Routes of Enteral Nutrition
There are numerous ways of feeding somebody via their own gut, and most of them involve some sort of tube. The following is a list of complications associated with having an enteral feeding tube inserted:
- Traumatic insertion (eg. resulting in epistaxis, or damage to abdominal organs in the case of PEG insertion)
- Poor placement, eg. into the lung (or worse)
- Oesophageal or gastric perforation
- Increased tendency towards gastro-oesophageal reflux
- Pressure areas due to prolonged tube dwell time (eg. pressure on the nares)
- Sinusitis (for nasal tubes)
- Poor oral hygiene( for oral tubes)
- Oesophageal stricture
- Discomfort in the awake patient
This has been explored in the CICM past papers. Typically, the examiners have wanted their candidates to compare three different feeding methods in terms of their advantages and disadvantages. In fact both Question 20 from the first paper of 2008 and Question 15 from the first paper of 2003 asked about NG vs PEG vs PEJ. In short, the nasogastric route has the advantages of simple insertion and the benefit gastric defensive mechanisms, but has a non-zero complication rate related to oesopageal sphincter dysfunction, aspiration, gastric erosion, and patient discomfort. The PEG bypasses the nose mouth and oesophagus and has all the aforementioned physiological advantages of nasogastric feeding with none of the disadvantages; however it must be placed surgically, and still does not prevent aspiration. A feeding jejunostomy prevents aspiration better than the other tubes, but does not benefit from the bactericidal action of gastric acid, it more difficult to place, and is more susceptible to blockage (as it is a finer tube).
This tube-related topic - though exploring routes of enteral nutrition as opposed to specific tubes - is sufficiently equipment-related to merit a re-exploration in the Equipment and Procedures section as Chapter 3.13 (A comparison of enteral feeding tubes).
Nasogastric route of insertion
- Easy to insert
- Least uncomfortable in the awake patient
- The tubes are cheap
- With a basic sump tube, one can aspirate the gastric contents and assess the residual volume, thereby keeping an eye on gastric emptying function
- Traumatic to the mucosa: the coagulopathic patient will have a deluge of epistaxis.
- In the long term, can cause sinusitis
- In the long term, can cause pressure areas on the nares or upper lip
- It requires radiological confirmation of placement
- It is easily dislodged by a delirious patient
- It may increase aspiration risk because the gastro-oesophageal sphincter is less competent when there is something constantly in it
Orogastric route of insertion
- Easy to insert (especially with direct laryngoscopy)
- Fewer pressure are complications with long term use
- Less traumatic to mucosa; its the route of choice for the patient with no platelets.
- The path of insertion is less direct than with the nasal insertion
- Intolerably uncomfortable for the awake patient
- May cause pressure areas on the lips
- May interfere with oral hygiene care (in the sense that another tube in the mouth is something else to get in the nurses' way)
Gastric tip position
- Easy to insert
- The stomach is tolerant of bolus feeding
- Gastric food delivery buffers gastric acids and protects the gastric mucosa
- The gastric acid has a bactericidal action which helps prevent gastroenteritis
- Gastric secretions (gastric pepsin and lipase) facilitate absorption of feeds, which means one is not limited to any specialised feed mixtures
- There is suspicion that this results in poorer feed tolerance and increased risk of aspiration (see below)
Post-pyloric tip position
- Reasonably easy to insert...
- Decreased risk of aspiration, some would argue (but studies show that the risk of complications from enteral nutrition is the same, regardless of whether you put the tip in the stomach or past the pylorus)
- One must wait for the tip to migrate into the duodenum.
Jejunal tip position
- Decreased risk of aspiration, some would argue.
- Decreased stimulus to pancreatic secretion; the expect result is that even though you are feeding the patient, the pancreas "rests" and therefore you don't have any further autophagy in the context of acute pancreatitis. How responsive is the necrotic pancreas to those secretory signals? Perhaps, not very.
- Not so easy to place. Sometimes it may be easier to insert this percutaneously, or by endoscopic guidance.
- One must often wait for the tip to migrate into the jejunum
- It is impossible to administer large boluses of food: the jejunum is only so big.
- Gastric mucosa is unprotected from acid, and loses the trophic stimulus of food.
- The feeds do not benefir from the bactericidal eactivity of stomach acid
- Absorption may be impaired due to the loss of gastric pepsin and lipase; specialised mixtures may be required
Fine bore tubes
(as compared to the sump tubes)
- Improved tolerance ( a softer tube)
- Easier migration past the pylorus
- Less traumatic insertion (depending on the operator)
- Better tolerated in the long term, as the softer plastic is less prone to causing pressure areas, and the narrower calibre is less prone to causing sinusitis.
(as compared to the sump tubes)
- Cannot aspirate through these. Impossible to say, whether the feeds are being tolerated or not (until the patient vomits).
- The softer tube can kink more easily.
- The narrow bore can clog more easily.
Percutaneous feeding tubes: the PEG and PEJ
- Improved tolerance in the awake patient
- None of the facial pressure are complications
- No sinusitis or mucositis
- No risk of oesophageal stricture
- Better tolerance in the extremely long term (one can have a percutaneous tube for their entire life)
- Needs to be placed by someone with expertise, under anaesthetic, and at least with endoscopic guidance (if not surgically under direct vision)
- May result in a fistula (in fact, will definitely form one while the tube is in situ- and this may or may not heal once the tube is removed)
- The tract takes time to mature. If the tube is removed prior to 4 or so weeks, there fistula is still immature, and it is impossible to re-insert the tube (because the tissue planes move apart and the orifice becomes forever lost)
- Skin erosion and ulceration may take place.
A tabulated summary of enteral feeding routes
The CICM fellowship exam frequently asks the candidates to compare enteric feeding routes. In order to simplify the retention of this information, I present the comparison as a table.