Key Facts

Nutritional assessment and optimisation are essential components of perioperative care. Malnourished patients have significantly worse surgical outcomes.

Epidemiology

~30-40% of surgical patients are malnourished at admission. Malnutrition is an independent risk factor for post-operative complications, with 2-3× increased complication rates. Annual cost of malnutrition-related disease in UK: ~£13 billion.

Aetiology

Causes of malnutrition in surgical patients:

• Disease-related: Cancer, IBD, chronic pancreatitis, malabsorption
• Reduced intake: Anorexia, nausea, dysphagia, pain, depression
• Increased requirements: Sepsis, burns, trauma, major surgery (catabolic state)
• Iatrogenic: Prolonged fasting, missed meals, NBM policies

Pathophysiology

• Catabolic state post-surgery: Cortisol, catecholamines → protein breakdown, gluconeogenesis, insulin resistance
• Muscle wasting (sarcopenia): Reduced functional capacity, impaired respiratory function, delayed mobilisation
• Impaired immune function: Increased susceptibility to SSI, pneumonia, UTI
• Impaired wound healing: Reduced collagen synthesis, poor granulation tissue
• Gut mucosal atrophy: Starvation/TPN → loss of gut barrier → bacterial translocation → sepsis

Screening and Assessment

MUST Score:

Components of MUST:

1. BMI: <18.5 (2), 18.5-20 (1), >20 (0)
2. Weight loss in 3-6 months: >10% (2), 5-10% (1), <5% (0)
3. Acute disease effect: Acutely ill AND likely no intake >5 days (2)

Signs of Malnutrition

• Weight loss, muscle wasting, loss of subcutaneous fat
• Fatigue, weakness
• Poor wound healing
• Peripheral oedema (hypoalbuminaemia)
• Glossitis, angular stomatitis (micronutrient deficiency)

Red Flags — Refeeding Syndrome

• Occurs when malnourished patients (BMI <16, prolonged starvation, alcohol dependence) are refed
• Onset within 1-5 days of refeeding
• Hypophosphataemia (most dangerous — can cause cardiac arrest, respiratory failure, rhabdomyolysis)
• Hypokalaemia, hypomagnesaemia
• Fluid overload, Wernicke's encephalopathy (thiamine deficiency)

Bedside

• MUST screening: On admission and weekly
• Food charts: Document actual intake
• Weight: Baseline and serial measurements
• Body composition: Mid-arm circumference, handgrip strength (sarcopenia assessment)

Bloods

• Albumin: Reflects inflammation more than nutrition (negative acute phase reactant); low albumin predicts worse outcomes but is not a direct measure of nutritional status
• Pre-albumin (transthyretin): Shorter half-life (~2 days) — better reflects recent nutritional changes
• U&Es: K⁺, Mg²⁺, PO₄³⁻ (refeeding risk assessment)
• Micronutrients: Vitamin B12, folate, iron, zinc, vitamin D (if deficiency suspected)
• Glucose: Insulin resistance in catabolic state

Pre-operative Nutritional Optimisation

• Malnourished patients: High-protein, high-energy oral supplements (e.g., Fortisip, Ensure) for ≥7-14 days pre-operatively
• ERAS carbohydrate loading: Clear carbohydrate drink 2-3 hours pre-operatively — reduces insulin resistance, nausea, thirst
• Severe malnutrition: Consider delaying elective surgery for nutritional rehabilitation
• Iron deficiency: IV iron for anaemia correction (NICE NG24)

Post-operative Nutrition

• ERAS: Early oral intake within 24 hours (including after GI surgery — safe and beneficial)
• Avoid prolonged NBM: No evidence supports routine prolonged fasting after GI surgery
• Oral nutritional supplements: If unable to meet requirements from diet alone

Enteral Nutrition (If Oral Insufficient)

• NG feeding: Short-term (days-weeks)
• NJ feeding: After upper GI surgery
• PEG/RIG: If long-term feeding anticipated (>4-6 weeks)
• Standard feeds: 1 kcal/mL; high-energy: 1.5 kcal/mL
• Start at low rate, increase over 24-48 hours (especially in refeeding risk patients)

Parenteral Nutrition (TPN)

• Only when gut not usable: Intestinal failure, prolonged ileus, short bowel syndrome, high-output enterocutaneous fistula
• Via central line (PICC or tunnelled CVC)
• Contains amino acids, glucose, lipid, electrolytes, vitamins, trace elements
• Complications: Line sepsis, metabolic derangement, liver dysfunction, refeeding syndrome

Preventing Refeeding Syndrome

• Identify at-risk patients: BMI <16, >10% weight loss in 3-6 months, little/no intake for >5 days, alcohol dependence
• Start feeding slowly: 10 kcal/kg/day initially → increase over 4-7 days
• Supplement: Thiamine 200-300mg/day for first 10 days; phosphate, potassium, magnesium — check daily and replace
• Monitor: Daily U&Es, PO₄, Mg²⁺, Ca²⁺ for first week

Referral Criteria

• MUST score ≥2 — dietitian referral
• Need for TPN — nutrition support team
• Refeeding risk — senior review, dietitian, careful monitoring

• Malnourished surgical patients: 2-3× higher complication rates, 2× longer hospital stay, increased mortality
• Pre-operative nutritional optimisation: Reduces complications by ~30-50%
• Early enteral feeding: Reduces SSI and pneumonia compared to delayed feeding
• Refeeding syndrome: Mortality ~25-40% if severe (cardiac arrest from hypophosphataemia); preventable with careful refeeding and electrolyte replacement
• TPN: Complications in ~15-30% (line sepsis most common)

Daily Nutritional Requirements (Adult)

MUST Screening Summary