Maintenance Fluid Calculator

Maintenance Fluid Calculator

Formulas for Maintenance Fluids

A commonly used guideline in pediatrics is based on weight bands. These formulas, sometimes known informally as the “100/50/20” rule (for daily total), provide a quick approximation of fluid needs.

Infusion Rate

Once you’ve determined the total fluid volume needed per day, you can calculate the infusion rate by dividing by 24 to get mL per hour:

Using a Maintenance Fluid Calculator

1. Enter Weight:
   • Specify whether you’re using kilograms (kg) or pounds (lb).
   • If using pounds, the calculator will convert to kilograms internally (1 lb ≈ 0.45 kg).
2. Select Correct Formula:
   • The calculator automatically checks your patient’s weight range and applies the correct formula (0–10 kg, 10–20 kg, or >20 kg).
3. Review Daily Fluid Requirement:
   • The output will show how many mL/day are required to maintain basic fluid needs.
4. Check Hourly Infusion Rate:
   • Dividing by 24 yields the mL/hour rate if you plan to administer fluids continuously.
5. Adjust as Needed:
   • These formulas provide approximate maintenance values.
   • Consider underlying conditions (e.g., fever, renal issues) that may require more or less fluid.

Practical Tips & Considerations

1. Check Clinical Context:
   • The numbers provided by the maintenance fluid formula should be validated against the patient’s overall clinical picture.
   • Fluid requirements may differ in cases of renal insufficiency, cardiac issues, or high insensible losses (e.g., burn patients).
2. Monitor Intake & Output (I&O):
   • Continuously track the patient’s ins and outs to ensure they are neither over- nor under-hydrated.
   • Adjust daily fluid totals when necessary.
3. Fever or Excessive Losses:
   • Fever, diarrhea, vomiting, or increased respiratory rate can significantly increase fluid requirements.
   • Some clinicians add additional fluid for every 1°C rise in fever above normal.
4. Special Populations:
   • Neonates, infants, and the elderly may have different fluid requirements.
   • Always consult pediatric or geriatric references for precise adjustments.
5. Use in Adults:
   • While designed primarily for children, these formulas can be a quick reference for adult maintenance, though many adults are better served by an estimate of 30–35 mL/kg/day or other specialized calculations.

Example Calculation Walkthrough

References

1. Holiday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics. 1957;19(5):823–832.