Maintenance fluids

How it is calculated

Per day (100-50-20): 100 mL/kg for each of the first 10 kg, 50 mL/kg for each kg between 10 and 20, and 20 mL/kg for each kg above 20.

Per hour (4-2-1): 4 mL/kg/h for the first 10 kg, 2 mL/kg/h from 10 to 20 and 1 mL/kg/h above 20. It is a simplification and gives 4 % less than dividing the daily figure by 24.

Worked example with 25 kg: per day, 10 × 100 + 10 × 50 + 5 × 20 = 1000 + 500 + 100 = 1600 mL. Per hour, 10 × 4 + 10 × 2 + 5 × 1 = 40 + 20 + 5 = 65 mL/h.

Source: Holliday and Segar, Pediatrics, 1957.

Keep in mind

• Support calculation: it does not replace clinical judgement. Check with a professional before prescribing intravenous fluids.
• It only covers baseline maintenance. It does not include replacing a deficit (dehydration) or ongoing losses (diarrhoea, vomiting, fever, burns, drains).
• Not applicable to newborns under 14 days old or to situations that require fluid restriction (heart or kidney failure, meningitis, brain injury, inappropriate ADH secretion).
• Choosing the type of fluid is a clinical decision: isotonic solutions are now recommended for hospitalised children to avoid hyponatraemia.
• If the patient can drink, the oral route is preferable.