10. Enteral nutrition
Paula Murphy
LEARNING OBJECTIVES
By the end of this chapter the reader will be able to:
• Gain an insight into the evidence base for enteral nutrition;
• Understand the different routes by which enteral nutrition can be delivered, the indications for each route and their associated complications;
• Understand the role of some special substrates used in enteral feeding and examine the evidence base for their use; and
• Understand the principles of medical ethics and how these affect enteral tube feeding decisions.
Introduction
The term enteral nutrition includes all nutrients delivered via the gastrointestinal tract. For the purpose of this chapter, enteral nutrition will refer to the administration of nutrients by tube to the gastrointestinal tract. In the mid-1970s the techniques of enteral nutrition became established following Dobbie and Hoffineister’s successful administration of a liquid diet by tube via a pump. 1 Emphasis is now placed on enteral over parenteral provision of nutrients because of general consensus that the gut should be used whenever possible and parenteral nutrition reserved for when the gut is nonfunctional or where enteral access is not feasible.
Enteral tube feeding (ETF): the evidence
Before reaching any conclusions on the effectiveness of ETF, the quality of available evidence must be considered. In a climate where resources are limited there is a need for established proof of efficacy from large, well-designed, high-quality randomised controlled trials. Good quality research in nutrition support is difficult to achieve as frequently it is not feasible or ethical to have ‘no nutrition’ as a control. Randomised placebo-controlled trials, although considered the gold standard for establishing clinical efficacy, 2 are not always possible for some groups of patients, e.g. patients who are likely to recover from prolonged unconscious state in an ICU setting or CVA patients with an unsafe swallow. In such patient groups a randomised controlled trial could not be performed as it would be unethical to withhold feeding.
An extensive systematic review and meta-analysis of enteral tube feeding concluded that ETF can increase nutritional intake, attenuate loss of body weight and lean tissue, improve functional outcomes and reduce mortality and complications in some patient groups. 3 This review included 74 trials (2769 patients) of ETF in the hospital setting. Most of the trials (80%) had a Jadad score of 2 or less (the higher the score, the better the study design; highest score is 5). This was largely due to the fact that for completeness both randomised ( n = 33) and non-randomised controlled trials ( n = 41) were examined and few of the studies were placebo controlled or blinded.
Many studies examine the impact of nutrition support on surrogate end points such as body weight, nitrogen balance and immunological parameters. Demonstration of improvement in these parameters does not translate into improved clinical outcome. A review of randomised controlled trials that examined the ability of enteral nutrition to influence morbidity and mortality failed to find any high-quality evidence that enteral nutrition has any beneficial effect on clinical outcome. 4 Data from low-quality randomised controlled trials suggest potential benefit to postoperative infectious complications, reduced infection rates in ICUs and improved mortality in chronic liver disease. 4 Low-quality evidence tends to show larger treatment effects, suggesting that artificial nutrition may be even less effective than the data suggest.
The NICE Nutrition Support Guideline (2006) provides recommendations for clinical practice. 5 These guidelines are the result of examination of systematic reviews, meta-analyses and randomised controlled trials of ETF. They do not include observational studies because of the potential bias associated with observational study designs. They conclude: ‘although enteral tube feeding does increase nutritional intakes the evidence that this benefits outcomes such as length of hospital stay or mortality is not clear’. Consequently it is recommended that ‘enteral tube feeding should not be given to people unless they are malnourished or at risk of malnutrition and have inadequate or unsafe oral intake and a functional accessible gastrointestinal tract’. 5
When making a decision on the need for artificial nutrition support, factors such as the patient’s current nutritional status, medical condition, duration of inadequate oral intake, methods of nutrition support available and whether nutrition support is in the patients’ best interest must be considered. 5 Artificial nutrition support is a medical intervention with associated costs and morbidity. There is little doubt of the value of artificial feeding in patients with swallowing difficulties or patients requiring prolonged ventilation who are expected to recover. In these situations it would be unethical to withhold feeding. The controversy exists in the intermediate group of patients who are unable to meet their requirements from oral intake alone.
Enteral feeding access routes
Gastric feeding
Orogastric (OG)
May be used in patients with basal skull fractures requiring enteral feeding. A tube is passed orogastrically as if placed blindly by the nasal route, it may be malpositioned and enter the brain.
Nasogastric (NG)
This is the route of choice for short-term nutrition support (though it can be used for longer term nutrition support) in the absence of vomiting, gastro-oesophageal reflux, ileus or intestinal obstruction. Small-bore feeding tubes provide access to the gastrointestinal tract. These are inexpensive, can be inserted at the bedside and easily removed if no longer needed. Although useful, tubes are not without complications and morbidity associated with tube placement is now being appreciated. On the release of Patient Safety Alert 05, 6 the NPSA was aware of 11 deaths and one case of serious harm in the UK due to misplaced nasogastric feeding tubes over a two-year period. This alert required immediate action by NHS acute trusts, primary care organisations and local health boards in England and Wales to:
• Provide staff, carers and patients with information on correct and incorrect testing methods. The use of pH indicator paper for measuring aspirate is recommended. Radiography is also recommended but not for routine use;
• Carry out individual risk assessment prior to nasogastric tube feeding; and
• Report misplacement incidents via local risk management reporting systems. 6
Complications continue to be reported. It is important to note that the standard confirmatory methods recommended by the NPSA may be unreliable with the use of 24-hour feeding or proton pump inhibitors. The ‘gold standard’ may be endoscopic or radiologic placement of feeding tubes but this is not cost effective for routine tube placement in most hospitals and not always feasible in unwell patients. There is a need for institutional protocols for safe tube placement as well as the development and adoption of new technology for safe insertion. One example of such technology is an electromagnetic sensing device that tracks and displays the path of feeding tubes during the placement procedure. There are also reports of technologies in which feeding tubes are coupled with a CO 2 sensor. 7 Regardless of the placement technique, inadvertent displacement can occur even in cooperative patients in the course of routine nursing care, in movement of patients during washing or dressing, transport through the hospital or if the patient changes position and the tube becomes caught on extraneous devices. A ‘nasal bridle’, first described in 1980 in the context of head and neck cancer patients, 8 has since been found to be a safe and effective method for preventing the accidental removal of nasoenteric feeding tubes. 9
Gastrostomy
Gastrostomy feeding tubes pass through the abdominal wall directly into the stomach and can be placed endoscopically (PEG), surgically (PG) or radiologically (RIG). Patients selected for gastrostomy tube feeding should be at high risk of malnutrition and unlikely to recover their ability to feed orally in the short term. The concept of gastrostomy feeding must be acceptable to the patient and their family or carers before tubes are placed. It has the advantage over NG feeding in that patients should receive more of their feed as there is less interruption from tube displacement. 10 Ethical considerations should be taken into account prior to placement, which should always be for medical reasons and not for administrative convenience (saving money, time or manpower). 11 Common indications for gastrostomy placement are outlined in Table 10.1.
| Indication | Example |
|---|---|
| Neurological disorders of swallowing | CVA, Parkinson’s disease, motor neurone disease |
| Long-term partial failure of intestinal function requiring supplementary nutrition support | Cystic fibrosis, Crohn’s disease |
| Cognitive impairment and decreased consciousness | Head injury |
| Oncology disorders | Upper GI tumours: tubes may be placed for palliative care in nonoperable cases or may be placed prior to treatment and removed when the patient has recovered adequate oral intake |
Gastrostomy tube placement options
Surgery
Surgical placement of feeding tubes is associated with higher morbidity and mortality and tends to be used only when endoscopic or radiologic placement is not possible or an adjunctive procedure if the patient is undergoing surgery.
Endoscopy (PEG)
Endoscopic placement has now largely replaced surgical placement. Patients should be fasted for at least 8 hours prior to the procedure, and given appropriate sedation and routine antibiotic prophylaxis. Techniques used for placement include the pull-through method (‘pull’ technique), the Seldinger technique (‘push’ technique), or direct puncture.
Contraindications to PEG placement include serious coagulation disorders, severe ascites, peritonitis, severe psychosis, a limited life expectancy and interposed organs, e.g. liver, colon. 11 Endoscopic placement may fail in obese patients and patients with a high stomach or large hiatus hernia, oropharyngeal cancer or oesophageal strictures.
Feeding is not without complications (Box 10.1). Complication rates are similar irrespective of the placement technique used. Major complications have been reported to arise in 3% of cases and minor complications in 20%. 12 Direct procedure-related mortality rates vary between 0.7% and 2.0%. Thirty-day mortality rates of 10-28% have been reported. 12 Such high death rates may reflect inappropriate patient selection. The FOOD trial collaboration demonstrated a benefit from early nasogastric tube feeding after a CVA but an increase in mortality in those patients randomised to early PEG placement. 13 Pre-assessment has been identified as the dominant factor responsible for a reduction in 1-week post PEG mortality. There is an increasing view that patient selection should be a function of a multidisciplinary nutrition team. The 2005 National Confidential Enquiry into Patient Outcome and Death (NCEPOD) report, ‘Scoping our Practice’ pertaining to deaths after therapeutic endoscopy, 14 contains three main considerations relating to PEG placement.
Box 10.1 1. Immediate (arising from the procedure itself)
• Respiratory, e.g. aspiration, respiratory depression, airway obstruction
• Bleeding, e.g. bleeding from the abdominal wall, inadvertent puncture of another intra-abdominal structure during needle passage
• Peritonitis
2. Early (occurring within the first 4 weeks)
• Infection, e.g. peristomal infection, abdominal wall abscess
• Displacement: if the internal retention disc becomes displaced before the gastrocutaneous fistulous tract becomes established
• Peritoneal leakage without displacement
• Aspiration pneumonia: patient may aspirate oral secretions
3. Late (4 weeks or beyond)
• Displacement
• Leakage
• Hypergranulation
• Tube dysfunction, e.g. blockage or splitting of tube
• Buried bumper. This is a particular problem in tubes with a silicone internal retention disc. The disc embeds within the gastric mucosa which then overgrows the bumper and eventually obstructs the passage of feed
• Obstruction. This can be a problem with detachment of the internal bumper or detachment of the external fixation device
• Tumour implantation. This has been reported when tubes are placed preoperatively in patients with oropharyngeal cancer15
1. The decision to place a PEG feeding tube requires an in-depth assessment of the potential benefits to the individual.
2. All patients referred for PEG placement should be reviewed by a multidisciplinary team.
3. There is a need for more comprehensive national guidelines for the use of PEG feeding including issues of patient selection.
Radiologically inserted gastrostomy (RIG)
Most involved in enteral nutrition are familiar with the PEG but many are less familiar with the RIG. In fact the main difference between a PEG and a RIG is simply the method of placement.
RIG placement
As with all invasive procedures fully informed consent is obtained. A fine bore nasogastric or orogastric tube is then passed under screening guidance. Because of the very fine nature of this tube and the use of X-ray control it is virtually always possible to pass the tube, even in the presence of obstructing tumours of the oropharynx or oesophagus. The stomach can then be inflated with air or carbon dioxide. Using an aseptic technique and with local anaesthesia to the abdominal wall, the inflated stomach can then be punctured with a needle under X-ray guidance. Depending on the type of tube being inserted, the stomach may be fixed to the anterior abdominal wall at this stage with the use of stay sutures. The stomach is then re-punctured and a wire inserted. The tract can then be dilated over the wire to the size required by the selected tube. The tube is usually held in position by an inflatable balloon within the stomach.
There have been some modifications to this technique to allow the insertion of the typical PEG type tube with an internal ‘mushroom’, rather than a balloon. 16 This type of tube is often preferable because the aftercare is simpler and the same as for a standard PEG. The main disadvantage of the technique is that it is more fiddly and time-consuming to insert. In addition the tube is usually inserted via the mouth and most would consider this a contraindication with head and neck cancers, due to the risk of seeding tumour in the gastrostomy track. 15 Therefore for this latter group of patients a traditional RIG is usually the method of choice, unless a gastrostomy is placed at the time of surgery.
Due to the differences in the methods of insertion, a RIG is often possible when PEG is not. This may be due to variations in the position of the stomach or difficulty intubating the patient with an endoscope. It is only on very rare occasions that RIG is not feasible. If a PEG insertion has failed, speak to a radiologist before a surgeon.
In summary, a RIG is simply an alternative method of inserting a gastrostomy. It is indicated for patients with oropharyngeal cancer; when PEG has been unsuccessful; if endoscopic skills are not readily available or on an individual patient basis when a specific tube may be required. Most radiology departments in the UK will have an interventional or gastrointestinal radiologist who will be happy to advise.
Gastrostomy tube types
Table 10.2 provides an overview of different types of gastrostomy tubes.
| Standard gastrostomy | Traction removable device | Balloon device | LPGD | |
|---|---|---|---|---|
| Initial placement | Endoscopy or surgery | Endoscopy or radiology or surgery | Radiology or surgery | Surgery or radiology but usually after initial percutaneous gastrostomy placement |
| Held in place by: | External fixation plate and internal retention disc | Deforming device (flexible end) | Balloon inflated with 5–20 mL water | Balloon inflated with 5 mL water or cage design |
| Replacement | Suitable for long-term use | Suitable for long-term use | 3–4 months | 3–4 months |
| Possible indication | Post CVA, Parkinson’s disease, MND | Post CVA, nutrition support pre chemo- or radiotherapy for head and neck carcinoma | Nutrition support pre chemo- or radiotherapy for head and neck carcinoma | Nutrition support in cystic fibrosis |
| Removal | Endoscopy | Bedside | Bedside (deflate balloon and apply gentle traction) | Bedside (balloon device: deflate balloon and apply gentle traction, cage device: removal with obturator) |
| Example | Freka PEG (Fresenius Kabi), Flocare PEG (Nutricia Advanced Medical Nutrition) | Corflo PEG (Merck Serono), Vygon MIC PEG | Vygon MIC gastrostomy tube, Corflo G tube (Merck Serono), Flocare gastrostomy tube (Nutricia Advanced Medical Nutrition) | Corflo CuBBY (Merck Serono), MIC-KEY (Vygon), Freka Button (Fresenius Kabi), Kangaroo Skin Level Cage Gastrostomy |
Standard gastrostomy tubes
These are held in place with an external fixation plate and internal retention disc (Figure 10.1). The traditional method of removing these tubes is by endoscopy. Another method for removal involves cutting the tube at skin level and allowing the inner components to be eliminated intestinally. 17 This method has advantages in terms of time and resources but is not without risk and has been associated with perforation and peritonitis. 18,19 It is not recommended by manufacturers.
 |
| Figure 10.1 • Reproduced with kind permission of Fresenius Kabi. |
Routine removal and replacement of these tubes is not necessary and with careful handling they can stay in situ for many years. Tubes are removed if they are no longer required, when broken, when deteriorating or when complications occur such as infection or erosion into the abdominal wall. Patients can take oral diet and fluids immediately after removal and the puncture canal heals rapidly when covered externally with a sterile compress. 11 Percutaneous gastrostomy tubes should not be removed for at least 14 days after insertion to ensure that a fibrous tract is established that will prevent intraperitoneal leakage. If a gastrostomy tube is inadvertently removed, a urethral catheter can be inserted through the tract and feeding recommenced until the tube is replaced.
Gastrostomy tubes with balloons or flexible ends
Those with flexible ends are designed to be removed by external traction (Figure 10.2). Balloon gastrostomy tubes are held in place by a balloon inflated with 5–20 mL water (Figure 10.3). These are particularly suitable where it can be anticipated that there will only be a temporary requirement for enteral tube feeding or if further endoscopy is not possible. Both removal and replacement can take place at the bedside. Replacement is recommended approximately every 3–4 months.
 |
| Figure 10.2 • Reproduced with kind permission of Merck Serono. |
 |
| Figure 10.3 • Reproduced with kind permission of Merck Serono. |
Low profile gastrostomy devices (LPGDs)
These devices are held in position by a balloon inflated with 5 mL water (Figure 10.4). In general it is recommended that LPGDs be placed secondarily after initial percutaneous gastrostomy tube placement with a mature established stoma canal (minimum 4 weeks post initial placement). It is recommended that tubes are replaced every 3–4 months. They require an extension tube for feeding that needs to be replaced every 2 weeks. LPGDs are cosmetically appealing to patients and tend to be used more in younger patients. 11 They are composed of an internal stabilizer, a shaft, an external stabilizer, a connecting tube and an antireflux valve to prevent gastric contents from leaking onto the skin. The shaft must be of appropriate length for if too short, patients may develop pressure necrosis of the skin or the internal stabilizer may become embedded in the wall of the stomach. If an adult patient gains or loses 4 kg the shaft length should be re-evaluated.
 |
 |
| Figure 10.4 • Reproduced with kind permission of Covidien plc. |
Postpyloric feeding—the evidence
The postpyloric route may be considered where there is upper GI dysfunction, e.g. delayed gastric emptying, an increased risk of aspiration or reflux, or to facilitate early postoperative enteral feeding. Feed should always be delivered beyond the ligament of Treitz as there are no medical reasons for any kind of duodenal feeding. 11
Aspiration and reflux
Postpyloric feeding has frequently been the route of choice in patients at risk of aspiration and reflux; however, there is conflict in the literature as to whether it definitely reduces the rate of either. Poor tube position and continued aspiration of oropharyngeal secretions have been identified as possible factors in recurrent aspiration in PEG-J and PEJ patients. Usually the nasogastric route is technically simpler and has been shown in most circumstances to achieve similar nutrient delivery. No significant differences have been reported for mortality, length of stay in intensive care or hospital, incidence of pneumonia, vomiting or diarrhoea in patients fed by the nasogastric compared with the nasojejunal route. 5 Consequently it has been recommended that postpyloric feeding may be considered in patients at high risk of aspiration, in malnourished patients undergoing major intra abdominal surgery, and in patients intolerant of gastric feeding despite the use of promotility agents. 5
Early postoperative enteral tube feeding
Studies on early postoperative enteral tube feeding, compared to standard practice of ‘nil by mouth’ until return of gastrointestinal function, do not support the use of early enteral tube feeding. 5 However, the studies examined did not focus on very malnourished patients who might benefit from this approach. One such group is upper GI cancer patients. In a large multicentre trial, more than 300 malnourished patients with GI cancer were randomly assigned to receive enteral or parenteral isocaloric and isonitrogenous feeding regimens. 20 Postoperative complications were significantly lower at 34% in the enterally fed patients compared with 49% in those parenterally fed and postoperative stay was also reduced in the enterally fed group. Further benefits of postoperative enteral feeding with an immune-enhancing formula in this patient group on reduction in postoperative infectious complications have been reported. 21,22 More recently a randomised controlled trial involving 121 upper GI cancer patients randomised to receive early enteral nutrition via a needle catheter jejunostomy or conventional management, remaining nil by mouth until deemed safe to commence oral fluids, found a significant reduction in length of hospital stay and major complications in the early enteral nutrition group. 23
Nasojejunal
This route is appropriate if postpyloric feeding is likely to be needed short term. Single and double lumen tubes are available, the latter enabling gastric aspiration and jejunal feeding, and are appropriate for postoperative feeding or for patients with gastric stasis (Table 10.3).
| Placement | Indication | Example | ||
|---|---|---|---|---|
| Nasojejunal (NJ) | Single lumen | Bedside (self-propelling if gastric motility is normal) | Pancreatitis, risk of aspiration | Flocare Bengmark (Nutricia Advanced Medical Nutrition) |
| Single lumen | Endoscopy, radiology, surgery | As above | COMPAT STAY PUT (Fresenius Kabi) | |
| Double lumen | Endoscopy, radiology, surgery | Postoperative, gastroparesis | Freka Easy In (Fresenius Kabi), NJ feeding tube (DOBBHOFF) | |
| Triple lumen | Endoscopy, radiology, surgery | Postoperative, gastroparesis | Freka Trelumina (Fresenius Kabi) | |
| DPEJ/PEG-J | Endoscopy, radiology | As for NJ but where feeding is needed longer term | Freka PEG combination with intestinal tube (Fresenius Kabi), Jejunostomy tube via PEG (Merck Serono) | |
| Needle catheter jejunostomy (NCJ) | Surgery | Postoperative | Freka Surgical Jejunostomy Set (Fresenius Kabi), Vygon MIC jejunostomy tube |
Tube placement
The placement of a fine bore feeding tube beyond the pylorus can be difficult and a number of approaches have been described including placement at surgery, by endoscopy, under fluoroscopic guidance and blind introduction at the bedside. Fluoroscopy and endoscopy are highly effective for placement of small bowel tubes but these methods are expensive, require expertise not readily available 24 hours a day and require patient transfer to specialised areas of the hospital where the procedures are performed. Placement of small bowel feeding tubes by the blind nasoenteric approach is technically challenging with most studies showing a success rate of 15–30%. 24 Success with placement is influenced by the technique and degree of expertise of the clinician. The Bengmark tube (Nutricia Advanced Medical Nutrition, UK) is designed to pass spontaneously into the duodenum but in the absence of normal gastric motility trans pyloric passage cannot be relied upon.
In order to improve the success rate at postpyloric placement, modifications have been made to the feeding tubes including lengthening of the tube, altering the profile of the tip and adding various types of weights. Weights added to the distal end of tubes have not been found to have any advantage over unweighted tubes in terms of ability to pass into the jejunum or ability to keep the tube in place for longer. Prokinetic agents have been used to improve the likelihood of passage but are only recommended in patients with high gastric residuals for economic reasons as well as to avoid potential side effects. 24 Blind ‘active’ placement techniques have been described with 88–90% success. 25 One such technique is the Corpak 10-10-10 protocol that uses a fine bore 8F tube (originally called a Corpak tube), placed 10 minutes after administration of 10 mg metoclopramide and all but 10 cm of the 109-cm tube is inserted. After blind placement, tube position must be confirmed by abdominal X-ray.
Electromagnetic sensing devices that can track and display the path of feeding tubes during the placement procedure have also been used for both nasogastric and nasojejunal tube placement.
Jejunostomy
Jejunostomy tubes are appropriate for patients requiring longer term feeding and at risk of oesophageal reflux or aspiration (though the risk is not eliminated) or to facilitate early postoperative feeding following abdominal surgery.
Jejunostomy tube placement options
Open surgery
Surgical placement of jejunostomy tubes has been performed for over 100 years. Tubes pass through the abdominal wall into the jejunum. A variety of techniques can be used, e.g. Witzel jejunostomy, roux-en-y-jejunostomy, needle catheter jejunostomy and laparoscopic jejunostomy. Witzel jejunostomy involves formation of a serosal tunnel and is more likely to become infected. A number of cases of small bowel necrosis have been reported with this technique of placement. 26 Needle catheter jejunostomy is more frequently used nowadays and generally performed at the time of gastrointestinal surgery to enable postoperative enteral feeding. The tube is inserted immediately before the laparotomy wound is closed. The technique involves inserting a needle obliquely through the mesenteric border of the jejunum and a Seldringer technique is then used to insert the feeding tube through the abdominal wall. The catheter is secured to the abdominal wall with a purse string suture. The intestinal loop is fixed by 2–3 stitches to the parietal peritoneum and finally a small silicone plate preventing the catheter from slipping is fixed with two stitches to the skin at the site of the tube exit. 27
Tubes require diligent nursing care as they are easily occluded and difficult if not impossible to replace unless a mature tract has developed. They should be flushed with water (as per local policy) before and after every feed or medication given. Any drugs given via the tube should be elixirs or suspensions rather than syrups. Minor technical complications have been reported (catheter luminal obstruction, local cellulitis) but these may be reduced by a good insertion technique and careful postoperative management. Major, life-threatening complications are rare but have been reported. 28,29
Percutaneous endoscopic jejunostomy
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