When patients cannot use their gastrointestinal tracts for nutrition, parenteral nutrition may be used to maintain or improve the patient's nutritional status. This form of intravenous treatment provides all the nutrients that are delivered to the patient. This treatment may be temporary or long-term.
The harmful effects of malnutrition on the overall health of a patient are well documented. Poor nutrition is associated with slowed or impaired recovery from illness and surgery. For wound healing, tissue maintenance, and faster recovery, patients need optimal nutritional intake. When a patient is unable to take in enough food on his own, there are two options. Enteral feeding is preferred because it is less invasive, has a lower risk for infection, and is safer than the parenteral method. Though enteral feeding is the preferred route of nutritional intake, parenteral nutrition plays an important role in many clinical situations. Patients who cannot consume enough nutrients on their own, or who cannot eat at all because of an illness, surgery, or an accident, may be fed through an intravenous line.
Patients receiving parenteral nutrition need to be monitored closely to ensure that the therapy is providing adequate amounts of fluids, minerals, and other nutrients that are needed. Laboratory testing will take place on a regular basis to monitor the patient's status.
Parenteral nutrition, also known as hyperalimentation, is subdivided into two categories: partial parenteral nutrition and total parenteral nutrition. These categories differ by the makeup of the solutions and the site of administration.
Partial parenteral nutrition (PPN) is normally prescribed for patients who can tolerate some oral feedings but cannot ingest adequate amounts of food to meet their nutritional needs. It is usually administered through a peripheral intravenous catheter. Two types of solutions are commonly used in a number of combinations for PPN: lipid emulsions and amino acid-dextrose solutions.
Total parenteral nutrition (TPN) is given when a patient requires an extended period of intensive nutritional support. It is usually administered through a central venous catheter. TPN solutions contain high concentrations of proteins and dextrose. Various components like electrolytes, minerals, trace elements, and insulin are added based on the needs of the patient. Total parenteral nutrition provides the calories a patient requires and keeps the body from using protein for energy. TPN is given using an infusion pump.
Both of these types of nutrition may be administered either in a medical facility or in the patient's home. Home parenteral nutrition normally requires a central venous catheter, which must first be inserted in a fully equipped medical facility. After it is inserted, therapy can continue at home.
The physician orders the particular PPN or TPN solution as well as any additional nutrients or drugs that should be added. The doctor also specifies the rate at which the solution will be infused. The IV (intravenous) solutions are prepared under the supervision of a doctor, pharmacist, or nurse, using techniques to prevent bacterial contamination.
In the case of home parenteral nutrition, the solution is delivered to the patient's home on a regular basis and should be kept refrigerated. The solution should be allowed to come to room temperature before it is connected to the patient.
Patients who have been receiving parenteral nutrition for more than a few days, and have been given permission to start eating again, should reintroduce foods gradually. This will give the digestive tract time to start functioning again.
Patients receiving PPN or TPN are at risk for a number of very serious complications. These complications may result from the IV solutions or from the central venous catheter.
Fluid imbalances may occur in patients receiving parenteral nutrition. The extreme hyperosmolarity of the solutions may cause fluid shifts in the body. This hyperosmolarity is caused by the concentrations of dextrose and amino acids. The increased levels of dextrose may cause hyperglycemia, which may in turn cause the dextrose to move into the interstitial spaces into the plasma. This can cause a series of events that may lead to dehydration and hypovolemic shock. If the patient's heart or kidneys function poorly, the situation may develop into congestive heart failure and pulmonary edema. The patient should be monitored closely for signs of these complications. Accurate records of intake and output should be maintained, and daily weights recorded. Serum electrolytes and glucose are also monitored.
Another possible complication for those receiving parenteral nutrition is a variety of electrolyte imbalances. Daily serum electrolyte levels are normally ordered to find imbalances. Sodium and potassium imbalances are seen frequently among patients receiving PPN and TPN, especially when insulin is part of the intravenous solution. Hypercalcemia may also occur, although it may be more closely associated with the hazards of immobility than the parenteral therapy itself.
Enteral nutrition— Nutrition provided by introducing nutritional substances into the intestines.
Hyperosmolarity— An increased concentration of osmotically active particles in solution.
Another complication associated with parenteral nutrition is infection at the site of the central venous catheter. For patients receiving long-term therapy, the risk of infections spreading to the entire body (sepsis) is fairly high. Measures should be taken to prevent infections at the catheter site. This includes regular sterile dressing changes, and prompt reporting of any signs of redness, swelling, or drainage.
For those on short-term parenteral therapy, the goal is to provide adequate nutritional supplementation until the patient can transition back to solid foods. Patients receiving long-term therapy should have their nutritional needs met, with a goal of avoiding potential complications.
Health care team roles
A variety of members of the health care team may be involved in the decisions to order parenteral nutrition and in the care required to administer it. These include:
Howard, Lyn. "Enteral and Parenteral Nutrition Therapy." In Harrison's Principles of Internal Medicine. 14th ed., Vol. 1. New York: McGraw-Hill, 1998.
Ignatavicius, Donna D., et al. Medical-Surgical Nursing Across the Health Care Continuum. Philadelphia: W.B. Saunders Company, 1999.
Nguyen, Hung Q., et al. "Internist's Guide to Total Parenteral Nutrition." Internal Medicine 21 (April 2000): 37.