Fluid Management in Pediatric Anesthesia

Fluid Management in Pediatric Anesthesia

Fluid Management in Pediatric Anesthesia

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Pediatric Fluid Physiology - Tiny Tot Hydration

  • Body Water: Higher Total Body Water (TBW) in pediatrics (Neonate 75-80%, Preterm up to 85%). Extracellular Fluid (ECF) is ~45% of body weight (Adult ~20%), contracts rapidly postnatally.
  • Physiological Factors:
    • ↑ Basal Metabolic Rate (BMR).
    • ↑ Surface Area to Volume ratio → ↑ Insensible water losses (skin, respiratory).
  • Renal Immaturity:
    • ↓ Glomerular Filtration Rate (GFR) at birth; reaches adult levels by 1-2 years.
    • Limited urine concentrating and diluting capacity.
    • Potential for Na⁺ wasting, especially in preterm infants.
  • Maintenance Fluid Calculation (📌 4-2-1 Rule):
    • $0-10 \text{ kg: } 4 \text{ mL/kg/hr}$
    • $10-20 \text{ kg: } +2 \text{ mL/kg/hr for this portion}$
    • $>20 \text{ kg: } +1 \text{ mL/kg/hr for this portion}$

⭐ Neonates are obligate glucose consumers; hypoglycemia can occur quickly with inadequate intake, often coexisting with dehydration.

Body Fluid Composition: Pediatric vs Adult ICF and ECF)

Preoperative Fasting & Deficits - Empty Tummy Rules

  • NPO Guidelines (📌 "2-4-6-8" Rule):
    • Clear liquids (water, clear juice): 2 hrs
    • Breast milk: 4 hrs
    • Infant formula: 6 hrs
    • Light meal (toast, milk): 6 hrs
    • Heavy/Fried meal: 8 hrs
  • Fluid Deficit Calculation:
    • Maintenance (4-2-1 Rule):
      • First 0-10 kg: $4$ ml/kg/hr
      • Next 10-20 kg: $2$ ml/kg/hr
      • Above 20 kg: $1$ ml/kg/hr
    • Deficit = Total Hourly Maintenance × Fasting Hours
    • Replace: 50% in 1st hr, 25% in 2nd hr, 25% in 3rd hr.

⭐ Prolonged fasting beyond guidelines offers no added safety, risking hypoglycemia and dehydration, especially in neonates and infants.

Pediatric NPO Guidelines and 4-2-1 Rule

Intraoperative Fluid Management - In-Op Juice Juggling

  • Goal: Maintain euvolemia, electrolyte & glucose balance.
  • Maintenance (📌 4-2-1 Rule):
    • $0-10 \text{ kg}$: 4 mL/kg/hr
    • $11-20 \text{ kg}$: 2 mL/kg/hr
    • $>20 \text{ kg}$: 1 mL/kg/hr
    • Use isotonic crystalloids (RL, Plasmalyte).
  • Deficit Replacement (NPO): (Maintenance rate × NPO hours). Give 50% in 1st hr, 25% in 2nd, 25% in 3rd.
  • Ongoing Losses:
    • Third space: 1-10 mL/kg/hr (surgery-dependent).
      • Minimal trauma: 1-3 mL/kg/hr
      • Moderate trauma: 3-7 mL/kg/hr
      • Major trauma: 7-10 mL/kg/hr
    • Blood loss: Replace 3:1 with crystalloid, 1:1 with colloid/blood.
  • Monitoring: Urine output (1-2 mL/kg/hr), vitals.
  • Glucose: Neonates/infants may need dextrose in IVF (Target GIR 4-6 mg/kg/min).

⭐ Neonates have limited renal concentrating ability; careful to avoid fluid overload.

Fluid Choices & Monitoring - Potion Selection & Watchful Eyes

Fluid Selection:

  • Crystalloids (Go-to):
    • Isotonic (Bolus/Deficit): Ringer's Lactate (RL), Normal Saline (NS, 0.9% NaCl). Bolus: 10-20 ml/kg.
    • Maintenance (Holliday-Segar formula based):
      • Neonates: D5 0.2% NaCl + 20 mEq/L KCl.
      • Children: D5 0.45% NaCl + 20 mEq/L KCl.
    • Limit intraop dextrose unless specific risk (e.g., neonates, prolonged fasting, <6 months old).
  • Colloids (e.g., Albumin 5%): For significant protein loss or large volume resuscitation if crystalloids are insufficient.

Watchful Eyes (Monitoring):

  • Key Vitals: Heart Rate (HR), Blood Pressure (BP) (age-appropriate cuff), Capillary Refill Time (CRT) (<2 sec).
  • Urine Output (UOP): Target >1-2 ml/kg/hr.
  • Labs: Hematocrit (Hct), glucose, electrolytes as clinically indicated.

⭐ Neonates are particularly susceptible to hypoglycemia and hyponatremia. Maintenance fluids should typically contain glucose (e.g., D5 or D10) and appropriate sodium (e.g., 0.2% NaCl).

High‑Yield Points - ⚡ Biggest Takeaways

  • Maintenance fluids calculated by Holliday-Segar (4/2/1 rule).
  • Neonates: limited renal concentration, ↑ insensible losses.
  • Hypoglycemia risk is high; monitor glucose, consider dextrose-containing fluids for maintenance in neonates/infants.
  • Prefer isotonic crystalloids (NS, RL) intraoperatively; avoid hypotonic solutions.
  • Blood volume: Neonates 85-90 mL/kg, Infants 80 mL/kg, Children 70-75 mL/kg.
  • Replace third-space losses judiciously.
  • Monitor closely for fluid overload due to small circulatory volume and immature kidneys.

Practice Questions: Fluid Management in Pediatric Anesthesia

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Amount of ORS to be given in the first 4 hours to a child with some dehydration is

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Minimum alveolar concentration is highest at the age of _____

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Minimum alveolar concentration is highest at the age of _____

6 months

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