Nutrition support in surgical patients

Nutritional Assessment - Sizing Up The Patient

• Screening Tools: Identify at-risk patients using:
  • Nutritional Risk Screening (NRS-2002): Score ≥ 3 indicates high risk.
  • Malnutrition Universal Screening Tool (MUST).

• Key Markers:
  • Prealbumin (PAB): Most sensitive indicator for acute nutritional changes (2-day half-life).
  • Albumin: Marker for chronic malnutrition (20-day half-life); < 3.0 g/dL is significant.
  • BMI: $BMI = kg/m^2$.

⭐ Prealbumin's short half-life (~2 days) makes it a superior marker for acute changes in nutritional status compared to albumin (~20 days).

Indications & Timing - The When and Why

• Indications for Nutritional Support:

  • Inadequate oral intake anticipated for > 7-10 days.
  • Severe malnutrition (e.g., albumin < 3.0 g/dL, weight loss > 10-15%).
  • Hypercatabolic states: major trauma, severe sepsis, burns.

• Timing: Early initiation is key. Prefer enteral routes if the gut is functional.

⭐ In moderately malnourished patients, delaying surgery for 7-10 days to provide preoperative nutritional support can reduce postoperative complications.

Enteral vs. Parenteral - Gut Instincts

📌 Mnemonic: 'If the gut works, use it!'

Prioritize Enteral Nutrition (EN) whenever the GI tract is functional, even if trophic ('trickle') feeds are all that is tolerated.

• Enteral Nutrition (EN): "Tube Feeds"

  • Route: Nasogastric, PEG, or jejunostomy tube.
  • Benefits: Maintains gut integrity, ↓ infection risk, ↓ bacterial translocation, cheaper.
  • Contraindications: Mechanical bowel obstruction, ileus, hemodynamic instability (shock), intractable vomiting/diarrhea.

• Parenteral Nutrition (PN): "IV Feeds"

  • Indication: Non-functional or inaccessible GI tract for > 7 days.
  • Types:
    • Total (TPN): Central line. For long-term support.
    • Peripheral (PPN): Peripheral IV. Short-term (< 2 weeks), lower calorie.
  • Risks: Catheter-related bloodstream infection (CRBSI), hyperglycemia, electrolyte shifts, hepatic steatosis.

⭐ Enteral nutrition helps maintain gut mucosal integrity and reduces the risk of bacterial translocation compared to parenteral nutrition.

Complications & Monitoring - Navigating The Risks

• Refeeding Syndrome: Potentially fatal shift in fluids & electrolytes.
  • ⚠️ Key findings: Severe ↓$PO₄³⁻$, ↓$K⁺$, ↓$Mg²⁺$, and vitamin (thiamine) deficiency.
  • Occurs in chronically malnourished patients started on aggressive nutritional support.

⭐ The hallmark of refeeding syndrome is severe hypophosphatemia, which can lead to cardiac failure, rhabdomyolysis, and seizures.

• Parenteral Nutrition (PN) Complications:

  • Infectious: Central line-associated bloodstream infection (CLABSI).
  • Metabolic: Hyperglycemia, hypertriglyceridemia.
  • Hepatic: Cholestasis, steatosis (fatty liver).

• Monitoring Schedule:

  • Daily: Glucose, electrolytes (PO₄³⁻, K⁺, Mg²⁺).
  • Weekly: Liver function tests (LFTs), triglycerides.

High‑Yield Points - ⚡ Biggest Takeaways

• Enteral nutrition (EN) is strongly preferred over parenteral nutrition (PN) to preserve gut mucosal integrity and prevent bacterial translocation.
• Initiate nutritional support if a patient is unlikely to resume oral intake within 5-7 days.
• Key risks of PN include central line infections (CLABSI), refeeding syndrome, and liver dysfunction.
• Refeeding syndrome is characterized by severe hypophosphatemia upon re-feeding a malnourished patient.
• Prealbumin is a more sensitive indicator of acute nutritional changes than albumin.