Early enteral feeding

A problem

Well over a hundred years ago, the bold Irish physician Robert Graves overturned established dogma by feeding patients with fevers, showing that sick patients did better when fed. Unfortunately "even" today we still neglect the nutrition of our patients, sometimes with devastating consequences. Because there is often a delay between our starving the patient and his ultimate demise, we may invoke other explanations for the "adverse outcome". We also sometimes get away with starvation, because the patient has enough reserves to last him through his period of malnutrition, or is lucky. Which patients are less likely to be "lucky"? People at extreme risk are those with pre-existing malnutrition, and those with major physical insults such as extensive burns, major trauma, substantial operations, sepsis, and major neurological insults. In short, most ICU patients!

How common is malnutrition? Most surveys suggest that it is extremely common, with up to 12% of in-hospital patients being severely malnourished, and anything up to 50% of patients being "at high risk for malnutrition". This works out to about 15 million people in USA hospitals being at risk, and correlates with poor outcome. The corresponding increases in costs are substantial, (up to 35-75% per patient), with major and minor complications increased by up to 200%, and duration of hospital stay prolonged by up to 90%. Research sponsored by the Kings Fund estimated potential cost savings achievable by addressing the problem of malnutrition at 266 million pounds per year for the United Kingdom.

In short, when faced with the average ICU patient, we should probably not ask the question "Should I feed this patient?" but rather say "How am I going to feed this patient?"

Identifying malnutrition

A host of indices and screening tools have been used to identify malnourished patients, and those at risk for malnutrition. These include:

Fortunately, none of these has been shown to be better than a careful history and thorough examination, performed by a physician giving specific attention to nutritional concerns. An example of this is the "Subjective Global Assessment".

A substantial number of reasonable quality papers attests to the safety and benefit of early feeding in post-operative patients. This is especially true in patients with burns, abdominal trauma, and severe head trauma. The problem is that often we do not identify those patients at risk .

Technical Problems with achieving Early Feeding

The main problem with Early Feeding is that the best methods of feeding are often relatively difficult to achieve. We therefore succumb to laziness, choose an inadequate method, and hope that it will work. The main reason for technical problems is lack of anticipation. It is far easier to achieve a portal of nutrition if one perceives that a patient is at high risk for malnutrition and takes the appropriate measures at the time of surgery.

How should we feed? The easiest method (and by far the worst) is to give total parenteral nutrition (TPN). TPN is harmful for a variety of reasons, not the least of which are complications associated with catheter insertion (with a rate of 3-12%, including subclavian artery injuries and pneumothoraces), as well as such complications as sepsis in 2.8 to 14%, and venous thrombosis in 45-59%, although only about 2.5-4.8% of cases have clinical evidence of complications of venous thrombosis. There is also mounting suspicion that TPN is immunosuppressive, and a recent study shows that ICU stay, total duration of hospitalisation, and infection rates are far greater in patients given lipid with their TPN [ J Trauma, 1997 43 pp52-8 ], as is common practice. Finally, TPN is extremely expensive, far more expensive than enteral feeding!

It has almost become dogma that enteral feeding is superior to parenteral feeding. There is a large amount of experimental evidence to substantiate this assertion, with some clinical studies to back it up. There is a strong suggestion that infection rates are decreased in seriously ill patients fed enterally as opposed to parenterally. The problem is one of a portal of access. Initially, there would appear to be many options, including:

But on close examination a lot of these fall away in the critically ill. Oral and Nasogastric feeds are sometimes feasible, especially the latter, but gastroparesis after operation, especially after abdominal surgery, often lasts for up to 48 hours, and may be even more prolonged, especially in those with serious intra-abdominal problems, or diabetic gastroparesis. Gastrostomies are of value in people with severe central nervous system injuries, and are indeed far preferable to nasogastric feeds in such patients, but otherwise have the same limitation of gastroparesis.

Most ICU studies of early enteral feeding have used "needle catheter jejunostomies" which are easy to perform at surgery, are usually well- tolerated, and have a very low complication rate (e.g. 1-2%) in experienced hands. Problems arise with less-than-experienced surgeons.

We believe that nasojejunal feeds are ideal. If the tube is placed at the time of surgery as a co-operative effort between the anaesthetist at the head of the table and the surgeon standing on the left of the patient, then placement should not be a problem. Ideally the tube should be over 120 cm long (preferably about 150cm so that it can be fed through to the proximal jejunum, but these tubes are far more expensive). Putting food into the distal duodenum or proximal jejunum almost always ensures that adequate absorption will occur. "Post-operative ileus" is a very transient phenomenon in the small bowel, lasting for perhaps a few hours rather than the 48 hours seen with the stomach and 72 hours with the colon.

Patients on nasoenteric tube feeds should not be lain flat, as this will greatly increase their risk of aspiration into the lungs, even if an endotracheal tube is present. (It's generally extremely silly to lie any ICU patient flat, as this also often compromises their pulmonary function in other ways)! Tube position should be checked if there is any possibility that the tube has been malpositioned, for example placed in the lungs. Complications will then be uncommon.

The problem is not so much ileus as lack of anticipation

What should we be giving?

Confusion still reigns about what we should feed our patients. The glib answer is "normal food" but there are certain caveats:

Traditionally we have not given enough protein to our patients. There is now evidence that we should be giving 1 to 1.5 g/kg of quality protein in our ICU enteral feeds. We have also probably been giving too much energy. In the past we recommended that the non-protein calorie to nitrogen ratios should be about 150:1, whereas we now believe that these should be about 100:1 or perhaps even less. {This emphasis on "nitrogen" is a legacy from measuring nitrogen excretion in the urine as a surrogate marker of protein requirements. Generally amino acids are about one sixth nitrogen, so we can estimate that for every 1.5g of protein we should be giving about 20 kcal or less, which in a 70kg man works out to perhaps 100g of protein and <= 2000 kcal per day}.

Most of the discussion and indeed argument about fibre has neglected the basic point - that there is substantial evidence that if we don't give fibre in the diet, we systematically malnourish the large bowel. The colonic enterocyte is dependent on the colonic lumen for the vast majority of its energy supply - up to about 85% - and probably cannot compensate by obtaining large amounts of food from the bloodstream. This is because it obtains its energy from butyric acid , which is derived from bacterial digestion of fibre. If we don't provide fibre, we don't feed the colonic enterocyte adequately. Period. This is excessively silly, as the 1000 billion or so bacteria within the body are largely found in the colon. If we systematically malnourish the colonic enterocyte and then disturb the normal flora with broad-spectrum antibiotic therapy, what do we expect?

There is little or no evidence that patients benefit from "elemental" and "semi-elemental" diets, unless their small bowel function is grossly deranged. Such ill-advised predigested diets have little place in ICU unless there is very little mass of bowel left, or the bowel is grossly diseased.

We are very concerned that current recommendations (RDAs and so on) for vitamin supplementation are inadequate for ICU patients. Unfortunately, there are few good guidelines.

Some evidence suggests that overfeeding is even worse than not feeding patients at all. This goes for both enteral and parenteral feeding. Unfortunately, ICU patients are very variable in their energy and food requirements, with only about one in three actually fitting into conventional predictive formulas for energy requirements. A large number will have increased energy requirements, and some will have "subnormal" needs. To identify this it's ideal to have a metabolic cart, but few of us can afford the luxury. It may be better to marginally underfeed the patient with quality high-protein, fibre-containing food than overfeed him/her. Perhaps we should only provide about 80% of energy requirements!

Fear of Feeding!

We are often too cautious in our feeding. Waiting for bowel sounds is just plain silly, as bowel function can be quite normal without any bowel sounds whatsoever. ICU patients often have scanty or no air in the bowel, yet food may be well absorbed [Shelly & Church, Anaesthesia 1987 (42) pp207-9 ].

There is also no evidence that starting with small amounts of food is beneficial, unless the patient has been starved for a prolonged period of time, in which case it might be wise to watch out for the refeeding syndrome. Generally, we should give decent amounts of food from the start.

Diarrhoea is more commonly related to prolonged, excessive and inappropriate antibiotic therapy than incorrect feeding. It may occur if we overfeed the patient, as it is then the bowel's way of protesting about the excessive amount of food. Diarrhoea is never an indication to stop enteral feeding, and will often disappear if feeding is continued, perhaps at a slightly lower rate if one suspects that too much food is being given.

It is often asserted that patients on inotropic support should not be fed enterally. I have not been able to find any literature to support this contention, and believe it to be totally incorrect, provided the patient has been adequately resuscitated. It is obviously silly (and asking for trouble) to try and enterally feed a patient who is inadequately resuscitated, but in the resuscitated patient who is still inotrope dependent, I can see no reason not to feed enterally. This is a rather controversial topic.

Formerly we believed that in acute pancreatitis the pancreas should be rested, and that enteral feeding would stimulate the pancreas and worsen the outcome. Evidence is now emerging that this is completely incorrect, and in fact patients do better if fed enterally.
[ Kalfarentos et al. Brit J Surg 1997 (84) pp1665-9 ]

Similarly, patients with colonic anastomoses can be fed soon after surgery without compromise. See for example [ Hartsell et al, Arch Surg 1997 132 pp518-21 ] and [ Reissman et al, Ann Surg 1995 222 pp73-7 ]. This is in keeping with experimental evidence that excluding a colonic suture line from the colonic contents decreases colonic healing. Probably our old friend butyrate, again.


Many people protest that comments such as those above are "evangelical", and excessive. This should be seen in context - most doctors, and I am afraid, probably most intensivists are still steeped in tradition, and do not feed patients adequately. We are all guilty of failing to anticipate the need to feed. I kick myself when I think of the times when I have sent (for example) a patient with an abdominal aortic aneurysm that has gone sour back to theatre, and not asked the surgeon to insert a nasojejunal tube while back in theatre, knowing that the patient will do poorly in the post-operative period, and that a large part of this poor outcome will be related to bad feeding. When we have overcome these problems, changed our paradigm, and are enthusiastically feeding patients who need to be fed, then I will probably turn around and start whingeing about all these fanatics who feed too soon. For now, I'm an evangelist!


The literature is vast. Here are just a few articles that we thought to be worth browsing through.