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Fluids, Electrolytes, and Nutrition in Pediatric Surgical Patients

Fluid and Electrolyte Management

  • Fluid Balance in Neonates:
    • Higher insensible water losses due to immature skin barrier, especially in premature infants.
    • Fluid losses related to gestational age:
      • Premature infants (<1500g): 45-60 mL/kg/day.
      • Term infants: 30-35 mL/kg/day.
    • Additional fluid losses: Radiant heat warmers, phototherapy, and respiratory distress can increase fluid requirements.
  • Fluid Requirements:
    • First few days of life: Conservative fluid recommendations.
    • By the fourth day of life, infants require 100-130 mL/kg/day for maintenance.
    • Surgical conditions like gastroschisis and necrotizing enterocolitis (NEC) increase fluid needs.
  • Indicators of Adequate Perfusion:
    • Urine output: Ideal minimum is 1-2 mL/kg/day.
    • Newborns' urine concentration: Up to 700 mOsm/kg.
  • Electrolyte Requirements:
    • Sodium: 2-4 mEq/kg/day.
    • Potassium: 1-2 mEq/kg/day.
    • Maintenance fluids: 5% dextrose in 0.45% saline with 20 mEq/L of potassium.
  • Special Fluid Considerations:
    • Gastric losses: Replace with 0.45% saline with 20 mEq/L potassium.
    • Diarrhea, pancreatic, and biliary losses: Replace with isotonic lactated Ringer solution.
    • Hypovolemia from hemorrhage: Corrected with blood products, e.g., 10-20 mL/kg packed RBCs, plasma, or 5% albumin.

Nutrition in Infants

  • Energy Requirements:
    • Vary with age and clinical condition.
    • Appropriate weight gain is the best crude indicator of adequate caloric intake.
    • Infants require about 120 calories/kg/day to achieve a 1% weight gain/day.
    • Breast milk and standard infant formulas provide 20 calories/ounce.
  • Special Nutritional Formulas:
    • High-calorie formulas for infants with fluid restrictions or insufficient calorie intake.
    • Hypoallergenic, lactose-free, and amino acid-based formulas are available for GI conditions.
  • Feeding Techniques:
    • For infants with stressed GI tracts, start with continuous enteral feeding, transitioning to gastric bolus feeding.
    • Monitor tolerance by assessing abdominal girth, gastric residuals, and stool output.

Carbohydrate, Protein, and Fat Requirements

  • Carbohydrates:
    • Stored as glycogen in the liver and muscles, but newborns have a smaller glycogen reserve.
    • Minimum glucose infusion rate: 4-6 mg/kg/min for neonates, increasing to a maximum of 10-12 mg/kg/min in total parenteral nutrition (TPN).
  • Protein:
    • Protein intake: ~15% of total daily calories.
    • Infants: 2-3.5 g/kg/day.
    • By 12 years, protein requirement is halved, reaching 1 g/kg/day by 18 years.
    • In TPN, protein is started at 0.5 g/kg/day, increased by 0.5 g/kg/day until the target of 3.5 g/kg/day is reached.
  • Fat:
    • Major source of nonprotein calories and essential for preventing fatty acid deficiency.
    • Lipid infusions: Start at 0.5 g/kg/day, advancing to 2.5-3.5 g/kg/day.
    • In cases of unconjugated hyperbilirubinemia, fat administration should be cautious to avoid kernicterus.

Total Parenteral Nutrition (TPN)

  • Indications: For infants unable to achieve adequate enteral nutrition.
  • Duration: Infants can only endure 2-3 days of starvation before needing TPN.
  • Monitoring:
    • Steady infusion rates to meet daily fluid and nutrient needs.
    • Gradual daily increase in nutrient concentrations until targets are met.
  • Complications:
    • Cholestasis: Common in surgical infants on prolonged TPN, indicated by elevated serum bile acids and direct bilirubin.
    • Treatment: Transition to enteral feeding and consider omega-3 fat emulsions (Omegaven) to prevent TPN-induced cholestasis.
    • Medium-chain triglyceride (MCT) formulas and supplementation with fat-soluble vitamins in enteral nutrition.

This summary captures all essential points regarding fluids, electrolytes, and nutrition in pediatric surgical patients, addressing fluid balance, nutrition, and TPN management.