with hypertonic soup, boiled milk, water and baking soda, or improperly diluted infant formula. Volume has been restored, but free water has not. The degree of volume depletion may be underestimated and the patient may appear less ill clinically than fluid losses indicate. Usually, at least a 10% volume deficit exists with hypernatremic volume depletion.

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