## The 4-2-1 Rule for Pediatric Fluid Maintenance The 4-2-1 rule is a mnemonic for calculating hourly maintenance fluid requirements in children based on body weight. ### Calculation Method **Key Point:** The rule breaks down as follows: - First 10 kg: 4 mL/kg/hour - Second 10 kg: 2 mL/kg/hour - Each additional kg above 20 kg: 1 mL/kg/hour ### Application to 25 kg Child 1. First 10 kg: 10 × 4 = 40 mL/hour 2. Second 10 kg: 10 × 2 = 20 mL/hour 3. Remaining 5 kg: 5 × 1 = 5 mL/hour 4. **Total: 40 + 20 + 5 = 65 mL/hour** ### Clinical Pearl **High-Yield:** This rule applies to maintenance fluids only and does not account for: - Deficit replacement (from preoperative fasting) - Third-space losses (surgical trauma) - Ongoing losses (bleeding, urine output) These must be calculated separately and added to the maintenance requirement. ### Mnemonic **Mnemonic: "4-2-1 Rule" = 4 mL (first 10 kg), 2 mL (second 10 kg), 1 mL (each kg >20 kg)** ### Common Fluid Composition for Maintenance Typical maintenance fluid is 0.2% saline with 5% dextrose (D5 0.2% NS) to provide: - Sodium: ~30 mEq/L - Chloride: ~30 mEq/L - Dextrose: 50 g/L (prevents ketosis) [cite:Miller's Anesthesia Ch 41]
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