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Artificial nutrition and nutritional support and refeeding syndrome
UNDERNUTRITION AND CLINICAL NUTRITION
Artificial nutrition and nutritional support and refeeding syndrome
number of staff involved will vary depending on the numbers of patients and complexity of nutritional support provided, but doctor, dietitian, nutrition nurse and pharmacist are essential. Percutaneous enteral access requires regular gastroenterology or GI surgical commitment to providing this. Managing unstable intestinal failure patients with longer term parenteral nutrition requires a wide portfolio of skills including gastroenterology, biochemistry, surgery and interventional radiology, in addition to a larger number of dietitians, nutrition nurses and dedicated pharmacy time. A key aspect of team function is the decision about the route of feeding and the input of a senior gastrointestinal physician or surgeon is invaluable in discussion with the ward team. The team should undertake regular patient review rather than simply providing guidelines for management.
Ruth F McKee
Abstract Artificial nutritional support is needed when a patient is unable to absorb sufficient nutrition from normal diet. NICE guidance recommends that enteral and parenteral nutrition is supervised by a multidisciplinary nutrition team and that clear goals of nutritional support are defined and reviewed regularly. The combination of nutrition and control of the systemic inflammatory response enables the patient to become anabolic. If possible the enteral route should be used, most commonly nasogastric feeding. Recent NPSA alerts have highlighted the risks of nasogastric tube misplacement and hospitals should have clear policies about checking tube position. Percutaneous gastrostomy feeding is useful for longer term enteral feeding. In the past decade jejunal feeding has reduced the use of parenteral feeding in critical care and upper gastrointestinal disease. Feeding into the distal small bowel beyond a fistula or a proximal stoma can also avoid parenteral nutrition. Parenteral nutrition may be life saving, but may also result in serious complications such as septicaemia due to line infection. Metabolic complications have been less common since ‘standard’ PN bags became widely available. Refeeding syndrome may occur in severely malnourished patients who recommence feeding. Complex electrolyte disorders, such as hypophosphataemia, hypomagnesaemia and hypokalaemia may result, owing to cellular utilization of phosphate. Feeding should be recommenced slowly with careful electrolyte monitoring.
Aims of nutritional support As part of the decision to institute artificial nutritional support, an expert dietitian should calculate the patient’s nutritional requirements and advise on the route of feeding. The nutritional goal depends upon the patient’s condition. While the patient is catabolic due to sepsis or injury, it is not possible to achieve positive nitrogen and energy balance, and the aim is to replace deficiencies and achieve ‘damage limitation’. Once the acute phase response is controlled by treatment of the underlying disease, the aim changes to maintenance and repletion of lost tissue.
Choice of route for nutritional support The gut should be used for feeding if at all possible e it is more physiological, simpler, and results in fewer complications. Figure 1 shows the thinking behind the choice of route, although it may be necessary to use more than one method either concurrently or consecutively to achieve sufficient absorption of nutrients.
Keywords Enteral nutrition; macronutrient requirements; nutritional screening; parenteral nutrition
Many patients in hospital are undernourished or at risk of becoming so because of inadequate intake. This increases the risk of complications and well-managed nutritional support is beneficial. This article deals with feeding using tubes and artificial nutrition, including both enteral and parenteral routes. It assumes that nutritional screening has already occurred, that dietetic assessment has concluded that dietary adjustments and oral supplements are insufficient, and that artificial nutritional support is considered necessary.
Short-term enteral nutrition A fine-bore nasogastric tube is the most common means of artificial nutrition, but has its own hazards. The National Patient Safety Agency has issued several alerts about the need to ensure that the tip lies within the stomach and remains there. Figure 2 shows a poster used to remind staff to check and document the pH of aspirate for this reason. Although nasogastric feeding is widespread, it can be difficult to achieve adequate intake and absorption of the prescribed feed because of feed interruptions and tolerance. The majority of patients are fed with standard complete formula feeds with an energy content of 1 kcal/mL, providing balanced nutrition including protein, energy, fluid, electrolytes and micronutrients in a volume of 25e30 mL/kg. Partially digested peptide feeds may be used if absorption is impaired, as in pancreatic disease. For particular circumstances, special feed formulas with, for example, a low potassium content (renal impairment) or a higher fat:carbohydrate ratio (pulmonary disease) are available. Nasojejunal feeding is most often used in patients who have gastric emptying problems, common in patients who are critically ill or have undergone upper gastrointestinal surgery. There may also be some benefit in patients with recurrent aspiration
Nutritional support teams In order to achieve adequate nutritional support without complication, a multiprofessional team is recommended.1 The
Ruth F McKee MD FRCS is a Consultant Colorectal Surgeon at Glasgow Royal Infirmary, UK. She has been involved in the nutrition support team there for many years and currently chairs the Greater Glasgow and Clyde Health Board Clinical nutrition group. She is a member of the Scottish National Nutrition Advisory Board and secretary of the British Association for Parenteral and Enteral Nutrition. Competing interests: none declared.
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Ó 2014 Elsevier Ltd. All rights reserved.
UNDERNUTRITION AND CLINICAL NUTRITION
Choice of type of nutritional support Is the patient malnourished or at risk? Yes Is the gut functioning adequately?
Yes Ensure access to food
Yes
No (or unsure)
Can the patient eat?
Long term/poor veins
Short term/good veins
Central line parenteral nutrition
Peripheral/PICC parenteral nutrition
Yes
No
Can he eat enough?
Long term? Yes
No
No (or unsure) Mechanical feeding problem
Poor intake
Alter consistency + supplements
Oral diet + supplements
Complete liquid diet
Oral diet + naso-enteral feed
Fine-bore tube
Percutaneous endoscopic gastrostomy
Gastric emptying or aspiration problems? Jejunal feeding via nasojejunal tube or percutaneous endoscopic gastrostomy with jejunal extension
PICC, peripherally inserted central catheter Figure 1
problems. A variety of tubes is available; these may have one, two or three lumens, and can be inserted endoscopically, using radiological screening or guided by a magnetic imaging system. Although the availability of nasojejunal feeding has significantly reduced the use of parenteral nutrition in critical care, it should be used only after careful consideration if there is any suggestion of small bowel ischaemia or ileus, as it may predispose to small bowel necrosis.
insertion of gastrostomy (PIG) by a ‘push’ method can be performed but this carries a higher risk of complications. Radiologically inserted gastrostomy (RIG) is more widely performed than PIG, but in practice the method used often depends on the local expertise available. There is evidence that in stroke patients PEG insertion should be avoided for at least the first 2 weeks, as mortality is high at this stage and many patients will improve their swallowing with time. If jejunal feeding is necessary for longer than a few weeks, this can be achieved in several ways: a jejunal extension can be placed endoscopically through a previous gastrostomy; a new transgastric gastrojejunal tube can be inserted by radiology; or a direct percutaneous endoscopic jejunostomy can be inserted. The choice of method generally depends on the local expertise. Surgical jejunostomy is performed as part of major upper GI resections to provide a reliable route for postoperative enteral feeding until adequate oral intake is achieved. It is relatively rare for surgical jejunostomy to be performed in isolation because the methods above have failed. In recent years a number of intestinal failure centres have promoted the use of enteroclysis e enteral tube feeding distal to a small bowel fistula or into a mucous fistula, which may enable enteral rather than parenteral nutrition if sufficient distal bowel is available for absorption. Radiological screening is often
Longer term enteral tube feeding Longer term enteral tube feeding is most often needed in patients with neurological disease or cancer of the head and neck or oesophagus. A feeding tube is inserted through the abdominal wall with the tip in the stomach. The most common tube is a percutaneous endoscopic gastrostomy (PEG) tube, which is inserted under sedation by an endoscopic operator and an assistant, who places a cannula and guidewire through the abdominal wall into the stomach. The endoscopist catches the guidewire and pulls this back up through the oesophagus and mouth, allowing the PEG tube to be attached and ‘pulled through’ the upper GI tract and out of the abdominal wall. If there is a possibility that head and neck tumours may be seeded to the abdominal wall using the PEG method, percutaneous
MEDICINE 43:2
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Ó 2014 Elsevier Ltd. All rights reserved.
UNDERNUTRITION AND CLINICAL NUTRITION
losses. Short-term PN can be provided using ‘standard’ PN bags available from commercial companies but prolonged PN will often require a prescription designed for the individual patient. All patients must also be given vitamins and trace elements e these are not included in many premixed bags for stability reasons, and should be added in the pharmacy sterile unit or given by separate infusion on the ward. Metabolic complications of PN are generally less common than line infection, provided excess amounts of feed are avoided and electrolyte abnormalities largely corrected before PN is commenced. Modern ‘standard’ PN bags are probably safer in inexperienced hands than compounded bags and the availability of a small number of alternative PN bags is usually a safe option for most patients. The development of jaundice or abnormal liver function tests is often attributed to PN, especially to its fat content, but in this situation abnormal liver function is often multifactorial. The most common contributing factor is sepsis, frequently intraabdominal, but often line sepsis. Antibiotics given to treat sepsis may also contribute and pre-existing liver damage may also be relevant. Once line sepsis has been excluded by blood culture from the line and peripheral blood, the contribution of PN should be considered. Explanations include: an excessive amount of energy being given in the PN excess energy being given as glucose, exceeding the glucose oxidation rate of the liver and leading to fat deposition use of pro-inflammatory fat emulsions, although modern preparations are less likely to have this effect than older fat emulsions based on soya bean. If no cause for liver dysfunction other than the feed content can be identified, whether to substitute an anti-inflammatory fat preparation or to remove fat completely from the prescription is open to debate.
Simplified representation of a poster explaining how to check NG tip position immediately after insertion. pH should also be checked regularly thereafter to ensure the tip does not move Fine bore nasogastric tube inserted for feeding
Aspirated and tested with pH paper
Aspirate obtained
pH
5.5
pH
5.5
Commence nasogastric feeding as directed by dietitian
No aspirate obtained
Order CXR and do not feed meantime
CXR reported by radiology Tube tip clearly below the diaphragm and curving to the left
Figure 2
necessary to position the enteroclysis tube adequately. Although it is possible to recycle the output from the proximal gut into the distal gut by this method, in some patients the practical difficulties of fluid balance cannot be overcome and parenteral nutrition is needed.
Intravenous nutrition In general, parenteral nutrition (PN) should be used only if the gut is inaccessible or not functioning. If possible, some oral diet or enteral tube feeding should be used in addition to PN to maintain gut mucosal integrity. This will not be possible in bowel obstruction or recent small bowel fistulation with intraabdominal sepsis. Although PN is associated with a number of serious complications2 there is no doubt that it can be lifesaving. PN should be given via a dedicated intravenous line inserted for that purpose. This may be a peripheral cannula (though this will need regular rotation to reduce the risk of chemical thrombophlebitis); a peripherally inserted central catheter (PICC); or a central line. The choice will depend on local expertise but also on the anticipated length of PN treatment, the availability of veins and the type of feed (low osmolality PN suitable for peripheral use has a high fat content). Line infection remains a common occurrence and meticulous line care is essential. The PN line should not be used for blood sampling or other infusions and aseptic technique should be used for all feed changes. The contents of the PN bag are guided by the patient’s requirements for nitrogen and energy, as calculated by the dietitian. Adjustment of electrolyte content and volume will be necessary in patients who need PN because of high GI tract
MEDICINE 43:2
Intestinal failure Although all doctors are familiar with the concept of organ failure, many are less familiar with the term ‘intestinal failure’, which has been used increasingly in the past 20 years. Intestinal failure has been defined as ‘a specific disease entity resulting from intestinal resection or disease-associated malabsorption and characterized by the inability to maintain protein-energy, fluid, electrolyte or micronutrient balance’.4 Patients with intestinal failure will require artificial nutritional support and a number of sub-types of intestinal failure have been described, which help describe the type and complexity of support which they require. Type 1 intestinal failure is common and self-limiting, is often a postoperative problem such as postoperative ileus, and can be managed in most hospitals with a nutrition team able to provide safe short-term parenteral nutrition. Type 2 intestinal failure describes a more serious situation with septic and/or metabolic complications, often in association with intra-abdominal sepsis or enterocutaneous fistulation; in addition to a well-functioning nutrition support team, this will require specialist surgery, interventional radiology, specialist wound care and critical care facilities. Type 3 intestinal failure refers to patients who need long-term home parenteral nutrition or intravenous fluids, but are generally stable. Achieving good outcomes in patients with
121
Ó 2014 Elsevier Ltd. All rights reserved.
UNDERNUTRITION AND CLINICAL NUTRITION
NICE recommended risk assessment for refeeding syndrome3 Patient has one or more of the following: C BMI less than 16 kg/m2 C Unintentional weight loss greater than 15% within the last 3e6 months C Little or no nutritional intake for more than 10 days C Low serum concentrations of potassium, phosphate or magnesium prior to feeding Or patient has two or more of the following: C BMI less than 18.5 kg/m2 C Unintentional weight loss greater than 10% within the last 3e6 months C Little or no nutritional intake for more than 5 days C A history of alcohol abuse or drugs including insulin, chemotherapy, antacids or diuretics National Institute for Health and Clinical Excellence (Feb 2006); from CG32 e Nutrition support in adults: Oral nutrition support, enteral tube feeding and parenteral nutrition. Manchester: NICE. Available from http://www.nice.org.uk/guidance/CG32. Reproduced with permission.
Table 1
feeds, and that serum electrolytes, particularly phosphate, are monitored daily. Once feeding is established, and as the patient improves, both the method and the content of the feed may change subject to regular review. There is no single simple measurement which will adequately describe a patient’s nutritional state. Weight and anthropometry (skin-fold thickness for fat stores; mid-arm muscle circumference for muscle bulk) will be affected by fluid balance, ascites and oedema. Many biochemical measurements are affected by the acute phase response. In particular, serum albumin is more dependent on the systemic inflammatory response than on nutritional state, and although it is a good general prognostic marker, it is not useful as a measure of nutrition. Many serum measurements of vitamins and trace elements are affected by the acute phase response, so these biochemical measurements are more useful in the stable outpatient than the acutely unwell inpatient. In complex patients, the skills of several members of the nutrition team may be needed in the assessment of progress and when making plans for future nutritional care. Patients who have had a prolonged and difficult
type 2 or type 3 intestinal failure requires significant and specific staff and facilities.
Monitoring for complications In the acute phase of nutritional support, there is inevitable emphasis on monitoring to detect complications. Complications of enteral tube insertion or parenteral line insertion should be excluded early after the procedures. This should be followed by daily monitoring to review fluid and electrolyte balance, glucose control and the occurrence of GI and infective complications. Refeeding syndrome Following the publication of guidelines by NICE in 2006, there has been increased awareness of the refeeding syndrome as a cause of death in patients receiving artificial nutrition.3 When feeding is recommenced in a malnourished patient (Table 1), phosphate is utilized in anabolism and a series of electrolyte shifts may take place leading to hypophosphataemia, hypomagnesaemia and abnormalities of serum sodium and potassium. In susceptible patients, care should be taken that feeding starts slowly (Table 2), that adequate vitamins are supplied with
NICE recommendations for management of refeeding risk3 The prescription for people at high risk of developing refeeding problems should consider: C Starting nutrition support at a maximum of 10 kcal/kg/day, increasing levels slowly to meet or exceed full needs by 4e7 days C Using only 5 kcal/kg/day in extreme cases (for example, BMI less than 14 kg/m2 or negligible intake for more than 15 days) and monitoring cardiac rhythm continually in these people and any others who already have or develop any cardiac arrythmias C Restoring circulatory volume and monitoring fluid balance and overall clinical status closely C Providing immediately before and during the first 10 days of feeding: oral thiamine 200e300 mg daily, vitamin B tablets, compound, strong, one or two tablets, three times a day (or full dose daily intravenous vitamin B preparation, if necessary) and a balanced multivitamin/trace element supplement once daily C Providing oral, enteral or intravenous supplements of potassium (likely requirement 2e4 mmol/kg/day), phosphate (likely requirement 0.3e0.6 mmol/kg/day) and magnesium (likely requirement 0.2 mmol/kg/day intravenous, 0.4 mmol/kg/day oral) unless pre-feeding plasma concentrations are high. Pre-feeding correction of low plasma concentrations is unnecessary. National Institute for Health and Clinical Excellence (Feb 2006); from CG32 e Nutrition support in adults: Oral nutrition support, enteral tube feeding and parenteral nutrition. Manchester: NICE. Available from http://www.nice.org.uk/guidance/CG32. Reproduced with permission.
Table 2
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UNDERNUTRITION AND CLINICAL NUTRITION
2 http://www.ncepod.org.uk/2010pn.htm. 3 http://www.nice.org.uk/guidance/CG32. 4 Lal S, Teubner A, Shaffer J. Aliment Pharmacol Ther 2006; 24: 19e31.
stay in hospital may need psychological and social support, in addition to physical rehabilitation.
Further information on nutritional support There has been increasing recognition that nutritional support requires good organization and resource to produce excellent results. This article has addressed some of the basic concepts of artificial nutritional support and further information is available from the British Society for Parenteral and Enteral Nutrition www.bapen.org.uk. A
Acknowledgements The other members of the Glasgow Royal Infirmary nutrition team have helped with comments on this article in addition to enormous amounts of work over the past few years: Mr Graeme Doherty, TPN pharmacist for GGC; Dr Ewan Forrest, Consultant Gastroenterologist; Mrs Dawn Jordan, Nutrition Nurse Practitioner; Mrs Fiona MacKay, Nutrition Nurse Specialist; Mrs Caroline Mills, Specialist Dietitian; Dr Dinesh Talwar, Consultant Biochemist.
REFERENCES 1 http://www.bapen.org.uk/professionals/publications-and-resources/ organisation-of-nutritional-support-in-hospitals.
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Ó 2014 Elsevier Ltd. All rights reserved.
Artificial nutrition and nutritional support and refeeding syndrome
number of staff involved will vary depending on the numbers of patients and complexity of nutritional support provided, but doctor, dietitian, nutrition nurse and pharmacist are essential. Percutaneous enteral access requires regular gastroenterology or GI surgical commitment to providing this. Managing unstable intestinal failure patients with longer term parenteral nutrition requires a wide portfolio of skills including gastroenterology, biochemistry, surgery and interventional radiology, in addition to a larger number of dietitians, nutrition nurses and dedicated pharmacy time. A key aspect of team function is the decision about the route of feeding and the input of a senior gastrointestinal physician or surgeon is invaluable in discussion with the ward team. The team should undertake regular patient review rather than simply providing guidelines for management.
Ruth F McKee
Abstract Artificial nutritional support is needed when a patient is unable to absorb sufficient nutrition from normal diet. NICE guidance recommends that enteral and parenteral nutrition is supervised by a multidisciplinary nutrition team and that clear goals of nutritional support are defined and reviewed regularly. The combination of nutrition and control of the systemic inflammatory response enables the patient to become anabolic. If possible the enteral route should be used, most commonly nasogastric feeding. Recent NPSA alerts have highlighted the risks of nasogastric tube misplacement and hospitals should have clear policies about checking tube position. Percutaneous gastrostomy feeding is useful for longer term enteral feeding. In the past decade jejunal feeding has reduced the use of parenteral feeding in critical care and upper gastrointestinal disease. Feeding into the distal small bowel beyond a fistula or a proximal stoma can also avoid parenteral nutrition. Parenteral nutrition may be life saving, but may also result in serious complications such as septicaemia due to line infection. Metabolic complications have been less common since ‘standard’ PN bags became widely available. Refeeding syndrome may occur in severely malnourished patients who recommence feeding. Complex electrolyte disorders, such as hypophosphataemia, hypomagnesaemia and hypokalaemia may result, owing to cellular utilization of phosphate. Feeding should be recommenced slowly with careful electrolyte monitoring.
Aims of nutritional support As part of the decision to institute artificial nutritional support, an expert dietitian should calculate the patient’s nutritional requirements and advise on the route of feeding. The nutritional goal depends upon the patient’s condition. While the patient is catabolic due to sepsis or injury, it is not possible to achieve positive nitrogen and energy balance, and the aim is to replace deficiencies and achieve ‘damage limitation’. Once the acute phase response is controlled by treatment of the underlying disease, the aim changes to maintenance and repletion of lost tissue.
Choice of route for nutritional support The gut should be used for feeding if at all possible e it is more physiological, simpler, and results in fewer complications. Figure 1 shows the thinking behind the choice of route, although it may be necessary to use more than one method either concurrently or consecutively to achieve sufficient absorption of nutrients.
Keywords Enteral nutrition; macronutrient requirements; nutritional screening; parenteral nutrition
Many patients in hospital are undernourished or at risk of becoming so because of inadequate intake. This increases the risk of complications and well-managed nutritional support is beneficial. This article deals with feeding using tubes and artificial nutrition, including both enteral and parenteral routes. It assumes that nutritional screening has already occurred, that dietetic assessment has concluded that dietary adjustments and oral supplements are insufficient, and that artificial nutritional support is considered necessary.
Short-term enteral nutrition A fine-bore nasogastric tube is the most common means of artificial nutrition, but has its own hazards. The National Patient Safety Agency has issued several alerts about the need to ensure that the tip lies within the stomach and remains there. Figure 2 shows a poster used to remind staff to check and document the pH of aspirate for this reason. Although nasogastric feeding is widespread, it can be difficult to achieve adequate intake and absorption of the prescribed feed because of feed interruptions and tolerance. The majority of patients are fed with standard complete formula feeds with an energy content of 1 kcal/mL, providing balanced nutrition including protein, energy, fluid, electrolytes and micronutrients in a volume of 25e30 mL/kg. Partially digested peptide feeds may be used if absorption is impaired, as in pancreatic disease. For particular circumstances, special feed formulas with, for example, a low potassium content (renal impairment) or a higher fat:carbohydrate ratio (pulmonary disease) are available. Nasojejunal feeding is most often used in patients who have gastric emptying problems, common in patients who are critically ill or have undergone upper gastrointestinal surgery. There may also be some benefit in patients with recurrent aspiration
Nutritional support teams In order to achieve adequate nutritional support without complication, a multiprofessional team is recommended.1 The
Ruth F McKee MD FRCS is a Consultant Colorectal Surgeon at Glasgow Royal Infirmary, UK. She has been involved in the nutrition support team there for many years and currently chairs the Greater Glasgow and Clyde Health Board Clinical nutrition group. She is a member of the Scottish National Nutrition Advisory Board and secretary of the British Association for Parenteral and Enteral Nutrition. Competing interests: none declared.
MEDICINE 43:2
119
Ó 2014 Elsevier Ltd. All rights reserved.
UNDERNUTRITION AND CLINICAL NUTRITION
Choice of type of nutritional support Is the patient malnourished or at risk? Yes Is the gut functioning adequately?
Yes Ensure access to food
Yes
No (or unsure)
Can the patient eat?
Long term/poor veins
Short term/good veins
Central line parenteral nutrition
Peripheral/PICC parenteral nutrition
Yes
No
Can he eat enough?
Long term? Yes
No
No (or unsure) Mechanical feeding problem
Poor intake
Alter consistency + supplements
Oral diet + supplements
Complete liquid diet
Oral diet + naso-enteral feed
Fine-bore tube
Percutaneous endoscopic gastrostomy
Gastric emptying or aspiration problems? Jejunal feeding via nasojejunal tube or percutaneous endoscopic gastrostomy with jejunal extension
PICC, peripherally inserted central catheter Figure 1
problems. A variety of tubes is available; these may have one, two or three lumens, and can be inserted endoscopically, using radiological screening or guided by a magnetic imaging system. Although the availability of nasojejunal feeding has significantly reduced the use of parenteral nutrition in critical care, it should be used only after careful consideration if there is any suggestion of small bowel ischaemia or ileus, as it may predispose to small bowel necrosis.
insertion of gastrostomy (PIG) by a ‘push’ method can be performed but this carries a higher risk of complications. Radiologically inserted gastrostomy (RIG) is more widely performed than PIG, but in practice the method used often depends on the local expertise available. There is evidence that in stroke patients PEG insertion should be avoided for at least the first 2 weeks, as mortality is high at this stage and many patients will improve their swallowing with time. If jejunal feeding is necessary for longer than a few weeks, this can be achieved in several ways: a jejunal extension can be placed endoscopically through a previous gastrostomy; a new transgastric gastrojejunal tube can be inserted by radiology; or a direct percutaneous endoscopic jejunostomy can be inserted. The choice of method generally depends on the local expertise. Surgical jejunostomy is performed as part of major upper GI resections to provide a reliable route for postoperative enteral feeding until adequate oral intake is achieved. It is relatively rare for surgical jejunostomy to be performed in isolation because the methods above have failed. In recent years a number of intestinal failure centres have promoted the use of enteroclysis e enteral tube feeding distal to a small bowel fistula or into a mucous fistula, which may enable enteral rather than parenteral nutrition if sufficient distal bowel is available for absorption. Radiological screening is often
Longer term enteral tube feeding Longer term enteral tube feeding is most often needed in patients with neurological disease or cancer of the head and neck or oesophagus. A feeding tube is inserted through the abdominal wall with the tip in the stomach. The most common tube is a percutaneous endoscopic gastrostomy (PEG) tube, which is inserted under sedation by an endoscopic operator and an assistant, who places a cannula and guidewire through the abdominal wall into the stomach. The endoscopist catches the guidewire and pulls this back up through the oesophagus and mouth, allowing the PEG tube to be attached and ‘pulled through’ the upper GI tract and out of the abdominal wall. If there is a possibility that head and neck tumours may be seeded to the abdominal wall using the PEG method, percutaneous
MEDICINE 43:2
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Ó 2014 Elsevier Ltd. All rights reserved.
UNDERNUTRITION AND CLINICAL NUTRITION
losses. Short-term PN can be provided using ‘standard’ PN bags available from commercial companies but prolonged PN will often require a prescription designed for the individual patient. All patients must also be given vitamins and trace elements e these are not included in many premixed bags for stability reasons, and should be added in the pharmacy sterile unit or given by separate infusion on the ward. Metabolic complications of PN are generally less common than line infection, provided excess amounts of feed are avoided and electrolyte abnormalities largely corrected before PN is commenced. Modern ‘standard’ PN bags are probably safer in inexperienced hands than compounded bags and the availability of a small number of alternative PN bags is usually a safe option for most patients. The development of jaundice or abnormal liver function tests is often attributed to PN, especially to its fat content, but in this situation abnormal liver function is often multifactorial. The most common contributing factor is sepsis, frequently intraabdominal, but often line sepsis. Antibiotics given to treat sepsis may also contribute and pre-existing liver damage may also be relevant. Once line sepsis has been excluded by blood culture from the line and peripheral blood, the contribution of PN should be considered. Explanations include: an excessive amount of energy being given in the PN excess energy being given as glucose, exceeding the glucose oxidation rate of the liver and leading to fat deposition use of pro-inflammatory fat emulsions, although modern preparations are less likely to have this effect than older fat emulsions based on soya bean. If no cause for liver dysfunction other than the feed content can be identified, whether to substitute an anti-inflammatory fat preparation or to remove fat completely from the prescription is open to debate.
Simplified representation of a poster explaining how to check NG tip position immediately after insertion. pH should also be checked regularly thereafter to ensure the tip does not move Fine bore nasogastric tube inserted for feeding
Aspirated and tested with pH paper
Aspirate obtained
pH
5.5
pH
5.5
Commence nasogastric feeding as directed by dietitian
No aspirate obtained
Order CXR and do not feed meantime
CXR reported by radiology Tube tip clearly below the diaphragm and curving to the left
Figure 2
necessary to position the enteroclysis tube adequately. Although it is possible to recycle the output from the proximal gut into the distal gut by this method, in some patients the practical difficulties of fluid balance cannot be overcome and parenteral nutrition is needed.
Intravenous nutrition In general, parenteral nutrition (PN) should be used only if the gut is inaccessible or not functioning. If possible, some oral diet or enteral tube feeding should be used in addition to PN to maintain gut mucosal integrity. This will not be possible in bowel obstruction or recent small bowel fistulation with intraabdominal sepsis. Although PN is associated with a number of serious complications2 there is no doubt that it can be lifesaving. PN should be given via a dedicated intravenous line inserted for that purpose. This may be a peripheral cannula (though this will need regular rotation to reduce the risk of chemical thrombophlebitis); a peripherally inserted central catheter (PICC); or a central line. The choice will depend on local expertise but also on the anticipated length of PN treatment, the availability of veins and the type of feed (low osmolality PN suitable for peripheral use has a high fat content). Line infection remains a common occurrence and meticulous line care is essential. The PN line should not be used for blood sampling or other infusions and aseptic technique should be used for all feed changes. The contents of the PN bag are guided by the patient’s requirements for nitrogen and energy, as calculated by the dietitian. Adjustment of electrolyte content and volume will be necessary in patients who need PN because of high GI tract
MEDICINE 43:2
Intestinal failure Although all doctors are familiar with the concept of organ failure, many are less familiar with the term ‘intestinal failure’, which has been used increasingly in the past 20 years. Intestinal failure has been defined as ‘a specific disease entity resulting from intestinal resection or disease-associated malabsorption and characterized by the inability to maintain protein-energy, fluid, electrolyte or micronutrient balance’.4 Patients with intestinal failure will require artificial nutritional support and a number of sub-types of intestinal failure have been described, which help describe the type and complexity of support which they require. Type 1 intestinal failure is common and self-limiting, is often a postoperative problem such as postoperative ileus, and can be managed in most hospitals with a nutrition team able to provide safe short-term parenteral nutrition. Type 2 intestinal failure describes a more serious situation with septic and/or metabolic complications, often in association with intra-abdominal sepsis or enterocutaneous fistulation; in addition to a well-functioning nutrition support team, this will require specialist surgery, interventional radiology, specialist wound care and critical care facilities. Type 3 intestinal failure refers to patients who need long-term home parenteral nutrition or intravenous fluids, but are generally stable. Achieving good outcomes in patients with
121
Ó 2014 Elsevier Ltd. All rights reserved.
UNDERNUTRITION AND CLINICAL NUTRITION
NICE recommended risk assessment for refeeding syndrome3 Patient has one or more of the following: C BMI less than 16 kg/m2 C Unintentional weight loss greater than 15% within the last 3e6 months C Little or no nutritional intake for more than 10 days C Low serum concentrations of potassium, phosphate or magnesium prior to feeding Or patient has two or more of the following: C BMI less than 18.5 kg/m2 C Unintentional weight loss greater than 10% within the last 3e6 months C Little or no nutritional intake for more than 5 days C A history of alcohol abuse or drugs including insulin, chemotherapy, antacids or diuretics National Institute for Health and Clinical Excellence (Feb 2006); from CG32 e Nutrition support in adults: Oral nutrition support, enteral tube feeding and parenteral nutrition. Manchester: NICE. Available from http://www.nice.org.uk/guidance/CG32. Reproduced with permission.
Table 1
feeds, and that serum electrolytes, particularly phosphate, are monitored daily. Once feeding is established, and as the patient improves, both the method and the content of the feed may change subject to regular review. There is no single simple measurement which will adequately describe a patient’s nutritional state. Weight and anthropometry (skin-fold thickness for fat stores; mid-arm muscle circumference for muscle bulk) will be affected by fluid balance, ascites and oedema. Many biochemical measurements are affected by the acute phase response. In particular, serum albumin is more dependent on the systemic inflammatory response than on nutritional state, and although it is a good general prognostic marker, it is not useful as a measure of nutrition. Many serum measurements of vitamins and trace elements are affected by the acute phase response, so these biochemical measurements are more useful in the stable outpatient than the acutely unwell inpatient. In complex patients, the skills of several members of the nutrition team may be needed in the assessment of progress and when making plans for future nutritional care. Patients who have had a prolonged and difficult
type 2 or type 3 intestinal failure requires significant and specific staff and facilities.
Monitoring for complications In the acute phase of nutritional support, there is inevitable emphasis on monitoring to detect complications. Complications of enteral tube insertion or parenteral line insertion should be excluded early after the procedures. This should be followed by daily monitoring to review fluid and electrolyte balance, glucose control and the occurrence of GI and infective complications. Refeeding syndrome Following the publication of guidelines by NICE in 2006, there has been increased awareness of the refeeding syndrome as a cause of death in patients receiving artificial nutrition.3 When feeding is recommenced in a malnourished patient (Table 1), phosphate is utilized in anabolism and a series of electrolyte shifts may take place leading to hypophosphataemia, hypomagnesaemia and abnormalities of serum sodium and potassium. In susceptible patients, care should be taken that feeding starts slowly (Table 2), that adequate vitamins are supplied with
NICE recommendations for management of refeeding risk3 The prescription for people at high risk of developing refeeding problems should consider: C Starting nutrition support at a maximum of 10 kcal/kg/day, increasing levels slowly to meet or exceed full needs by 4e7 days C Using only 5 kcal/kg/day in extreme cases (for example, BMI less than 14 kg/m2 or negligible intake for more than 15 days) and monitoring cardiac rhythm continually in these people and any others who already have or develop any cardiac arrythmias C Restoring circulatory volume and monitoring fluid balance and overall clinical status closely C Providing immediately before and during the first 10 days of feeding: oral thiamine 200e300 mg daily, vitamin B tablets, compound, strong, one or two tablets, three times a day (or full dose daily intravenous vitamin B preparation, if necessary) and a balanced multivitamin/trace element supplement once daily C Providing oral, enteral or intravenous supplements of potassium (likely requirement 2e4 mmol/kg/day), phosphate (likely requirement 0.3e0.6 mmol/kg/day) and magnesium (likely requirement 0.2 mmol/kg/day intravenous, 0.4 mmol/kg/day oral) unless pre-feeding plasma concentrations are high. Pre-feeding correction of low plasma concentrations is unnecessary. National Institute for Health and Clinical Excellence (Feb 2006); from CG32 e Nutrition support in adults: Oral nutrition support, enteral tube feeding and parenteral nutrition. Manchester: NICE. Available from http://www.nice.org.uk/guidance/CG32. Reproduced with permission.
Table 2
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2 http://www.ncepod.org.uk/2010pn.htm. 3 http://www.nice.org.uk/guidance/CG32. 4 Lal S, Teubner A, Shaffer J. Aliment Pharmacol Ther 2006; 24: 19e31.
stay in hospital may need psychological and social support, in addition to physical rehabilitation.
Further information on nutritional support There has been increasing recognition that nutritional support requires good organization and resource to produce excellent results. This article has addressed some of the basic concepts of artificial nutritional support and further information is available from the British Society for Parenteral and Enteral Nutrition www.bapen.org.uk. A
Acknowledgements The other members of the Glasgow Royal Infirmary nutrition team have helped with comments on this article in addition to enormous amounts of work over the past few years: Mr Graeme Doherty, TPN pharmacist for GGC; Dr Ewan Forrest, Consultant Gastroenterologist; Mrs Dawn Jordan, Nutrition Nurse Practitioner; Mrs Fiona MacKay, Nutrition Nurse Specialist; Mrs Caroline Mills, Specialist Dietitian; Dr Dinesh Talwar, Consultant Biochemist.
REFERENCES 1 http://www.bapen.org.uk/professionals/publications-and-resources/ organisation-of-nutritional-support-in-hospitals.
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