Maintenance Fluids Calculator (Pediatric) - Holliday-Segar

Calculate pediatric maintenance IV fluid rates using the Holliday-Segar method (4-2-1 rule). Provides hourly rate, daily fluid requirements, and fluid bolus volume for children.

What Are Maintenance Fluids?

Maintenance fluids are the baseline volume of intravenous (IV) fluids required to replace normal daily losses from metabolism, respiration, urination, and insensible losses (sweat, respiration). In pediatric patients, accurate fluid calculation is critical because children have higher metabolic rates per kilogram and smaller fluid reserves than adults, making them more vulnerable to both dehydration and fluid overload.

The concept of maintenance fluids was formalized by Holliday and Segar in 1957, who correlated caloric expenditure with water requirements. Their method remains the standard of care in pediatric medicine worldwide.

The 4-2-1 Rule (Holliday-Segar Method)

The 4-2-1 rule provides a simple, weight-based formula for calculating hourly maintenance fluid rates:

First 10 kg of body weight: 4 ml/kg/hr

Next 10 kg (11–20 kg): 2 ml/kg/hr

Each kg above 20 kg: 1 ml/kg/hr

The daily requirement is simply the hourly rate multiplied by 24. An alternative way to express the same formula for daily volumes is:

First 10 kg: 100 ml/kg/day | Next 10 kg: 50 ml/kg/day | Above 20 kg: 20 ml/kg/day

Quick Reference Table

Weight (kg)	Hourly Rate (ml/hr)	Daily Volume (ml/24h)	Bolus 20 ml/kg (ml)
5	20	480	100
10	40	960	200
15	50	1,200	300
20	60	1,440	400
25	65	1,560	500
30	70	1,680	600
40	80	1,920	800
50	90	2,160	1,000
70	110	2,640	1,400

4-2-1 Rule Visual Diagram

Types of Maintenance Fluids

Solution	Na+ (mEq/L)	Glucose	Common Use
D5 0.45% NS	77	5% dextrose	Standard maintenance for older children
D5 0.9% NS	154	5% dextrose	Preferred to prevent hyponatremia (current guidelines)
D5 0.2% NS	34	5% dextrose	Neonates (with close monitoring)
Lactated Ringer's	130	None	Bolus fluid, balanced crystalloid
Normal Saline (0.9%)	154	None	Bolus fluid, volume resuscitation

Important note: Current guidelines (including NICE and AAP) recommend isotonic fluids (0.9% NaCl with dextrose) for maintenance to reduce the risk of hospital-acquired hyponatremia, which was more common with hypotonic solutions.

Recognizing Dehydration in Children

Sign	Mild (3-5%)	Moderate (6-9%)	Severe (≥10%)
Mental status	Normal, slightly thirsty	Irritable, restless	Lethargic, obtunded
Heart rate	Normal	Increased	Tachycardic / thready
Skin turgor	Normal	Decreased (tenting)	Markedly decreased
Mucous membranes	Slightly dry	Dry	Parched / cracked
Tears	Present	Decreased	Absent
Urine output	Slightly decreased	Oliguria	Anuria
Fontanelle (infants)	Normal	Sunken	Very sunken
Capillary refill	< 2 sec	2–3 sec	> 3 sec

Fluid Bolus Guidelines

A fluid bolus is a rapid infusion of isotonic fluid (typically Normal Saline or Lactated Ringer's) given to treat hypovolemia or shock. The standard pediatric bolus is:

Fluid Bolus = 20 ml/kg, infused over 10–20 minutes

Reassess after each bolus for clinical improvement (heart rate, capillary refill, mental status)
May repeat up to 3 boluses (60 ml/kg total) before considering vasopressors
In neonates, use 10 ml/kg boluses due to higher risk of intraventricular hemorrhage
In suspected cardiac disease, use smaller boluses (5-10 ml/kg) and reassess frequently

Worked Example

A 15 kg child:

First 10 kg: 10 × 4 = 40 ml/hr
Next 5 kg: 5 × 2 = 10 ml/hr
Total hourly rate = 50 ml/hr

Daily fluids = 50 ml/hr × 24 = 1,200 ml/day

Fluid bolus = 15 kg × 20 ml/kg = 300 ml

Frequently Asked Questions

Why is it called the 4-2-1 rule?

The name comes from the three rates used in the formula: 4 ml/kg/hr for the first 10 kg, 2 ml/kg/hr for the next 10 kg, and 1 ml/kg/hr for each additional kg above 20 kg. This stepwise decrease reflects the decreasing metabolic rate per kilogram as body weight increases.

Does this formula apply to adults?

While the Holliday-Segar formula can technically be used for adults, it tends to overestimate needs in heavier patients. For adults, a common approach is to simply use 1.5 ml/kg/hr or 25-30 ml/kg/day, often capped at about 2,000-2,500 ml/day for most patients.

When should maintenance fluids be adjusted?

Adjustments are needed for: fever (increase by 10-12% per degree Celsius above 38), high ambient temperature, burns, third-spacing, renal failure (reduce), heart failure (reduce), SIADH (restrict), and ongoing losses (vomiting, diarrhea, surgical drains).

What about electrolytes?

Standard maintenance electrolyte requirements for children are approximately: Sodium 2-3 mEq/kg/day, Potassium 1-2 mEq/kg/day, and Chloride 2-3 mEq/kg/day. Adding 20 mEq/L of KCl to maintenance fluids is common practice once urine output is confirmed.