Starting TPN in ICU - Wellington ICU

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dedicated lumen for TPN (daily infusion set changes). - if requires TPN for > 2 months -> consider tunnelled line. - assess ... catheter related sepsis. - catheter ...
TPN in ICU

23/10/10 SP Notes OH PY Mindmaps Smith, P. J. et al (2010) “Parenteral Nutrition” British Journal of Hospital Medicine, Vol 17 (12) page M185-M189

INDICATIONS = unable to establish enteral feeding

General

- EN contraindicated (have low threshold to use perioperatively depending on nutritional state) - EN fails to meet nutritional requirements

Specific

- prolonged bowel obstruction and ileus - short bowel syndrome with severe malabsorption - severe dysmotility - high output intestinal fistulae - anastomotic break down - intolerance to EN

GENERAL

- ensure adequate central venous access (subclavian lines have lowest infection rates – aseptic insertion, 2% chlorhexidine in alcohol, permeable polyurethane dressings, antimicrobial catheters) - dedicated lumen for TPN (daily infusion set changes) - if requires TPN for > 2 months -> consider tunnelled line - assess why patient cannot be enterally fed -> this is known to be safer - 12 hourly reassessment of whether patient can be enterally fed - requires close liaising with dietician and pharmacy

ASSESSMENT OF NUTRITIONAL STATUS (CALORIC REQUIREMENTS)

- calculate Resting Energy Expenditure (using the Harris-Benedict equation)

REE (males) = 66.5 + (13.7 x body weight in kg) + (5.0 x height in cm) (6.8 x age in years) REE (females) = 66.5 + (9.6 x body weight in kg) + (1.7 x height in cm) (4.7 x age in years)

- use ideal body weight - resting energy expenditure in calories - multiply this by a stress factor to allow for effects of disease (no exercise = 1.2, very heavy exercise BD = 1.9)

- more accurate to measure REE by indirect calormetry - most hospitalized patients require 25-30kcal/kg/day - mechanically ventilated are on the lower aspect of range - burns and trauma patient may require 45kcal/kg/day

NUTRITIONAL REQUIREMENTS

Protein

- utilisation of exogenous protein = 1.5g/kg/day

- other techniques: -> non-protein calorie to nitrogen ratio (100-200kcal/g of nitrogen often used) -> nitrogen balance = (protein intake (g) / 6.25) – (urinary nitrogen (g) + 4) -> 4 = empirical factor added to account for non-urinary nitrogen loss (faeces and sweat)

- cystalline solutions of L-amino acids (varying essential amino acids)

Carbohydrates

- daily requirement of glucose = 4-5g/kg/day in severely catabolic patients

Lipids

- requirements 1g/kg/day - 1/3 of energy given as non-protein - advantages: prevents fatty acid deficiency and provides more concentrated calories - disadvantages: can cause pancreatitis, immunosuppression, overfeeding -> increase in CO2 production - check lipids daily and check clearance of lipids

Minerals and Micronutrients

- Na+, K+, Ca2+, Mg2+, phosphate -> guided by serum plasma levels

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- inorganic trace elements - organic vitamins (thiamine, folic acid, fat soluble vitamins D, E, K, A, water soluble vitamins B and C)

H2O

- 25-40mL/kg/day (+ losses)

MONITOR FOR COMPLICATIONS

- catheter related sepsis - catheter occlusion - hyperglycaemia - hypercholesterolaemia - refeeding syndrome (phosphate, K+, Mg2+) - abnormal LFT’s - trace elemental deficiency: > 2-4 weeks of poor nutrition - copper: anaemia, neutropenia - iodine: hypothyroidism - chromium: glucose intolerance - zinc: mental apathy, diarrhoea, rash - selenium: cardiomyopathy -> treatment: supplement, follow levels (serum, tissue, white cells)



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PRESCRIPTION

- total energy: 25 kcal/kg/day - protein: 1.5g/kg/day - carbohydrate: 4g/kg/day - lipids: 1g/kg/day - H2O: 30mL/kg/day + other losses - electrolytes - organic vitamins - inorganic trace elements

MY APPROACH

- exhaust all means of feeding enterally - dietician involvement - calculate requirements (caloric and nutritional) - start slowly - monitor for refeeding and complications - frequent reassessment about whether patient can be fed enterally

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