Parenteral nutrition

Overview

Parenteral nutrition, also known as total parenteral nutrition, involves feeding through a vein (intravenously), bypassing the entire digestive tract. Unlike enteral nutrition, which is delivered via a tube to the stomach or small intestine, parenteral nutrition delivers nutrients directly into the bloodstream. This approach is necessary for individuals with medical conditions that prevent their digestive systems from properly absorbing or tolerating food.

This specialized form of nutrition provides essential liquid nutrients, including carbohydrates, proteins, fats, vitamins, minerals, and electrolytes. Parenteral nutrition can be used either on its own or to supplement enteral feeding. It is particularly helpful for people who cannot consume adequate nutrition by mouth, either temporarily or over an extended period.

When administered outside of a hospital, this treatment is referred to as home parenteral nutrition. Some individuals may need this intravenous feeding for several weeks or months, while others might require it for life. The goal is to correct or prevent malnutrition by ensuring the body receives the necessary nutrients even when the digestive system is not functioning properly.

Types

Parenteral nutrition can be categorized into two main types: partial and total.

• Partial parenteral nutrition (PPN): PPN supplements regular food intake when it is insufficient to meet nutritional needs. It provides additional nutrients and calories to address malnutrition while the person continues to eat normally.
• Total parenteral nutrition (TPN): TPN is administered when a person cannot use their digestive system at all. It supplies complete nutrition intravenously, bypassing the digestive tract entirely. TPN is essential for conditions that prevent nutrient absorption or when the digestive system needs to rest and heal.

Parenteral nutrition can also be classified based on the type of vein used for delivery:

• Central parenteral nutrition (CPN): CPN is delivered through a central vein, typically the superior vena cava near the heart. This allows for the infusion of highly concentrated nutrients and higher calorie content. CPN is generally used for total parenteral nutrition.
• Peripheral parenteral nutrition (PPN): PPN is administered through a smaller peripheral vein, such as in the neck or limbs. It is typically used for partial nutrition on a short-term basis due to the convenience of accessing peripheral veins.

Reasons for undergoing the procedure

You may need parenteral nutrition for several reasons, including:

• Cancer: Digestive tract cancer can obstruct the bowels, hindering food intake, and cancer treatments like chemotherapy may impair nutrient absorption.
• Crohn’s disease: This inflammatory bowel disease can cause pain, bowel narrowing, and other issues that affect food intake and nutrient absorption.
• Short bowel syndrome: Present at birth or resulting from surgery that removes a significant portion of the small intestine, this condition limits nutrient absorption due to insufficient bowel length.
• Ischemic bowel disease: Reduced blood flow to the bowel can lead to complications that affect nutrient absorption.
• Abnormal bowel function: Conditions such as surgical adhesions, radiation enteritis, neurological disorders, or other issues can disrupt the movement of food through the intestines, impacting nutrient intake.

Risk

Parenteral nutrition is often viewed as less ideal compared to enteral feeding because of its higher risk of complications. Major concerns include the potential for bloodstream infections from the IV catheter and digestive tract atrophy when it is not being used. Additional risks associated with parenteral nutrition include:

• Infection: Bacteria from the IV catheter can infect the bloodstream, potentially leading to sepsis, a severe and life-threatening condition.
• Blood clots: These can form at the site where the catheter enters the vein.
• GI atrophy: The digestive tract can begin to atrophy after about two weeks of non-use, though GI function usually returns gradually.
• Glucose imbalances: Issues such as hyperglycemia or hypoglycemia are common and managed with adjustments in insulin and dextrose.
• Transient liver reactions: These can occur in response to the nutritional formula and are managed by modifying the formula.
• Parenteral nutrition-associated liver disease (PNALD): Long-term parenteral nutrition can lead to liver disease, affecting up to 50% of patients after five to seven years. This may be due to underdeveloped liver in premature infants or reduced gut bacteria in adults.
• Gallbladder problems: Lack of digestive system stimulation can cause bile to accumulate, leading to gallbladder issues. Healthcare providers may stimulate gallbladder contractions by adjusting the formula and encouraging minimal oral feeding.
• Bone demineralization: Long-term use of parenteral nutrition can result in osteoporosis or osteomalacia due to deficiencies in calcium, magnesium, and vitamin D. z

Additional potential risk may include:

• Injury during the catheter insertion
• Fluid overload
• Allergic reactions to lipid emulsions in the formula
• Hunger pangs

Before the procedure

Based on your medical history, BMI, and lab test results, your healthcare team will determine what nutrition you require. When creating your formula, collaboration between healthcare provider, nurses, nutritionists, and pharmacists is recommended. A healthcare provider will make your formula in 24-hour dosages that may be stored for up to seven days and need to be refrigerated until the day of usage. Remove the refrigerated formula from the refrigerator a few hours before using to enable it to come to room temperature for best results.

During the procedure

Parenteral nutrition is administered through a thin, flexible tube (catheter) inserted into a vein. Nutrition specialists will assist in selecting the best kind of catheter for you. Inserting the IV catheter involves two skin punctures. Your healthcare provider will administer anesthesia to numb the area and help you relax, then carefully clean and sterilize the sites.

The procedure starts with a needle threaded with a guidewire being inserted through the skin and into the vein. After removing the needle, the catheter tube is threaded over the guidewire, which is then withdrawn. To ensure precise placement, your healthcare provider may use a small ultrasound device during the procedure or an X-ray afterward to confirm the catheter’s correct position.

Parenteral nutrition can be administered by catheter in three main ways:

• Tunneled catheter: For example, a Hickman catheter, which has a portion of the tube outside the skin and another segment that is tunneled under the skin before entering the vein. The exit point of the catheter requires a small incision to allow the catheter to emerge. Temporary stitches are used to secure it in place for about four to six weeks.
• Fully implanted catheter: Fully placed beneath the skin, requiring access with a needle to administer the parenteral nutrition. The port is connected to the end of the catheter and placed under the skin through a separate small incision at the site.
• Peripherally inserted central catheter (PICC): A PICC is inserted into a vein in your upper arm and threaded into the superior vena cava. The needle port stays outside your body. This type of catheter is suitable for administering parenteral nutrition for less than six weeks.

For an external catheter, your healthcare provider will connect the external end to a tube leading to the IV bag with your nutritional solution. If you have an internal catheter, the IV bag is connected to a tube that links to a special needle called a Huber needle, which fits into the implanted port. The infusion process usually takes about 10 to 12 hours, often done overnight while you sleep.

Parenteral nutrition can be administered in hospitals, long-term care facilities, or at home. In all settings, maintaining strict sterile practices is essential to prevent infections. If you are receiving parenteral nutrition at home, you will be trained to recognize signs of contamination or infection. Additionally, you will need to change the dressings at the catheter insertion sites at least once a week and replace the tubing connecting the catheter to the infusion bag daily.

Your healthcare providers will closely monitor your fluid intake and output, regularly weigh and measure you, and perform frequent blood tests to ensure you maintain the correct balance of essential nutrients. They will adjust your formula as needed based on these assessments. Key aspects they will monitor include:

• Electrolytes and blood urea nitrogen/creatinine: To prevent dehydration or overhydration.
• Blood glucose levels: To avoid hyperglycemia or hypoglycemia.
• Mineral levels: To detect any deficiencies.
• Liver function indicators: Such as aminotransferases and bilirubin.

After the procedure

Your healthcare team will closely monitor your response to parenteral feeding through regular laboratory tests and fluid balance assessments, while also inspecting the catheter site. They will evaluate your readiness to transition from parenteral nutrition to either regular oral feeding or tube feeding during follow-up exams. Based on your individual needs, the team may help you gradually reduce or completely stop parenteral nutrition.

Though parenteral nutrition can be used long-term if necessary, enteral feeding and oral feeding are generally preferred when possible. Your healthcare team will work to transition you to these methods as soon as your condition allows, aiming to prevent complications linked to prolonged parenteral nutrition. This transition is a gradual process, especially due to any underlying gastrointestinal issues and the temporary atrophy of digestive functions. You’ll typically begin with a clear liquid diet, then move to a full liquid diet, and eventually reintroduce solid foods as your tolerance improves.

Outcome

Parenteral nutrition offers significant benefits, particularly for those recovering from severe illness or surgery, by allowing the gastrointestinal system time to heal. For long-term hospital patients, especially elderly individuals who struggle to meet their nutritional needs through eating or enteral nutrition, partial parenteral nutrition can provide essential support. In cases of permanently impaired gastrointestinal function or for extremely premature and critically ill infants who cannot feed normally, total parenteral nutrition can be life-saving. Once you successfully transition off parenteral nutrition, your healthcare team will monitor your weight and nutritional levels to ensure that oral nutrition and hydration are sufficient. If you experienced liver complications during parenteral nutrition, elevated enzyme levels may persist for years, though maintaining a healthy diet generally promotes positive long-term health.

Healthcare providers with specialized training will teach you and your caregivers how to properly prepare, administer, and monitor parenteral nutrition at home. Typically, the feeding cycle is scheduled for overnight infusion, freeing you from the pump during the day. Many individuals report that their quality of life while on parenteral nutrition is similar to those undergoing dialysis, though fatigue is a common issue for those receiving home parenteral nutrition.