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Parenteral (PN) and Enteral Nutrition (Tube Feeds)

Section 1: Parenteral Nutrition (PN)

What is Parenteral Nutrition (PN)?


Parenteral nutrition (PN) is a liquid that provides nutrition directly into the body's large veins. It provides you (or your child) with all of the nutrients, fluids, vitamins, and minerals needed to fuel the body. Since PN is infused straight into the bloodstream, it bypasses the intestine. This is beneficial in short bowel patients and other gastrointestinal disorders where the intestine does not absorb efficiently. Other common terms for parenteral nutrition include: hyperalimentation (very old term), total parenteral nutrition (TPN), or home parenteral nutrition (HPN).




What are the components of PN?


PN supplies the primary nutrients your body needs to sustain life, including the three primary sources of energy for your body: 1. Carbohydrates: This gives your body calories and is the primary energy component in PN. It is usually in the PN as glucose. 2. Protein: Helps your body repair tissue, build muscle, fight infections, and carry nutrients through the body. 3. Fat: Another good source of calories and energy. It also is needed to absorb vitamins A, D, E, K, helps to protect your vital organs, and conserve heat. In addition to the three main components, PN also contains micronutrients your body needs to function: 1. Vitamins: Usually, you are required to add these to your PN solution when you are on home TPN. These are what turn the PN solution yellow. Examples: vitamins A, D, E, and K. 2. Minerals: These may also be added to PN. Examples are zinc and copper. 3. Electrolytes: These are important for the function of most systems of the body. Examples: calcium, potassium, phosphorous, magnesium, and sodium. 4. Water: Water is important to keep you hydrated and your kidneys functioning. Medications: Sometimes you may add mediations to your PN solution. Commonly added medications cinlude:

  • Insulin: This helps to control your blood sugar.
  • Anti-acid: This helps with stomach acid secretion.
  • Octreotide: This is an anti-secretory medication and can help decrease diarrhea.




What are the different types of central lines that may be used to infuse TPN?


Peripherally Inserted Central Catheter (PICC):

  • This is a type of catheter (small, flexible plastic tube) inserted into a large vein in your upper arm.
  • The tip of the catheter ends just above the heart.
  • PICCs can be used for many months.
Tunneled Central Venous Catheter (CVC):
  • This type of catheter (small, flexible plastic tube) is inserted into a large vein in your chest, groin, or neck.
  • It usually is tunneled under your skin.
  • Most commonly, for long term PN use, the CVC will be placed in the chest.
  • This type of CVC can be used for years.
  • The following are types of tunneled CVC: Hickman®, and Broviac®.
Implanted Port
  • A particular type of tunneled CVC in which there is no exit point.
  • A round metal disc with a soft rubber top is placed just under the skin, and a catheter is tunneled to reach just above the heart.
  • To access, you must use a special needle poked into the disk under your skin.
Occasionally, a special, less concentrated PN form may be given into a vein through a peripheral line (cannula) in your arm. This is only used for a short period, usually as a bridge until a central line can be inserted. To see visuals of the types of catheters, please view this article.




What is important to monitor while on PN?


This will vary per center, however, it is usually important to record:

  • Weight
  • Fluid intake and output
  • Temperature
  • Uine-dipstick-for-sugar results
During the first few weeks or months, you usually will need weekly bloodwork. If you have been on PN for a long time, the frequency of blood monitoring may decrease.




Why does someone require PN?


Parenteral nutrition is given to people with certain gastrointestinal disorders, such as short bowel syndrome, who are unable to absorb enough nutrients. PN is delivered directly into the bloodstream (bypassing the gastrointestinal tract) through a central venous catheter (CVC). Common reasons people require PN (this list is not all-inclusive, rather, a snapshot):

  • Crohn's and Ulcerative Colitis
  • Motility diosrders, such as chronic intestinal pseudo-obstruction (CIPO)
  • Cancer, particularly that of the GI tract
  • Short bowel syndrome from congenital conditions
  • Stroke
  • Cystic fibrosis
  • ALS
  • Parkinson's Disease
  • Ischemic bowel disease
  • Necrotizing Enterocolitis (NEC)




How is PN started and cycled?


Every individual is different, but generally, PN is started as an inpatient in the hospital. The reason for this is that your team needs to closely monitor you (or your child) very closely at the beginning to ensure that your electrolytes and other blood levels stay in balance. Since many people starting PN are malnourished, they also are at risk of something called refeeding syndrome (see PN complications). At first, most individuals will start PN on a 24-hour continuous cycle. This means the PN runs throughout the entire day.

  • Initially, your PN will not contain all of the calories and nutrients your body needs.
  • Gradually over a few days to weeks your team will increase the glucose (energy/calories) in the PN until the full nutritional requirements are met.
  • Once met, your team will likely start to 'cycle' your PN.
    • Note: Not all people will be able to cycle PN and may have to remain on a continuous infusion. Your team will determine the best option for you.
  • Cycling your PN means that they will decrease the amount of time that your PN runs over.
  • Typically it will go down in increments, such as from 24 hours to 18 hours to 16 hours and finally ending at a 12-hour cycle.
  • Most people like to do their 12-hour cycle overnight; therefore, they can be free from PN throughout the day.




What are the types of lipid formulations for PN?


1. Intralipid: This is a soybean oil lipid emulsion (SOLE). SOLEs contain high amounts of a plant-based cholesterol-like compound called phytosterols, found in vegetable oils. These have been found to contribute to the development of cholestasis and disruption of bile acid homeostasis. 2. Mixed-lipid emulsions: These lipid emulsions contain various amounts of plant-based oils, fish oils, and medium-chain triglycerides (MCTs). The most commonly known is SMOFlipid® which consists of: 30% soybean oil, 30% MCTs, 25% olive oil, 15% fish oil. SMOFlipid® is currently indicated for use in adults "as a source of calories and essential fatty acids for PN when oral or enteral nutrition is not possible, insufficient, or contraindicated." 3. Omegaven®: This is a fish-oil lipid emulsion (FOLE). It contains minimal phytosterols and is rich in omega-3 fatty acids. It is currently FDA approved for children with parenteral-nutrition associated cholestasis. Research is continuously ongoing on the best lipid formulation to help prevent parenteral-nutrition associated liver disease (PNALD). To stay up-to-date on nutrition news, visit the Oley website.





Section 3: Enteral Nutrition

What is enteral nutrition?


In some situations, you (or your child) may not be able to eat enough food by mouth to maintain nutritional status. When this occurs, nutrition must be delivered in another way. One way nutrition can be delivered is via " enteral nutrition" or " tube feeding." Tube feeding is when a special formula containing the required carbohydrates, proteins, fats, vitamins, minerals, and fluids are delivered directly into the stomach or intestine via a tube.




What are the types of feeding tubes?


1. Nasogastric (NG) tube: This tube goes from the nose, down the throat, and into the stomach. They are commonly used for short-term needs. 2. Nasoduodenal tube: This tube goes from the nose, down the throat, through the stomach, and ends in the first portion of the small intestine, the duodenum. 3. Nasojejunal tube: This tube goes from the nose, down the throat, through the stomach, and ends in the second portion of the small intestine, the jejunum. 4. Gastrostomy tube (G-tube): This tube is inserted surgically through the skin and into the stomach. They are commonly placed for long-term use. 5. G-J tube: This tube has two ports, one is inserted through the skin into the stomach, and another extends into the jejunum, the second portion of the small intestine. 6. Jejunal tube (J-tube): This tube is inserted surgically and directly into the second portion of the small intestine, the jejunum. This type of tube is often recommended when the stomach does not function properly (such as in gastroparesis). The small intestine cannot handle large volumes of feeds like the stomach, so J-tube feeds usually require a pump over a period of time. Your (or your child's) team will determine the best type of tube for you. If you would like to see visuals of these tube options, please refer to the American College of Gastroenterology What are examples of Enteral Access?




What are the different types of enteral formulas?


1. Standard polymeric formulas: These contain whole proteins and require full digestion. They are nutritionally complete, containing all of the needed vitamins, minerals, and trace elements. Examples: Nutren® 1.5, Jevity® 1.5 Cal 2. Extensively hydrolyzed or peptide formulas: In these formulas, protein is partially broken down into units called peptides. Since they are partially digested, the formula moves through the stomach at an increased rate, which may improve tolerance. Examples: Peptamen®, Vital® 1.0 Cal 3. Elemental formulas: In these formulas, protein is broken down to the smallest unit, amino acids (the protein building blocks). This type of formula is commonly used in children with short bowel syndrome and motility disorders. Example: Tolerex® 4. Blenderized tube feeds: Formulas developed with real food. Must be extra-careful during preparation to avoid bacterial contamination. Always consult your team and dietician if you choose to make your own formulas for feeds to ensure you are providing all of the nutrients and fluids you (or your child) need. Example of the commercially available form: Compleat Organic Blends® 5. Disease and allergy specific formulas: These are formulas tailored to specific disease states and conditions. Examples include formulas for individuals with kidney disease, liver disease, milk allergies, lactose intolerance, pulmonary dysfunction, gastrointestinal (GI) dysfunction, and diabetes. Example: Glucerna® 1.5 Cal 6. Modular formulas: These formulas provide protein, fat, or carbohydrate as single nutrients or modular mixtures to adjust the nutrient mix. This allows the formula to be tailor-made for a specific individual.




What are characteristics to consider when choosing a tube feeding formula?


1. Amount of calories it supplies. 2. Is the formula isotonic or hypotonic? 3. Does the formula contain lactose? 4. Does the formula contain fiber? 5. The type of protein in the formula, is it intact or broken down? 6. The type and amount of fat in the formula.




What is the best tube feeding formula for a short bowel patient?


This is very individualized and is a trial and error process. You will need to work with your dietician and team to determine what will work best for you. For example, you may need a lactose-free formula if you cannot tolerate lactose, as well as an isotonic formula to avoid dehydration.




What are the ways tube feeds may be given?


1. Bolus feeds: This is when a specific amount of formula is given via a syringe over a short period. 2. Gravity feeds: This is when the formula is placed in a feeding bag hung from an IV pole. The tubing connects to the feeding tube, and a roller on the tubing controls the rate the formula enters. Adjusting the roller can make the rate faster or slower, depending on how well the feed is tolerated. 3. Pump-assisted feeds: This is when a pump infuses a feed at a specific rate over a designated period. Commonly used with J-tube feeds. There are many types of pumps available. Your (or your child's) team will determine the best way to deliver feeds. Generally, individual's with a short bowel will be started on continuous feeds and may transition to bolus feeds. Frequently, you (or your child) may do bolus feeds during the day, and a continuous feed overnight. This allows freedom from a pump during the day. The benefit of a continuous feed s that it allows the formula to move more slowly through the intestinal tract, increasing the likelihood of nutrient absorption. In the beginning, it will be a trial and error process. Do not become frustrated! It is normal not to 'get it right' the first time.




What are complications associated with enteral nutrition?


Possible complications can be divided into a few categories: Gastrointestinal: Result from infusing the formula.

  • Diarrhea: Consider changing the formula, adding fiber, or using an anti-diarrhea medication.
  • Constipation: Consider changing formula, adding fiber, providing adequate hydration, or adding stool softener.
  • Malabsorption
  • Nausea and vomiting: Consider changing the rate of infusion, or your team may add a medication to help increase motility.
Mechanical Complications: Aspiration: This is when formula enters the lungs instead of going into the stomach/intestine. Aspiration usually occurs when someone vomits and is a very serious complication. Try to keep your (or your child's) head elevated and avoid large bolus feeds to help prevent aspiration. If vomiting is an issue, it may be beneficial to directly give tube feeds into the small intestine versus the stomach (i.e., J-tube). Tube Clogging: It is common for the tube to become clogged, especially with blenderized, thick formulas. Prevent the tube from clogging by flushing the tube before and after each feed. Metabolic Complications: Just like PN, enteral nutrition can cause electrolyte imbalances and other metabolic abnormalities but are often not as severe. Common issues with enteral nutrition include:
  • Too much or too little sodium (hypernatremia or hyponatremia)
  • Dehydration
  • Hyperglycemia (high blood sugar)
  • Too much or too little potassium (hyperkalemia or hypokalemia)
Refeeding Syndrome:
  • If you (or your child) are severely malnourished, you may get "refeeding syndrome," in which there are rapid decreases in circulating levels of potassium, magnesium, and phosphate.
  • This occurs because there is a shift from stored body fat to carbohydrate as the primary fuel source. Blood insulin levels increase, causing the movement of electrolytes into cells for use in metabolism.
  • Refeeding adversely affects all organ systems and is a very serious medical situation.





Section 2: PN Complications

What are complications associated with PN?


PN complications can be broken up into 3 categories: 1. Metabolic complications. 2. Catheter-related (mechanical) complications. 3. Infection-related complications (sepsis). The complications can also be considered short-term or long-term. Short-Term Metabolic Complications:

  • Volume overload
  • Hyperglycemia and Hypoglycemia
  • Refeeding Syndrome (hypophosphatemia, hypomagnesemia, hypokalemia)
  • Electrolyte imbalances
Long-Term Metabolic Complications
  • Hepatic cholestasis
  • Hepatic steatosis
  • Cirrhosis and End-Stage Liver Disease




Hyperglycemia and Hypoglycemia


PN contains large amounts of glucose. This places individuals on PN at risk of developing hyperglycemia (too much glucose in the blood) or hypoglycemia (too little glucose in the blood). Hyperglycemia (High Blood Sugar)

  • Can result from the high amount of glucose infused over a short period
  • Generally, you will be required to use a urine dipstick test or glucose monitor to assess the levels of glucose (sugar) in your blood to determine if the level is too high.
  • Treatment: Your team may choose to add insulin to your PN or require you to give yourself insulin. Insulin is the hormone in your body that regulates sugar levels, signaling to cells to take in the glucose and store energy for later use.
Hypoglycemia (Low Blood Sugar)
  • This is when your blood sugar is too low.
  • This can occur when your PN is stopped too abruptly.
  • Signs and Symptoms of Hypoglycemia
    • Feeling shaky
    • Sweating, clamminess
    • Confusion
    • Fast heartbeat
    • Feeling lightheaded or dizzy
  • If you are having trouble with hypoglycemia, your team may choose to place your PN regimen on a taper schedule.
    • This means that the infusion starts off slowly over the first hour or two of your infusion, gradually increasing the infusion until it reaches full speed.
    • The hour or two before your PN cycle is going to end, you may also need to taper-down.
    • The tapers make it so your body is not shocked by massive amounts of glucose, which could cause the release of too much insulin, resulting in low blood sugar (hypoglycemia).




Refeeding Syndrome


Refeeding syndrome can occur upon initiation of PN if an individual is severely malnourished. When the body is in the starved state without carbohydrates, it uses protein and fat stores for energy. When PN is introduced and initiates carbohydrate metabolism, insulin production increases. This causes a movement of electrolytes into cells, particularly phosphate, leading to serious electrolyte and fluid disturbances in the body. It is a very serious situation and can be life-threatening if not treated. Fluid can shift into the lungs which causes serious breathing difficulties.

A hallmark of refeeding syndrome is hypophosphatemia (low phosphate levels), but concentrations of many electrolytes, such as potassium and magnesium, can become low.




Parenteral Nutrition Associated Liver Disease (PNALD) in Adults


Parenteral Nutrition Associated Liver Disease (PNALD) refers to liver dysfunction that results from the use of parenteral nutrition (PN) in individuals with a nonfunctioning intestine (intestinal failure). There are three main types of PNALD: 1. Steatosis (fatty liver): This is a benign condition but can progress to fibrosis and cirrhosis. Cirrhosis is scarring of the liver and is generally permanent. The portions of the liver that become cirrhotic are no longer functional. 2. Cholestasis: This is when the flow of bile from your liver is reduced or blocked. 3. Cholelithiasis (gallstones or gallbladder sludge): Commonly seen in short bowel patients on PN due to reduced concentration of bile acids from altered intestinal-liver (enterohepatic) circulation. Also, with limited oral intake, the gallbladder contracts less, leading to more concentrated bile and increased risk for developing stones. Steatosis and cholestasis can progress to end-stage liver disease and cirrhosis (scarring of the liver, no longer functional). Factors affecting PNALD:

  • Long-term PN use, more prolonged use = higher risk
  • Infusion of high amounts of lipids or dextrose = higher risk
  • Type of lipid emulsion, SMOFlipid®, and Omegaven® is shown to have better outcomes
Diagnosis: Diagnosis is based on bloodwork which assesses liver function tests such as alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP). bilirubin). A liver or gallbladder ultrasound may be used to visualize the liver or look for stones. Either a magnetic resonance elastogram or an ultrasound elastogram may be performed to assess for the presence of fibrosis (scarring). The gold standard is a liver biopsy to assess for fibrosis and cirrhosis. Treatment: The best option is to get you off of PN. If this is not possible, your team may be able to make adjustments to your PN solution, such as decreasing the amount of glucose or lipids. Also, your team may recommend the use of a different lipid formulation (see SMOFlipid® and Omegaven® for more information). If you have progressed to end-stage liver disease, a liver or multivisceral transplant may be recommended.




Parenteral Nutrition Associated Liver Disease (PNALD) in Children


Parenteral Nutrition Associated Liver Disease (PNALD) refers to liver dysfunction that results from the use of parenteral nutrition (PN) in indivduals with a nonfunctioning intestine (intestinal failure). Risk factors for development of PNALD in a child includes:

  • Premature birth
  • Disruption of the intestinal-liver (enterohepatic) circulation of bile acids
  • Slow intestinal motility resulting in with bacterial overgrowth
  • High parenteral protein, fat, and/or energy intake
  • Frequent line infections
  • Absence of oral feeds (inc. risk for biliary sludge)
  • Continuous PN infusion can lead to too much insulin in the blood and is accosiated with cholestatic liver disease in children
What are the possible forms of PNALD? 1. Steatosis (more common in adults): his is a benign condition but can progress to fibrosis and cirrhosis. Cirrhosis is scarring of the liver and is generally permanent. The portions of the liver that become cirrhotic are no longer functional. 2. Cholestasis (common in children): This is when the flow of bile from your child's liver is reduced or blocked. 3. Cholelithiasis (gallstones, gallbladder sludge): Commonly seen in short bowel patients on PN due to reduced concentration of bile acids from altered intestinal-liver (enterohepatic) circulation. Also, with limited oral intake, the gallbladder contracts less, leading to more concentrated bile and increased risk for developing stones. Diagnosis: Diagnosis is based on bloodwork which assesses liver function tests such as alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP). bilirubin). A liver or gallbladder ultrasound may be used to visualize the liver or look for stones. Either a magnetic resonance elastogram or an ultrasound elastogram may be performed to assess for the presence of fibrosis (scarring). The gold standard is a liver biopsy to assess for fibrosis and cirrhosis, but often this is not performed in a young child. Treatment: The best option is to get your child off of PN. If this is not possible, your child's team may be able to make adjustments to their PN solution, such as decreasing the amount of glucose or lipids. Also, your child's team may recommend the use of a different lipid formulation (see SMOFlipid® and Omegaven® for more information). If your child has progressed to end-stage liver disease, a liver or multivisceral transplant may be recommended.




Central Venous Catheter Occlusion or Thrombosis


Central Venous Catheter Thrombosis (CVT) occurs when a blood clot forms in a central line (the line that goes into your (or your child's) vein for infusing PN). You (or your child) can also have an occlusion in the central line from blood, a medication, or PN fluid precipitate (such as a lipid component). Signs and Symptoms:

  • Facial swelling
  • Swelling of the arm on the same side of the body as the catheter
  • Distended neck veins
If you are caring for a child, you should look for:
  • Any distress or breathlessness while infusing
  • Swelling in the neck or limbs
  • Stiffness or difficulty when flushing the line
  • Fluid coming out around the exit site of the line
How to help prevent this from happening?
  • Flush with 0.9% NS after every use of the line
  • If you do not use the line on a regular basis, flush the line at least once per week
  • If you start to feel your line becoming difficult to push, consult your team so they can get you a special solution a nurse can place in your line to help it flow better
Diagnosis: Your team may or may not choose to order a test to assess for a blood clot depending on the situation. If a test is ordered, it may be a venogram, MRI angiography, or Doppler ultrasound. All of these tests are able to view the flow of blood through your blood vessels. Treatment: Treatment will depend on the severity of your clot. In some cases, an anti-thrombolytic agent can be used. These medications are 'clot busters' and are placed directly into your line to break-up the clot. You may also be placed on some form of anticoagulation or blood thinner to help prevent future clots. In some cases, the central line must be removed and replaced.




Infection


Infection is one of the most common complications associated with PN use. Aseptic (sterile) technique is essential when setting up PN and doing anything with your (or your child's) central line. The most common organisms that lead to central line infections include:

  • Gram-positive organisms
  • Coagulase-negative staphylococci
  • Staphylococcus aureus
Signs and Symptoms: (oftentimes correlates with PN infusion)
  • Fever
  • Chills
  • Muscle aches and pains
  • Fatigue and lethargy
Diagnosis: Diagnosis is usually based on blood cultures. Blood cultures can take days to come back, so your (or your child's) team will often initiate a broad-spectrum course of antibiotics if there is clinical suspicion of a bloodstream infection. Treatment: Your team will determine the best antibiotic and antimicrobial treatment for you. Depending on the organism causing the infection often determines if your line will need to be removed and replaced. For example, if you have a fungal infection, gram-negative bacilli, valvular heart disease, multiple organisms, or endocarditis, the line is usually removed. Each case is individualized, and your team will determine the best course for you. Prevention:
  • Wash your hands before and after handling your PN or CVC.
  • Always scrub your catheter hubs for 15 seconds before and after each use.
  • Always cover your central line when taking a shower or getting wet.
  • Never let the tip of your PN tubing touch anything other than the connection with your catheter.
  • Perform cap changes about every 3 days.
  • When your catheter is not in use, be sure it is covered with a cap.
  • Remain completely sterile (completely free from bacteria) while doing dressing changes.





Section 4: Additional Resources

Helpful Animation from Transplant Unwrapped


Coming Soon: SIgn-Up to receive updates for the launch of the Transplant Unwrapped Kid's Website which will contain an animation on PN and Enteral nutrition for kids.




Helpful Website: The Oley Foundation


The Oley Foundation: Visit The Oley Foundation for more information on parenteral and enteral nutrition.




Helpful Website: Feeding Tube Awareness Foundation


Feeding Tube Awareness: Visit this website for a plethora of information on tube feeding for children and useful resources for parents.




Helpful Guide from Toronto General: Taking Care of PN


Taking Care of Your Home Parenteral Nutrition: A useful guide created by Toronto General.




Nestle Health Science Feeding Tube Video Series


Feeding Tube Videos: Nestle HealthScience has put together a set of useful introductory videos on tube feeding.




Page References


References here.




Helpful Download from Transplant Unwrapped


Parent's Guide to Central Venous Catheters (CVCs)





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