When nutrients can’t be given by mouth, they may be given through a tube (tube feeding) inserted into the gastrointestinal tract (entreat nutrition), or they may be given intravenously (parental nutrition). These methods may be used to feed people who are unwilling or unable to eat or who can’t digest and absorb nutrients.
Tube Feeding
Tube feeding is used in various situations, including recovery from burns and inflammatory bowel disease. A thin plastic feeding tube (a nasogastric tube) is passed through the nose and gently down the throat until it reaches the stomach or small intestine. Although the insertion of this tube is mildly uncomfortable, most people have little discomfort once it’s in place. If tube feeding must be used for a long time, the tube can be placed directly into the stomach or small intestine through a small incision in the abdominal wall.
The solutions used in tube feeding contain all the nutrients a person needs, including proteins, carbohydrates, fats, vitamins, and trace minerals. Fats supply 2 to 45 percent of the total calories.
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Problems with tube feeding are uncommon and rarely serious. Some people have diarrhea and abdominal discomfort. The esophagus can become irritated and inflamed by the nasogastric tube. Inhaling (aspirating) food into the lungs, a serious but rare complication, can be prevented by elevating the head of the bed to decrease regurgitation and by giving the solution slowly.
Intravenous Feeding
Intravenous feeding is used when people can’t receive adequate nourishment through a nasogastric tube. For instance, people who are severely malnourished and need to undergo surgery, radiation therapy, or chemotherapy or people who have severe burns, paralysis of the gastrointestinal tract, or persistent diarrhea or vomiting may be fed intravenously.
Intravenous feeding can supply part of a person’s nutritional requirements or all of them (total parenteral nutrition). A number of solutions are available, and they can be modified for people who have kidney or liver disease. Total parenteral nutrition requires a larger intravenous tube (catheter) than those normally used for intravenous fluids. Consequently, a larger vein, such as the subclavian vein located approximately under the collarbone, is used.
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A person receiving total parenteral nutrition is closely monitored for changes in weight and urine output and for signs of infection. If the blood levels of glucose become too high, insulin may be added to the solution. Infection is a constant risk because the catheter is usually left in place for a long time and the feeding solutions that pass through it have a high content of glucose-a substance in which bacteria can grow easily.
Total parenteral nutrition can cause other complications. The liver may enlarge if too many calories, particularly from fats, are consumed. The excess fat in the veins may also cause backaches, fever, chills, nausea, and a low platelet count. However, these problems occur in less than 3 percent of the people receiving total parenteral nutrition. Long-term total parenteral nutrition may produce bone pain.