Enteral Nutrition 1

Patients who have swallowing dysfunction, food refusal, gastrointestinal diseases, or unable to maintain their nutritional needs are prone to develop nutritional deficiencies due to inadequate caloric intake or absorption. During the last two decades, there has been a significant advance in enteral tube feeding, including new tubes, procedures, and formulas that have increased the possibility to feed all patients who have functioning gastrointestinal tract.

Enteral nutrition through tube feeding is used in various clinical settings. Tube feeding is needed in the neonatal period to meet the nutritional needs of premature babies. Children with gastrointestinal diseases, such as short-bowel syndrome, inflammatory bowel disease, malabsorption, severe intestinal dysmotility, chronic liver disease, eosinophilic gastroenteritis, hepatic failure also require enteral feeding. It is used in children with nongastrointestinal diseases, including congenital heart disease, pulmonary diseases (e.g. cystic fibrosis, bronchopulmonary dysplasia, respiratory failure), in cases with renal insufficiency, neurological disability, malnutrition/failure-to-thrive, feeding disorders, cancer, post-bone marrow transplantation, trauma and burns.

The selection of access and site for enteral feeding depends upon the following factors:

In patients requiring short-term feeding (usually less than 30 days), nasally placed tubes (nasogastric or nasojejunal tubes depending on the indication) are recommended because of their low cost, ease of placement, and lower complication rate.

If the tube feeding is needed for more than 30 days, gastrostomy tubes represent the most common method for enteral nutrition support. A G-J tube or a jejunostomy tube may be indicated for specific clinical scenarios, which will be discussed later.

Nasoenteric tubes (NETs) technically refer to any feeding tube that is placed nasally beyond the esophagus. Nasogastric tube (NGT) is the easiest method of enteral feeding. If tube is needed for only a few days, polyethylene tubes can be inserted. However, small and soft silicon nasogastric tubes are generally preferred as they provide more patient comfort, and possibly results in less local complications, gastroesophageal reflux and aspiration pneumonia. The NGT can be easily placed at the bedside.

Nasojejunal feeding or transpyloric feeding is indicated whenever there is a risk of aspiration, history of significant reflux, evidence of gastric dysmotility, acute pancreatitis, or superior mesenteric artery syndrome. Transpyloric feedings are an invaluable and well-tolerated method of feeding in critically-ill children. Tubes placed into the third portion of the duodenum or passing the ligament of Treitz are associated with a decreased risk of aspiration.

When a patient requires prolonged tube feeding (more then 30 days) gastrostomy should be considered. However, before the placement of a permanent feeding tube, it is necessary to prove that the patient tolerates the feeding regimen with a temporary nasogastric tube. GT can be placed in endoscopically, radiologically or surgically.

The main indications for the use of jejunostomy tube feeding includes aspiration, gastroparesis, insufficient stomach size due to previous resection, postoperative feeding after major procedures and superior mesentery artery syndrome.

Enteral feedings can be delivered as a bolus, gravity feeding or as continuous feeding by using a feeding pump. Bolus and gravity feeding is used in gastric feeding only, while continuous feeding is an option with every type of feeding.

The first step in nasogastric intubation is estimating the length of the tube to be inserted. A simple method to calculate this length is to extend the distal end of the tube from the tip of the patient's nose to the earlobe and then from there to the xiphoid process with the addition of 10-15 cm (4-6 in). A more accurate measurement for the distance between the nares and gastroesophageal junction is the formula used for pH probe placement:

The nares should be checked for obstruction and the tube passed down the more patent side. For patient comfort, topical vasoconstrictors, such as phenylephrine (Neo-Synephrine 0.5%), or oxymetazoline (Afrin 0.05%) may be sprayed into the nasal passages, at least 3 to 5 minutes before the procedure. In order to avoid gagging, the nares, nasopharynx and oropharynx should all be anesthetized at least 5 minutes before the procedure. However, in infants the local anesthetic may trigger cough and laryngeal spasm.

Before securing the NG tube, its position should be confirmed.

Successful placement of a nasojejunal tube depends on an individual's skill and experience. The tube placement can be attempted at the bedside, under fluoroscopic view, or endoscopically. Simple bedside placement is the preferred method. The initial phase of tube placement is the same as the nasogastric tube placement. Endoscopically or fluoroscopically-guided tube placement should be reserved for those patients for whom bedside techniques have not been successful.

Gastrostomy is the most frequently used method for long-term enteral feeding. It can be placed endoscopically, radiologically and surgically. Endoscopic placement is the recommended method over surgery, as it is faster, cheaper and permits feeding within few hours after the procedure. The contraindications of non-surgical placements are:

Antibiotic prophylaxis (e.g. ceftriaxone, cefazolin) is recommended 30 minutes prior to the procedure. A standard upper gastrointestinal endoscope is introduced into the stomach. After air insufflation, the stomach is slightly distended. With the combination of insufflation, transillumination and finger indentation on the abdominal wall, a site for PEG placement is identified. In most cases, the insertion site is along an imaginary line drawn from the umbilicus to the left axillary line in the subcostal region, and it is at the junction of the upper and the middle third of this line. After an aseptic field is created, local anesthetic (1% lidocaine) is injected into the selected area. The anesthetic syringe is advanced into the stomach lumen and can be seen by the endoscope. Next, withdraw the needle aspirating for air as the needle is removed. The appearance of air bubbles while the needle tip is in the wall may indicate the presence of an intervening hollow organ between the stomach and abdominal wall. If the illumination and the indentation are good and there is no suspicion of intervening bowel loop, a skin incision is made to accommodate the PEG tube. The length of incision depends on the size of feeding tube.

The possible complications of PEG tube placement include hemorrhage, infection, intestinal perforation, and peritonitis. Hemorrhage is a rare and results from the puncture of a vessel in the gastric wall. It can be stopped 14with increased traction on the internal bumper to tamponade the tract bleeding temporarily. Radiographic study should be performed in those patients who develop abdominal pain, vomiting, fever, and abdominal distention to evaluate for the above complications.

Several methods are used to remove PEG tubes, depending on the configuration of the inner bumper. Some tubes are designed such that they can be directly pulled through the stoma, whereas stiff or rigid bumpers are best managed by endoscopic removal. Among the many 15available tubes, we prefer using the Cor-Pak tube system. It has a collapsible intragastric disk (bumper), which is easy to remove by traction without the need for endoscopy (Fig. 1.2C). Additional advantage of the Cor-Pak system is that it can be converted to gastrojejunal feeding, at the time of PEG placement or later if needed. Simply cutting the tube externally at skin level and allowing the tube to pass in the stool is not recommended, as it may cause obstruction and require surgical intervention. When the skin level tube is in site, we pass a small (5Fr) feeding tube through it and aspirate gastric fluid to confirm the proper positioning. If there is any doubt we recommend checking the tube by injecting contrast material through the tube under fluoroscopy.

The initial PEG tube is changed after 2-3 months when a good tract has been formed. Skin level gastrostomy tubes (e.g. button-type) are commonly used as PEG replacement devices placed in the mature tract (Fig. 1.2D, E, F). The balloon replacement gastrostomy tubes are available in sizes from 12 Fr to 24 Fr, usually the same diameter as the PEG tube. If there is some leaking around the PEG, upgrading to a 2 Fr thicker button tube is recommended. The length of the tube can be assessed with a measuring device before the insertion of the skin level tube.

Gastrostomy tubes can be placed under fluoroscopy. PRG is less expensive than surgical or endoscopic placement. Using a technique similar to PEG placement, the gastrostomy tube is pulled or pushed over a fluoroscopically-placed guide wire. In one study the success rate for PRG placement was 98% in a group of patients in whom PEG was unsuccessful or who were not candidates for the PEG procedure.¹⁸

In one study, the cost of a PEG was $ 700 less than operative gastrostomy. This advantage, however, narrowed to approximately $100 if the tube required repeat endoscopy for a tube change and skin level device insertion.¹⁹

It is more difficult and time consuming to place a jejunal tube. Contraindications are the same as PEG placement, and are listed above.

Jejunal feeding is preferred in patients who require postpyloric feeding because of risk for aspiration, or have significant duodenogastric dysmotility, pancreatitis or superior mesentery artery syndrome. Jejunostomy is most commonly used to reduce the risk of aspiration. It is frequently used in critically-ill patients to avoid total parenteral nutrition (TPN). Aspiration cannot be fully prevented with jejunal feeding, however, its incidence is substantially reduced when combined with gastric decompression.

The percutaneous jejunostomy (PRJ) feeding tube is placed under fluoroscopic guidance. The tube can be inserted through an existing gastrostomy tube and advanced into the jejunum over a guide wire (indirect method). It can be inserted into the jejunum by direct percutaneous puncture near the ligament of Treitz.

Open surgical and laparoscopic techniques have been used with success to obtain jejunostomy access.

Tube feeding patients should be monitored especially in the initial stages for gastric residuals, reflux, vomiting, pulmonary symptoms, abdominal distention, urinary output, and stool frequency and consistency.

Acid precipitation of feeding formulas is an important factor in the occlusion of gastrostomy and NG feeding tubes.

Transnasally-placed tubes can cause nasopharyngeal erosions, soreness of the nose, sinusitis and otitis media. Changing the side of tube may resolve these problems.

Leaking of gastric juice around the tube site indicates that the internal part is not covering the tract completely. It leads to maceration and irritation of the skin predisposing to local infection, abscess formation and also promotes the development of granulation tissue (Fig. 1.2G).

Gastrocutaneous tracts may close in as little as 24 hours; thus, dislodged tubes should be replaced promptly. A Foley catheter can be used temporarily to maintain the patency of the fistulous tract.

Bleeding is a rare complication in the tube tract. If it occurs the external bumper should be tightened against the abdominal wall to compress the PEG tube tract. The compression should be released within 48 hours to avoid PEG tube tract wound breakdown. Surgical intervention is rarely necessary.

Ulcers may develop below the internal PEG tube bolster or on the gastric wall. Loosening of the external bolster releases the bolster from the gastric mucosa and aids healing. Ulcers occur more frequently with rigid bolsters.

Deterioration can be recognized if there is pitting, ballooning, and a characteristic smell. It does not present significant risk to the patient; however, the tube can break, develop leaks or come out while the patient is sleeping. If the later occurs, the tube site shrinks within an hour and often tract dilatation is necessary to insert the same size tube. In our practice, we replace the low profile tubes every 3-4 months. Microscopic examinations have demonstrated that fungal colonization is an important cause of PEG failure.²¹

Nasogastric, nasojejunal and gastrojejunal feeding tubes may get displaced during a procedure, during patient care, coughing, etc. When dislodgement of the feeding tube is suspected, feeding should be stopped immediately and a radiograph obtained to verify the position of the tube prior to restarting the feeding.

Refeeding syndrome may manifest in patients who previously had limited oral intake or in whom feeding is introduced rapidly. It occurs in approximately 25% of these patients. The signs of refeeding syndrome are glucose intolerance, fluid retention, and electrolyte imbalance with hypophosphatemia, hypomagnesemia, and hypokalemia. These signs are usually observed during the first few days after initiation of feeding. In these patients, the daily monitoring of electrolyte concentrations should be continued until nutritional goals are achieved and the electrolytes and glucose to stabilize. If the condition is left untreated, paralysis, respiratory failure, and even death can occur.

Aspiration is a risk in children with severe gastroesophageal reflux disease who are on nasogastric or gastrostomy feeding. Confirming the position of the tube radiographically both before initiating the feeding or when displacement is suspected, can reduce the incidence of aspiration. Reflux precautions, including the elevation of the head of the bed by 20-30 degrees during feeding, and using continuous feeding, decreases the risk of aspiration.

Feeding should not be started until the proper placement of the feeding tube is verified. The most important goal of the tube feeding is to meet the nutritional needs of the patient.

There are new components added to formulas in the last few years. These include nucleotides, soluble fiber, glutamine, arginine, and fructo-oligosaccharides.

Standard formulas are nutritionally complete and made of complex proteins, fats, carbohydrates, and contain adequate vitamins and mineral supply. They are for patients who have normal digestion and absorption with inability to ingest adequate calories and nutrients. The advantages of complete formulas are that they have low osmolality, do not contain lactose, and are palatable, easy to use, and sterile. Some 24of the complete formulas have fiber, which helps regulating bowel movements and prevents constipation, which is frequent in neurologically-damaged or postoperative patients.

One form of elemental formulas or hypoallergenic formulas are made from hydrolyzed (predigested) protein. Other elemental formulas have only amino acids. In addition, they usually have different ratios of medium-chain triglycerides essential fatty acids, vitamins and minerals.

Home-prepared, blenderized formulas can be administered through short gastrostomy tubes and cost less than standard commercial formulas. However, they require more time to prepare and they are not sterile with risk of being nutritionally incomplete. They can only be used with a close supervision of a nutritionist. This is used more in developing countries. Home-made preparations are more viscous and may contain chunks, which could easily block the tube.

Modular formulas contain only specific nutrients. They are added to commercial or home-prepared formulas to meet special nutrient needs. Examples of modular formulas are the following:

There are various specialized formulas that are available for children with special needs, such as premature infants, children with renal failure 25or inborn errors of metabolism. These formulas should be selected by the treating physician and dietitian who are familiar with the products and their particular uses.

Enteral tube feeding is widely used both in inpatient and outpatient setting in patients who otherwise cannot meet adequate nutritional requirements for various reasons. It is a valuable modality of treatment in acute and chronic illness. Complications can usually be avoided if care is taken. Patients should constantly be monitored for intolerance, complications, and assessed for a possible return to oral feeding.