Maintenance Fluid Dosing for a 36kg Pediatric Patient
For a 36kg child requiring maintenance intravenous fluids, administer approximately 1600 mL per 24 hours using 0.9% normal saline (isotonic saline) rather than hypotonic solutions.
Calculating Maintenance Rate
The traditional 4:2:1 formula (Holliday-Segar) provides the standard approach for maintenance fluid calculation 1:
- First 10 kg: 4 mL/kg/hr = 40 mL/hr
- Second 10 kg: 2 mL/kg/hr = 20 mL/hr
- Remaining 16 kg: 1 mL/kg/hr = 16 mL/hr
- Total: 76 mL/hr or approximately 1824 mL per 24 hours 1
For practical purposes, this rounds to approximately 1600-1800 mL per 24 hours or 65-75 mL/hr 1.
Fluid Composition: Normal Saline is Preferred
Use 0.9% normal saline (isotonic) as the maintenance fluid rather than hypotonic solutions 2, 3. The evidence strongly supports this recommendation:
- Hypotonic fluids (0.18% or 0.45% saline) significantly increase the risk of hyponatremia in hospitalized children 2
- In a randomized controlled trial, dextrose saline (0.18%) produced a mean fall in plasma sodium of 3.0 mEq/L greater than normal saline (95% CI 0.8-5.1 mEq/L; P=0.0063) 2
- The fluid type, not the administration rate, was the significant factor affecting sodium levels 2
Important Clinical Considerations
Electrolyte Supplementation
- Add 20 mEq/L of potassium chloride to maintenance fluids once adequate urine output is confirmed, as this permits repair of cellular potassium deficits without risk of hyperkalemia 4
Dextrose Addition
- For children requiring maintenance fluids, consider adding 5% dextrose to prevent hypoglycemia, particularly in younger children or those with limited glycogen stores 4, 2
- One patient in a clinical trial developed asymptomatic hypoglycemia when receiving normal saline without dextrose 2
Monitoring Requirements
- Measure plasma sodium at baseline and 12-24 hours after initiating maintenance fluids 2
- Monitor urinary volume, sodium, and creatinine to calculate fractional excretion of water and sodium for optimal fluid management 3
- Adjust fluid composition based on measured electrolytes rather than relying solely on estimated dehydration 3
Common Pitfalls to Avoid
Do not routinely use hypotonic maintenance fluids (0.18% or 0.45% saline) in hospitalized children, as this practice increases hyponatremia risk without clear benefit 2, 3. The traditional approach of using hypotonic fluids based on the assumption that they match normal oral intake does not account for the non-osmotic release of antidiuretic hormone that occurs in sick, hospitalized children 3.
Avoid the oversimplified approach of selecting fluids based solely on plasma sodium concentration and estimated dehydration without considering the child's overall physiology and ongoing losses 3.