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Daily Fluid Requirements

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Kilograms of Body Weight–Based Method (Pediatrics. 1957;19:823)

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  • 1–10 kg: 100 mL/kg/d and
  • 10–20 kg: 50 mL/kg/d and
  • >20 kg: 20 mL/kg/d

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BSA-Based Method (Pediatrics. 1960;25:496)

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  • See “BSA Nomogram and Calculations” in Chapter 1 for BSA calculation.
    • BSA (m2) × 1500–1600 mL/m2/d = Daily requirement

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  • Examples (22-kg child):
    • Daily (body weight–based method): (100 mL/kg/d × 10 kg) + (50 mL/kg/d × 10 kg) + 20 mL/kg/d × 2 kg) = 1540 mL/d (divide by 24 for hourly rate = 64 mL/h)
    • Daily (BSA-based method): 0.84 m2 × 1600 mL/m2/d = 1344 mL/d (divide by 24 for hourly rate = 56 mL/h)

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Glucose

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  • Included in IV fluids to prevent protein catabolism, 3–4 mg/kg/min (not calorically adequate; see TPN section in Chapter 4 for parenteral nutrition).
    • D5W = 5% glucose solution = 5 g glucose/dL = 5 g glucose/100 mL = 50 mg/mL water

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Sodium (Na)

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  • Maintenance: 2–3 mEq/kg/d
    • Normal saline (NS) = 0.9% saline = 154 mEq/L; ½ NS = 0.45% saline = 77 mEq/L; ¼ NS = 0.225% saline = 38 mEq/L
  • For 1x MIVF, the following saline concentrations approximate maintenance Na: D1/4NS for 0–20 kg and D1/2NS for >20 kg

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Potassium (K)

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  • Maintenance is age dependant.
    • Infant; 2–3 mEq/kg/d
    • Child: 1–2 mEq/kg/d
    • Adolescent: 1 mEq/kg/d
    • Adult: 0.5–1.0 mEq/kg/d
    • K should always be added if anticipated duration of IVF greater than 24 h
    • When providing 1x MIVF, adding KCl 20 mEq/L to IVF will approximate daily maintenance for all ages

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Modifications to Maintenance Daily Fluid Requirements:

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  • Calculations above are for 1x MIVF, assuming an average, hospitalized patient with caloric demands 20% to 30% above resting energy expenditure.
  • Any perturbation affecting fluid intake or output or energy demand or /utilization directly affects daily MIVF needs

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Increased Mivf Needs

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  • ↑ Fluid losses: Renal (renal tubular injury, hyperglycemia, diuretic administration, mannitol administration, diabetes insipidus), GI (vomiting, diarrhea, NG suction, burns (see Critical Care chapter)
  • ↑ Energy expenditure: Fever (↑ 12% for each °C over 37°C), radiant warmer, hyperthyroidism, hypermetabolic states

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Decreased Mivf Needs

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  • ↓ Fluid losses: Anuric or oliguric renal failure, SIADH, ventilation with humidified air (decreases insensible loss)
  • ↓ Energy expenditure: Coma, sedation, paralysis, hypothermia, hypothyroidism

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  • All calculations are based on the condition at the time of initiation of fluids; ongoing losses must be addressed as observed.
  • End points to follow in all patients: Clinical improvement, weight gain, urine output.
  • Bicarbonate administration should be avoided for initial replacement and then utilized only in extreme cases (serum HCO3 <8).
    • [Desired HCO3 (24 mEq/L) – current HCO3] × 0.5 × [wt in kg] = ...

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