GC185 Feed Him Up Before Surgery Surgical Nutrition, Enteral And Parenteral Feeding

Male, 57 years old. Dysphagia. Weight loss 6 kg over 3 months (10% of body weight). Previous weight ~60 kg, height 1.72 m, BMI 18.3. Endoscopy: oesophageal cancer partially occluding lumen.

Nutritional assessment parameters:

• Tricep skinfold thickness < 25th percentile — depleted calorie reserve (subcutaneous fat)
• Mid-arm circumference < 10th percentile — depleted protein reserve (muscle mass)
• Serum albumin 25 g/L (normal 35–50) — depleted circulating protein
• Total lymphocyte count 700/mm³ — severe depletion (immune compromise)

Management pathway:

1. Pre-operative: Enteral feeding via fine-bore nasogastric tube for 2 weeks (the tumour only partially occluded the lumen, so a tube could pass)
2. Surgery: Oesophagectomy
3. Post-operative: Parenteral nutrition immediately (can't eat after oesophagectomy)
4. Day 7: Resumed oral diet
5. Day 9: Parenteral nutrition stopped
6. Outcome: Uneventful recovery apart from superficial wound infection

Female, 50, previously healthy. Emergency appendicectomy → wound infection → pelvic abscess → paralytic ileus → pneumonia → needed mechanical ventilation.

Key teaching points:

• Even a previously healthy patient can develop severe catabolism from complications (sepsis, abscess, pneumonia)
• Post-operative parenteral nutrition was needed because she couldn't eat (paralytic ileus) and was in a hypercatabolic state
• She eventually recovered appetite and weight once complications resolved

This case illustrates that nutritional support is not just for the pre-operatively malnourished — it's also critical when complications lead to increased catabolism and prolonged nil-by-mouth status.

Malnutrition is defined as:

• Gross underweight: weight-for-height < 80% of ideal weight
• Recent weight loss of 10% or more over 3 months
• BMI 17–18.5

Why these thresholds matter:

• A BMI of 18.5 is the WHO cutoff for underweight. The lecture uses 17–18.5 as the malnourished range, which aligns with moderate malnutrition.
• 10% weight loss in 3 months represents significant protein-calorie depletion. The body has already consumed substantial fat stores and begun breaking down muscle for gluconeogenesis.
• Weight-for-height < 80% of ideal captures patients who may have a "normal" BMI numerically but are significantly below their frame-specific ideal.

Gross malnutrition is recognized readily by clinical examination. Less severe malnutrition can be detected by anthropometric and laboratory studies. ^[1]

This is a very high-yield slide — know the four categories:

Why short half-life proteins matter more than albumin for acute changes:

• Albumin half-life ≈ 20 days — so serum albumin reflects nutritional status over the past weeks
• Prealbumin (transthyretin) half-life ≈ 2 days — reflects recent nutritional intake and is more responsive to nutritional intervention
• However, albumin < 30 g/L remains a key surgical threshold for pre-operative nutrition indication ^[3]

Psoas muscle on CT is increasingly used as an objective, reproducible measure of sarcopenia (the lecture references Sabel et al, Ann Surg Oncol 2011). The cross-sectional area of the left and right psoas at L4 level correlates with outcomes in surgical oncology patients.

Four categories of causes:

1. Reduced oral intake — e.g., carcinoma of oesophagus (as in Case Study 1)
2. Increased GI loss — e.g., intestinal fistula, diarrhoea (malabsorption or excessive output)
3. Increased catabolism — e.g., burns, acute pancreatitis, sepsis (the body's metabolic demands exceed intake)
4. Cancer cachexia — a paraneoplastic syndrome driven by cytokines (TNF-α, IL-6, IL-1) causing muscle wasting that is not fully reversible with nutrition alone

Why cancer cachexia is distinct: Unlike simple starvation (where the body preferentially burns fat and preserves muscle), cancer cachexia involves a cytokine-driven preferential loss of skeletal muscle. This is why cancer patients look disproportionately wasted compared to their calorie deficit.

Three major consequences:

Two approaches:

1. Increase nutrient intake — this is the subject of the rest of the lecture
2. Eradicate the cause of malnutrition — e.g., drainage of abscess, resection of cancer

This is logical: you can't simply "feed more" if the patient has an undrained abscess driving ongoing catabolism, or an obstructing tumour preventing intake.

Operation induces an enhanced catabolic response to surgery, increased proteolysis and decreased immunocompetence. Intensive nutritional therapy can reduce the net catabolic response to surgery, improve protein synthesis which is critical for maintaining muscular, respiratory, metabolic and immunologic functions.

The metabolic response to surgery (covered in CFB 24) involves:

• Ebb phase (0–48 hours): Reduced metabolic rate, conservation of energy
• Flow phase (days to weeks): Catabolic → anabolic transition. During the catabolic phase, cortisol, catecholamines, and glucagon drive proteolysis, lipolysis, and gluconeogenesis. Nutrition counteracts this by providing substrate to spare endogenous protein breakdown.

With parenteral nutrition:

• Relative risk reduction of 21% for major complications
• Relative risk reduction of 32% for case-fatality
• Saves hospital cost

Four indications for perioperative nutritional support:

1. Malnourished patient undergoing major surgery (pre-op optimization)
2. Major operations with long period ( > 7 days) of fasting after surgery (e.g., oesophagectomy, pancreaticoduodenectomy)
3. Postoperative complications (sepsis, fistula, ileus — leading to increased catabolism and absent oral food intake)
4. ↑ catabolism + absent oral food intake

From senior notes, additional thresholds for initiating pre-operative nutritional support ^[3]:

• Weight loss > 10% within 6 months
• Albumin < 30 g/L
• BMI < 18.5
• SGA Grade C (severely malnourished)

Pre-operative: oral or enteral or parenteral (about 2 weeks) Post-operative: parenteral then enteral or oral

The hierarchy of feeding routes (from senior notes, consistent with lecture) ^[2][4]:

Why enteral is preferred over parenteral (from senior notes, aligning with lecture principles) ^[2]:

• Luminal nutrients maintain mucosal integrity → ↓ mucosal atrophy → ↓ loss of absorption surface
• ↓ Bacterial translocation across gut wall → ↓ sepsis
• Cheaper, fewer complications
• Stimulates peristalsis and gut hormones

Protein: amino acid 300 mg N/kg/day Carbohydrate: glucose 30 cal/kg/day Fat: Long-chain triglyceride + Medium-chain triglyceride, at most 1 g/kg/day Protein:calorie ratio = 1 g N : 100–150 kcal

Why simultaneous calorie + protein infusion matters:

Principle: caloric source infused with protein simultaneously to spare protein for anabolism. ^[1]

If you infuse amino acids without calories, the body will use those amino acids for gluconeogenesis (burning protein for fuel) rather than for building new proteins (anabolism). By co-infusing glucose and/or fat as calorie sources, you signal the body (via insulin secretion) to use amino acids for protein synthesis instead.

Equipment:

• Silicone catheter (Hickman or Broviac catheter) with tip in central vein (SVC)
• Intravenous fluid administration set or tubing
• Bag or bottle containing nutrients

Insertion methods:

1. Direct exposure of cephalic vein or external jugular vein (surgical cut-down)
2. Percutaneous puncture of subclavian vein (Seldinger technique — more common)

Catheter tip position: Must be in the superior vena cava. This is confirmed by post-insertion CXR before feeding commences. ^[4]

Additional access details (from senior notes) ^[4]:

• Infra-clavicular subclavian approach preferred for TPN (catheter lies flat on chest wall, easier to dress and maintain)
• IJV/EJV exit site is on the neck — movement disrupts dressings → ↑ sepsis risk
• Femoral site is least desirable (↑ infection risk)
• PICC line: inserted into peripheral vein (e.g., cephalic vein in arm) and advanced into central venous system

3-in-1 TPN system: all macronutrients in one bag 2 bags in Y connection: amino acids/dextrose in one bag, fat in another, connected via Y-tubing

Slow infusion, regulated by infusion pump.

Functioning GI tract that can be used safely. Examples:

• Burns (hypercatabolic but GI tract intact)
• Upper GI tract obstruction (can bypass with tube placed beyond obstruction)
• Chemotherapy (mucositis may allow enteral if tolerated)
• Radiotherapy

Nasogastric or nasoduodenal tube Gastrostomy Jejunostomy Use of radiopaque tube or marker at tip (to confirm position on X-ray)

Starts at dilute strength (e.g., half strength) and low volume ( < 30 mL/hr) Continuous infusion (by pump) preferred to bolus feeding Solution must not be allowed to stand at room temperature > 6 hours (bacterial growth risk) Check residual volume in stomach every 4 hours in continuous feedings or before each bolus feeding Avoid feeding in supine or flat position (aspiration risk — elevate head of bed to 30–45°)

Poor tolerance indicated by: vomiting, abdominal distension, diarrhoea Gastric residue > 50% of volume given in previous 4-hour feeding → withhold feeding

Three risk factors for aspiration during enteral feeding:

1. Depressed sensorium (e.g., sedated, encephalopathic, post-stroke)
2. Increased gastro-oesophageal reflux (e.g., gastroparesis, hiatal hernia)
3. Over-feeding (excessive volume → gastric distension → reflux)

From Maksim Surgery Notes, consistent with lecture principles:

• Pre-operative carbohydrate loading up to 2 hours before operation (complex carbohydrates with maltodextrins 12.5%)
• This optimizes post-operative hyperglycaemia control by enhancing insulin sensitivity
• Early resumption of oral intake post-operatively:
  • Lower GI surgery: Day 0 after flatus
  • Upper GI surgery: Day 1 (except oesophagectomy — requires jejunostomy tube feeding)
  • Contrast study (gastrografin swallow) if uncertain about anastomotic integrity

• Ebb phase (24–48h): Temporary shutdown to conserve energy
• Flow phase: Catabolic state → anabolic state
• Nutrition during the flow phase's catabolic component aims to minimize protein loss

• Solids and non-human milk: 6 hours
• Infant formula: 6 hours
• Breast milk: 4 hours
• Clear fluids: 2 hours (the "2-4-6" rule)

These are pre-anaesthesia fasting guidelines — distinct from perioperative nutritional support, but they interact because prolonged unnecessary fasting worsens nutritional status.

"Which of the following reasons support the fact that parenteral nutrition is given through a central line?" A. Large amount of fluid could be delivered within a short period of time. B. Patient's hand could be freed. C. Patient's venous pressure can be measured at the same time. D. The high flow of blood can rapidly dilute the concentrated parenteral nutrition. ✓

Rationale: TPN is hyperosmolar (high dextrose concentration). Peripheral veins cannot tolerate this osmolarity → thrombophlebitis. Central veins (SVC) have high blood flow that rapidly dilutes the infusate, preventing osmolar damage to the vein wall. Options A, B, and C are incidental benefits but NOT the primary reason. The lecture explicitly states TPN requires central vein access because of "high dextrose concentration" for "full nutritional support." ^[1][5]

"A 40-year-old gentleman underwent deceased donor liver transplantation for his decompensated liver cirrhosis. He developed a right subhepatic abscess with percutaneous pigtail drainage done on postoperative day 10. He recovered from the operation well but he lost 20 kg. What is the MOST LIKELY reason of his weight loss?" A. Excessive blood loss during the two procedures B. Lack of nutrition support during recovery phase C. Mobilisation of amino acid and fatty acid from muscle and fat ✓ D. Prolonged use of antibiotic and immunosuppressants

Rationale: This tests understanding of the metabolic/catabolic response to surgery. Major surgery + septic complication (abscess) → prolonged catabolic flow phase → mobilisation of endogenous protein (muscle) and fat for fuel and acute-phase protein synthesis. This is the body's physiological stress response. Blood loss (A) doesn't cause 20 kg weight loss. Lack of nutrition (B) could contribute but isn't the primary driver — it's the catabolic response itself. Antibiotics/immunosuppressants (D) don't cause this degree of weight loss. ^[7]

"A 68-year-old man presents with progressive dysphagia for 3 weeks. He is cachexic on inspection." Most appropriate initial diagnostic investigation? Answer: E. Contrast swallow study

Rationale: Progressive dysphagia + cachexia → likely oesophageal carcinoma. A contrast swallow study is the appropriate initial investigation to demonstrate the site and nature of obstruction. This connects to Case Study 1 from the lecture — the malnourished oesophageal cancer patient. ^[7]

No other directly relevant past paper questions were identified in the indexed context for this specific lecture topic.