Maxfacts

Thinking about enteral feeding needs consideration of food in a wider sense, nutrition, complete and balanced diets, general well-being - in some ways similar to all these aspects when thinking about oral food intake, though with some distinct differences. A slightly more in-depth discussion of these aspects, of advantages and disadvantages of different options, seems reasonable. Understanding how feeding tubes are placed and that replacing an existing tube is a straightforward intervention may be useful and/or reassuring. Finally, a rare and very specific risk for metastasis from head & neck malignancies associated with gastrostomy is described.

Some general aspects of tube feeding with commercial formulae

The following is concerned with the advantages and disadvantages of commercial formulae for tube feeding in terms of tolerance, nutrition and daily routines; it applies to all types of feeding tubes.

The advantages of commercial formulae for tube feeding are primarily the ease of use and ticking all the boxes for the quantities of macro- and micronutrients to fulfil nutrition requirements. Nobody will starve when relying on feeding with commercial formulae. Commercial formulae can be used for all types of feeding schemes and work for bolus feeding as well as for slow-drip feeding with or without a pump. This is important from a practical point of view: if too much food is given too fast, for some this may lead to vomiting or aspiration. Commercial formulae are designed to be dense in calories and other macronutrients, with a near-liquid consistency such that the formation of blockages should be minimised (but still this is a common event; feeding tubes tend to have a small diameter), all with a view to ease and convenience of use.

There is a price for the convenience of use, a long list of common adverse effects and intolerances. All of these are related to the composition of formulae, their single biggest disadvantage, and a simple fact about the functioning of our digestive systems. Nature has not foreseen that we feed our body on a non-varied diet of highly concentrated, highly processed and high sugar-density concoctions. Our bodies are not made to digest small volumes of extremely sugar-rich liquids as their main supply of food. Hence, digestive problems are commonly encountered with commercial formulae, including nausea, vomiting, diarrhoea, constipation, bloating, indigestion and reflux. Typically, it is necessary to use medications to counteract such effects (antacids to counteract indigestion and reflux symptoms, antiemetics to combat vomiting, electrolytes to maintain balance, etc).

Compositions of commercial formulae are all similar variations of the same theme, with some preparations designed to be easier to digest, and some preparations supposedly more useful to feed people with diabetes. Common components of commercial formulae are

• carbohydrates - corn starch and corn syrup, simple sugars (glucose, fructose, sucrose) and sugar polymers (such as maltodextrin), sugar alcohols (such as xylitol);
• fats - various mono-, di- and triglycerides, fish oils, plant-derived oils from soy beans, corn, rapeseed, sunflower, palm oils);
• proteins - soy-derived products, cow milk derivatives (casein, whey proteins (lactalbumin));
• micronutrients - vitamins, minerals and other trace elements.

Standard formulae are made up from slightly varied recipes of the above components. It is interesting to note that most of these ingredients are extremely cheap. If somebody is feeding exclusively on commercial formulae, high sugar contents of the order of 4 to 5 times daily recommendations for glucose invariably lead to constant elevated blood sugar levels or intense glycaemic spikes, depending on the feeding schemes used. So called elemental formulae follow slightly different recipes and slightly different mixes of components, designed for easier digestion. Elemental formulae tend to have a slightly lower fat content and most of the protein components are hydrolysed (broken down) or sometimes are added in the form of amino acids. Special formulae for diabetic people are on offer, with lower carbohydrate / sugar and higher fat content than standard formulae. The carbohydrates in these formulations tend to have slightly higher glycaemic indices and thus are a little less likely to trigger intense blood glucose spikes. Despite these slightly less unhealthy formulations, it can be difficult to feed diabetic people in this way and to manage their often complicated dietary needs, especially avoiding hyper- and/or hypoglycaemic crises when juggling tube feeding with insulin dosage.

Another common reason for the need to use special formulae are allergic reactions to standard formulae. Many of the usual main components of commercial formulae are common food allergens, including products manufactured from soy, cow milk, wheat or corn. It is difficult to avoid allergens on a commercial formula diet, which in part may explain some of the common and the more serious intolerances to formulae.

There does not seem to be much systematic research into the long-term health effects of commercial-formulae based diets. It would be surprising if the effects of unhealthy and non-nutritious components and concentrations of components in formulae would have different effects from those of a similarly unhealthy diet taken orally (such as increased risk to develop diabetes, cardiovascular diseases, or liver damage).

Perhaps the best use one can make of commercial formulae is as a short-term staple diet to bridge the time until returning to oral food. For long-term tube feeding, the best use of commercial formulae is probably to use them as a supplement to good quality, however texture-modified, oral food. Partial tube feeding can be a useful fall-back option when it is just too much hard work to eat enough by mouth to maintain body weight (begging the question, though, what the nutritional benefits are from eating empty sugar calories). Some people report that they use the sugar rush from formula as a wake-up-call, lazy breakfast option. For those who can eat by mouth, even if with difficulties, there are tasty ways to maximise the energy / calorie and nutrition content of oral foods without all the extra-sugar.

Clever, and usually quite straightforward oral food preparations can help to minimise the need for formula and tube feeding for many people. If the individually best feeding regime is a combination of some proportion of oral food intake and tube feeding, the most sensible approach is to eat as much enjoyable food as possible by mouth and cherish the taste and smell of the food (whatever suits best), and only fill remaining intake gaps with formula tube feeding.

When oral food intake is not an option at all, some people will have to rely on a formulae-based diet. This typically occurs when somebody is unable or unwilling to deal with alternatives such as blended liquid diets (see below), or has no support with such alternative preparations, or if such alternative tube feeds are less well tolerated than a formulae-based diet. Also, in a care-institution setting it is likely that only formula feeding is provided

General good practice when dealing with formulae tube feeding has excellent oral hygiene as a high priority, especially if somebody is on a nil-by-mouth regimen. Under these conditions the normal oral self-cleaning mechanisms are severely impaired and the risk to acquire infections is enhanced. Further hygiene considerations include meticulous hand hygiene and cleanliness of all tube-feeding equipment, as well as prompt handling of formulae. Commercial formulae are sterile while in the unopened container. However, once opened their high concentrations of nutrients and especially sugars make them marvellous breeding grounds for bacteria. Watching out for signs of rare significant complications is advised. Significant complications include serious gastric haemorrhages, major tube leakages, infections, and aspiration with the risk to develop pneumonia. It is a good idea to keep some kind of food diary so that any unmet nutritional needs can be spotted early.

Home-made, blended liquid diet for tube feeding

Blended liquid diets are an alternative for many, but not for all who rely on tube feeding. For this to be a good alternative, some willingness to engage with aspects of nutrition and balanced healthy diets, cooking and taking back control of one’s everyday life are essential. Considering blended liquid diets is probably mainly relevant for medium- to long-term enteral feeding.

Advantages and disadvantages of blended liquid diets, prepared from home-made ‘real’ foods apply to all types of feeding tubes. Again, just like with the discussion of commercial formulae (see above), the following discussion concentrates on aspects of tolerance, nutrition and daily routines. Currently there is something of a rediscovery of blended liquid diet tube feeding, with some advocating it passionately and others less so. Increased advocating of blended liquid diets can be explained by the numerous unpleasant and adverse effects of commercial formulae (see above), as well as by the fact that more people live longer with conditions where long-term tube feeding is required. For the moment, there is a lack of sound evidence about advantages and disadvantages as well as the long-term effects, quite like the lack of robust information about commercial formulae.

The practicalities of a blended liquid diet suitable for tube feeding are straightforward and mainly involve a reasonably powerful blender or food processor and a couple of fine-meshed sieves. That is essentially the same kit as one needs to prepare texture-adapted, soft foods for oral consumption. Any normal foods and mixtures of foods that add up to a balanced diet and can be finely blended / sieved are on the menu as long as they can be prepared as a thin smooth puree, or can be diluted to a consistency that will easily travel through the feeding tube and do not leave a sticky residue that would be difficult to flush out. Common sense is a vital ingredient here and is much supported by a transparent drinking straw for a test run, if in doubt. All other arguments are similar to those for preparing adapted oral foods, with one big difference: tube feeding does not provide a taste experience. A blended liquid diet typically works best as a bolus-feeding scheme rather than a more continuous drip feed.

The advantages of blended liquid diets cover several aspects of food intake. Technically, a blended liquid diet is the closest approximation of a normal, varied diet that would otherwise be taken by mouth. As the choice of ingredients is entirely under the control of the user, it is easy to avoid any allergens and other ingredients that give rise to digestive problems. As taste is not an issue with tube feeding, it is even easier to prepare varied healthy meals. If somebody is not convinced of the taste of broccoli, when blended with a tube-feeding meal this is not an issue. The feeding experience on blended liquefied meals is reported by users as much more natural and satisfying. Most users can tolerate a larger volume of a blended meal than of commercial formula. This is of practical importance in order to eat enough. A blended meal does not have the same density of calories as a commercial formula would, but that can be compensated for by a larger food volume (and by adding suitable nutritious components to the meal, rather than sugar).

Blended meals can return a sense of normality to somebody’s life, even if tube feeding is there to stay: blended meals take away some of the medicalisation of tube feeding. It makes a difference to be in control of everyday routines and to be able to take good care of oneself. It also makes a difference to essentially eat the same, or very similar, foods as the rest of the family and friends do. Strangely, the nutrition requirements of somebody relying on tube feeding with a blended diet have great potential as a learning experience and to get a whole family / group of friends to eat more balanced and healthy diets. Users of blended liquid diets have reported repeatedly that there are fewer problems with constipation (as blended whole foods have a larger volume and contain a good mixture of fibres), reflux and indigestion. There seems to be a generally improved tolerance of blended liquid diets as compared with commercial formulae, again repeatedly reported by users. Some users report improved skin and hair conditions when using a balanced blended diet. When there are opportunities to increase, over time, oral food intake, it is easier to do so when one is already in ‘normal food’ mode.

The regularly quoted disadvantages of blended liquid diets for tube feeding are often perceived rather than factual, and/or can be easily avoided. Some feel that there is a risk of not meeting all nutritional needs with such a diet. That is easily mitigated by keeping a food diary and by becoming a little more knowledgeable about the components of a healthy diet – knowledge that everybody should have anyway! This applies to macro- and micronutrients.

Some feel it is too much trouble. In fact, it is not a lot of extra-work, compared with managing tube feeding on commercial formulae. Batch cooking helps, especially when the collection of ‘ready (proper) meals’ in the freezer starts growing after a few days, and blending a meal takes only seconds. An infection risk from the non-sterile home-cooked food is sometimes quoted (there is no evidence that the infection risk is higher than with commercial formulae). As long as decent normal kitchen and food hygiene is observed, there is not really any reason why there should be an increased risk of food poisoning. A reasonable additional precaution to prevent food poising is not to opt for extended periods of slow-drip feeding, but use bolus feeding instead. Another regularly raised concern is the risk for tube blockages. Blockages also occur when using commercial formulae. With blended diets, it is wise to avoid some known trouble makers, make extensive use of fine-meshed sieves to have a smooth preparation, and use a test run through a transparent drinking straw if in doubt. Careful flushing of the feeding tube with water before and after meals is another useful precaution.

General good practice when dealing with blended liquid diet tube feeding has excellent oral hygiene as a high priority, especially if somebody is on a nil-by-mouth regimen. Under these conditions the normal oral self-cleaning mechanisms are severely impaired and the risk to acquire infections is enhanced. Further hygiene considerations include meticulous hand hygiene and cleanliness of all tube-feeding equipment, as well as all the kitchen equipment and safe food storage. Watching out for signs of rare significant complications is advised. Significant complications include serious gastric haemorrhages, major tube leakages, infections, and aspiration with the risk to develop pneumonia. It is a good idea to keep some kind of food diary so that any unmet nutritional needs can be spotted early. On a purely practical and purely empirical note, according to user reports some foods seem to be notoriously difficult to blend and liquefy properly, so should be avoided or only used in small amounts, and/or should be well diluted with a suitable liquid, and/or should always be passed through a fine-meshed sieve before feeding. These trouble makers include ‘sticky’ carbohydrates (potatoes and pasta in particular, which can also be difficult to eat by mouth), undercooked stringy vegetables and grains (such as green beans or celery), some seeds (including the small seeds in some berries, such as strawberries or blueberries).

Methods to insert feeding tubes

Techniques to insert fine bore nasogastric tubes are legion and many nurse specialists, junior and sometimes senior doctors have developed their own techniques. This is one approach that has worked. Remember gastrostomy tubes have higher complication rates.

Gloves and a pinafore (apron) of some description are a good idea. Explain the procedure to the patient and have them at 50 to 60 ° upright, with neck in neutral position. Place a small amount of lidocaine gel in the chosen nostril after ensuring it is patent (open). Keep a small drink of water handy. Select a tube; check the guidewire is lubricated and does not protrude. If a tracheostomy tube is present, the cuff should be deflated to allow passage of the tube. Lubricate the tube and introduce it into the nostril; pass it horizontally along the nasal floor. There is usually a little resistance as the tube reaches the nasopharynx; press past this and ask the patient to swallow (use the water if this helps). The tube should now pass easily down the oesophagus, entering the stomach at 40 cm. Secure the tube to the forehead with sticky tape and only now remove the guidewire, being careful to shield the patient’s eyes. Inject air into the tube and listen for bubbling over the stomach. Confirm position with a chest radiograph (some systems require leaving a radio-opaque guidewire in prior to X-ray investigation: check the tube you are using).

Potential problems and solutions:

• nasal patency - select the least narrow nostril, use a lubricant, and, if necessary, a smaller tube and topical vasoconstrictor;
• gagging/vomiting - Not a problem in terms of insertion; and unpleasant as it sounds it is actually useful. All sphincters are open and the tube will pass quickly and easily;
• tube coiling into mouth - cooling the tube makes it more rigid and often helps. As a last resort, topical anaesthesia and direct visualisation with a laryngoscope or nasendoscope, while an assistant passes the tube, may be necessary;
• tube pulled out by patient - if they must have the tube, consider a nasogastric tube ‘bridle’ designed for this problem or a stitch to the septum or soft tissue of the nose. This is not pleasant but is actually better for all concerned than constantly replacing a tube or the more invasive alternative – gastrostomy;
• refeeding syndrome - patients who have been starved for more than five days and are then fed enterally or parenterally are at risk for this electrolyte and fluid imbalance characterised by severe hypophosphataemia (low levels of phosphates) with other biochemical disturbances.  This can be avoided by supplementation with B vitamins and graded biochemical correction;

Percutaneous endoscopic gastrostomy (PEG): the feeding tube is placed directly in the stomach through the abdominal wall at endoscopy. An endoscopist’s area of expertise.

Radiologically inserted gastrostomy (RIG):  this is the X-ray (or ultrasound) guided version of a PEG. It needs a nasogastric tube in place to inflate the stomach. A radiologist’s area of expertise.

Parenteral feeding: it is hazardous and expensive, and fortunately rarely necessary in maxillofacial surgery. Central or peripheral lines are required and need to be maintained. Parenteral feeding is neither as safe nor efficient as enteral feeding. It should be avoided if at all possible.

Specific metastasis risk associated with gastrostomy

There is a specific and unique issue with the placement of a gastrostomy in the context of head and neck malignancies. It has been known for approximately 30 years that a small but significant risk exists for the (rare, estimated 0.5 to 3 %) seeding of metastases from head and neck tumours at the gastrostomy site. The most common procedures to place a PEG involve the use of an endoscope and/or pushing /pulling along the mouth – oesophagus – stomach line to place the tube securely without the need for open surgery. For a long time it was assumed that this placement method is the reason for this unique seeding of metastases at the PEG site, by enabling the mobilisation and transport of malignant cells from the mouth / throat to the stomach. It has been described as something akin to surgically transplanting malignant cells from one location to another. This hypothesis of direct seeding appears reasonable, especially if only a brief period of time elapses between PEG placement and a diagnosis of metastasis at the PEG site.

However, it has been established that a similar risk level for seeding of metastases at the PEG site exists for other surgical methods of PEG placement, where specifically any direct contact with malignant cells is avoided. These methods are rarely used, involve open surgery to the wall of the abdomen (and thus are associated with other morbidities), but completely omit any direct involvement of the mouth/throat/oesophagus passage during the PEG placement by using alternatives such as local radiological control of the tube insertion. Accordingly, the placement technique as such cannot be the main, or only, mechanism for the seeding of metastases.

Any mechanism that explains this unique PEG-site metastasis thus has to look beyond the mechanics of the tube-placement techniques. The usual haematogenous and/or lymphatic routes of spread of cancer cells may well be in action but the relevance and role of these in this very specific and unique metastasis pattern are unclear. Current attempts to explain this form of metastasis consider the combined effects of several contributing factors in creating a favourable local environment at the PEG site for the establishment of metastases.

Some malignant cells may be naturally mobilised from the primary tumour and get swallowed, arriving in the stomach this way. In most circumstances, the strongly acidic stomach environment would not provide particularly favourable conditions for these cells to settle, survive and grow a new tumour. However, the PEG stoma is a permanent wound to which the body naturally reacts by inflammation and locally increased circulation to provide a healing environment. This healing environment is also a more favourable environment for the establishment of metastatic cells. In addition, a common need to manage reflux and indigestion arising as a very common adverse effect of tube feeding (see above) by long-term use of powerful antacid medications, in particular proton pump inhibitors, may well reinforce the mechanism by strongly lowering the acidity of the stomach environment. Much lower acidity combined with the effects of proton pump inhibitors on the mucosa of the stomach, could promote the survival of mobilised malignant cells, make it easier for these cells to adhere to the stomach wall and establish new growth.

It is also reasonable to assume that more than one factor is at play. It has been noted that the development of PEG-site metastases is often associated with the presence of other distant metastases from the primary tumour (approximately 50 %). One way to tentatively explain this finding would be to ascribe the entire course of events to a particularly aggressive tumour phenotype (the combined effects of the genetic characteristics of the tumour and the host environment). This would also explain the typically poor prognosis of such findings (although, by definition metastasis beyond the first echelon nodes (in the neck) has a dismal prognosis). If endoscope transfer was the reason for the secondary deposit, it could be considered a second primary rather than a metastasis but not if another mechanism is in effect). Clearly, a much better characterisation of tumour genetics will help to elucidate such mechanisms of tumour spread in general. Bizarrely, the unique and rare occurrence of PEG-site metastases from head and neck malignancies eventually may help to understand much more general aspects of tumour biology leading to the establishment of distant metastases.

From the current findings, it can be postulated reasonably that the method of PEG placement plays a less significant role than tumour biology. However, it is currently impossible to predict individual risk and/or to avoid the development of PEG-site metastases. It is, therefore, most important for patients, carers and clinicians to be vigilant and look out for any suspicious signs & symptoms arising at the PEG site.