3.3 Neonatal Parenteral & Enteral Nutrition

Neonatal Parenteral Nutrition (PN)

Neonatal Parenteral Nutrition (PN) is critical for very low birth weight (VLBW; <1500g) infants and those with congenital gastrointestinal anomalies who cannot tolerate enteral feeds. Preterm infants have high metabolic demands but lack nutritional reserves; without immediate PN, they enter a catabolic state, risking growth failure and poor neurodevelopmental outcomes.

PN Components & Clinical Management

1. Dextrose

Dextrose is the primary source of carbohydrates, providing 3.4 kcal/gram.

• Administration: Initiated on DOL 1 at a Glucose Infusion Rate (GIR) of 4 to 6 mg/kg/min. It is advanced by 1 to 2 mg/kg/min daily to a target of 11 to 12 mg/kg/min (maximum 15 mg/kg/min).
• Osmolality Limits: Dextrose concentrations above 12.5% are hypertonic and must be administered through a central venous catheter (UVC or PICC) to prevent peripheral chemical phlebitis. Central lines can tolerate dextrose concentrations up to 25% to 30%.

2. Amino Acids (Protein)

Amino acids prevent muscle breakdown, promote growth, and facilitate positive nitrogen balance.

• Administration: Started within the first 24 hours of life at 1.5 to 3.0 g/kg/day, and advanced daily to a goal of 3.5 to 4.0 g/kg/day.
• Clinical Significance: Early administration of amino acids prevents "transient neonatal catabolism" and does not cause metabolic acidosis or hyperammonemia in stable preterm infants.

3. Intravenous Lipids (Fat)

Lipids provide essential fatty acids (linoleic and alpha-linolenic acids) to prevent Essential Fatty Acid Deficiency (EFAD), which can develop within 72 hours of birth without lipid intake. Lipids also provide a dense caloric source (9 kcal/gram).

• Administration: Started on DOL 1 or 2 at 1.0 to 2.0 g/kg/day and advanced by 0.5 to 1.0 g/kg/day to a maximum of 3.0 g/kg/day.
• Monitoring: Serum triglyceride levels must be monitored. Keep triglycerides <150 to 200 mg/dL. If levels exceed this threshold, the lipid infusion rate must be decreased to prevent pulmonary lipid deposition and displacement of bilirubin from albumin.
• Complication: Prolonged PN (>2-3 weeks) carries a high risk of Parenteral Nutrition-Associated Cholestasis (PNAC), also known as Intestinal Failure-Associated Liver Disease (IFALD), characterized by direct hyperbilirubinemia (>2.0 mg/dL).

4. Calcium and Phosphorus

These minerals are essential for fetal bone mineralization, 80% of which occurs during the third trimester. Preterm infants are at high risk for Metabolic Bone Disease (MBD) of prematurity (osteopenia).

• Calcium-to-Phosphorus Ratio: To optimize bone retention, calcium and phosphorus must be administered in a specific ratio. The ideal ratio is 1.7:1 to 2:1 by weight (or 1.3:1 to 1.7:1 molar ratio).
• Precipitation Risk: Calcium and phosphorus can form an insoluble precipitate (calcium phosphate) in the PN bag or IV tubing, which can cause catheter occlusion or fatal pulmonary emboli. Factors that increase the risk of precipitation include:
  • High temperatures (e.g., incubator heat).
  • High pH (alkaline solutions).
  • Low dextrose or low amino acid concentrations (amino acids act as buffers to keep calcium and phosphorus in solution).
  • Adding calcium before phosphorus during PN compounding (always mix phosphorus first, then add calcium last with thorough agitation).

5. Trace Elements & Vitamins

• Standard Additions: Zinc, copper, manganese, selenium, and chromium.
• Biliary Obstruction / Cholestasis: Copper and manganese are excreted in bile. If direct bilirubin is >2.0 mg/dL (indicating cholestasis), copper and manganese must be held or significantly reduced to prevent toxic accumulation in the liver and basal ganglia.
• Renal Failure: Selenium and chromium are excreted renally. In the presence of acute kidney injury or oliguria, these elements must be restricted.

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Enteral Nutrition

Enteral feeds should be initiated as soon as hemodynamic stability is achieved.

Benefits of Human Breast Milk

Human breast milk (HBM) is the gold standard for neonatal nutrition.

• Immunological Factors: HBM contains high levels of Secretory IgA (provides local gut mucosal immunity), lactoferrin (binds iron, inhibiting bacterial growth), lysozyme (destroys bacterial cell walls), and oligosaccharides (act as prebiotics).
• Clinical Outcomes: Strongly associated with a reduced incidence of Necrotizing Enterocolitis (NEC), late-onset sepsis, and retinopathy of prematurity (ROP).
• Fortification: Preterm breast milk lacks sufficient protein, calcium, and phosphorus for VLBW infants. Once enteral intake reaches 100 mL/kg/day, Human Milk Fortifier (HMF) is added to breast milk to increase caloric density (usually to 22 or 24 kcal/oz) and mineral content.

Trophic Feeding (Minimal Enteral Nutrition)

Trophic feeds are small, sub-nutritional volumes of milk designed to prime the gastrointestinal tract rather than provide total caloric support.

• Volume & Schedule: 10 to 20 mL/kg/day, divided and administered every 2 to 6 hours.
• Timing: Initiated within the first 24 to 72 hours of life in stable preterm infants.
• Benefits: Stimulates the secretion of gut hormones (gastrin, motilin), promotes intestinal mucosal hyperplasia, reduces mucosal atrophy from fasting, improves future feeding tolerance, decreases time to reach full enteral feeds, and reduces the duration of PN and central line use.

Enteral Feeding Protocol & Holding Criteria

Enteral feeds are advanced cautiously in preterm infants (typically 10 to 30 mL/kg/day) to minimize the risk of NEC. Nurses must vigilantly monitor for signs of feeding intolerance.

Holding Criteria (Enteral Feeding Interruption)

Feeds should be held and the provider notified if the infant exhibits:

1. Abdominal Distension: An increase in abdominal girth of >2 cm from baseline, visible bowel loops, abdominal wall erythema, or tenderness.
2. Bilious or Bloody Residuals: Green (bilious) or bloody gastric aspirates indicate bowel obstruction or necrosis. (Note: Small, clear, or milky/curded residuals do not require holding feeds).
3. Emesis: Active, persistent, or bilious emesis.
4. Blood in Stool: Gross blood or guaiac-positive (occult) blood in the stool.
5. Systemic Instability: Unstable vital signs, severe apnea/bradycardia spells, or hemodynamic instability requiring vasopressor support.

• Exam Trap: The presence of umbilical catheters (UAC or UVC) is not an absolute contraindication to initiating trophic feeds in a hemodynamically stable infant. However, feeds should not be advanced rapidly while umbilical lines are in place.