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Enteral nutrition - Modes of delivery

Nutritional support can be provided by both enteral and parenteral routes depending on the requirements and given medical circumstances. The advantage of enteral nutrition is that it is more physiological, has fewer complications, is less expensive and is associated with improved immune function and decreased likelihood of gut bacterial translocation. However, with less cooperative or unconscious/intubated patients and in those with mechanical obstruction in the upper GI tract or with motility disorders of the stomach, feeding by mouth may not be possible. Under these circumstances, nasogastric (Ryle’s tube) feed is the most commonly used and practical route of feeding, provided that the stomach is functional. If however, the stomach is not functional, a nasoenteral tube (nasoduodenal/nasojejunal) can provide the answer as it can bring the nutrients directly to the duodenum and jejunum bypassing the sluggish stomach. This is most applicable in immediate post-operative states, cases of burns or any condition causing delayed stomach emptying and particularly where early feeding is deemed necessary. This method may require radiographic or endoscopic placement of the feeding tube in the small intestine. The insertion could also be done blindly by turning the patient on his right and allowing the peristaltic motion of stomach to propel the tip of the tube through pylorus and into duodenum. This, of course being a blind procedure may be time consuming but with practice most of the ICU staff could be trained to insert it at the bedside. Transnasal intubations even with soft and fine bore tubes may cause nasal trauma, sinus infection, bleeding, bronchial placement or injury. Further, the small intestine tolerates intermittent feeding poorly, so continuous delivery of nutrients may be necessary with nasoenteral tubes.

Next, the feeding tube can be directly put into stomach endoscopically (percutaneous endoscopic gastrotomy-PEG) or surgically (gastrostomy) this procedure is indicated in patients who have either a long-term neurological swallowing impairment or in patients with upper GI obstruction where insertion of the nasogastric tube is difficult. One of the major complications, through rare but potentially fatal, is a leakage at the insertion site and around the tube into the peritoneal cavity resulting in severe peristomal infection, fasciitis or peritonitis. As commonly believed, this procedure does not obviate problems of pulmonary aspiration especially in critically ill patients or those with gastric outlet stenosis. PEG can be extended to PEG-jejunal feeding can completely obviate the risk of aspiration pneumonia. Continuous oropharyngeal secretions or poor tube positions are the usual causes for recurrent aspiration pneumonia in these patients. PEG-J feeding tubes with their smaller diameter are more prone to occlusion, fracture and leakage.

Every intensivist working in a surgical intensive care unit must be familiar5 with the use of jejunostomy tubes (J-tube) which are inserted directly into the proximal jejunum. There are three methods to place the J-tube – Transnasal, transgastric or by jejunostomy. The advantages and relative disadvantages of the first two methods have been already discussed. One useful aspect of a combined transgastric tube (combined gastrostomy/jejunostomy) is that it allows gastric aspiration and jejunal feeding at the same time. Jejunostomy is an open surgical procedure using 14 F or larger tube which is directly placed in jejunum by a purse-string controlled enterotomy (Witzel technique) or alternatively tunneling any 1.5 mm diameter catheter into the jejuna lumen through a needle (needle catheter technique). Both techniques require suture fixation of the bowel to the site of catheter entry in the abdominal wall in order to prevent intra-abdominal leakage of small bowel contents and feeds. This can however occur if the tube is accidentally removed before an enterocutaneous tract has developed.

A new type of self migratory NJ tubes (known as ‘tiger tubes’) is available. These tubes have innovative soft flaps on the side of the distal half of the tube lodging into the stomach mucosa and which help the tube to gently propel from stomach to jejunum with the help of peristalsis. This tube has a success rate of > 90% and it can be passed at the bedside even by an intensivist.

J-tube enables continuous feeding flowing surgery, however, diarrhea remains a common problem requiring adjustments of volume and concentration feeds. Similarly, small bowel ileus can prevent adequate J-feeding. The worst possible mishap in a critically ill patient receiving early post-operative feeding could be a massive intestinal infraction. Though such cases have been reported occasionally, it would be wise to withhold J-feeds in unstable patients on vasopressors and thereby avoid increased metabolic demands on an already underperfused gut.

Finally, at the end of an emergency laprotomy or major GI surgery, a surgeon should not forget to consider J-tube placement. If indicated, it would be best to do it at this stage as opposed to doing it later.