Enteral tube nutrition is indicated for patients who have a functioning gastrointestinal (GI) tract but cannot ingest enough nutrients orally because they are unable or unwilling to take oral feedings. (See also Overview of Nutritional Support.)
Compared with parenteral nutrition, enteral nutrition has the following advantages:
Specific indications for enteral nutrition include the following:
Other indications may include bowel preparation for surgery in seriously ill or undernourished patients, closure of enterocutaneous fistulas, and small-bowel adaptation after massive intestinal resection or in disorders that may cause malabsorption (eg, Crohn disease).
If tube feeding is needed for ≤ 4 to 6 weeks, a small-caliber, soft nasogastric or nasoenteric (eg, nasoduodenal) tube made of silicone or polyurethane is usually used. If a nasal injury or deformity makes nasal placement difficult, an orogastric or other oroenteric tube can be placed.
Tube feeding for > 4 to 6 weeks usually requires a gastrostomy or jejunostomy tube, placed endoscopically, surgically, or radiologically. Choice depends on physician capabilities and patient preference.
Jejunostomy tubes are useful for patients with contraindications to gastrostomy (eg, gastrectomy, bowel obstruction proximal to the jejunum). However, these tubes do not pose less risk of tracheobronchial aspiration than gastrostomy tubes, as is often thought. Jejunostomy tubes are easily dislodged and are usually used only for inpatients.
Feeding tubes are surgically placed if endoscopic and radiologic placement is unavailable, technically impossible, or unsafe (eg, because of overlying bowel). Open or laparoscopic techniques can be used.
Liquid formulas for enteral tube feeding commonly used include feeding modules and polymeric or other specialized formulas.
Feeding modules are commercially available products that contain a single nutrient, such as proteins, fats, or carbohydrates. Feeding modules may be used individually to treat a specific deficiency or combined with other formulas to completely satisfy nutritional requirements.
Polymeric formulas (including blenderized food and milk-based or lactose-free commercial formulas) are commercially available and generally provide a complete, balanced diet. For oral or tube feedings, they are usually preferred to feeding modules. In hospitalized patients, lactose-free formulas are the most commonly used polymeric formulas. However, milk-based formulas tend to taste better than lactose-free formulas. Patients with lactose intolerance may be able to tolerate milk-based formulas given slowly by continuous infusion.
Specialized formulas include hydrolyzed protein or sometimes amino acid formulas, which are used for patients who have difficulty digesting complex proteins. However, these formulas are expensive and usually unnecessary. Most patients with pancreatic insufficiency, if given enzymes, and most patients with malabsorption can digest complex proteins. Other specialized formulas (eg, calorie- and protein-dense formulas for patients whose fluids are restricted, fiber-enriched formulas for constipated patients) may be helpful.
Patients should be sitting upright at 30 to 45° during tube feeding and for 1 to 2 hours afterward to minimize incidence of nosocomial aspiration pneumonia and to allow gravity to help propel the food.
Tube feedings are given in boluses several times a day or by continuous infusion. Bolus feeding is more physiologic and may be preferred for patients with diabetes. Continuous infusion is necessary if boluses cause nausea.
For bolus feeding, total daily volume is divided into 4 to 6 separate feedings, which are injected through the tube with a syringe or infused by gravity from an elevated bag. After feedings, the tube is flushed with water to prevent clogging.
Nasogastric or nasoduodenal tube feeding often causes diarrhea initially; thus, feedings are usually started with small amounts of dilute preparations and increased as tolerated. Most formulas contain 0.5, 1, or 2 kcal/mL. Formulas with higher caloric concentration (less water per calorie) may cause decreased gastric emptying and thus higher gastric residuals than when more dilute formulas with the same number of calories are used. Initially, a 1-kcal/mL commercially prepared solution may be given undiluted at 50 mL/hour or, if patients have not been fed for a while, at 25 mL/hour. Usually, these solutions do not supply enough water, particularly if vomiting, diarrhea, sweating, or fever has increased water loss. Extra water is supplied as boluses via the feeding tube or IV. After a few days, the rate or concentration can be increased as needed to meet caloric and water needs.
Jejunostomy tube feeding requires greater dilution and smaller volumes. Feeding usually begins at a concentration of ≤0.5 kcal/mL and a rate of 25 mL/hour. After a few days, concentrations and volumes can be increased to eventually meet caloric and water needs. Usually, the maximum that can be tolerated is 0.8 kcal/mL at 125 mL/hour, providing 2400 kcal/day.
Complications of enteral tube feeding are common and can be serious (see table Complications of Enteral Tube Nutrition).
Complications of Enteral Tube Nutrition
Consider enteral tube nutrition for patients who have a functioning gastrointestinal tract but cannot ingest enough nutrients orally because they are unable or unwilling to take oral feedings.
If tube feeding is expected to last > 4 to 6 weeks, consider a gastrostomy or jejunostomy tube, placed endoscopically, surgically, or radiologically.
A polymeric formula is the most commonly used and usually the easiest formula to give.
Keep patients sitting upright at 30 to 45° during tube feeding and for 1 to 2 hours afterward to minimize incidence of nosocomial aspiration pneumonia and to allow gravity to help propel the food.
Check patients periodically for complications of tube feedings (eg, tube-related, formula-related, aspiration).