Question 1

What is the maintenance fluid calculator used for?

Accepted Answer

The maintenance fluid calculator determines the baseline intravenous (IV) fluid rate needed to maintain normal hydration in hospitalized patients who cannot take fluids orally. It calculates hourly infusion rates and daily fluid volumes based on body weight using the Holliday-Segar method (4-2-1 rule). This is used for routine maintenance hydration, not for resuscitation or replacement of specific deficits. The calculator is essential in pediatrics, emergency medicine, and hospital medicine.

Question 2

What is the Holliday-Segar method (4-2-1 rule)?

Accepted Answer

The Holliday-Segar method, also called the 4-2-1 rule, calculates maintenance fluid requirements based on weight: 4 mL/kg/hr for the first 10 kg, plus 2 mL/kg/hr for the next 10 kg (11-20 kg), plus 1 mL/kg/hr for each kg above 20 kg. For example, a 25 kg child needs: (10 × 4) + (10 × 2) + (5 × 1) = 40 + 20 + 5 = 65 mL/hr. This method has been validated and is standard in pediatric and adult medicine since 1957.

Question 3

How do you calculate maintenance IV fluids for pediatric patients?

Accepted Answer

For pediatric patients, use the Holliday-Segar method: First 10 kg: 100 mL/kg/day or 4 mL/kg/hr. Second 10 kg (11-20 kg): add 50 mL/kg/day or 2 mL/kg/hr. Each kg above 20 kg: add 20 mL/kg/day or 1 mL/kg/hr. For a 15 kg child: (10 kg × 100) + (5 kg × 50) = 1,000 + 250 = 1,250 mL/day or 52 mL/hr. Use isotonic fluids (D5 0.45% or 0.9% NaCl) with 20 mEq/L KCl after urine output confirmed.

Question 4

What IV fluids are used for maintenance therapy?

Accepted Answer

Common maintenance IV fluids include: D5 0.45% NaCl (dextrose 5% in half-normal saline) - traditional pediatric fluid, D5 0.9% NaCl (dextrose 5% in normal saline) - now preferred to prevent hyponatremia, Lactated Ringer's - for patients needing balanced electrolytes, and D5W (dextrose 5% in water) - rarely used alone. Add potassium chloride 20 mEq/L to maintenance fluids after adequate urine output is confirmed. Isotonic fluids are preferred over hypotonic to reduce hyponatremia risk.

Question 5

When should you adjust maintenance fluid rates?

Accepted Answer

Adjust maintenance fluids for: Fever (increase 10% for each degree Celsius above 37°C), ongoing losses (add replacement for vomiting, diarrhea, nasogastric drainage), increased insensible losses (tachypnea, high ambient temperature), decreased needs (hypothyroidism, increased ADH), renal or cardiac dysfunction (may need restriction), and clinical assessment (adjust based on physical exam, vital signs, urine output). Monitor weight, urine output, electrolytes, and clinical status to guide adjustments.

Question 6

What is the maximum maintenance fluid rate for adults?

Accepted Answer

For adults, maintenance fluid rates are typically capped at 100-150 mL/hr (2,400-3,600 mL/day) even for very large patients. Alternative adult maintenance calculation: 25-30 mL/kg/day for average adults, adjusted for age and clinical status. For a 70 kg adult: 25 × 70 = 1,750 mL/day or approximately 73 mL/hr. Very obese patients should use ideal body weight, not actual weight, to avoid excessive fluid administration.

Question 7

What is the difference between maintenance and resuscitation fluids?

Accepted Answer

Maintenance fluids replace normal daily losses (urine, stool, insensible losses) in stable patients - given at calculated hourly rates (e.g., 50-100 mL/hr). Resuscitation fluids rapidly replace existing deficits in unstable patients with shock or severe dehydration - given as boluses (10-20 mL/kg over 10-30 minutes). Maintenance is for ongoing needs; resuscitation is for immediate deficit correction. After resuscitation, transition to maintenance fluids for continued hydration.

Question 8

How do you monitor maintenance fluid therapy?

Accepted Answer

Monitor maintenance fluids by: measuring urine output (should be 0.5-2 mL/kg/hr), tracking daily weights (stable weight indicates appropriate balance), assessing vital signs (heart rate, blood pressure), checking for edema or dehydration signs, monitoring electrolytes (sodium, potassium, chloride) every 12-24 hours initially, and evaluating fluid balance (intake vs output). Adjust rates based on these assessments to maintain euvolemia.

Question 9

Are there special considerations for neonates?

Accepted Answer

Yes, neonates have unique fluid requirements. Day 1 of life: Start with 60-80 mL/kg/day and increase gradually. Days 2-7: Increase by 20-30 mL/kg/day up to 140-160 mL/kg/day by day 7. Premature infants need higher volumes (up to 180-200 mL/kg/day) due to greater insensible losses from immature skin. Monitor weight loss (acceptable 5-10% in first week), urine output, serum sodium, and glucose. Neonates require careful individualization and frequent reassessment.

Question 10

How accurate is this maintenance fluid calculator?

Accepted Answer

This calculator uses the validated Holliday-Segar method, which has been the standard for maintenance fluid calculation since 1957. The calculation is mathematically precise. However, actual fluid requirements vary based on clinical condition, ongoing losses, metabolic rate, and individual factors. Use calculated rates as a starting point and adjust based on clinical assessment, urine output, electrolytes, and patient response. This calculator provides evidence-based estimates but clinical judgment is essential for safe fluid management.

Maintenance Fluid Calculator - Holliday-Segar & 4-2-1 Rule Calculator

Fluid Requirements

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

Example: 25 kg Child

How Maintenance Fluid Calculation Works

The 4-2-1 Rule Formula

Clinical Application Guidelines

Sources & References

Maintenance Fluid Calculation Examples

8 kg Infant (Under 10 kg)

15 kg Child (11-20 kg Range)

30 kg Child (Above 20 kg)

70 kg Adult

Frequently Asked Questions

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