Paediatric fluid and paediatric dosing are the same skill: a number per kilogram, worked from scratch, shown line by line, and then checked against a ceiling. Run maintenance through the 4–2–1 rule, turn a dehydration grade into millilitres and decide whether this child gets 20 or 10 mL/kg, then calculate a drug dose and watch what happens when the per-kilogram answer collides with the maximum adult dose.
Start with the weight
Weigh in kilograms and record only kilograms. A pounds-for-kilograms confusion produces a 2.2-fold overdose and is the commonest source of paediatric weight errors.
The 4–2–1 rule replaces obligatory losses in a child who is not currently depleted. Maintenance is not resuscitation, and a depleted child does not get better on a maintenance rate.
Try these
Both rules appear on the right, along with why they disagree and where they converge. Use one of them consistently and treat the other as a sanity check, never as proof.
What else is true of this child?
Three habits prevent most of the harm. Weigh in kilograms only. Show the arithmetic in your own working before you draw anything up. Check the calculated dose against the maximum adult dose — and when the per-kilogram answer is larger, the adult maximum wins.
Maintenance4 mL/kg/h for the first 10 kg, 2 for the next 10, 1 thereafter