Surgical nutrition

Malnutrition causes:
- Delayed wound healing
- Reduced ventilatory capacity
- Reduced immunity and increased risk of infection
Does improving nutritional status influence outcome?
Currently the topic of intensive investigation

Nutritional assessment

Clinical assessment
- Weight loss
- 10% =mild malnutrition
- 30% = severe malnutrition
- Body mass index
Anthropometric assessment
- Triceps skin fold thickness
- Mid arm circumference
- Hand grip strength
Blood indices
- Reduced serum albumin, prealbumin or transferrin
- Lymphocyte count
‘End-of-bedogram’
No index of nutritional assessment shown to be superior to clinical assessment

Methods of nutritional support

Use gastrointestinal tract if available
Prolonged post-operative starvation is probably not required
Early enteral nutrition reduced post-operative morbidity

Enteral feeding

Prevents intestinal mucosal atrophy
Supports gut associated immunological shield
Attenuates hypermetabolic response to injury and surgery
Cheaper than TPN and has fewer complications
Polymeric liquid diet
- Short peptides, medium chain triglycerides and polysaccharides
- Vitamins and trace elements
Elemental diet
- L-amino acids, simple sugars
- Expensive and unpalatable
- High osmolarity can cause diarrhoea
Enteral feed can be taken orally or by NGT
Nasoenteral tube - usually fine bore
Long term feeding can be by:
- Surgical gastrostomy, jejunostomy
- Percutaneous endoscopic gastrostomy
- Needle catheter jejunostomy
Rate of infusion – often started at low rate and increased
Strength of initial feed – often diluted and strength gradually increased
Complications of enteral feeding
- Malposition and blockage of tube
- Gastrooesophageal reflux
- Feed intolerance

Parenteral nutrition

Intestinal failure = ‘A reduction in functioning gut mass below the minimal necessary for adequate digestion and absorption of nutrients’
Useful concept for assessing need for TPN
Can be given by either a peripheral or central line

Indications for total parenteral nutrition

Absolute indications
- Enterocutaneous fistulae
Relative indications
- Moderate or severe malnutrition
- Acute pancreatitis
- Abdominal sepsis
- Prolonged ileus
- Major trauma and burns
- Severe inflammatory bowel disease

Peripheral parenteral nutrition

Hyperosmotic solution
Significant problem with thrombophlebitis
Need to change cannulas every 24- 48 hours
No evidence to support it as a clinically important therapy
Composition - 12g nitrogen, 2000 Calories

Central parenteral nutrition

Hyperosmolar, low pH and irritant to vessel walls
Typical feed contains the following in 2.5L
14g nitrogen as L amino acids
250g glucose
500 ml 20% lipid emulsion
100 mmol Na⁺
100 mmol K⁺
150 mmol Cl^-
15 mmol Mg²⁺
13 mmol Ca²⁺
30 mmol PO₄^2-
0.4 mmol Zn²⁺
Water and fat soluble vitamins
Trace elements

Complications of subclavian and jugular central venous lines

10% of central lines develop significant complications

Problems of insertion
- Failure to cannulate
- Pneumothorax
- Haemothorax
- Arterial puncture
- Brachial plexus injury
- Mediastinal haematoma
- Thoracic duct injury
Problems of care
- Line and systemic sepsis
- Air embolus
- Thrombosis
- Catheter breakage

Monitoring of parenteral nutrition

Feeding lines should only be used for that purpose
Drugs and blood products should be given via separate peripheral line
5% patients on TPN develop metabolic derangement
Nutrition should be monitored:
- Clinically – Weight
- Biochemically twice weekly
- FBC, U+Es, LFTs,
- Mg²⁺, Ca²⁺, PO₄^2-, Zn²⁺
- Nitrogen balance
Blood cultures on any sign of sepsis

Metabolic complications of parenteral nutrition

Hyponatraemia
Hypokalaemia
Hyperchloraemia
Trace element and folate deficiency
Deranged LFTs
Linoleic acid deficiency

Bibliography

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