IV Maintenance Fluids Calculator

Variables and formula

This calculator determines the fluid requirement that needs to be corrected in pediatric patients based on weight (because total body water relies on weight). There are two calculation methods used, the Holliday-Segar nomogram and the 4 – 2 – 1 rule.

The main limitation of the calculator is that it cannot be applied to newborns (the first 28 days after full term pregnancy) or to any infant weighing less than 3.5 kg.

The rule of thumb in water loss (and water requirement) is that hospitalized patients require approximately 100 mL/ 100 kcal/day, to replace insensible and urinary water loss.

The first calculation method uses the Holliday-Segar Nomogram guidelines to determine the Daily Volume, as introduced in the table below:

The fluid rate in mL/hr can then be calculated as Daily volume / 24.

The 4 – 2 – 1 rule is based on the following:

The fluid replenishment recommended by the calculator needs to be adapted by clinicians based on the past, current and prospective hydration status of the patient.

Cases of under dosing may result in continuing the dehydration and can lead to renal insufficiency. If overdosed, the patient may develop edema or fluid overload.

In case the pediatric patient suffers from a renal condition or is a patient with burns, the above methods may not be sufficient.

About maintenance fluid therapy

When the body cannot preserve the normal volume of fluids and the electrolyte balance, fluid replenishment becomes necessary to ensure homeostasis and to make sure cardiac output is optimized.

Total water loss is broken into three components:

■ Respiratory loss: 20%;

■ Transcutaneous loss: 30%;

■ Urine: 50%.

The ongoing losses of water and electrolytes due to physiologic processes (respiration, sweat, urine and stool) are to be replenished first and then the deficits caused by illnesses and physiologic abnormalities are addressed.

There are three types of circumstances that influence intravascular fluid balance:

■ Preoperative;

■ Intraoperative;

■ Postoperative.

In febrile children there is a higher transcutaneous evaporative water loss which leads to rapid dehydration. The most common cause of dehydration in pediatric patient remains diarrheal fluid loss, which contributes to electrolyte loss (diarhea varying from isotonic to hypo-osmolar).

References

1. Oh TH. Formulas for calculating fluid maintenance requirements. Anesthesiology. 1980; 53(4):351.

2. Holliday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics. 1957; 19(5):823-32.

3. Meyers RS. Pediatric Fluid and Electrolyte Therapy. J Pediatr Pharmacol Ther. 2009; 14(4): 204–211.

4. Aker J, O'Sullivan C. The selection and administration of perioperative intravenous fluids for the pediatric patient. J Perianesth Nurs. 1998; 13(3):172-81.