Maintenance fluid requirements

What is this for?

Maintenance fluids replace ongoing insensible and urinary losses in a patient who is not receiving adequate oral intake. The Holliday–Segar tiers give 100 mL/kg for the first 10 kg, 50 mL/kg for the next 10 kg, and 20 mL/kg thereafter. Above 20 kg this collapses to the familiar 1500 mL + 20 mL/kg shorthand.

How to use it

1. Enter the patient's weight.
2. Read the Holliday–Segar total, which is the tiered calculation, and compare it against the 30–40 mL/kg/day adult range.
3. Divide by 24 for an hourly rate, which is shown for you in the result panel.

Worked example

Calculate maintenance fluid requirements for a 70 kg adult.

Answer: 1500 + 20 × (70 − 20) = 1500 + 1000 = 2500 mL/day, or about 104 mL/hr. The 30–40 mL/kg range gives 2100–2800 mL/day, which brackets it.

Clinical pearls & pitfalls

• Above 20 kg, the tiered Holliday–Segar method and the 1500 + 20 × (kg − 20) shorthand give identical answers. The shorthand is not an approximation.
• The hourly version of Holliday–Segar is the 4-2-1 rule: 4 mL/kg/hr for the first 10 kg, 2 for the next 10, 1 thereafter. It is the same arithmetic divided by 24.
• Holliday–Segar was derived in children and overestimates requirements in large adults, which is why the adult 30–40 mL/kg/day range exists as a cross-check.
• Hypotonic maintenance fluids in hospitalised children have been associated with hyponatraemia. Current guidance favours isotonic maintenance fluid in most paediatric inpatients.

Assumptions & limitations

• Provides maintenance only. Deficit replacement, ongoing losses, and third-spacing must be calculated and added separately.
• Must be reduced in heart failure, oliguric renal failure, SIADH, and cerebral oedema. Applying a maintenance rate uncritically in these settings causes harm.
• Derived in a paediatric population; the extrapolation to large adults is imperfect and progressively overestimates requirements.
• Says nothing about what fluid to give. Composition — tonicity, potassium, glucose — is a separate clinical decision.

References

• Holliday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics. 1957;19(5):823-832.
• Feld LG, et al. Clinical practice guideline: maintenance intravenous fluids in children. Pediatrics. 2018;142(6):e20183083.
• National Institute for Health and Care Excellence. Intravenous fluid therapy in adults in hospital. NICE Clinical Guideline CG174.

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