Nutrition in Surgical Patients

Nutritional Assessment & Needs - Fuel Gauge Check

• Screening: MUST, NRS-2002 identify at-risk patients.
• Assessment (ABCD):
  • Anthropometry: BMI, triceps skinfold, MAC.
  • Biochemical:
    • Albumin < 3.5 g/dL (chronic, t½ 20d).
    • Prealbumin < 15-20 mg/dL (acute, t½ 2-3d).
    • Transferrin < 200 mg/dL (t½ 8-10d).
    • TLC < 1500/mm³.
  • Clinical: >10% weight loss/6mo, muscle wasting, edema.
  • Dietary: Intake recall.
• Daily Needs Estimation:
  • Energy: 25-35 kcal/kg (Harris-Benedict for BEE).
  • Protein: 1.2-2.0 g/kg (↑ in stress).
  • Fluid: 30-35 mL/kg.

⭐ Exam-favourite fact: Prealbumin (half-life 2-3 days) is a more sensitive indicator of acute nutritional changes than albumin (half-life 20 days).

Metabolic Response to Surgery - Stress Storm Surge

• Ebb Phase (Initial Shock): ~12-24h post-insult.
  • ↓ Metabolic rate, ↓ temperature, ↓ $O_2$ consumption.
  • Hormonal surge: ↑ Catecholamines, ↑ Cortisol, ↑ Glucagon.
  • Goal: Conserve energy, maintain perfusion.
• Flow Phase (Catabolic): Days to weeks.
  • Hypermetabolism (↑ Basal Metabolic Rate 1.5-2x), ↑ temperature, ↑ $O_2$ consumption.
  • Features: Protein catabolism (negative nitrogen balance), hyperglycemia (insulin resistance), ↑ lipolysis.
  • Hormonal: Sustained ↑ Cortisol, ↑ Glucagon.

  ⭐ The 'flow' phase of metabolic stress is characterized by hypermetabolism, hyperglycemia, ↑ cortisol, ↑ glucagon, and significant protein catabolism.

• Anabolic Phase (Recovery):
  • Protein repletion, positive nitrogen balance, tissue repair.

Enteral Nutrition - Tube Feed Triumph

"If the gut works, use it!" - Preserves gut integrity, ↓ bacterial translocation.

• Principle: Preferred route if GI tract is functional.

  ⭐ Early EN (within 24-48 hours) in critically ill/post-op patients ↓ septic complications & ICU stay.

• Indications:
  • Unable to meet nutritional needs orally (e.g., dysphagia, major trauma, burns, critical illness).
  • Functional & accessible GI tract.
• Access Routes:
  • Short-term (<4-6 weeks): Nasogastric (NG), Nasoduodenal (ND), Nasojejunal (NJ).
  • Long-term (>4-6 weeks): Gastrostomy (PEG), Jejunostomy (PEJ).
• Contraindications:
  • Complete mechanical intestinal obstruction, paralytic ileus.
  • Severe shock, intestinal ischemia, bowel perforation.
  • High-output enterocutaneous fistula (>500 mL/day) not bypassable distally.
  • Severe intractable vomiting/diarrhea.
• Complications:
  • Aspiration pneumonia (⚠️ Elevate Head of Bed 30-45°).
  • GI: Diarrhea, cramping, bloating, nausea/vomiting.
  • Mechanical: Tube displacement, occlusion, erosion.
  • Metabolic: Refeeding syndrome, electrolyte imbalance.

Parenteral Nutrition - IV Lifeline Logic

• Indications: Non-functional GI tract > 7 days (or < 7 days if severe malnutrition). E.g., short bowel, severe pancreatitis, prolonged ileus.
• Types:
  • TPN (Total): Central line; high osmolality (> 900 mOsm/L); for long-term.
  • PPN (Peripheral): Peripheral vein; lower osmolality (< 900 mOsm/L); short-term (< 2 weeks), supplemental.
• Components: Dextrose ($3.4 \text{ kcal/g}$), amino acids ($4 \text{ kcal/g}$), lipids ($9 \text{ kcal/g}$ or $1.1-2 \text{ kcal/mL}$ for IVFE). Vitamins, minerals.
• Complications:
  • Metabolic: Hyperglycemia, electrolyte shifts.

  ⭐ Refeeding syndrome: Hallmark is severe hypophosphatemia (📌 Phosphate Plummets); monitor PO4.

  • Catheter: Infection, thrombosis.
  • Hepatic: Steatosis, cholestasis (long-term).
• Monitoring: Glucose, electrolytes (K, PO4, Mg), LFTs, triglycerides.

High‑Yield Points - ⚡ Biggest Takeaways

• Pre-operative nutritional status (albumin, weight loss) strongly predicts post-operative outcomes.
• Early EN preferred over PN: maintains gut integrity, reduces sepsis.
• Immunonutrition (arginine, glutamine) may benefit select major GI surgery patients.
• Beware refeeding syndrome in severely malnourished; monitor electrolytes (K, PO4, Mg).
• Initiate nutrition support if oral intake inadequate >7 days or anticipated.
• Goals: 25-30 kcal/kg/day calories, 1.2-1.5 g/kg/day protein.
• PN for: non-functional gut, prolonged ileus, or high-output fistulas.