Sometimes a person with cancer cannot properly nourish their body through eating and drinking, and their doctor may recommend alternative modes of nutritional support. If the gastrointestinal (GI) tract is functioning normally, a feeding tube is usually the best alternative to eating and drinking. But in some cases, providing nutrition via the GI tract is not an option.
In these situations, your doctor may recommend parenteral nutrition-nutrition delivered directly to your bloodstream-which bypasses normal digestion in the stomach and bowel when they are obstructed or not functioning normally.
Normal digestion involves the GI tract breaking down food and drink into small particles which are absorbed into the bloodstream. These particles are then delivered to the liver for "processing and packaging", and then finally distributed to various parts of your body that need energy. Parenteral nutrition is a special mixture of proteins, carbohydrates (sugars), fats, and vitamins and minerals that are already in digested form and can be infused directly into the bloodstream to provide the nutrients your body needs to function properly.
At first glance nutrition by IV may sound better than a feeding tube, but it is always preferable to use the GI tract as the primary route of nutrition. This is partly because parenteral nutrition carries the risk of liver damage, but also because of the serious complications related to leaving the intestines unused for a prolonged period of time.
These include alterations in the bacteria normally present in the bowel, which results in overgrowth of bacteria more likely to cause disease, and the risk of bacterial translocation-when bacteria that live inside the wall of the bowel invade the bowel wall and get into other parts of your body. While these risks are small when parenteral nutrition is needed for only a short period of time, they can be serious and should always be considered in the decision to use alternative means of nutritional support.
While bypassing the digestive tract is not an ideal approach to nutrition, parenteral nutrition can be an excellent temporary mode of nourishment for patients with cancer and other diseases. It is most often used in cases of bowel obstruction (by a tumor or scar tissue from surgery) and malabsorption, but there are a number of other scenarios in which parenteral nutrition is helpful-including the following:
Short bowel syndrome-when a large amount of bowel is surgically removed and the remaining bowel is not enough to perform all digestive functions
Mesenteric ischemia-when the bowel is damaged from lack of blood flow and needs time to heal
Gastrointestinal fistula-when the bowel is leaking into another area of the body or through the skin typically following surgery or radiation
Parenteral nutrition may also be used as a supplement when the bowel can tolerate small feedings, but not enough to meet standard nutritional requirements. Small amounts of parenteral nutrition can be given by most intravenous lines (IV), but full nutritional support can only be infused into what is called a "central line", or a catheter inserted into a large blood vessel typically located in the chest. There are various types of central lines, including Port-a-caths, Hickmans, Broviacs, and PICCs (peripherally inserted central catheter). If your doctor recommends parenteral nutrition, you will probably need to have one of these special catheters placed.
The decision to start parenteral feedings can be difficult because of the known associated risks, but this recommendation is typically only made when nutrition through the GI tract is not an option. It is important to remember that parenteral nutrition is typically safe when used for short periods of time, and the risks of parenteral nutrition are often overshadowed by the risks of not getting proper nourishment.