What is parenteral nutrition?
Parenteral nutrition means feeding intravenously (through a vein). "Parenteral" means "outside of the digestive tract." Whereas enteral nutrition is delivered through a tube to your stomach or the small intestine, parenteral nutrition bypasses your entire digestive system, from mouth to anus. Certain medical conditions may require parenteral nutrition for a short or longer time. Some people need it to supplement their diet, and some people need to get all of their calories intravenously.
What are the two types of parenteral nutrition?
Parenteral nutrition can be partial or total.
- Partial parenteral nutrition (PPN) is parenteral nutrition given to supplement other kinds of feeding. If you’re eating but still have malnutrition, healthcare providers may offer you partial parenteral nutrition to replace missing elements in your diet or give you additional calories.
- Total parenteral nutrition (TPN) is complete nutrition delivered intravenously to people who can’t use their digestive systems at all. TPN might be required when certain conditions impair your ability to process food and absorb nutrients through your digestive tract, or when you need to avoid using your digestive system for a while so it can heal.
Sometimes parenteral nutrition is classified by the type of vein that is used to deliver the nutrition.
- Central parenteral nutrition (CPN) is delivered through a central vein — usually, the superior vena cava located under your collarbone, which goes directly to your heart. The larger central vein allows a larger catheter to deliver higher concentrations of nutrition with higher calories. For this reason, CPN is used to deliver total parenteral nutrition.
- Peripheral parenteral nutrition (PPN) is delivered through a smaller, peripheral vein, perhaps in your neck or in one of your limbs. PPN is used to provide partial parenteral nutrition temporarily, using the quicker and easier access of the peripheral vein.
What does parenteral nutrition contain?
Parenteral nutrition is a chemical formula with standard variations and can be customized to your specific nutritional requirements. It may include different amounts of any of the six essential nutrients that your body requires: water, carbohydrates, proteins, fats, vitamins and minerals. Even when you receive total parenteral nutrition, your formula will be tailored to you based on lab results. Parenteral nutrition is complete enough to replace mouth feeding for as long as necessary — even for life.
When is partial parenteral nutrition used?
Partial parenteral nutrition is often given temporarily to people who need an immediate boost of calories before transitioning to a longer-term solution — either enteral feeding or gradually resuming mouth feeding. PPN is also commonly given to long-term hospital patients who tend to have general malnutrition for a variety of reasons.
When is total parenteral nutrition used?
You might need total parenteral nutrition if your digestive system isn’t functioning or if you have a gastrointestinal disease that requires you to give it complete rest. Some people might just need general nutrition therapy but might have medical reasons why enteral feeding won’t work for them.
Specific conditions that may require TPN include:
- Abdominal surgery.
- Intestinal ischemia.
- Small or large intestinal obstructions.
- Intestinal pseudo-obstruction.
- Prolonged ileus.
- Gastrointestinal bleeding.
- Radiation enteritis.
- Extremely premature birth.
- Necrotizing enterocolitis.
- Prolonged diarrhea.
- Inflammatory bowel diseases.
- Short bowel syndrome.
- Persistent chyle leak.
- Graft-versus-host disease of the gut.
How will I be prepared for parenteral nutrition?
Your healthcare team will determine your nutritional needs based on your health history, BMI and lab test results. Guidelines recommend that doctors, nurses, nutritionists and pharmacists collaborate to design your formula. A specialist will prepare your formula in 24-hour doses. All doses must be refrigerated until the day they are used and can be stored for up to seven days. Refrigerated formulas should be taken out a few hours prior to use to adjust to room temperature.
How is the parenteral nutrition IV installed?
Placing the IV catheter in your body will require two points of penetration through your skin. Your healthcare provider will offer you anesthesia to numb the pain and help you relax and carefully clean and sterilize the two points. They’ll begin by inserting a needle threaded with a guidewire through the skin into your vein. Then they’ll remove the needle, place the catheter tube over the guidewire and remove that. They might use a small ultrasound device to guide the placement of the catheter or an X-ray to confirm the correct placement afterward.
There are three types of catheters they might use:
- External “tunneled” catheter. The external catheter tunnels under your skin and out a separate exit point chosen for your comfort. The exit point requires a small incision for the catheter to come out, and temporary stitches to hold it in place for four to six weeks.
- Fully implanted catheter. An implanted catheter remains completely under your skin, with a needle insertion port attached at the end. The port is attached to the end of the catheter under the skin through a separate small incision at the site.
- Peripherally inserted central catheter (PICC). A PICC catheter is inserted into a vein in your upper arm and threaded into your superior vena cava. The needle port remains outside of your body. PICC can be used when parenteral nutrition is required for less than six weeks.
How is parenteral nutrition administered?
If you have an external catheter, you or your healthcare provider will attach the external end to another tube that connects to the IV bag with your nutrition solution. If you have an internal catheter, you’ll attach the IV bag to a tube connected to a special needle (called a Huber needle) that inserts into the implanted port. The parenteral nutrition infusion takes about 10 to 12 hours to fully transfer from the IV bag into your body. You may choose to take it at night while you sleep.
Parenteral nutrition can be administered in a hospital, long-term care facility or at home. Healthcare providers administering parenteral nutrition are careful to maintain strict sterile standards to prevent infection. Anyone administering parenteral nutrition at home will receive thorough training in how to recognize signs of contamination or infection. You’ll also change the dressings at the incision sites at least once a week and change the tubing connecting the catheter to the infusion bag every day.
How will I be monitored during parenteral nutrition?
Healthcare providers will constantly monitor your fluid intake and output and periodically weigh and measure you. They will also take regular blood tests to make sure you have the right balance of essential nutrients and adjust your formula accordingly. Some of the things they will monitor include:
- Electrolytes and blood urea nitrogen/creatinine — to prevent dehydration or overhydration.
- Blood glucose — to prevent hyperglycemia or hypoglycemia.
- Mineral levels — to screen for deficiencies.
- Liver function indicators — including aminotransferases and bilirubin.
How will I be transitioned from parenteral nutrition to enteral or oral feeding?
While parenteral nutrition can be used long-term if necessary, enteral feeding is better and oral feeding is ideal. Your healthcare team will want to transition you to one of these, or a combination of the two, as soon as your body allows, to avoid the long-term complications of parenteral feeding.
The transition is gradual, both because of your underlying gastrointestinal condition and because certain functions of the digestive tract can begin to atrophy when it hasn't been used for a while. Your healthcare team will probably start you on a clear liquid diet. If you tolerate that well, you’ll transition to a full liquid diet, and finally, solid food.
Risks / Benefits
What are the benefits of parenteral nutrition?
The primary advantage of parenteral nutrition is to give your gastrointestinal system a chance to heal from severe illness or surgery. For long-term hospital patients, especially geriatric patients who have trouble sustaining their nutritional needs through eating or with enteral nutrition, partial parenteral nutrition can provide an important boost to help their bodies manage their other difficulties. For people with permanently impaired gastrointestinal function, or for extremely premature and sick infants who haven’t yet developed the ability to feed normally, total parenteral nutrition can be life-saving.
What are the risks or complications of this procedure?
Parenteral nutrition is considered less ideal than enteral feeding because of the higher risk of complications involved. The primary concerns are infection of the bloodstream from the IV catheter and atrophy of the digestive tract when it isn’t being used. There are other risks, however.
The most common complications include:
- Infection. Bacteria from the IV catheter can infect your bloodstream. If the infection spreads throughout your body, it can lead to sepsis, a life-threatening complication.
- Blood clots can form at the site where the catheter meets the vein.
- GI atrophy can begin to occur after about two weeks. GI function usually returns gradually.
- Glucose imbalances (hyperglycemia or hypoglycemia) are common. These are treated with insulin and dextrose adjustments.
- Transient liver reactions to the nutritional formula can occur. Healthcare providers manage these by adjusting the formula.
- Parenteral nutrition-associated liver disease (PNALD) is a complication of long-term parenteral nutrition. Liver disease affects up to 50% of patients after five to seven years. We don’t know exactly why. In premature infants, it may be because their liver isn’t fully developed. In adults, it might be related to the diminished gut bacteria that results when your gut isn’t being used.
- Gallbladder problems can result when the lack of stimulation from the digestive system causes bile to accumulate without being released normally into the small intestine. Your healthcare providers may be able to stimulate gallbladder contractions by varying your formula and encouraging at least a small amount of oral feeding
- Bone demineralization (osteoporosis or osteomalacia) can develop in people who receive long-term parenteral nutrition, possibly due to vitamin and mineral deficiencies (calcium, magnesium and vitamin D).
Other possible complications include:
- Injury during the insertion of the catheter.
- Fluid overload.
- Reactions to lipid emulsions in the formula due to food allergies.
- Hunger pangs.
Recovery and Outlook
What is the long-term outlook after parenteral nutrition?
After you have successfully weaned from parenteral nutrition, your healthcare team will continue to monitor your weight and nutrition levels for a while to make sure your oral nutrition and hydration are sufficient. If you had liver complications during parenteral nutrition, those higher enzyme levels may persist for years. However, with a healthful, nutritious diet, your long-term health outlook is good.
A note from Cleveland Clinic
Parenteral nutrition is an extreme intervention, but someday you or your child may need it. Parenteral nutrition may sustain you or your child through a difficult interval in their or your health. If that interval is long, you may end up administering parenteral nutrition at home. It may start as an inconvenience, but will soon evolve into just another routine. During parenteral nutrition, your healthcare team will continue to monitor your nutritional needs and reactions with extreme care. When the time comes to wean from parenteral nutrition, they will help you return to ordinary eating with equal care.
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