Role of enteral and parenteral nutrition in the patient with gastrointestinal and liver disease

Best Practice & Research Clinical Gastroenterology Vol. 20, No. 3, pp. 441–466, 2006 doi:10.1016/j.bpg.2005.11.004 available online at http://www.sciencedirect.com

2 Role of enteral and parenteral nutrition in the patient with gastrointestinal and liver disease Rebecca J. Stratton*

BSc (Hons) PhD RD

Senior Research Fellow

Trevor R. Smith

BM MRCP

Clinical Nutrition Research Fellow Institute of Human Nutrition, School of Medicine, University of Southampton, Southampton General Hospital, Tremona Road, Southampton SO16 6YD, UK

This chapter discusses a number of key issues: the importance of nutritional support, both enteral (oral nutritional supplements, enteral tube feeding) and parenteral nutrition in the treatment of the nutritionally compromised patient with gastrointestinal and liver disease; prescribing and monitoring nutritional support; refeeding syndrome; practicalities, indications and contraindications and complications of using enteral and parenteral nutrition; choosing feeds with an optimal nutrient composition for nutritional support, including specific feeds for disease states; the evidence base for using nutritional support in the patient with gastrointestinal and liver disease. Key words: diet therapy; dietary supplements; enteral nutrition; parenteral nutrition; nutritional support; malnutrition.

Treatment of patients with or at risk of malnutrition is essential to prevent the debilitating consequences of malnutrition on physical and psychological function and clinical outcome (which includes a poorer response to, and recovery from, surgery, illness and infection). Routine screening with a valid, evidence-based tool, such as the ‘Malnutrition Universal Screening Tool’ (‘MUST’, www.bapen.org.uk) should be undertaken to identify those at risk of malnutrition in all health care settings.1 Following identification of malnutrition, as part of the care plan for treatment, appropriate nutritional support should be given promptly and monitored regularly. Figure 1 provides an algorithm to help decisions about which method of nutritional support is required. * Corresponding author. Tel.: C44 2380 796317; fax: C44 2380 794980. E-mail address: [email protected] (R.J. Stratton).

1521-6918/$ - see front matter Q 2005 Elsevier Ltd. All rights reserved.

Nutritional support indicated Seek expert advice from a dietitian or nutrition support team.

Oral nutritional support Liquid oral nutritional supplements, dietetic counselling and dietary fortification

Yes

But requires texture modification (e.g. swallowing difficulty)

Regularly monitor intake. If inadequate

Consider thickeners and additional nutritional support

Is oral nutrition possible and safe?

No

Does the gastrointestinal tract function adequately? Yes

Tube feeding

Short term < 2-4 wk Fine bore nasoenteral tube

Long term > 4 wk

Limited tube feeding possible?

* For all patients, treat underlying conditions, ensure help with feeding and help/advice on special diets as required (gluten free, low sodium, diabetic, texture modification)

Parenteral nutrition

Short term < 2-4 wk

Consider long-term tube placement Regularly monitor adequacy

No

Peripheral PN Feeding prolonged or poor peripheral access

Figure 1. Algorithm for deciding the right method of nutritional support.

Long term > 4 wk Central venous PN

442 R. J. Stratton and T. R. Smith

Patient with or at risk of malnutrition on screening*

Consider need for modified feeds/diet according to clinical condition (reduced sodium, pre-digested etc.)

Novel developments in gastrointestinal nutrition 443

Nutritional treatment of malnutrition (nutritional support), overseen by a dietitian or a nutrition support team, can encompass: † † † † †

modification of the diet with dietary fortification and counselling use of oral nutritional supplements (single nutrient and multi-nutrient) enteral tube feeding (ETF) parenteral nutrition (PN) combinations of these therapies.

The treatment of malnutrition should be undertaken alongside management of the underlying causes of malnutrition. These can include the disease or condition, the symptoms associated with the disease and side effects of treatment (e.g. ascites, gastrointestinal symptoms of nausea, vomiting, diarrhoea etc. anorexia) and psychosocial problems. The optimal treatment strategy for malnutrition should be devised for the individual patient, whilst considering a number of factors: † Whether the individual is safely and physically able to eat and drink. If so, consideration is needed of the likely adequacy of intake, which may be severely compromised by anorexia, other side-effects of disease and any dietary modifications required (e.g. low sodium, pre-digested, see below). In addition to the diet, oral nutritional supplements and feeding via tube may be required to ensure an adequate nutritional intake. † If the individual is not safely able to eat and drink and oral intake is contraindicated, non-oral means of feeding are required (ETF). If feeding into the GI tract is contraindicated, then intravenous feeding (parenteral nutrition) is considered. When there is uncertainty about the functioning of the gut, a combination of tube feeding and parenteral nutrition may be optimal. † The method of nutritional support chosen varies depending on the goals of treatment, which should be set from the commencement of therapy. Relevant factors include the duration and location of nutritional support and the clinical condition and wishes of the individual patient. In the community, the ability of individuals and their carers to manage nutritional support need to be considered. † Nutritional treatments may need to be modified (in texture, composition, consistency and quantity) if there are symptoms (e.g. nausea, swallowing problems, severe anorexia, electrolyte disturbances etc.) associated with the disease or its treatment. † Deficiencies of micronutrients (e.g. vitamins, minerals, trace elements) frequently coexist with protein-energy malnutrition 2,3. Nutritional treatment of malnutrition in the patient with gastrointestinal or liver disease should consider the provision of micronutrients in addition to energy and protein. All micronutrient deficiencies should be corrected. † Active nutritional treatment may not be appropriate for the terminally ill or dying patient. For more information on the ethics of withholding or withdrawing feeding, refer to.4 Many individuals with malnutrition, both in hospital and in the community, can be managed orally. However, this chapter concentrates on the use of enteral nutrition (oral nutritional supplements, ETF) and PN. In some patients, it is obvious that artificial nutritional support (via tube or intravenously) is necessary from the time of the first consultation (e.g. unconscious, intestinal failure, unable to swallow, major surgery such as oesophagogastrectomy, aggressive chemotherapy). Whenever, the gut is available,

444 R. J. Stratton and T. R. Smith

enteral nutrition should primarily be used, as it is simpler, more physiological and cheaper than intravenous feeding but in some cases, a combination of enteral and parenteral nutrition may be warranted in order to meet nutritional requirements.

PRESCRIBING NUTRITIONAL SUPPORT When prescribing nutritional support, an individual’s nutritional requirements should be assessed. Requirements for energy, protein, fluid, vitamins, minerals and trace elements should all be considered and the extent of the shortfall between requirements and current or anticipated dietary intake assessed. Requirements for energy and nutrients will depend on the age, gender and clinical condition of the individual patient, their body weight and nutritional status, nutrient losses (e.g. gastrointestinal losses), any therapeutic requirements (e.g. sodium restriction for ascites) and the goals of treatment. The requirement for nutrients will also differ if nutritional support is delivered intravenously. Requirements should be reviewed regularly as they will vary with the stage and severity of illness and may be affected by other treatments, including surgery etc. Energy requirements Total energy expenditure has three main components, resting energy expenditure, physical activity and the thermic effect of food (post-prandial thermogenesis). There are equations that can be used to estimate the resting energy expenditure component, most of which have been developed for healthy subjects, such as the Schofield equations.5 However, disease, infection, surgery and other traumas can increase resting energy expenditure to differing degrees (generally increased by 0–25%) for days or months, depending on the severity of the condition. Partial starvation (O10% weight loss) can reduce resting energy expenditure. Normograms can aid your calculations.6 Physical activity and diet-induced thermogenesis also need to be taken into account when considering energy requirements by adding a combined factor (e.g. C10% for a bedbound immobile patient to C25% for a patient who is mobile on a ward). Typically patients have reduced physical activity compared with healthy subjects, which offsets any increase in basal metabolism so that total energy requirements are not usually substantially elevated in disease. In general, estimates suggest that 30–35 kcal/kg body weight/day is sufficient for most patients (in total 1500–2500 kcal daily). For some acute conditions, it may be pragmatic to reduce the intake to below ‘calculated requirements’ for energy balance and weight maintenance, depending on the goals of treatment. For example, energy provision may be reduced in the obese or in the critically ill, unstable patient. In other patient groups (e.g. decompensated liver disease), greater energy intakes may be required (35–45 kcal/kg body weight/day). In all cases, calculations should be made on the basis of ‘dry’ body weight and so adjustments for oedema and ascites (minimal w2 kg, moderate 5 kg, severe O10 kg) should be made.1 Administration of excess energy and nutrients should be avoided to prevent metabolic complications that adversely affect patient outcome. In the catabolically sick, unstable patient or in the severely nutritionally depleted patient, provision of nutrition support should be undertaken cautiously (this may involve feeding patients w50% of their estimated requirement initially) and monitored frequently.

Novel developments in gastrointestinal nutrition 445

The two main energy substrates are carbohydrates (e.g. glucose) and lipids (e.g. triglycerides). The requirements for these energy substrates are usually comparable to those of healthy subjects. Glucose provision should not exceed 4–5 g/kg body weight/day and lipid provision is usually around 1–1.5 g/kg body weight/day with lower values for the critically ill (0.8–1.0 g/kg/day). Essential fatty acids should be supplied (usually 3.0–4.5% of total energy as fat is sufficient to prevent deficiencies) and for some groups, provision of fat as omega-3 fatty acids (fish oil) may be beneficial.7–9 Enteral and parenteral use of medium chain triglycerides (MCT), as opposed to long chain triglycerides (LCT), may be indicated. Oral supplements, tube feeds and intravenous lipid emulsions can contain mixtures of MCT and LCT. For intravenous infusions, ‘structured lipids’ (‘man-made lipids’) are being developed, resulting in triglycerides with random arrangements of fatty acids, which can include omega-3 fatty acids (from fish oil), at the 1,2 and 3 glycerol positions. Omega-3 enriched lipid emulsions may exert anti-inflammatory and immunomodulatory effects. Structured lipids may be superior to LCT or MCT/LCT emulsions for PN but further research is needed. For more information, refer to.9,10 As the requirements for energy are affected by disease and other variables, measurement of energy expenditure using indirect calorimetry (ventilated hood system) is preferable to estimates. For information on measuring energy expenditure, refer to.11,12 Protein requirements For healthy individuals in energy balance, the WHO recommends a mean intake of 0.12 g nitrogen/kg body weight/day (1 g NZ6.25 g protein). For depleted patients, those with inflammation or infective disease and other catabolic stress (e.g. burns, post major surgery), the requirements for nitrogen may be greater, at least in the early stages of disease or injury.13 During acute and critical illness, achieving positive nitrogen balance is an unrealistic goal and may be harmful. Nitrogen losses increase with increasing nitrogen intake, and high nitrogen intakes lead to metabolic burden. Therefore, in such patients, provision of 0.20 (0.17–0.25) g nitrogen/kg body weight/day should be sufficient.13 Daily nitrogen intakes should be monitored and regimens adjusted in consultation with a dietitian as the condition changes. An adequate protein intake from nutritional support should provide all the essential amino acids. There may be modifications to the amount and type of protein supplied by enteral and parenteral feeds depending on the clinical condition of the patient. In particular, in intravenous solutions, a number of amino acids previously considered ‘non-essential’ in the diet, can now be included, such as histidine, serine, arginine, taurine, cystine, tyrosine and glutamine, some of which are provided as dipeptides due to their instability in intravenous solutions (e.g. L-alanylL-glutamine, glycyl-L-tyrosine). Enteral feeds for use in patients with gastrointestinal disease and other conditions (e.g. critical illness) may also be supplemented with arginine, taurine, choline, glutamine and other important protein sources. The role of glutamine, arginine and other specific nutrients and the benefits of including these nutrients in nutritional support regimens for the patient with gastrointestinal or liver disease are discussed further in this issue and in Grimble and Grimble 1998.14 The intake of protein may be reduced or the source of protein altered (e.g. increased branched chain amino acids and reduced aromatic amino acids) in the

446 R. J. Stratton and T. R. Smith

treatment of hepatic encephalopathy. In chronically encephalopathic patients, some restriction of protein may be warranted if all other causes of encephalopathy have been investigated and eliminated or treated. However, in many cases patients nutritional (and protein) intakes are severely limited and further restrictions are unnecessary. During acute decompensation of liver disease and grade IV encephalopathy, protein restriction is not recommended and full protein requirements should be met, as appropriate. Branched chain amino acid supplementation may be of benefit in advanced cirrhosis and hepatic encephalopathy. In the largest RCT published (n 174), compared with equicaloric or equicaloric-equinitrogenous lactoalbumin or maltodextin supplementation, oral BCAA supplementation led to significantly lower hospital admission rates and reduced combined event rates (significantly different to lactoalbumin group only) whilst liver function tests were stable or improved.15 Anorexia and quality of life benefits were also suggested. Indeed, BCAA may have a role as antianorexia and anticachexia agents but this requires further investigation.16 Compliance with oral supplementation of BCAA and formulae containing BCAA is typically poor.15 A Cochrane review of 11 RCT (1 oral, 3 enteral, 7 parenteral BCAA supplementation) assessed the effects of BCAA in hepatic encephalopathy. The review suggested significant improvements in encephalopathy at the end of treatment but no effect on survival. However, trial methodology was poor.17 Individual studies of oral or intravenous BCAA supplementation have shown conflicting effects on survival and encephalopathy (for a review, refer to17,18). Vitamins, minerals and trace elements The provision of an adequate amount of vitamins, minerals and trace elements is important when prescribing nutritional support, whether orally, enterally or parenterally.19 Individuals with protein energy malnutrition, common in those with gastrointestinal and liver disease, frequently have deficiencies of micronutrients and these should be corrected. In some cases, increased provision of some micronutrients, including antioxidants, may be indicated.20 For oral nutritional supplements and tube feeds, European Union Legislation includes a directive on Dietary Foods for Special Medical Purposes, which includes guidelines on the vitamin and trace element content of feeds (see Table 1). As these are ranges based on a daily intake of 2000 kcal, advice from a dietitian should be sought about the most appropriate enteral feeds and micronutrient supplements to use for an individual patient. The recommended intakes of micronutrients differ for enteral and PN support. The gut is the most important organ regulating the availability of some trace elements into the body, sometimes absorbing less than 10 per cent of that delivered. Prolonged administration of intravenous trace elements may therefore result in toxicity. In contrast, the requirements for vitamins are often higher in parenterally fed patients. They are absorbed from the gut more readily than most trace elements and therefore vitamin deficiencies are common in patients with gastrointestinal disease. Some vitamins may degrade during the preparation and storage of PN solutions, which taken together with their increased requirement in many disease states, results in the need for generous vitamin provision in those requiring PN. The American Medical Association have published guidelines for the provision of micronutrients21 in PN, which are summarised in Table 1.

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Table 1. Vitamins and trace elements in enteral and parenteral nutrition. EC directive Vitamin

Minimum

A (mg) B1 (mg) B2 (mg) B6 (mg) Niacin (mg) B12 (mg) Folate (mg) Biotin (mg) C (mg) D (mg) E (mg) K (mg) Trace element Iron (mg) Zinc (mg) Copper (mg) Manganese (mg) Selenium (mg) Chromium (mg) Molybdenum (mg) Iodide (mg) Fluoride (mg)

Maximum

700 1.2 1.6 1.6 18 1.4 200 15 45 10 10 70

3600 10 10 10 60 14 1000 150 440 50 60 400

10 10 1.2 1 50 25 70 130 0

40 30 10 10 200 300 360 700 4

Parenteral nutrition 1000 3.0 3.6 4.0 40 5 400 100 100 5 10 – 1–2 2.5–4.0 0.5–1.5 0.15–0.8 30–60 7–13 15–30 100–200 1–3

Fluid and electrolytes The intake of fluid and electrolytes is an integral part of nutritional support, whether delivered orally, enterally or parenterally. Usually between 1.5 and 3.0 l of fluid are given to adults receiving enteral or PN. As a guide, 30–35 ml/kg body weight/day of fluid is required, with additional requirements for those with fever and losses of other body fluids. Electrolyte requirements also vary but a provision of 1–1.5 mmol/kg/day of sodium, chloride and potassium and 0.3–0.7 mmol/kg/day of phosphate is a general guide. In standard enteral and parenteral regimens, daily intakes of sodium are 80–100 mmol, potassium 60–150 mmol and phosphate

Table 2. Approximate electrolyte content of intestinal effluents (mmol/l). Effluent Gastric Pancreatic Biliary Small intestinal Diarrhoea

Sodium 60 140 140 100 60

Potassium 15 5 5 10 30

Chloride – 90 35 25 45

90 75 100 100 45

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15–40 mmol. Fluid balance is frequently managed badly and deficits or excesses of fluid/saline may cause problems for patients (e.g. excess of fluid may delay return of GI function or increase complications post-surgery). High fluid and electrolyte requirements are seen in patients with high output gastrointestinal fistulas and Table 2 gives approximate electrolyte contents of intestinal effluents. Patients with other losses (e.g. from gastric aspiration, severe diarrhoea, short bowel, excessive sweating, severe burns, polyuria) may also have increased fluid and electrolyte requirements. In contrast, fluid intake may need to be reduced in the oedematous patient and in those with renal, hepatic or cardiac failure or recent head injury. Daily weighing, fluid intake charts, serum biochemistry and daily examination of the patient (for dehydration, oedema) etc. is necessary for monitoring. Fibre and synbiotics Fibre is necessary to maintain the functioning of the gastrointestinal tract and for general health. Fibre may have clinical benefits in the treatment of some gastrointestinal and liver diseases and associated symptoms (including constipation and diarrhoea, cirrhosis and encephalopathy) but a systematic review suggests that more research is needed to ascertain the benefits of fibre supplementation of enteral feeds.22 The main site of action of fibre is in the colon. The fermentation of some soluble fibres (e.g. insulin, fructoligosaccharides, galactooligosaccharides) has a prebiotic effect (stimulate growth of beneficial bifidobacteria and lactobacilli), which may improve the body’s resistance to pathogens. Anaerobic fermentation produces beneficial short chain fatty acids (mainly acetate, butyrate, propionate), which are a mucosal energy source, stimulating mucosal cell proliferation, mucus production and mucosal blood flow, they aid salt and water absorption and may have anti-inflammatory effects. Less soluble fibre can act as a bulking agent increasing stool output and frequency and reducing colonic transit time. Patients receiving enteral nutrition (either oral nutritional supplements or tube feeding) may benefit from feeds containing a mix of insoluble and soluble fibres, particularly if receiving long term tube feeding as a sole source of nutrition, in order to maintain gut integrity, function and flora. For those receiving PN, it is acknowledged that to maintain gut integrity and function, where possible and appropriate, some feeding into the gut should be maintained. Pre- and probiotics, either supplied alone, or as part of an enteral feed, may be beneficial for some patient groups (e.g. pancreatitis, short bowel, inflammatory bowel disease, transplantation, cirrhosis), potentially improving the microbial composition of

Research agenda † research is required to ascertain the requirements for energy, macronutrients (fat, protein, carbohydrate) and micronutrients (vitamins, minerals, trace elements) and the requirement for other nutritional substrates (e.g. omega-3 fatty acids, probiotics) for patients with specific gastrointestinal and liver diseases and to identify the optimal feed compositions (enteral and parenteral) to meet these specific requirements

Novel developments in gastrointestinal nutrition 449

the GI tract and gut barrier function reducing the risk of infection and sepsis. Early trials suggest synbiotics (fermentable fibre and live bacteria) may have clinical benefits (e.g. reduce the incidence of infections) in some groups (liver transplant,23 biliary cancer patients undergoing hepatectomy,24 acute pancreatitis (review25)) but not others (e.g. critically ill patients,26 elective surgical patients27). In cirrhosis patients, fermentable fibre and live bacteria has been shown to improve gut flora, plasma ammonia concentrations, neuropsychological tests, endotoxaemia and Child-Turcotte-Pugh scores.28 A dietitian or nutrition support team should be involved in the prescription of enteral and parenteral feeding regimens, including the optimal energy and nutrient provision, and undertake regular review and monitoring of the efficacy of nutritional support.

MONITORING NUTRITIONAL SUPPORT It is essential that all patients receiving artificial nutrition support are fully assessed before the start of feeding and are closely monitored during feeding, particularly early after instigation. Monitoring allows quantification of nutritional status, including any losses, to enable daily estimation of replacement requirements, maintenance of metabolic balance, detection of toxicity/deficiency states, and early detection of complications. In addition to recordings of temperature, pulse and blood pressure, baseline laboratory measurements should include a full blood count, urea and electrolytes (including calcium, magnesium and phosphate), and liver function tests. A micronutrient screen should be considered in severely depleted patients, and when prolonged treatment is envisaged. Clinical monitoring Before, during and after nutrition support, nutritional assessment of the patient should be undertaken. During acute illness, one of the aims of nutritional support is to prevent or slow any loss of body weight and tissue. During this time it is unrealistic to expect improvements in body composition to occur but functional outcomes can be improved (e.g. muscle strength) (see sections on page 15 and 20). During convalescence and chronic illness, nutritional support can improve body weight, composition and aid the return of function. Monitoring of nutritional status can include. body weight, which should be measured regularly (weekly or even daily in hospital if monitoring fluid status). If weighing is difficult, mid upper arm circumference can be measured with a tape measure and the changes over time can be used as a proxy for percent weight change. For more information, see the ‘Malnutrition Universal Screening Tool’ ‘MUST’.1 Oral intake (where appropriate) and total intake by all feeding routes should be monitored with the use of food charts and records made of nutritional support delivery. Appetite and GI function should be regularly assessed. Functional tests can also be useful to monitor response to nutritional support, including measures of skeletal muscle strength (hand grip dynamometry), respiratory muscle strength (peak expiratory flow rate), quality of life, activities of daily living (elderly) and psychological tests.

450 R. J. Stratton and T. R. Smith

Other regular monitoring should include blood pressure, pulse and temperature and accurate fluid balance records are required irrespective of the method of nutrition support. The access route used to deliver nutrition support should also be assessed on a daily basis. The position of enteral feeding tubes should be recorded, which should include a pH measurement of gastric aspirates of 5 or less in those patients with a nasogastric tube. Nasojejunal and gastrostomy tubes should be inspected and assessed radiologically if there is any suggestion that the tube has been displaced. Intravenous feeding lines should be assessed on a daily basis for evidence of local or systemic sepsis, and dressings should be changed regularly. Laboratory monitoring The frequency with which laboratory measurements are obtained will be governed by the condition of the patient. Frequent monitoring of urea and electrolytes (including magnesium and phosphate) is required for at least the first week in all patients receiving artificial nutrition support, but the frequency of these tests can reduce as the patient stabilises. Blood glucose should be measured 12 hourly for the first 2 days and daily thereafter. Hyperglycaemia is common in critical illness, particularly in those who are parenterally fed, and is associated with septic complications. Even minimally raised glucose concentrations have been shown to be deleterious,29 therefore, some patients may require more intensive monitoring of glycaemic control. Overall, critically ill patients and those who are severely malnourished are at particular risk of metabolic complications and therefore should be monitored more closely (see below). Liver function tests and a full blood count should be checked at least twice a week. Serum albumin concentrations increase with nutritional repletion and recovery from illness. The long half-life, in addition to the influence of the acute phase response and changes in vascular permeability and fluid balance, limits the value of this measurement as a nutritional marker. Similarly, other protein markers (including pre-albumin, retinol binding protein, transferrin) are poor indicators of nutritional status in the acutely ill as they are influenced by other non-nutritional factors including inflammatory status and liver or renal function. Consequently, a combination of nutritional and clinical measures should be used in monitoring patients on nutritional support and changes in protein markers should always be interpreted with caution. Refeeding syndromes Starvation is accompanied by adaptive changes and micronutrient deficiencies such that malnourished individuals have abnormalities including deficiencies of vitamins and trace elements; whole body depletion of intracellular potassium, magnesium, and phosphate; increased intracellular and whole body sodium and water; low insulin concentrations and a partial switch from carbohydrate metabolism to ketone metabolism to provide energy. Organ function may be impaired and starved individuals may have poor cardiac reserve and an inability to excrete an excess salt and water load. Giving nutrients and fluid to malnourished patients will reverse these changes leading to an increase in demands for electrolytes and micronutrients, and a simultaneous shift of sodium

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and water out of cells. Over-rapid or unbalanced nutrition support can, therefore, precipitate micronutrient deficiencies and dangerous changes in fluid and electrolyte balance. The problems of refeeding are less likely to arise with oral feeding since starvation is usually accompanied by a ‘protective’ loss of appetite. Nutritional support can precipitate refeeding problems since excessive feeding levels can be achieved easily and exaggerated if the products do not include adequate vitamins, phosphate or electrolytes. The two widely recognized problems of refeeding are those of the classical ‘Refeeding Syndrome’30 and the ‘Wernicke-Korsakoff Syndrome’.31 Refeeding syndrome Refeeding Syndrome occurs on feeding when a range of life-threatening clinical and biochemical abnormalities arise: † † † † † †

Cardiac failure, pulmonary oedema and dysarrhythmias Acute circulatory fluid overload or circulatory fluid depletion Hypophosphataemia Hypokalaemia Hypomagnesaemia and occasionally hypocalcaemia Hyperglycaemia

Patients at risk are those with a BMI less than 18.5 kg/m2, recent weight loss in excess of 10% or no nutritional intake for more than 7 days. Those with a BMI less than 16 kg/m2 or recent weight loss greater than 15% are at the highest risk. Groups of patients at risk include those with postoperative ileus, alcoholics, anorexia nervosa, prolonged fasting (e.g. in-patients kept ‘nil by mouth’ for multiple investigations), stroke patients and those taking certain drugs (insulin, chemotherapy, antacids, diuretics). Patients at risk of refeeding syndrome should be fed very cautiously for the first few days, with generous electrolyte and phosphate supplementation. The presence of normal serum electrolytes does not exclude the risk of refeeding syndrome as these patients often have a whole body electrolyte depletion of thousands of mmol. The suggested approach by some authorities that correction of electrolyte abnormalities should be undertaken prior to commencing feeding may provide a false sense of security. Severely malnourished individuals may be unable to correct intracellular electrolyte status unless simultaneous feeding is given to encourage membrane transfer.32 Clinical management should include: † Restore and monitor circulatory volume, fluid balance and electrolytes; † ECG monitoring (high risk patients) for at least the first 48 hours of feeding; † Daily monitoring of potassium, phosphate, magnesium, and glucose during the first week; † Generous supplementation of Potassium (2–4 mmol/kg/day), Phosphate (0.3– 0.6 mmol/kg/day) and Magnesium (0.1–0.2 mmol/kg/day) even in the presence of apparently normal serum electrolyte concentrations; † Intravenous thiamine and other B vitamin supplements, together with a complete vitamin and trace element preparation;

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† Restricted energy provision, starting at 20 kcal/kg/day for the first 48 hours, gradually increasing to meet estimated needs by day 4–6. Those at highest risk should start at 10 kcal/kg/day. † Seek urgent opinion from a Nutrition Support Team or a Senior Dietitian.

Wernike–Korsakoff syndrome The Wernike–Korsakoff syndrome is caused by acute thiamine deficiency, when refeeding of malnourished patients precipitates increased thiamine demand as starving cells switch back to carbohydrate metabolism. The syndrome of acute neurological abnormalities comprises of one or more of the following: † † † †

Apathy and disorientation Nystagmus, opthalmoplegia or other eye movement disorders Ataxia Severe impairment of short-term memory often with confabulation

It is seen particularly frequently in alcoholics, who may have depleted stores of thiamine, and also in any patient with chronic vomiting, including those with hyperemesis gravidarum and gastric outlet obstruction. Patients should be managed as for the refeeding syndrome. Thiamine should be started prior to receiving feed or IV 5% dextrose in those at risk. Intravenous thiamine (Pabrinex ICII OD) should be given for 3 days, along with oral thiamine 100 mg QDS and Vitamin B Complex (including nicotinamide, pyridoxine hydrochloride and riboflavin).

Practice points † patients identified with or at risk of malnutrition should be promptly treated using diet, oral nutritional supplements, tube feeding, PN or combinations of these therapies as appropriate (Figure 1). Involve a dietitian or nutrition support team where possible † the underlying cause of malnutrition (e.g. disease, side-effects of treatment) should be managed and treated alongside the use of nutritional support † adequate provision of energy, protein and other nutrients (including vitamins, minerals and trace elements) and fluid is required with nutritional support † the goals of treatment should be defined on commencement of nutrition support, with consideration of the patients’ clinical condition, the anticipated duration of treatment and the wishes of the patient † regular monitoring of nutritional support is required, the frequency of which will depend on the method of feeding (oral, tube, parenteral) and the clinical condition of the individual † patients at risk of refeeding syndrome should have cautious introduction of nutrition support, with close monitoring in addition to adequate electrolyte and micronutrient provision, to prevent life-threatening complications

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ENTERAL NUTRITION The European Society for Clinical Nutrition and Metabolism (ESPEN) (www.espen.org) and the National Institute for Clinical Excellence (NICE) (www.nice.org.uk) are publishing guidelines on the use of nutritional support (oral, enteral and parenteral nutrition), including the evidence supporting its use. The best way of giving nutritional support, if feasible, is orally. In addition to the diet (counselling, fortification), oral nutritional supplements should be considered for patients with GI and liver disease who are malnourished or at risk of malnutrition and can be managed orally.

ORAL NUTRITIONAL SUPPLEMENTS Oral nutritional supplements are typically multi-nutrient containing a mix of macronutrients (protein, carbohydrate, fat) and micronutrients (vitamins, minerals, trace elements). Most are liquid feeds but there are also puddings and bars available. In the community, prescribable and non-prescribable supplements are available. Oral nutritional supplements can be nutritionally complete, nutritionally incomplete (e.g. fat free or lacking some essential micronutrients) or modular (e.g. usually containing one or two macronutrients only) (Figure 2). The most commonly used supplements are polymeric and contain protein, carbohydrate and fat, together with electrolytes, minerals, trace elements, and vitamins. Feeds that are ‘predigested’ (e.g. protein as peptides and/or amino acids (elemental), fat as medium chain triglycerides) can be used when gastrointestinal capacity (digestion, absorption) is limited. The palatability of such feeds may affect compliance when taken orally, particularly if required for long-term use (Figure 2). Disease-specific oral nutritional supplements are available for use in those with other conditions (e.g. liver disease (low sodium feeds, branched-chain amino acid supplemented feeds), inflammatory bowel disease, renal dialysis, wound care, cancer etc.). Indications and practicalities Indications for oral nutritional supplements include disease-related malnutrition, which may occur in many patient groups, including those with cancer, the elderly, surgical patients and others with severe acute or chronic diseases. Malnutrition can be identified using a screening tool, such as ‘MUST’ (www.bapen.org.uk), and clinical judgement. Other indications include pre-operative preparation of a malnourished patient, inflammatory bowel disease, short bowel syndrome, intractable malabsorption (can include patients with a range of gastrointestinal (including pancreatic) and liver diseases), post total gastrectomy, dysphagia, bowel fistulas and dialysis (continuous ambulatory peritoneal dialysis, haemodialysis) Liquid oral nutritional supplements may be a good strategy for the malnourished patient with anorexia. They tend not to suppress food intake substantially.33 The efficacy of oral nutritional supplements maybe limited if compliance is poor, which can be an issue with long-term supplementation of the chronically sick patient in the community. In such cases, a more energy dense supplement taken as small doses or as a ‘medication’ as opposed to ‘food’ may aid compliance. Varied flavours and a choice of different supplement types and consistencies may also help.

Modular feeds (Macronutrients) Liquids/powders added to food, drink or used orally as a supplement or in tube feeding

Energy only

Carbohydrate

Protein only

Polymeric feeds (Whole protein) Mostly liquids

With fat

Fat

Combined carbohydrate and fat

With fibre

Without fat (juice type, mostly used orally)

Pre-digested feeds (Modified protein)

Disease specific

Feeds may contain fat as medium chain triglycerides (MCT) or fat content may be reduced

Peptide

Elemental (amino acids)

Without fibre

Combined energy and protein modular supplements

Malabsorption: pre-digested feeds

Hepatic: Reduced sodium; Modified protein (branched chain amino acids)

Diabetes: Modified carbohydrate and fat content to improve glycaemic control Immune enhancing diets (cancer, critical care): Feeds enriched with omega-3 fatty acids, and/or arginine, glutamine

* If given as a sole source of nutrition, ensure a nutritionally complete feed is chosen. Not all feeds are nutritionally complete. Figure 2. Enteral feeds (oral nutritional supplements and tube feeds).

454 R. J. Stratton and T. R. Smith

Enteral (oral or tube) feed*

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Specific supplements may be indicated for the patient with malabsorption. For example, supplements containing medium chain triglycerides (with or without other nutrients) may be indicated for patients with steatorrheoa associated with pancreatic diseases, HIV infection, intestinal lymphangiectasia, surgery of the intestine, chronic liver disease and liver cirrhosis. For those with liver disease, supplements that are low in aromatic amino acids and richer in branched chain amino acids are also available and may be beneficial. Benefits of oral nutritional supplements Current evidence from systematic reviews and meta-analyses8,34–37 suggests that nutritional supplements are an effective treatment for patients with or at risk of malnutrition. In general, with supplementation: † Total nutritional intake is significantly improved in most patient groups and food intake tends not be reduced. † Improvements in body weight and composition and in growth in children occur. In hospital patients, supplements attenuate weight loss and in community patients weight gain occurs and is more likely in those who are underweight (BMI! 20 kg/m2). Improvements in weight are related to improvements in physical function. † Functional improvements can occur, including increased muscle strength, walking distances, activities of daily living, immunological benefits, reduced fatigue, improved wound healing and prevention of pressure ulcers. † Clinical outcome (mortality and complication rates) can be improved. † Studies suggest oral nutritional supplements reduce hospital length of stay and a cost analysis shows they may reduce health care costs.38 In those with gastrointestinal/liver disease, including those undergoing surgery, oral nutritional supplements have been shown to improve nutritional intake, improve functional recovery (e.g. hand grip strength, liver function), reduce infections and other complications and reduce health care use (reduced readmission rates, shorter hospital stays). For a detailed review, refer to.36

Practice points † liquid oral nutritional supplements are an effective treatment for diseaserelated malnutrition, a common condition associated with gastrointestinal and liver diseases † a wide variety of supplements exist for use in patients with gastrointestinal and liver disease, including those with severe malabsorption, ascites and encephalopathy † dietitians can advise on the optimal oral nutritional support strategy † establish goals for treatment (e.g. improvement in intake, appetite, weight, function) and monitor the efficacy of supplements regularly † if supplements are insufficient to ensure an adequate intake and recovery, consider ETF

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ENTERAL TUBE FEEDING For patients who are unable to consume sufficient orally (anorexia, requirement for unpalatable diet, physical difficulties eating and drinking), or for whom oral intake is unsafe and contraindicated (e.g. unconscious, unsafe swallow, post-operatively (in some instances)), tube feeding is indicated (Figure 1). Indications/contraindications for enteral tube feeding The general indications and contraindications of ETF are summarised in Table 3. In cases where there is doubt about the use of enteral nutrition, a time-limited trial can be used. ETF may also be given together with PN where there is uncertainly about GI function. Access routes for enteral tube feeding The feed can be delivered through a variety of routes using different tubes, which will vary depending on the patient group (e.g. patients with abnormal upper gastrointestinal anatomy and those at risk of aspiration) and the duration of treatment (short or long term). There are fine bore nasoenteral tubes (nasogastric, nasoduodenal, nasojejunal), gastrostomy tubes (surgical, percutaneous endoscopic or fluoroscopic) and jejunostomy tubes (surgical, percutaneous endoscopic or fluoroscopic). Most patients in hospital are fed for short periods of time and nasogastric feeding, using a fine bore feeding tube (polyurethane) is indicated. Large bore tubes (e.g. Ryle’s tubes) should not be used for feeding as they are uncomfortable and are more prone to complications (including gastric reflux, pharyngitis etc.). Tubes should be placed by a trained health professional and correct positioning should be checked to ensure there is no malpositioning into the lungs or elsewhere (e.g. intracranial in those with facial injuries or mechanical abnormalities of the upper airways/GI tract). Nasogastric tube positioning can be confirmed, at least initially, by X-ray. New recommendations by the National Patient Safety Agency in the UK suggest that tube positioning should also be checked before every feeding episode by aspirating stomach contents (pH 5 or less using an approved pH indicator paper). Litmus paper and auscultation should not be used (For more information, refer to the National Patient Safety Agency guidelines, www.npsa.nhs.uk). Secure fixing of the tube to the nose and face is essential to reduce the risk of extubation, either accidentally or deliberately by patients. Double-lumen nasoenteral tubes, which allow feeding and concurrent aspiration, may be suitable for some post-operative patients, ICU patients and others with gastric stasis or gastroparesis that require enteral nutritional support. For longer term ETF into the stomach, percutaneous endoscopic gastrostomy is the most common route used.39 For patients at increased risk of regurgitation of feed and/or pulmonary aspiration, gastric atony or gastroparesis, post-pyloric feeding into the duodenum or jejunum should be considered. This could include feeding post-operatively following major upper gastrointestinal surgery, post-head injury or neurosurgical patients, short term feeding in ICU and multiple trauma patients, some patients with a cerebrovascular accident and some diabetics with neuropathy. If short term, a nasoduodenal or nasojejunal tube can be used. If long term tube feeding is indicated, a jejunostomy (endoscopic, surgical) may be used, although this is much less commonly used than gastrostomy feeding. For more information about tube placement, removal and other routes of feeding, refer to guidelines from the British Society of Gastroenterologists.32

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Table 3. Guidelines for the use of enteral tube feeding in the adult patient (Elia, 1996). 1

2

3

4

Conditions where tube feeding should be a part of routine care (a) Protein-energy malnutrition (greater than 10% weight loss) with little or no oral intake for 5 days (b) Less than 50% of the required oral nutrient intake for the previous 7–10 days (c) Severe dysphagia or swallowing-related difficulties, e.g. head injury, strokes, motor neurone disease (d) Major, full-thickness burns (e) Massive small bowel resection (in patients with 50–90% small bowel resection, ETF is given to hasten gut regeneration and return to oral intake, often in combination with parenteral nutrition) (f) Low-output enterocutaneous fistulae (!500— ml/day)a (elemental diets may hasten closure of fistula) Conditions where tube feeding would normally be helpful (a) Major trauma (see 1(a) and (b) above) (b) Radiation therapy (see 1(a) and (b) above) (c) Mild chemotherapy (see 1(a) and (b) above) Conditions where tube feeding is of limited or undetermined value (a) Immediate postoperative period or post-stress period if an adequate oral intake will be resumed within 5–7 days (b) Acute enteritis (c) Less than 10% of the small intestine remaining (parenteral nutrition is usually indicated) Conditions/situations in which tube feeding should not be used (a) Complete mechanical intestinal obstruction (b) Ileus or intestinal hypomotility (c) Severe uncontrollable diarrhoea (d) High-output fistulae (e) Severe acute pancreatitis (f) Shock (g) Aggressive nutritional support not desired by the patient or legal guardian, in accordance with hospital policy and existing law (h) Prognosis not warranting aggressive nutritional support

If the fistula is proximal, the feeding should be distal. If the fistula is distal, sufficient proximal length must be present to allow sufficient absorption. Fistulae due to malignancy, radiation and distal obstruction are unlikely to close spontaneously. a See guidance on refeeding syndrome.

Administration techniques and complications Most tube feeding involves the use of a pump and a sterile administration set to deliver continuous infusions of feed over many hours, during the day, night or both (typically for 12–16 hours overnight to allow mobilisation during the day). Sometimes boluses of feed are given (200–400 ml over 20–60 minutes), often by syringe, at intervals during the day with gastric but not jejunal tube feeding. The timing and rate of tube feeding will vary depending on the site of feeding (e.g. gastric or jejunal), GI function and patients’ tolerance of tube feeding. A summary of complications associated with tube feeding is shown in Table 4 and for more details, refer to.32,40 Social factors should also be considered in the patient on home artificial nutrition.

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Enteral tube feeds A variety of nutritionally complete tube feeds are available for use in adults and children. These liquid feeds typically have similar nutritional compositions, although the energy densities (0.5–2 kcal/ml) and protein contents may vary (Figure 2). Standard polymeric feeds (1 or 1.5 kcal/ml) are the most commonly used. Fibre-containing feeds are also available which may or may not be suitable for the patient with gastrointestinal or liver disease. For long term enterally fed patients (home-based), those with constipation or diverticular disease may benefit from a fibre-containing feed. There is also an extensive range of specialist tube feeds that vary in composition and others that are recommended for use in disease-specific groups. For patients with gastrointestinal or liver disease, these include: † Peptide, amino acid and medium chain triglyceride based feeds that may be used in patients with malabsorption (pancreatic insufficiency including cystic fibrosis, short bowel syndrome, inflammatory bowel disease, radiation enteritis etc.). † Feeds enriched with glutamine, short-chain fatty acids, other nutrients (e.g. taurine, choline) and growth factors may be beneficial for gastrointestinal structure and function. † Low sodium/low electrolyte feeds (and feeds enriched in branched chain amino acids) that may be used in patients with liver disease (and encephalopathy). † Feeds enriched with omega-3 fatty acids, arginine, glutamine and other immunomodulating ingredients for use in patients with critical illness.41 † Feeds with modified fat, carbohydrate and fibre contents for patients with diabetes.42 The choice of feed and the quantity of feed prescribed will depend on the patients’ general clinical condition, gastrointestinal function, their nutritional requirements and their nutritional status (severely underweight, underweight etc.). The amount of tube feed given will also depend on whether tube feeding is used as the sole source of nutrition (e.g. in patients who are unable to swallow food due to a neurological condition or an obstructive cancer) or in addition to food intake (e.g. in patients who have a poor appetite due to cystic fibrosis, COPD, infections or cancer) or in combination with PN. A dietitian or nutrition support team can advise on the choice of tube feed and devise a feeding regimen (quantity, timing, rate of feeding delivery). Benefits of enteral tube feeding ETF is an effective means of providing nutritional support, either as a sole source of nutrition, or as a supplement to oral diet or intravenous feeding. Systematic reviews and meta-analyses have highlighted the benefits of tube feeding in patients with or at risk of malnutrition, including those with gastrointestinal or liver disease and those undergoing surgery.8,36,43 In general, these include improvements in nutritional intake, significant attenuation of weight loss, functional improvements (wound healing, prevention of pressure ulcers, improved immune function, muscle strength) and better clinical outcome (reduced mortality, fewer complications). More specifically, tube feeding can reduce disease activity/inflammation in those with Crohn’s disease, hasten

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Table 4. Some complications with enteral tube feeding. Complication

Enteral

Mechanical

Tube blockage by feed or tube kinking Tube malposition (e.g. into trachea) Insertion trauma Nasogastric damage to nasal septum, oesophagus, stomach, perforation (rare) Gastrostomy/enterostomy damage to stomach, small bowel, bleeding, peritonitis, leakage, irritation and infection around site Loss of tube into GI tract Diarrhoea or constipation, bloating, cramps Aspiration pneumonia/regurgitation Fluid and electrolyte disturbances Hypo- and hyper-natraemia, kalaemia, phosphataemia, glycaemia Infection around ostomy site Infection of feed or administration set (very rare if commercial feed and set used according to guidelines) Aspiration pneumonia may precipitate respiratory distress Effects on self image Anxiety and depression Social isolation (if unable to eat, if confined to bed/home)

Feed/flow related Metabolic* Infections

Organ dysfunction Psychological

* See guidance on refeeding syndrome.

recovery of bowel function and reduce rates of re-operation and mortality in those with severe pancreatitis/peritonitis. Tube feeding may improve hepatic reserve and significantly reduce mortality in patients with cirrhosis, reduce complications in obstructive jaundice patients undergoing surgery, improve liver function in those with alcoholic liver disease and reduce infections in liver transplant patients.36 Enteral nutrition in gastrointestinal surgical patients The effect of enteral nutrition (oral nutritional supplements and ETF) on clinical outcome in GI surgical patients was addressed in a systematic review of 18 randomised controlled trials (n 907 patients undergoing a variety of procedures, including gastrectomy, hemicolectomy, cholecystectomy, hemigastrectomy, laparotomy and resection, oesophagogastrectomy, pancreatoduodenectomy). Meta-analysis of all trials showed enteral nutrition significantly reduced post-operative complications (wound, respiratory and other infections, post-op ileus, wound dehiscence, respiratory complications, unresolved peritonitis with relaparotomy) (odds ratio (OR) 0.357 (95% CI 0.252–0.507)).44 In separate meta-analyses, complications were significantly reduced by oral nutritional supplements (250–600 kcal/days for 7 days–10 weeks, OR 0.385 (95% CI 0.213–0.696) and ETF (831–2852 kcal/days for !11 days, OR 0.331 (95% CI 0.196-0.557)). Enhanced recovery after surgery (ERAS) There is emerging evidence to suggest that clinical outcome can be improved by adopting a multi-modal approach to the nutritional management of patients undergoing

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Practice points † etf is an effective means of increasing nutritional intake when used as a sole source of nutrition or as a supplement to oral or intravenous feeding and there is evidence of clinical benefits when it is used appropriately † tube feeding is usually delivered with continuous infusions (12–16 hours) via nasoenteral tube (for short term) or by gastrostomy (for long term) † a variety of standard and specialised feeds exist for use in patients with gastrointestinal and liver disease, including ‘pre-digested’, low sodium and branched chain amino acid enriched feeds † etf should be undertaken with the supervision of a dietitian or nutrition support team and should be regularly monitored to prevent complications and to ensure that the goals of treatment are reached gastrointestinal surgery. Traditional metabolic and nutritional care of patients undergoing major elective surgery has emphasised pre-operative fasting and reintroduction of oral nutrition up to 5 days after surgery. Recent studies have demonstrated that an enhanced recovery can be achieved by modulating the metabolic status of the patient before, during and after surgery. Oral fluid and carbohydrate loading up to 2 hours prior to anaesthesia is safe in most patients, and can attenuate post-operative insulin resistance, improve patient well-being and reduce hospital stay.45,46 Epidural anaesthesia is used to control pain more effectively and reduce both post-operative ileus and the metabolic response to injury by blocking visceral sympathetic and parasympathetic pathways.47 Opiate analgesia is avoided as this contributes to post-operative ileus, nausea and vomiting. This allows the early use of oral/enteral nutrition, thereby reducing the requirement for maintenance intravenous fluids. Excess intravenous fluids (in particular 0.9% saline) contribute to post-operative gastrointestinal tract dysfunction, prolong hospital stay, and adversely affect overall clinical outcome.48

PARENTERAL NUTRITION Indications for parenteral nutrition In situations where partial or complete intestinal failure has occurred and oral nutrition or ETF is not possible or has failed, PN should be considered. A small number of patients require long-term PN, but in most cases the use of PN is restricted to a few days or weeks. Specific indications include complete intestinal obstruction, ileus or severe dysmotility, severe pancreatitis, high intestinal fistulae, short bowel syndrome, or severe intestinal inflammatory disease, for example small bowel Crohns disease or severe mucositis following cytotoxic therapy. Even where PN is used to cover all of the patients’ nutritional requirements, the GI tract should be utilised as much as possible. Minimal enteral feeding will maintain gut hormone secretion, enzyme production, mucosal absorptive capacity and resistance to bacterial translocation. Intestinal

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function should be reassessed regularly with the aim of transferring to oral or ETF support when it is safe and feasible to do so. Access routes for parenteral nutrition All nutrient solutions should be administered via a dedicated feeding line, through volumetric pumps with in-line air alarms. The lines used can be either peripheral feeding lines or central venous catheters. The decision to commence PN is never an emergency and catheter insertion should always be planned and performed using a full aseptic technique. PN administered via a peripheral line has the advantage of ease of venous access, avoiding the morbidity associated with central line insertion. Tolerance of fluids infused into peripheral veins is dependent on their osmolarlity, pH and infusion rates. Small diameter catheters (22–24F) should be used and midlines (20 cm peripheral catheters) are better tolerated than standard cannulae. Hypertonic solutions are irritant to veins, causing pain, phlebitis and thrombosis. Larger volume bags and the addition of lipid emulsions reduce the osmolarlity, thereby improving tolerance. Where suitable peripheral access cannot be achieved or low volume, lipid free PN is required, a central venous catheter is used. This can be inserted centrally or peripherally to position the catheter in the superior vena cava. Lines should be inserted by trained operators to avoid the early complications of line insertion (local haematoma, arterial puncture, pneumothorax). Late mechanical complications include blocked catheters, for which urokinase, 70% ethanol or hydrochloric acid locks can be used, depending on the cause of the blockage. Central vein thrombosis is relatively common, however, the clinical manifestations are uncommon. It is a dangerous complication associated with high rates of morbidity and mortality in severe cases. Catheter related sepsis remains the most serious complication of central venous catheters. Common causes of catheter infection include leaking lines due to poor connections, use of lines for other reasons (CVP measurement, blood sampling) and inadequate aseptic technique when accessing lines. PN bags are another potential source of sepsis, and for this reason all bags should be prepared in a pharmacy aseptics unit without further addition of drugs or electrolytes being made on the ward. Meticulous line care is vital and nutrition specialist nurses have an important role in developing protocols and education of ward staff. Patients presenting with suspected line sepsis should have their PN stopped temporarily and blood cultures taken peripherally and from all catheter lumens. It is reasonable to attempt sterilisation of a long term tunnelled line, although this is unlikely to be successful in the setting of fungal or resistant bacterial infections. For non-tunnelled lines, in general the best approach is to remove the line and replace after 24 hours of appropriate antibiotic therapy. Complication of parenteral nutrition The complications associated with the use of PN can be divided into line related complications, which have been covered in the previous section, and metabolic complications. Complications can be minimised by the use of appropriate protocols and the active involvement of a nutrition support team. PN overrides many of the body’s homeostatic mechanisms and presents a large osmolar load to the circulation. The major intracellular electrolytes (potassium, magnesium and phosphate) are more rapidly moved into cells and risks of refeeding are

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high (see guidance on refeeding syndrome). All patients therefore require close monitoring and those at particular risk should have restricted energy provision during the early phase of nutrition support. Hyperglycaemia is common in patients receiving PN and is largely due to the insulin resistance associated with severe disease. It can be managed by reducing the glucose intake or by administering insulin. Avoiding even minimal hyperglycaemia in critical illness with the use of intensive insulin therapy has been shown to improve clinical outcome.29 Abnormal liver function tests are frequently observed, but are often related to the underlying disease, sepsis, drugs and small bowel bacterial overgrowth rather than PN per se. Excessive administration of glucose and lipid may result in steatosis due to hyperinsulinaemia, lipogenesis and direct fat deposition in hepatocytes. Cholestatic liver disease is a serious complication, which may progress to cirrhosis and liver failure in those requiring long term home PN. The aetiology of this disease is not known but contributing factors include interruption to the enterohepatic circulation of bile acids, which increases the lithogenicity of bile; bacterial overgrowth with portal endotoxaemia, leading to the production of hepatotoxic secondary bile acids and cytokines; no oral intake resulting in reduced gallbladder motility and biliary sludge; specific nutrient deficiencies including choline, taurine and carnitine.49,50 Long-term patients who take little nutrition from other sources are at risk of micronutrient deficiencies. This is usually due to inadequate intravenous provision, which can be compounded by excessive intestinal losses. Metabolic bone disease is also a problem in those requiring home PN. Several factors may contribute including corticosteroid therapy, the underlying disease, immobility, vitamin D toxicity, amino acid infusions and inflammatory cytokines. Patients should be monitored with bone density measurements every 2 years.6 Benefits of parenteral nutrition There is little doubt that for patients with complete, irreversible intestinal failure, PN support is life saving. The use of PN in other clinical situations, often for short term use, is more controversial. Several studies have failed to show evidence of beneficial clinical outcome with the use of PN.51,52 This may reflect serious underlying disease in hospitalised patients, although it is also possible that nutritional requirements during severe illness have been misunderstood.53 Overfeeding in particular may contribute to many of the metabolic and infective complications documented in some studies. Many studies have also randomised patients to receive PN when ETF could have been utilized. These studies have also tended to exclude severely malnourished patients, even though they are likely to respond to intravenous feeding.36 Although meta-analyses have not shown improvements in clinical outcome with PN overall, they have shown improvements in complication rates among malnourished patients.51,54 A large trial investigating the routine use of peri-operative PN that did not demonstrate any overall benefit did indicate a significant reduction in non-infectious complications in those who were severely malnourished (5.3 versus 42.9%).55 When GI cancer patients with a history of weight loss of more than 10% of usual body weight were randomised to receive perioperative PN or standard therapy, the parenterally fed group had significantly lower complication (37 versus 57%) and mortality (0 versus 11%) rates, with no significant difference in length of postoperative stay.56 Due to the potential complications associated with PN, its use should be restricted to those who are unable to tolerate oral/enteral nutrition support. Many of the

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Practice points † pn should only be used where oral nutrition or ETF is contraindicated or has failed. Some patients may require a combination of enteral and parenteral support † pn is an effective means of nutrition support when used appropriately and has been shown to improve outcome in malnourished patients undergoing gastrointestinal surgery † patients should be closely monitored by a nutrition support team to avoid the metabolic complications associated with its use † meticulous line care must be undertaken at all times published studies have not examined the use of PN in this setting and, therefore, caution should be exercised in interpretation of the literature. If oral or tube feeding is not possible, patients at risk of malnutrition should be managed with appropriately monitored PN, at levels that avoid hyperglycaemia and other metabolic complications.

Enteral versus parenteral nutrition? For some patients, there is a debate over which method of artificial nutrition should be used, ETF or PN. For patients undergoing surgery for gastrointestinal cancer, tube feeding (usually post-pyloric) may be more effective than PN. In a recent systematic review and meta-analysis, complications, infective complications, sepsis scores and hospital stay were significantly lower in those randomised to tube feeding than intravenous feeding.8 It is not clear if these differences are due to the benefits of tube feeding or detrimental effects of intravenous nutrition (and in particular overfeeding). Similarly, other reviews suggest that when the gut functions, enteral is better than PN for hospitalised patients and for specific patient groups,36,57,58 including those with acute pancreatitis.59 Generally, if the gut functions, feeding should be undertaken enterally as tolerated and supplemented with PN as required.

SUMMARY Nutritional support, including dietary modification, oral nutritional supplements, tube feeding and PN, plays an integral part in the treatment of the patient with gastrointestinal and liver disease, in whom malnutrition and nutritional deficiencies are common. Following prescription of adequate energy, macro- and micronutrients and fluid, regular monitoring of nutritional support is required to prevent the associated complications of these therapies and to ensure their efficacy. Ideally, a dietitian or nutrition support team should be involved in the prescription and monitoring of enteral and PN. Nutritional support has a number of clinical benefits, including improved intake and nutritional status, functional recovery, fewer complications and reduced mortality. For some patients, tube feeding or PN may be a life saving treatment providing the only source of nutrition if oral intake is contraindicated or in cases of intestinal failure. A range of standard and modified feeds

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Research agenda † large, well-designed randomised controlled trials are required to ascertain the efficacy of specific nutrients, and oral nutritional supplements, tube and intravenous feeds containing these key ingredients in the treatment of gastrointestinal and liver diseases, including an assessment of both clinical and cost outcomes † trials should consider the most effective methods of nutritional support (e.g. routes (oral versus ETF versus PN), timing, rate of feeding) for different patient groups, including their use in the perioperative period enable the nutritional treatment of a variety of gastrointestinal and liver diseases and associated conditions, including malabsorption, inflammatory bowel disease, postsurgical patients and liver disease (encephalopathy, ascites). Increasingly new enteral and parenteral feeds are being formulated with specific nutrients that may also benefit this patient group (prebiotics and probiotics and other immune modulating nutrients (including omega-3 fatty acids, arginine etc.)). More research is needed to ascertain the optimal amount, composition and timing of feeding enterally and parenterally and the role of specific nutrients and disease-specific feeds in the quest to effectively treat the whole spectrum of gastrointestinal and liver diseases that are often associated with malnutrition.

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