How are fluid requirements calculated for the treatment of severe dehydration?

Updated: Dec 07, 2018
  • Author: Lennox H Huang, MD, FAAP; Chief Editor: Timothy E Corden, MD  more...
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Alternatively, daily maintenance (not including pathologic ongoing loss) fluid requirements may be roughly estimated as follows:

  • Less than 10 kg = 100 mL/kg

  • 10-20 kg = 1000 + 50 mL/kg for each kg over 10 kg

  • Greater than 20 kg = 1500 + 20 mL/kg for each kg over 20 kg

Severe dehydration by clinical examination suggests a fluid deficit of 10-15% of body weight in infants and 6-9% of body weight in older children. The daily maintenance fluid is added to the fluid deficit. In general, the recommended administration is one half of this volume administered over 8 hours and administration of the remainder over the following 16 hours. Continued losses (eg, emesis, diarrhea) must be promptly replaced.

If the child is isonatremic (130-150 mEq/L), the sodium deficit incurred can generally be corrected by administering the remaining fluid deficit after phase 1 plus maintenance as 5% dextrose in 0.45-0.9% sodium chloride. Potassium (20 mEq/L potassium chloride) may be added to maintenance fluid once urine output is established and serum potassium levels are within a safe range.

An alternative approach to the deficit therapy approach is rapid replacement therapy. With this approach, a child with severe isonatremic dehydration is administered 20-40 mL/kg of isotonic sodium chloride solution or lactated Ringer solution over 15-60 minutes. As perfusion is restored, the child improves and is able to tolerate an oral rehydration solution for the remainder of his rehydration. This approach is not appropriate for hypernatremic or hyponatremic dehydration.

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