How to calculate maintenance fluid requirements in children:
1. Body Surface Area Method (commonly used in children >10 kg):
1500–2000 mL/m2/day ÷ 24 = fluid rate in mL/hr
Example: Calculate maintenance fluids in mL/hr for a child with a BSA = 0.8 m2.
Answer: 1500 mL/m2/day × 0.8 m2 = 1200 mL/day ÷ 24 hr = 50 mL/hr
2000 mL/m2/day × 0.8 m2 = 1600 mL/day ÷ 24 hr = 66.6 mL/hr
Range: 50–66.6 mL/hr.
2. Body Weight Method
| <10 kg | 100 mL/kg/day |
| 11–20 kg | 1000 mL + 50 mL/kg for each kg >10 |
| >20 kg | 1500 mL + 20 mL/kg for each kg >20 |
Example: Calculate maintenance fluids in mL/hr for a child weighing 25 kg.
Answer: 1500 mL + 20 mL/kg × 5 kg = 1500 mL + 100 mL = 1600 mL
1600 mL ÷ 24 hr = 66.6 mL/hr
Daily Electrolyte Requirements in Children
| Sodium | 2–6 mEq/kg/day |
| Potassium | 2–4 mEq/kg/day |
| Calcium | 1–4 mEq/kg/day* |
| Magnesium | 0.3–0.5 mEq/kg/day |
| Phosphorous | 0.5–2 mmol/kg/day* |
Conditions That May Alter Fluid Requirements in Children
Oral Rehydration Therapy (ORT)
ORT is as effective as IV therapy in managing fluid and electrolytes in children with mild to moderate dehydration due to diarrhea. Commercially available premixed ORT solutions typically contain low concentrations of glucose (2–3%), 45–75 mEq/L sodium, 20–25 mEq/L potassium, 30–35 mEq/L of citrate (bicarbonate source). Low sugar content provides little caloric support but facilitates intestinal sodium and water absorption. All commercially available ORT solutions are equally safe and effective, and are preferred over household remedies (e.g., colas, juices, chicken broth) that are not formulated based on the physiology of acute diarrhea.
*Neonates may require the higher end of the calcium and phosphorous dosage range due to rapid bone development.