Transcript Slide 1

Nutrition – Use and indications
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Malnutrition leads to poor wound healing, post-operative
complications and sepsis.
Adequate nutritional support is important for critically ill patients
and should be provided early during the illness.
Evidence for improved outcome from early nutritional support exists
for patients with trauma and burns.
Enteral nutrition is indicated when swallowing is inadequate or
impossible but gastrointestinal function is otherwise intact.
Parenteral nutrition is indicated where the gastrointestinal tract
cannot be used to provide adequate nutritional support, e.g.
obstruction, ileus, high small bowel fistula or malabsorption.
Parenteral nutrition may be used to supplement enteral nutrition
where gastrointestinal function allows partial nautritional support.
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Consequences of malnutrition
Underfeeding
Loss of muscle mass
Reduced respiratory function
Reduced immune function
Poor wound healing
Gut mucosal atrophy
Reduced protein synthesis
Overfeeding
Increased VO2
Increased VCO2
Hyperglycaemia
Fatty infiltration of liver
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Calorie requirement
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Various formulae exist to calculate the patient’s basal
metabolic rate but they are often misleading in critical
illness.
Metabolic rate can be measured at the bedside by
indirect calorimetry but most patients will require 20002700 Cal/day or less if starved or underweight.
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Nitrogen requirements
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Nitrogen excretion can be calculated in the absence of
renal failure according to the 24th urea excretion.
Nitrogen (g/24h) = 2 + Urinary urea
(mmol/24h) x 0.028
However, as with most formulae, this method lacks
accuracy.
 Most patients require 7-14g/day.
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Other requirements
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The normal requirements of substrates, vitamins and
trace elements are tabled opposite.
Most critically ill patients require folic acid and vitamin
supplementation during nutritional support, e.g. Solvitio.
Trace elements are usually supplemented in parenteral
formulae but should not be required during enteral
nutrition.
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Normal daily requirements (for a 70kg adult)
Water
2100ml
Energy
2000-2700Cal
Nitrogen
7-14g
Glucose
210g
Lipid
140g
Sodium
70-140 mmol
Potassium
50-120 mmol
Calcium
5-10 mmol
Magnesium
5-10 mmol
Phosphate
10-20 mmol
Vitamins
Thiamine
16-19mg
Riboflavin
3-8mg
Niacin
33-34mg
Pyridoxine
5-10mg
Folate
0.3-0.5mg
Vitamin C
250-450mg
Vitamin A
2800-3300iu
Vitamin D
280-330iu
Vitamin E
1.4-1.7iu
Vitamin K
0.7mg
Trace elements
Iron
Copper
Managanese
Zinc
Iodide
Flurodie
1-2mg
0.5-1.0mg
1-2ug
2-4mg
70-140 ug
1-2mg
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Enteral nutrituion
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Routes include naso-gastric, naso-duodenal, gastrostomy
and jejunostomy.
Nasal tube feeding should be via a soft fine born tube to
aid pateint comfort and avoid ulceration of the nose or
oesophagus.
Prolonged enteral feeding may be accomplished via a
percutaneous gastrostomy.
Enteral feeding provides a more complete diet than
parenteral nutrition, maintains structural integrity of the
gut, improves bowel adaptation after resection and
reduces infection risk.
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Feed Composition
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Most patients tolerate an iso-osmolar, non-lactose feed.
Carbohydrates are provided as sucrose or glucose polymers (other
than lactose).
Protein may be as whole protein or oligopeptides. There is evidence
that oligopeptides are better absorbed than free amino acids in
‘elemental’ feeds.
Fats may be provided as medium chain or long chain triglycerides.
Medium chain triglycerides are better absorbed. A standard feed will
be formulated at 1Cal/ml.
Special fees are available for special purposes, e.g. high protein, fat
or carbohydrate requirements, restricted salt, concentrated (1.5 or
2Cal/ml) for fluid restriction, or glutamine enriched.
Impact is a formula supplemented with arginine, nucleotides and
fish oil; it may reduce hospital stay and infectious complications in
critically ill patients.
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Complications
Tube placement : tracheobronchial intubation,
nasopharyngeal perforation, intracranial penetration
(basal skull fracture), oesophageal perforation
 Reflux
 Pulmonary aspiration
 Nausea and vomiting
 Diarrhoea : large volume, bolus feeding, high osmolality,
infection, lactose intolerance, antibiotic therapy, high fat
content
 Constipation
 Metabolic : dehydration, hyperglycaemia, electrolyte
imbalance
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Parenteral nutrition
Feed composition
 Carbohydrate is normally provided in the form of concentrated
glucose. While it is possible to provide the body’s energy
requirements with glucose alone, it si advantageous to provide 3040% of total calories as lipid (i.g. soya bean emulsion).
 The nitrogen source should contain appropriate quantities of all
essential and most of the non-essential amino acids.
 There should be a high branched chain amino acid content and a
high concentration of glycine should be avoided.
 Carbohydrate, lipid and nitrogen sources are usually mixed into a
large bag in a sterile pharmayc unit. Vitamins, trace leements and
appropriate electrolyte concentration can be achieved ina single
infusion, thus avoiding multiple connections.
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Choice of parenteral feeding route
Central venous
 A dedicated central venous catheter (or lumen of a
multi-lumen catheter) is placed under sterile conditions.
A subcutaneous tunnel is often used to separate the skin
and vein entry sites.
 This probably reduces the risk of infection and certainly
identifies the special purpose of the catheter.
 It is important that blood samples are not taken and
other injections or infusions are not given through the
feeding lumen.
 The main advantage of the central venous route is that it
allows infusion of hperosmolar solution, providing
adequate energy intake in reduced volume.
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Peripheral venous
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Parenteral nutrition via the peripheral route requires a
solution with osmolality <800mOsm kg.
Either the volume mus be increased or the energy
content (particularly from carbohydrate) reduced.
Peripheral cannulae sites must be changed frequently
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Complications
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Catheter related
misplacement
infection
Thromboembolism
Fluid excess
Hyperosmolar hyperglycaemic state
 Electrolyte imbalance
 Hypophosphataemia
 Metabolic acidosis
Hyperchloraemia
Metabolism of cationic amino acids
 Rebound hypoglycaemia
high endogenous insulin levels
 Vitamin deficiency
folate : pancytopenia
thiamine : encephalopathy
vitamin K : hypoprothrombinaemia
 Vitamin excess
vitamin A: dermatitis
vitamin D: hypercalcaemia
 Fatty liver
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