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Nutrition – Use and indicationsNutrition – Use and indications

Malnutrition leads to poor wound healing, post-operative Malnutrition leads to poor wound healing, post-operative complications and sepsis.complications and sepsis.

Adequate nutritional support is important for critically ill Adequate nutritional support is important for critically ill patients and should be provided early during the illness. patients and should be provided early during the illness.

Evidence for improved outcome from early nutritional support Evidence for improved outcome from early nutritional support exists for patients with trauma and burns.exists for patients with trauma and burns.

Enteral nutrition is indicated when swallowing is inadequate or Enteral nutrition is indicated when swallowing is inadequate or impossible but gastrointestinal function is otherwise intact. impossible but gastrointestinal function is otherwise intact.

Parenteral nutrition is indicated where the gastrointestinal tract Parenteral nutrition is indicated where the gastrointestinal tract cannot be used to provide adequate nutritional support, e.g. cannot be used to provide adequate nutritional support, e.g. obstruction, ileus, high small bowel fistula or malabsorption.obstruction, ileus, high small bowel fistula or malabsorption.

Parenteral nutrition may be used to supplement enteral Parenteral nutrition may be used to supplement enteral nutrition where gastrointestinal function allows partial nutrition where gastrointestinal function allows partial nautritional support. nautritional support.

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Consequences of malnutrition Consequences of malnutrition

UnderfeedingUnderfeeding OverfeedingOverfeeding

Loss of muscle massLoss of muscle mass Increased VOIncreased VO22

Reduced respiratory function Reduced respiratory function Increased VCOIncreased VCO22

Reduced immune function Reduced immune function HyperglycaemiaHyperglycaemia

Poor wound healingPoor wound healing Fatty infiltration of Fatty infiltration of liverliver

Gut mucosal atrophy Gut mucosal atrophy

Reduced protein synthesisReduced protein synthesis

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Calorie requirement Calorie requirement

Various formulae exist to calculate the patient’s Various formulae exist to calculate the patient’s basal metabolic rate but they are often basal metabolic rate but they are often misleading in critical illness.misleading in critical illness.

Metabolic rate can be measured at the bedside Metabolic rate can be measured at the bedside by indirect calorimetry but most patients will by indirect calorimetry but most patients will require 2000-2700 Cal/day or less if starved or require 2000-2700 Cal/day or less if starved or underweight.underweight.

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Nitrogen requirements Nitrogen requirements

Nitrogen excretion can be calculated in the Nitrogen excretion can be calculated in the absence of renal failure according to the 24absence of renal failure according to the 24thth urea urea excretion. excretion.

Nitrogen (g/24h) = 2 + Urinary urea Nitrogen (g/24h) = 2 + Urinary urea

(mmol/24h) x 0.028(mmol/24h) x 0.028

However, as with most formulae, this method However, as with most formulae, this method lacks accuracy. lacks accuracy.

Most patients require 7-14g/day.Most patients require 7-14g/day.

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Other requirementsOther requirements

The normal requirements of substrates, vitamins and The normal requirements of substrates, vitamins and trace elements are tabled opposite.trace elements are tabled opposite.

Most critically ill patients require folic acid and Most critically ill patients require folic acid and vitamin supplementation during nutritional support, vitamin supplementation during nutritional support, e.g. Solvitio.e.g. Solvitio.

Trace elements are usually supplemented in Trace elements are usually supplemented in parenteral formulae but should not be required parenteral formulae but should not be required during enteral nutrition. during enteral nutrition.

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Normal daily requirements (for a 70kg adult)Normal daily requirements (for a 70kg adult)

WaterWater 2100ml2100ml Trace elementsTrace elementsEnergyEnergy 2000-2700Cal2000-2700Cal IronIron 1-2mg1-2mgNitrogenNitrogen 7-14g7-14g CopperCopper 0.5-1.0mg0.5-1.0mgGlucoseGlucose 210g210g ManaganeseManaganese 1-2ug1-2ugLipidLipid 140g140g ZincZinc 2-4mg2-4mgSodiumSodium 70-140 mmol70-140 mmol IodideIodide 70-140 ug70-140 ugPotassiumPotassium 50-120 mmol50-120 mmol FlurodieFlurodie 1-2mg1-2mgCalciumCalcium 5-10 mmol5-10 mmolMagnesiumMagnesium 5-10 mmol5-10 mmolPhosphatePhosphate 10-20 mmol10-20 mmol

VitaminsVitaminsThiamineThiamine 16-19mg16-19mgRiboflavinRiboflavin 3-8mg3-8mgNiacinNiacin 33-34mg33-34mgPyridoxine Pyridoxine 5-10mg5-10mgFolateFolate 0.3-0.5mg0.3-0.5mgVitamin CVitamin C 250-450mg250-450mgVitamin AVitamin A 2800-3300iu2800-3300iuVitamin DVitamin D 280-330iu280-330iuVitamin EVitamin E 1.4-1.7iu1.4-1.7iuVitamin KVitamin K 0.7mg0.7mg

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Enteral nutrituionEnteral nutrituion

Routes include naso-gastric, naso-duodenal, Routes include naso-gastric, naso-duodenal, gastrostomy and jejunostomy. gastrostomy and jejunostomy.

Nasal tube feeding should be via a soft fine born Nasal tube feeding should be via a soft fine born tube to aid pateint comfort and avoid ulceration tube to aid pateint comfort and avoid ulceration of the nose or oesophagus. of the nose or oesophagus.

Prolonged enteral feeding may be accomplished Prolonged enteral feeding may be accomplished via a percutaneous gastrostomy. via a percutaneous gastrostomy.

Enteral feeding provides a more complete diet Enteral feeding provides a more complete diet than parenteral nutrition, maintains structural than parenteral nutrition, maintains structural integrity of the gut, improves bowel adaptation integrity of the gut, improves bowel adaptation after resection and reduces infection risk.after resection and reduces infection risk.

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Feed Composition Feed Composition

Most patients tolerate an iso-osmolar, non-lactose feed. Most patients tolerate an iso-osmolar, non-lactose feed. Carbohydrates are provided as sucrose or glucose polymers Carbohydrates are provided as sucrose or glucose polymers (other than lactose).(other than lactose).

Protein may be as whole protein or oligopeptides. There is Protein may be as whole protein or oligopeptides. There is evidence that oligopeptides are better absorbed than free evidence that oligopeptides are better absorbed than free amino acids in ‘elemental’ feeds.amino acids in ‘elemental’ feeds.

Fats may be provided as medium chain or long chain Fats may be provided as medium chain or long chain triglycerides.triglycerides.

Medium chain triglycerides are better absorbed. A standard Medium chain triglycerides are better absorbed. A standard feed will be formulated at 1Cal/ml.feed will be formulated at 1Cal/ml.

Special fees are available for special purposes, e.g. high protein, Special fees are available for special purposes, e.g. high protein, fat or carbohydrate requirements, restricted salt, concentrated fat or carbohydrate requirements, restricted salt, concentrated (1.5 or 2Cal/ml) for fluid restriction, or glutamine enriched. (1.5 or 2Cal/ml) for fluid restriction, or glutamine enriched.

Impact is a formula supplemented with arginine, nucleotides Impact is a formula supplemented with arginine, nucleotides and fish oil; it may reduce hospital stay and infectious and fish oil; it may reduce hospital stay and infectious complications in critically ill patients. complications in critically ill patients.

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ComplicationsComplications

Tube placement : tracheobronchial intubation, Tube placement : tracheobronchial intubation, nasopharyngeal perforation, intracranial nasopharyngeal perforation, intracranial penetration (basal skull fracture), oesophageal penetration (basal skull fracture), oesophageal perforationperforation

RefluxReflux Pulmonary aspirationPulmonary aspiration Nausea and vomitingNausea and vomiting Diarrhoea : large volume, bolus feeding, high Diarrhoea : large volume, bolus feeding, high

osmolality, infection, lactose intolerance, antibiotic osmolality, infection, lactose intolerance, antibiotic therapy, high fat contenttherapy, high fat content

ConstipationConstipation Metabolic : dehydration, hyperglycaemia, Metabolic : dehydration, hyperglycaemia,

electrolyte imbalanceelectrolyte imbalance

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Parenteral nutrition Parenteral nutrition

Feed composition Feed composition Carbohydrate is normally provided in the form of Carbohydrate is normally provided in the form of

concentrated glucose. While it is possible to provide the concentrated glucose. While it is possible to provide the body’s energy requirements with glucose alone, it si body’s energy requirements with glucose alone, it si advantageous to provide 30-40% of total calories as lipid advantageous to provide 30-40% of total calories as lipid (i.g. soya bean emulsion).(i.g. soya bean emulsion).

The nitrogen source should contain appropriate quantities The nitrogen source should contain appropriate quantities of all essential and most of the non-essential amino acids. of all essential and most of the non-essential amino acids.

There should be a high branched chain amino acid content There should be a high branched chain amino acid content and a high concentration of glycine should be avoided.and a high concentration of glycine should be avoided.

Carbohydrate, lipid and nitrogen sources are usually mixed Carbohydrate, lipid and nitrogen sources are usually mixed into a large bag in a sterile pharmayc unit. Vitamins, trace into a large bag in a sterile pharmayc unit. Vitamins, trace leements and appropriate electrolyte concentration can be leements and appropriate electrolyte concentration can be achieved ina single infusion, thus avoiding multiple achieved ina single infusion, thus avoiding multiple connections.connections.

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Choice of parenteral feeding routeChoice of parenteral feeding route

Central venousCentral venous A dedicated central venous catheter (or lumen of a A dedicated central venous catheter (or lumen of a

multi-lumen catheter) is placed under sterile multi-lumen catheter) is placed under sterile conditions. A subcutaneous tunnel is often used to conditions. A subcutaneous tunnel is often used to separate the skin and vein entry sites. separate the skin and vein entry sites.

This probably reduces the risk of infection and This probably reduces the risk of infection and certainly identifies the special purpose of the certainly identifies the special purpose of the catheter. catheter.

It is important that blood samples are not taken and It is important that blood samples are not taken and other injections or infusions are not given through the other injections or infusions are not given through the feeding lumen. feeding lumen.

The main advantage of the central venous route is The main advantage of the central venous route is that it allows infusion of hperosmolar solution, that it allows infusion of hperosmolar solution, providing adequate energy intake in reduced volume.providing adequate energy intake in reduced volume.

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Peripheral venousPeripheral venous

Parenteral nutrition via the peripheral route requires Parenteral nutrition via the peripheral route requires a solution with osmolality <800mOsm kg. a solution with osmolality <800mOsm kg.

Either the volume mus be increased or the energy Either the volume mus be increased or the energy content (particularly from carbohydrate) reduced. content (particularly from carbohydrate) reduced.

Peripheral cannulae sites must be changed Peripheral cannulae sites must be changed frequently frequently

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ComplicationsComplications

Catheter relatedCatheter related misplacementmisplacementinfectioninfectionThromboembolismThromboembolism

Fluid excessFluid excess Hyperosmolar hyperglycaemic stateHyperosmolar hyperglycaemic state Electrolyte imbalanceElectrolyte imbalance HypophosphataemiaHypophosphataemia Metabolic acidosisMetabolic acidosis HyperchloraemiaHyperchloraemia

Metabolism of cationic amino acidsMetabolism of cationic amino acids Rebound hypoglycaemiaRebound hypoglycaemia high endogenous insulin levelshigh endogenous insulin levels Vitamin deficiency Vitamin deficiency folate : pancytopeniafolate : pancytopenia

thiamine : encephalopathythiamine : encephalopathyvitamin K : hypoprothrombinaemiavitamin K : hypoprothrombinaemia

Vitamin excessVitamin excess vitamin A: dermatitisvitamin A: dermatitisvitamin D: hypercalcaemiavitamin D: hypercalcaemia

Fatty liverFatty liver