Holliday-Segar Method: Paediatric Maintenance Fluid Calculation

Every day, across every paediatric ward, PICU, and emergency department, the same fundamental question arises: how much IV fluid does this child need? Too little and the child becomes dehydrated; vital organ perfusion falls and metabolic derangements worsen. Too much and the child develops dangerous dilutional hyponatraemia — a serious and preventable cause of neurological injury and death in hospitalised children.

The Holliday-Segar method — developed by Malcolm Holliday and William Segar in 1957 — provides the universally used formula for calculating maintenance fluid requirements in children based on body weight. Its simplicity has made it the cornerstone of paediatric fluid prescription for over six decades, and the 4-2-1 rule derived from it is one of the most important numbers sequences in paediatric medicine.

Why Children Need Different Fluid Calculations Than Adults

Children cannot simply be dosed as small adults for fluid therapy. They differ from adults in several important physiological ways:

Higher body water percentage: Neonates are ~75–80% water; adults ~60%. Small absolute changes in fluid balance represent larger proportional changes.
Higher metabolic rate per kg: Children have higher energy expenditure and therefore higher insensible water losses (through breathing and skin) per kilogram of body weight.
Higher surface area to weight ratio: Greater evaporative losses through skin and lungs proportional to body weight.
Immature renal concentrating ability: Infants cannot concentrate urine as effectively as older children and adults, making them more vulnerable to both dehydration and fluid overload.
Higher risk of hyponatraemia: Children's brains occupy a higher proportion of their skull volume, making them more susceptible to cerebral oedema from hyponatraemia-driven water shifts into brain tissue.

The Holliday-Segar Formula — Daily Fluid Requirements

Holliday-Segar — Daily Maintenance Fluid (mL/day)

First 10 kg: 100 mL/kg/day
Next 10 kg (10–20 kg): 50 mL/kg/day
Each kg above 20 kg: 20 mL/kg/day

Maximum: Adults typically capped at 2,000–2,500 mL/day regardless of weight above 70–80 kg.

The 4-2-1 Rule — Hourly Maintenance Rate

The daily requirement divided by 24 gives the hourly rate. This produces the memorable 4-2-1 rule used at the bedside for IV infusion rate calculation:

mL/kg/hour

For the first 10 kg of body weight

mL/kg/hour

For the next 10 kg (10–20 kg)

mL/kg/hour

For each kg above 20 kg

👶 Use the RxMedCalc Holliday-Segar Calculator — enter weight in kg to instantly get daily, hourly, and 8-hourly maintenance fluid requirements with IV fluid prescription guidance.

Worked Examples

📋 Example 1 — Infant 8 kg

Daily: 8 kg × 100 mL/kg = 800 mL/day

Hourly (4-2-1): 8 kg × 4 mL/kg/hr = 32 mL/hour

📋 Example 2 — Child 15 kg

Daily: (10 × 100) + (5 × 50) = 1,000 + 250 = 1,250 mL/day

Hourly (4-2-1): (10 × 4) + (5 × 2) = 40 + 10 = 50 mL/hour

📋 Example 3 — Child 28 kg

Daily: (10 × 100) + (10 × 50) + (8 × 20) = 1,000 + 500 + 160 = 1,660 mL/day

Hourly (4-2-1): (10 × 4) + (10 × 2) + (8 × 1) = 40 + 20 + 8 = 68 mL/hour

Quick Reference Table

Weight (kg)	Daily Maintenance (mL/day)	Hourly Rate (mL/hr)
3 kg (neonate)	300	12.5
5 kg	500	20
10 kg	1,000	40
12 kg	1,100	44
15 kg	1,250	50
20 kg	1,500	60
25 kg	1,600	65
30 kg	1,700	70
40 kg	1,900	75
50 kg+	2,000–2,500	80–100

Which IV Fluid to Use — The Isotonic Shift

For decades, hypotonic fluids (0.18% NaCl in 4% dextrose — "one-fifth normal saline") were standard for paediatric maintenance. This has now changed. Major guidelines including NICE (2015), BPSU, and IAP now recommend isotonic saline (0.9% NaCl) as the default maintenance fluid for most hospitalised children, because hypotonic fluids carry a significant risk of hospital-acquired hyponatraemia.

Fluid	Na content	Indication	Risk
0.9% NaCl (Normal Saline)	154 mEq/L	Most hospitalised children — standard maintenance	Hyperchloraemic acidosis with large volumes
0.9% NaCl + 5% Dextrose	154 mEq/L	Most common prescription — provides glucose for energy	Hyperglycaemia if rate too fast
Ringer's Lactate (Hartmann's)	130 mEq/L	Near-isotonic alternative; better acid-base profile	Slightly lower Na than 0.9% saline
0.45% NaCl (half-normal saline)	77 mEq/L	Specific situations only — fluid restriction, renal disease under specialist guidance	Hyponatraemia if used inappropriately
0.18% NaCl in 4% Dextrose	30 mEq/L	No longer recommended for routine maintenance	High risk of dilutional hyponatraemia

⚠️ Hospital-acquired hyponatraemia from hypotonic fluids causes cerebral oedema, seizures, and can be fatal. NICE 2015 mandates isotonic saline for maintenance in all hospitalised children > 1 month unless specifically indicated otherwise. Prescribe 0.9% NaCl ± dextrose as default.

Electrolyte Additions to Maintenance Fluids

Maintenance fluids replace ongoing electrolyte losses as well as water. Standard electrolyte requirements for children are:

Sodium: 2–4 mEq/kg/day — met by isotonic saline at standard maintenance rates
Potassium: 2–3 mEq/kg/day — typically added as KCl 20 mEq/L to maintenance fluid once urine output is confirmed (> 1 mL/kg/hour). Never give potassium without confirmed urine output.
Glucose: 5–8 mg/kg/min for neonates; lower for older children. Dextrose 5% provides ~3.3 mg/kg/min glucose at maintenance rate for a 10 kg child — adequate to prevent hypoglycaemia but not sufficient for nutritional needs.

✅ Always confirm urine output before adding potassium to IV fluids. Hyperkalaemia from potassium supplementation in a child with unrecognised oliguria is a preventable and potentially fatal error.

Adjustments for Special Situations

Fever

For every 1°C above 37.5°C, insensible losses increase by approximately 10–12%. A child with a temperature of 39.5°C needs approximately 20–25% more fluid than the calculated maintenance. However, rather than automatically increasing IV rate, reassess whether the child can tolerate oral/NG fluids, and target IV supplements to compensate for ongoing losses specifically.

Post-Operative Patients

Post-operative children are at particular risk of SIADH (syndrome of inappropriate ADH secretion) — ADH release from surgical stress causes water retention. The older practice of using hypotonic fluids post-operatively is now recognised as dangerous. Use isotonic saline at the calculated maintenance rate; consider fluid restriction to 50–66% of maintenance in the immediate post-operative period if urine output is adequate.

Critically Ill Children (PICU)

In critically ill children, the Holliday-Segar calculation is a starting point only. PICU patients often require significantly less maintenance fluid due to reduced insensible losses (intubated, humidified circuits) and risk of fluid overload contributing to worse outcomes. Aim to provide the minimum necessary while monitoring fluid balance closely.

Neonates (< 28 days)

Neonatal fluid requirements are managed differently from older infants and children:

Day 1: 60–80 mL/kg/day
Day 2: 80–100 mL/kg/day
Day 3 onwards: 100–150 mL/kg/day (increasing as renal maturation allows higher urine output)
Preterm infants require more careful titration — insensible losses are higher through thin skin, especially in very low birth weight infants under radiant warmers or phototherapy

Common Errors in Paediatric Fluid Prescription

Error	Consequence	Prevention
Using adult fluid volumes for large children	Fluid overload, pulmonary oedema	Always calculate from weight using 4-2-1; cap at adult maximum
Prescribing hypotonic saline (0.18%) routinely	Dilutional hyponatraemia, cerebral oedema, seizures	Use 0.9% NaCl (± dextrose) as default per NICE 2015
Adding potassium without confirming urine output	Hyperkalaemia → cardiac arrhythmia	Always confirm urine output > 1 mL/kg/hr first
Forgetting to add maintenance on top of deficit replacement	Ongoing under-resuscitation	Deficit replacement + maintenance are separate calculations — add them
Using estimated weight rather than actual weight	Systematic over- or under-dosing	Always weigh the child; use APLS tape/formula only when scales unavailable
Not monitoring blood glucose in small infants on IV fluids	Hypoglycaemia	Monitor BGL 4-hourly in infants < 6 months on IV fluids

Key Takeaways

Holliday-Segar daily: 100 mL/kg (first 10 kg) + 50 mL/kg (next 10 kg) + 20 mL/kg (above 20 kg)
4-2-1 rule hourly: 4 mL/kg/hr for first 10 kg + 2 mL/kg/hr for next 10 kg + 1 mL/kg/hr above 20 kg
Default IV fluid: 0.9% NaCl ± 5% dextrose — isotonic saline is now standard (NICE 2015)
Do not use 0.18% NaCl routinely — high risk of dilutional hyponatraemia
Add KCl 20 mEq/L only after confirming urine output > 1 mL/kg/hr
Neonates have different daily requirements — start at 60–80 mL/kg/day on Day 1
Holliday-Segar is maintenance only — add separately calculated deficit and ongoing loss replacement
Monitor blood glucose 4-hourly in infants under 6 months on IV fluids

References

Holliday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics. 1957;19(5):823-832.
NICE. IV fluids in children: intravenous fluid therapy in children and young people in hospital. Clinical Guideline NG29, 2015.
Moritz ML, Ayus JC. Prevention of hospital-acquired hyponatremia: a case for using isotonic saline. Pediatrics. 2003;111(2):227-230.
Indian Academy of Pediatrics. IAP Textbook of Pediatrics — Fluid and Electrolyte Management. 6th Edition, 2022.
Friedman AL. Pediatric hydration therapy: historical review and a new approach. Kidney Int. 2005;67(1):380-388.

This article is for educational purposes based on Holliday-Segar 1957, IAP and NICE NG29 guidelines. Paediatric IV fluid prescriptions must be written by a qualified clinician with regular monitoring of electrolytes, fluid balance, blood glucose, and clinical response.

Built by an MBBS, AFIH Certified Physician in Punjab, India | RxMedCalc.com