Question 1

What is the 4-2-1 rule for pediatric maintenance fluids?

Accepted Answer

Maintenance IV fluid rate per hour is calculated as: 4 mL/kg/hr for the first 10 kg of body weight, plus 2 mL/kg/hr for the next 10 kg, plus 1 mL/kg/hr for each kilogram above 20. A 25-kg child needs (4 × 10) + (2 × 10) + (1 × 5) = 65 mL/hr.

Question 2

What fluid should I use for pediatric maintenance?

Accepted Answer

The 2018 AAP guideline recommends isotonic fluids — D5NS or D5LR — for most hospitalized children older than 28 days. Hypotonic fluids (D5 ½ NS, D5 ¼ NS) substantially increase the risk of hospital-acquired hyponatremia and are no longer routine first-line.

Question 3

How do I calculate maintenance fluids in 24 hours instead of per hour?

Accepted Answer

Use the daily Holliday-Segar formula: 100 mL/kg/day for the first 10 kg, 50 mL/kg/day for the next 10 kg, 20 mL/kg/day for each kg above 20. A 25-kg child needs (10 × 100) + (10 × 50) + (5 × 20) = 1600 mL/day, which is 65 mL/hr — the same answer.

Question 4

Does the 4-2-1 rule work in adults?

Accepted Answer

The formula extrapolates well into the adult range and is commonly used as a quick maintenance estimate, especially in younger / healthier adults. Most adult hospitalized patients receive an empiric ~1–1.5 mL/kg/hr or a fixed rate (e.g., 75–125 mL/hr) instead, with adjustments for clinical state.

Tier	Weight in tier	Rate
First 10 kg	10 kg	4 mL/kg/hr × 10 = 40 mL/hr
10–20 kg	8 kg	2 mL/kg/hr × 8 = 16 mL/hr

Pediatric Maintenance Fluids (4-2-1)

References

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