Enteral tube feeding is the delivery of liquid nutrients through a tube directly into the gastrointestinal tract. In pediatric cases, it is used for children and infants with a functioning gastrointestinal (GI) tract who are not able to orally ingest adequate nutrients.
Conditions indicating tube feeding can include:
- Gastrointestinal disorders of absorption, digestion, uptake and utilization, secretion, or storage of nutrients, including congenital anatomical or metabolic disorders, severe allergies, severe gastroesophageal reflux, and food refusal behavior.
- Neuromuscular disorders, such as cerebral palsy, muscular dystrophy, spinal cord defects, or damage to the central nervous system.
- Cardiopulmonary disorders and conditions of hypermetabolism (e.g., burns, some forms of cancer).
- Prematurity and/or failure to thrive.
It is important to distinguish between enteral and parenteral feeding:
- Enteral feeding delivers digestible nutritive formula through a tube into an intact, functioning gastrointestinal system, bypassing problems with normal oral ingestion.
- Parenteral feeding, also called total parenteral nutrition (TPN), delivers a more elemental formula intravenously, directly into the circulatory system, when the gastrointestinal system is malfunctioning or otherwise compromised, bypassing both ingestion and digestion.
The types of enteral tube feeding are classified according to the point from which the tube enters the body and the point to which the nutrient formula is delivered:
- Nasogastric tube (NG) from the nose to the stomach.
- Nasoduodenal tube from the nose to duodenum (the first or upper part of the small intestine, immediately below the stomach).
- Nasojejunal tube from the nose to jejunum (the next or middle part of the small intestine, and before the much longer ileum).
- Gastrostomy tube (GT) from a surgical opening in the skin, through the abdominal wall, and directly into the stomach.
- Jejunostomy tube (JT) from a surgical opening in the skin, through the abdominal wall, and directly into the jejunum.
Diagram of the Digestive System
A physician’s choice of which type of tube feeding to use depends on anatomical, digestive, and feeding behavior factors, as well as expected duration of the tube feeding. Nasogastric and gastric tube feeding are the most commonly used.
Nasogastric Tube Feeding (NG-Tube)
Nasogastric intubation is a medical process not requiring surgery by which a flexible tube is passed through the nose, down through the throat and esophagus, and into the stomach. Its main purpose is for feeding and for administration of drugs or other medically indicated oral agents.
Nasogastric intubation is not advisable for patients with facial trauma, skull fracture, esophageal abnormalities or certain deformities, problematic mental state, or an impaired airway.
Typically minor complications can include sore throat, sinusitis, or nose bleeds. Rarely, more significant complications may require immediate medical attention and consideration of surgical alternatives to nasal insertion.
Sometimes the goal of short-term enteral feeding in patients with gastroparesis or other contraindications must be to deliver the enteral solution beyond the pylorus of the stomach. Endoscopic methods allow the precise location of the tube in the small intestine, either the duodenum or the jejunum. Complications can be feeding tube migration back into the stomach during the withdrawal of the endoscope or by inadvertent shifting during feeding, but it is correctable. Unlike nasogastric intubation, these procedures are not suitable for a trained parent or caregiver.
Gastric Tube Feeding (G-Tube)
The most common surgical procedure for insertion of a feeding tube into the stomach is percutaneous endoscopic gastrostomy (PEG). An endoscope is directed through the mouth and esophagus into the stomach of the sedated patient. The endoscope provides a powerful light source to reveal its position in the stomach as viewed from outside the body. A soft guide wire or suture is inserted through a small incision, grasped by the endoscope, and pulled up through the esophagus. The PEG tube can then be pulled back down into the stomach and out through the incision, with the delivery end of the tube retained in the stomach by a balloon tip or retention dome. The surgery is simple, involves little risk or discomfort, and takes about 20 minutes. Feeding tubes placed in this manner are not painful and when not in use can be taped to the skin to prevent moving around under clothing.
Gastric tubes are favored for long-term use, last up to six months and can be replaced without additional surgery.
In patients for whom the stomach as the point of delivery is problematic, the jejunum or duodenum are alternate targets for percutaneous placement of feeding tubes, similar to PEG but by jejunostomy or duodenostomy.
As with all types of feeding tubes, the physician’s choice or PEG must consider all patient-specific factors. Contraindications include existing peritonitis or abdominal wall infection, high risk of aspiration, or unusual GI anatomy (such as malrotation).
Complications that may result from percutaneous insertion include cellulitis (infection around the incision point), peritonitis (infection within the abdominal cavity), gastric separation, and tube migration within the GI tract or back into the abdominal cavity.
Tube Feeding Administration
Tube feedings of infants and children can be administered by continuous gravity drip, regulated infusion pump, periodic bolus, or some combination. When oral feeding is also possible, the best combination is a regular schedule of normal and tube feeding that fits the needs and routines of the child and the family.
For periodic bolus feeding, the enteral formula is delivered at regular times each day, with each feeding lasting up to half an hour. Bolus refers to the discrete volume of nutrient material moving through the GI tract. Advantages of bolus feeding include reduced expense, convenience, freedom of movement between feedings, and similarity to a normal eating schedule. Disadvantages can include an increased possibility of aspiration compared to continuous drip feeding, and in some cases diarrhea, bloating, and cramping when the necessary volume is too large.
For continuous drip feeding, a direct gravity system is normally used, with the container of enteral formula placed higher than the patient’s stomach. While enteral formula may be delivered 24 hours a day, this is not advisable as it limits the child’s freedom of movement and may contribute to hypoglycemia. Typically, continuous drip is administered for several hours during the night so that smaller regular bolus or oral feedings can be administered during the day. Gravity drip may be inconsistent in delivery rate and must be frequently monitored.
For regulated infusion pump feeding, an electronic pump is used to control and measure the intake without any interruption, and as with gravity drip, may be administered during the night to reduce interference with normal daytime activities. It is the most expensive option.
The choice of an enteral formula is specific to the patient, and a range of prepared formulas are available commercially. Home formula preparation is also an option. The selection of an enteral formula should be with by the direction and guidance of a doctor or nutritionist. The condition and capacity of the GI tract, any underlying disease, allergies or food intolerance, and age must be considered in determining an appropriate formula. Likewise, the type of tube and its placement are considered for effects of viscosity, tonicity, and amount and frequency of administration.
Osmolality and Tonicity
Osmolality is a measure of the concentration of chemical compounds (amino acids, carbohydrates, electrolytes) present (by weight) that affect the osmotic behavior of the formula. Tonicity is a measure of the osmotic behavior relative to the normal body fluids. A formula with a higher effective osmolality (hypertonicity) than normal body fluids will draw water into the GI tract to dilute the concentration. Too much water in the GI tract can cause nausea, cramping, distention, and diarrhea. If the effective osmolality is too low (hypotonicity), affected cells will swell or even burst causing serious inflammation and other complications. The preferred condition is isotonicity, in which the enteral formula and the cells of the GI tract are in osmotic equilibrium until acted on by normal digestive processes.
Types of enteral formulas include:
- Standard formulas are nutritionally complete, intended for patients with normal GI-tract who cannot ingest adequate nutrients and calories. They are usually isotonic, convenient and sterile.
- Home-prepared formulas are more time-consuming but less expensive than commercial standard formulas. Infant formula or milk is often used as a base for blenderizing a complete dietary formula as directed by a doctor or nutritionist. These formulas are more effectively delivered through a gastric tube (G tube), since they can tend to be too viscous to pass through the narrower nasogastric tube (NG tube) without clogging.
- Elemental formulas contain predigested nutrients and essential vitamins and minerals. Their advantage is that little digestion is required and excretion of stool is minimal. Their disadvantage is high molality, and if infused too rapidly can cause osmotic diarrhea. They are also more expensive.
- Modular formulas contain specific nutrients, to be added to commercial or home-prepared formulas to meet special nutritional needs.
- Specialized formulas are designed for special cases identified by a doctor or nutritionist, usually involving prematurity or congenital errors of metabolism.
The nutrient composition of complete enteral formulas will include:
- Carbohydrate sources must be water soluble and easily digestible or absorbed in the GI tract. Common carbohydrate sources include corn syrup solids, hydrolyzed cornstarch, maltodextrin (starch-derived polysaccharide), and other forms of glucose (monosaccharide or simple sugar).
- Lipids are a high calorie energy source. Corn or soybean oil are commonly used. Fat content provided by lipids is adjusted as, for example, glucose intolerance calls for higher fat content while intestinal malabsorption calls for lower fat content.
- Proteins may be delivered intact or partially predigested, or as free amino acids. Common sources are caseinates (a form of dairy protein) or soy protein. Polymeric formulas use intact proteins. Oligomeric formulas contain enzymatically hydrolyzed (predigested) proteins. Monomeric formulas contain free amino acids.
- Water, as the enteral formula solute and essential for hydration, determines the caloric density of the formula. Lower caloric density is about 85% water; higher caloric density is about 70% water.
- Micronutrients, in adequate volume, insure complete nutrition as 100% of RDA (recommended daily allowance) for vitamins and minerals. The volume required varies greatly among products and among patients by age and weight. Some disease-specific formulas are not nutritionally complete.
- Fiber, usually insoluble soy polysaccharide, is added to control stool consistency. Sources of soluble fibers including oat fiber, guar gum, and pectin are also used. Fiber can be a complication for patients on restricted fluids or with delayed GI motility.
Some widely available commercially prepared pediatric enteral formulas include: Compleat Pediatric, Neosure, Nutren Junior, Pediasure, Peptamen Junior, Pediatric Peptinex, Resource Just for Kids, among others. Most of these brand labels provide a range of formula options, including additional fiber.
Link to key G-Tube and NG-Tube Feeding Sites
Gaining and Growing: Enteral Feeding for Children
National Center for Biotechnology Information (NCBI)
NCBI Nasogastric Intubation Videos
North American Society for Pediatric Gastroenterology, Hepatology and Nutrition (NASPGHAN)
“Enteral Formula Selection: A Review of Selected Product Categories” Practical Gastroenterology: Nutrition Issues in Gastroenterology, Series #28, June 2005
“Pediatric Enteral Nutrition” JPEN: Journal of Parenteral and Enteral Nutrition, Jan/Feb 2006, Axelrod et. al.
Baker, Baker, and Davis (1994). Pediatric Enteral Nutrition. Jones & Bartlett Publishers.
Multiple sources for “pediatric tube feeding” and “pediatric enteral feeding” at pubmed.gov
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