Pediatric Maintenance Fluids (4-2-1)
Holliday-Segar maintenance rate with the 2018 AAP isotonic-fluid recommendation surfaced.
- Writing maintenance fluid orders for a hospitalized child or adolescent
- Estimating expected urine output (~1 mL/kg/hr is roughly two-thirds to one-half of maintenance rate)
- Cross-applicability to ED / urgent care, where pediatric fluid math is high-volume
- The 4-2-1 rule is for maintenance — it does not replace deficit calculations or ongoing-loss replacement (gastroenteritis, third-spacing, burns).
- Use isotonic fluids in most hospitalized children. Hypotonic maintenance fluids (D5 ¼ NS, etc) are a major iatrogenic source of hyponatremia and are no longer recommended for routine use per the 2018 AAP guideline.
- Adjust upward for fever (~12% per °C above 37), tachypnea, burns, radiant warmer, and ongoing losses.
- Adjust downward for fluid restriction (CHF, SIADH, post-op, oliguric AKI).
- For obese children, some references cap maintenance based on ideal body weight to avoid overshoot.
Pediatric fluid math is simple but error-prone — the 4-2-1 rule is universally taught yet routinely miscalculated, especially in older children where the third tier dominates. The bigger error, though, is fluid choice: a generation of hospital-acquired hyponatremia traces back to using hypotonic maintenance fluids by reflex.
Maintenance rate
56mL/hr
Per 24 hr
1400mL/day
| 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 |
Holliday-Segar (4-2-1)
- 4 mL/kg/hr for the first 10 kg
- 2 mL/kg/hr for the next 10 kg (10–20)
- 1 mL/kg/hr for each kg above 20
Use isotonic fluids in hospitalized children
The 2018 AAP guideline recommends isotonic maintenance fluids (D5NS or D5LR) rather than hypotonic fluids for most hospitalized children >28 days, because hypotonic fluids markedly increase the risk of hospital-acquired hyponatremia.
Frequently asked
What is the 4-2-1 rule for pediatric maintenance fluids?
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.
What fluid should I use for pediatric maintenance?
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.
How do I calculate maintenance fluids in 24 hours instead of per hour?
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.
Does the 4-2-1 rule work in adults?
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.