Daily Fluid Maintenance Requirement for a 15.5 kg Child
For a healthy 15.5 kg child, the daily fluid maintenance requirement is 1,275 mL per day (approximately 53 mL/hour), calculated using the Holliday-Segar formula. 1
Calculation Method
The Holliday-Segar formula remains the standard approach for calculating maintenance fluid needs in pediatric patients beyond the neonatal period 1:
- First 10 kg of body weight: 100 mL/kg/day (= 1,000 mL)
- Next 10 kg of body weight (10-20 kg): 50 mL/kg/day
- For 5.5 kg: 5.5 kg × 50 mL/kg = 275 mL
- Total daily requirement: 1,000 mL + 275 mL = 1,275 mL/day
Alternatively expressed as an hourly rate: approximately 53 mL/hour 1
Physiological Basis
Water requirements parallel energy needs at approximately 1 kcal per 1 mL of water 1. This relationship accounts for:
- Insensible water losses from skin and lungs (consuming 0.5 kcal per 1 mL water lost) 1
- Urinary and stool losses 1
- Metabolic water production from nutrient oxidation 1
Electrolyte Requirements
When providing maintenance fluids, appropriate electrolyte supplementation should be included 1:
- Sodium: 2-3 mmol/kg/day
- Potassium: 1-3 mmol/kg/day
- Chloride: 2-3 mmol/kg/day
These requirements are based on approximately 1-3 mmol of sodium and potassium per 100 kcal intake, similar to the composition of human breast milk 1
Critical Clinical Modifications
The standard calculation assumes a healthy, well-hydrated child. Individual patients may require significant deviations from these baseline requirements 1:
Increased fluid needs occur with:
Decreased fluid needs occur with:
- Renal failure 1
- Congestive heart failure 1, 2
- Critical illness 1
- Mechanical ventilation in temperature-controlled environments 1
- Cardiac defects (may require restriction to 60-80 mL/kg/day) 2
Fluid Type Selection
For sick children requiring intravenous maintenance hydration, isotonic fluid should be used, especially during the first 24 hours 1. This recommendation stems from evidence showing increased risk of hospital-acquired hyponatremia and potentially fatal hyponatremic encephalopathy with traditional hypotonic saline solutions 1
Common Pitfalls to Avoid
- Do not use hypotonic saline (Na 35-77 mmol/L in 5% dextrose) as routine maintenance fluid in acutely ill or postoperative children, as this significantly increases the risk of dangerous hyponatremia 1
- Do not apply adult-based formulas to young children, as metabolic rates and body composition differ significantly 1
- Do not ignore clinical context: The calculated value represents a starting point that must be adjusted based on ongoing assessment of hydration status, urine output, and clinical condition 1