Normal Maintenance Requirements
It is clinically useful to begin fluid therapy by estimating normal maintenance requirements using the estimated caloric expenditure method. The resting energy expenditure in healthy children is vastly different from those with an acute disease and/or illness or after surgery.
The commonly used method for approximating water loss (and therefore the water requirement) is based off of the Holliday-Segar nomogram. This formula is based on the energy expenditure of healthy children, with 1 mL of fluid provided for each kcal expended, or 1500 mL/m2 per day.
Holliday and Segar collated information from a number of studies, including their own, and concluded the following:
- Water loss (and therefore water requirement) is a function of caloric expenditure.
- Total daily water requirement to replace insensible and urinary water loss in the hospitalized patient is approximately 100 ml/100kcal/day. This means that for every 100 kcal burned, the patient utilizes 100 ml of fluid.
- Caloric expenditure, and therefore the water requirement, for the hospitalized patient can be estimated from the nomogram shown below.
The diagram below is taken from their original publication "The maintenance need for water in parenteral fluid therapy", Pediatrics 1957. Holliday and Segar determined how many calories a patient burns as a factor of weight.
Holliday MA and Segar WE. p. 823-8232, Pediatrics 1957
The Holliday-Segar nomogram approximates daily fluid loss, and therefore the daily fluid requirements, as follows:
- 100 ml/kg for the 1st 10 kg of wt.
- 50 ml/kg for the 2nd 10 kg of wt.
- 20 ml/kg for the remaining wt.
Even though it is correct to think about fluid requirements on a 24-hour basis, the delivery pumps used in hospitals are designed to be programmed for an hourly infusion rate. The 24-hour number is often divided into approximate hourly rates for convenience, leading to the "4-2-1" formula.
- 100 ml/kg/24-hours = 4 ml/kg/hr for the 1st 10 kg
- 50 ml/kg/24-hours = 2 ml/kg/hr for the 2nd 10 kg
- 20 ml/kg/24-hours = 1 ml/kg/hr for the remainder
Calculate the maintenance water required for a 17kg child? Click here for the answer.
Calculate the maintenance water required for 30 kg child? Click here for the answer.