Enteral tube nutrition is indicated for patients who have a functioning GI tract but cannot ingest enough nutrients orally because they are unable or unwilling to take oral feedings. Compared with parenteral nutrition, enteral nutrition has the following advantages:
Better preservation of the structure and function of the GI tract Lower cost Probably fewer complications, particularly infections Specific indications for enteral nutrition include the following: Prolonged anorexia Severe protein-energy undernutrition Coma or depressed sensorium Liver failure Inability to take oral feedings due to head or neck trauma Critical illnesses (eg, burns) causing metabolic stress 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).
Procedure
If tube feeding is needed for ≤ 4 to 6 wk, 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 wk 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.
Formulas
Liquid formulas 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.
Administration
Patients should be sitting upright at 30 to 45° during tube feeding and for 1 to 2 h 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/h or, if patients have not been fed for a while, at 25 mL/h. 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/h. 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/h, providing 2400 kcal/day.
Complications
Complications are common and can be serious (see Table: Complications of Enteral Tube Nutrition).
Complications of Enteral Tube Nutrition
| Problem | Effects | Comments |
| Tube-related | ||
| Presence of tube | Damage to the nose, pharynx, or esophagus Sinusitis |
The tube, particularly if large, can irritate tissues, causing them to erode. Sinus ostia can become blocked. |
| Blockage of tube lumen | Inadequate feeding | Thick feedings or pills can block the lumen, particularly of small tubes. Sometimes blockages can be dissolved by instilling a solution of pancreatic enzymes or other commercial products. |
| Misplacement of a nasogastric tube intracranially | Brain trauma, infection | A tube may be misplaced intracranially if the cribriform plate is disrupted by severe facial trauma. |
| Misplacement of a nasogastric or orogastric tube in the tracheobronchial tree | Pneumonia | Responsive patients immediately cough and gag. Obtunded patients have few immediate symptoms. If misplacement is not recognized, feedings enter the lungs, causing pneumonia. |
| Dislodgement of a gastrostomy or jejunostomy tube | Peritonitis | After being dislodged, a tube may be replaced into the peritoneal cavity. If tubes were originally placed using invasive techniques, replacement is more difficult and more likely to cause complications. |
| Formula-related | ||
| Intolerance of one of the formula’s main nutrient components | Diarrhea, GI discomfort,* nausea, vomiting, mesenteric ischemia (occasionally) | Intolerance occurs in up to 20% of patients and 50% of critically ill patients and is more common with bolus feedings. |
| Osmotic diarrhea | Frequent, loose stools | Sorbitol, often contained in liquid drug preparations given through feeding tubes, can exacerbate diarrhea. |
| Nutrient imbalances | Electrolyte disturbances, hyperglycemia, volume overload, hyperosmolarity | Body weight and blood levels of electrolytes, glucose, Mg, and phosphate should be frequently monitored (daily during the first week). |
| Other | ||
| Reflux of tube feedings or difficulty with oropharyngeal secretions | Aspiration | Aspiration may occur even though tubes are placed correctly and the head of the bed is elevated if patients have either of these problems. |
| *GI discomfort may have other causes, including reduced compliance of the stomach due to shrinkage caused by lack of feeding, distention due to volume of feeding, and decreased gastric emptying due to dysfunction of the pylorus. | ||
