Total Parenteral Nutrition (TPN)

Parenteral nutrition is the intravenous introduction of nutrients needed for metabolic functioning.

Total parenteral nutrition (TPN) contains glucose, amino acids, vitamins, and minerals.

Lipids are fat emulsion of 10%-20 percent. It contains triglycerides, egg phospholipids, glycerol, and water. If lipids are needed with TPN, they are given intermittently or mixed in with the TPN solution.

Total nutrient admixture (TNA) is a highly concentrated form of parenteral nutrition that is given through a central vein. It contains a dextrose solution of 20% or higher. Higher glucose concentration should be administered through a central venous line because the high venous flow rate rapidly dissipates the high osmolarity. TNA is indicated for parenteral nutrition needed for more than 7 days.

Peripheral Parenteral nutrition (PPN) is given through a peripheral vein and has a lower concentration of glucose that should not exceed 12.5%. Higher concentrations of glucose have a high osmolarity that can cause damage to the peripheral venous endothelium, resulting in venous thrombosis and sclerosis. PPN has fewer calories and usually a larger percentage of calories are provided by lipids rather than carbohydrates. PPN is indicated for parenteral nutrition needed for less than 7 days. PPN is not used in some facilities because the risk of infection outweighs the short term nutritional benefits.

The goals of nutrition therapy for the patient include preventing unwanted weight loss and skin breakdown, promoting positive nitrogen balance, and maintaining visceral and somatic protein stores. The patient needs adequate calories and protein to achieve these goals, but providing them can be very difficult during acute illness or injury. The keys to successful nutrition therapy are identifying malnutrition or nutritional risks and intervening early (Collins & Navarre, 2003).

Illness and injury promote catabolism and hypermetabolism, so the patient is burning calories faster to keep up with his body's demands. If he doesn't get adequate nutrition, his body will break down lean muscle for glucose, which could slow healing and prolong his recovery (Collins & Navarre, 2003). TPN reduces morbidity and mortality, promotes tissue repair, and enhances the immune response (Merck, n.d.). Parenteral nutrition is indicated when a there is an extended period where a patient cannot tolerate enteral nutrition or where complete bowel rest is indicated. Some conditions causing this are (Merck, n.d.):

• Paralytic ileus
• Intestinal obstruction
• Acute pancreatitis
• Malabsorption
• Persistent vomiting
• Severe diarrhea
• Congenital anomalies
• Major abdominal surgery

TPN may also be used for patients with significant burns, major trauma, or sepsis. Severely malnourished patients may be given TPN before and after major surgery, radiation therapy, or chemotherapy to improve and maintain their nutritional status.

In 2001, the American Gastroenterological Association presented the following contraindications for TPN in adults (Henninger, 2004):

• Cancer patients undergoing chemotherapy or radiation therapy
• Alcoholic hepatitis
• Mild acute pancreatitis
• Acute colitis
• Crohn's disease (steroid therapy is indicated as being more effective)
• Acquired immunodeficiency syndrome (AIDS)
• Pulmonary disease

Patients receiving TPN must be closely monitored. Glucose should be monitored several times a day until stable, and then at least daily. Intake and output as well as weight should also be monitored daily. Lab tests that are monitored daily when TPN is initiated are CBC, plasma urea, electrolytes including magnesium and phosphate, and blood gases (Merck, n.d.). The frequencies of the lab test are reduced when the patient stabilizes. Liver function tests, plasma proteins, prothrombin time, plasma and urine osmolality, calcium, magnesium, and phosphate should be measured twice a week (Merck, n.d.). A 24-hour urine test for urine urea nitrogen is done weekly. A nutritional assessment should be repeated at 2 week intervals (Merck, n.d.).

Compromises in nutrition can increase the morbidity and mortality of critically ill patients; however, TPN is sometimes not used because of the risk of infectious complications is thought to be greater then the nutritional benefits of TPN (Deshpande, 2003). The complications of TPN may be metabolic (relating to the nutritional formula) of nonmetabolic (faults in the delivery techniques).

Nonmetabolic complications that may occur during placement of the central line include pneumothorax, hematoma, and air embolism. Proper placement of the central line catheter tip must always be confirmed by chest x-ray before infusion.

Thromboembolism and catheter-related sepsis are the most common serious complications of TPN therapy. Common organisms include Staphylococcus aureus, Candida sepsis, Klebsiella pneumoniae, Pseudomonas aeruginosa, S. albus, and Enterobacter sepsis. Fever during TPN should be investigated. If no cause is found and the temperature remains elevated for > 24 to 48 h, central catheter infusion should be stopped (Merck, n.d.). Before the catheter is removed, blood for culture should be drawn directly from the central catheter and catheter infusion site. After removal, 2 to 3 in of the catheter tip should be cut off with a sterile scalpel or scissors; placed in a dry, sterile culture tube; and sent for bacterial and fungal culture (Merck, n.d.).

Central venous catheter related infections greatly increase morbidity, mortality, and length of stay. One study found that bloodstream infections could be reduce from 22.9/1000 catheter days to 6.2/1000 catheter day when a uniform protocol stressing sterile insertion and proper site care was instituted (Deshpande, 2003). Facility policies for the care and use of central and peripheral lines should be followed closely when administering TPN. Central line catheters impregnated with antiseptics and coated with antibiotics are now available and are associated with a significant decrease in infectious complications (Deshpande, 2003).

Refeeding syndrome occurs when malnourished patients are introduced to normal nutrition orally, enterally or parenterally (Marinella, 2003). When the body is starved over time, and is then flooded with nutrients, the body cannot manage the nutrients and a hypermetabolic state ensues. Electrolyte depletion of potassium, magnesium, and phosphorus, fluid shifts, and glucose derangements can result in cardiac failure, muscle weakness, immune dysfunction, peripheral edema, hyperglycemia, osmotic diuresis, decreased gastric motility, ketoacidosis, malignant ventricular dysrhythmias, dyspnea, myalgia, rhabdomyolysis, diaphragmatic weakness and death (Marinella, 2003). Conditions that may cause severe malnutrition are anorexia nervosa, chronic vomiting, malignancy, and alcoholism (Marinella, 2003). Patients at risk for refeeding syndrome should have any type of nutrition, including parenteral nutrition slowly commenced, and frequent monitoring of serum electrolytes is needed (Marinella, 2003).

There are some standard, weight based TPN formulas. Additionally, TPN may also be formulated individually for a patient, particularly in the case of preexisting disease. The TPN formula and administration rate is a physician order; but, a specialized pharmacist, nurse, or dietician may be assisting and making recommendations. TPN is prepared in the pharmacy. The solution is prepared using aseptic technique under a laminar-flow filtered-air hood. The solutions are usually made up in liter batches. A patient without hypermetabolism or severe chronic disease requires 2 L of the standard formula per day (Merck, n.d.). Lipid emulsions supplying essential fatty acids and triglycerides may be used in addition to a basic solution.

TPN solution should be started slowly at 50% of the calculated patient requirements, making up the balance of fluid with 5% dextrose or normal saline. Energy and nitrogen sources should be given simultaneously (Merck, n.d.). The amount of regular insulin given (added directly to the TPN solution) depends on blood glucose estimations. The usual starting dose is 5 to 10 U regular insulin/L TPN fluid containing 25% dextrose in the final concentration (Merck, n.d.).

Remove TPN and lipids from the refrigerator at least an hour before hanging. TPN solution should be clear, not cloudy. Lipids will be white. Do not use the fluid if cracking or creaming of the fluid is present because it may indicate fluid separation.

TPN must be administered using an IV pump and infused via a dedicated line or lumen of the central venous catheter (CVC). TPN should be filtered with a 0.2 micron filter. Lipids may not be filtered. If so a 1.2 micron filter is needed to avoid clogging up the fluid. Line integrity should not to be compromised except for changing the bag or line. No bolus injections may be given into a TPN line. TPN should be infused at a constant rate over 24 hours unless otherwise ordered (MedAU, n.d.). Once a patient is stabilized, cyclic TPN can be provided in a shorter time if appropriate.

The facilities procedure for site care and line changes should be followed. When flushing a central line, use a 10 cc syringe or larger. Smaller syringes exert excessive pressure that might break the line. The power flushing technique creates turbulence in the line for more effective clearing of the line. To do this you briskly inject 2 ml of saline, stop very briefly, and then inject another 2 ml. Continue this process until you have completed the flush. As you inject the last 2 ml, clamp the catheter. This provides positive pressure to keep blood from backing up into the catheter. When flushing central lines, keep in mind the acronym SASH.

  S     Saline flush prior to using the line to administer any medication. Heparin is not compatible with other medications. If you inject medication into the line without clearing the heparin flush, the medication may precipitate.
     
  A     Administer the medication.
     
  S     Saline flush to clear the medication from the line before administering the heparin flush.
     
  H     Heparinize the catheter when not in use.

To make the desired heparin flush solution of heparin 10 units/ml:

1. Use a 10 cc syringe
   
2. Draw up 1 ml of heparin (100 units/ml)
   
3. Dilute with 9 ml of normal saline
   

Result = 10 cc of heparin: 10 units/ml

The following sections include flushing volumes recommended in the Lippincott Manual of Nursing Practice (Nettina, 2001). However, you need to follow the policy of the facility where you are working. You also need to consider the length of the tubing from point of entry to termination point.

A central venous access device (VAD) can be either tunneled or non-tunneled. A central venous non-tunneled catheter is a long flexible catheter that is threaded into a brachial, femoral, jugular or subclavian vein. The central catheter may have either a single, double or triple lumen. Each lumen ends at a different point along the catheter. Therefore, you can use each lumen for a different purpose. Flush each lumen with 5-10 ml. of 10 units/ml heparin twice each day or after each infusion, or according to your institution’s policy.

Central venous tunneled catheters are longer lasting central lines. The catheter runs under the skin for 10 cm instead of going directly through the skin into the vein. Fibrotic tissue that grows around the cuff acts as a barrier to microorganisms and prevents catheter dislodgement. It should be flushed with 2 ml. of 10 units/ml heparin every day. If it is accessed at least every 8 hours, there is no need for a heparin flush between infusions.

The procedure is different for a Groshong catheter because it has a valve. For the Groshong catheter, flush with 10 ml. normal saline every week. After drawing blood from the catheter, flush with 10-20 ml. of normal saline. No heparin flush is needed for the Groshong catheter.

A venous access port (VAP) is an implanted device that is entirely under the skin. There are no external parts. It has a reservoir in a subcutaneous pocket on the chest wall. The reservoir is attached to a catheter that terminates in the superior vena cava, or at the junction of the superior vena cava and the right atrium. The reservoir is usually metal with a “rubber stopper” that is self-sealing. The reservoir is accessed through the “rubber stopper.” Ports are accessed with a special needle that is non-coring. A common brand is called a Huber needle. These needles have an angled or deflected point that slices the silicone septum of the device upon entry, rather than coring it as a conventional needle does. Using a conventional needle will damage the device. The Huber needle may be straight or bent at a right angle.

Ports may have a top entry or side entry. You can palpate the reservoir to find the rubbery feeling access. To enter the port, you should hold the reservoir between your fingers and thumb to secure it. Insert the non-coring needle through the skin and through the septum until you feel it hit the bottom of the reservoir.

After accessing a port, flush with 5 ml. normal saline followed by 5 ml. of 1:100 units/ml heparin. If the port is not being used, it should be flushed every 4 weeks with 5-7 ml. of 1:100 units /ml heparin.

Peripherally Inserted Central Venous Catheters (PICC)

PICCs are usually inserted into the basilic, median cubital or cephalic vein on the inner aspect of the arm, near the elbow. A PICC should be flushed with 2-3 ml. of heparin 10 units/ml every day.

TPN may be used for long-term administration in the home setting. This enables persons who have lost small-bowel function to lead useful lives. Extensive training of the patient and/or caregivers is needed to avoid contamination risks and incorrect administration.

Psychological challenges that arise may be that the Individual experience difficulties in dealing with their new body image, and their dependence on a new method of feeding. TPN can also cause changes in a person's sleeping habits. Sleep deprivation due to multiple bathroom visits during the night, noise of equipment, and problems finding a comfortable position that will not effect the equipment during sleep time is a common difficulty faced by TPN patients. One solution is to infuse some or all the TPN nutrition during the day. Another solution is to keep a bed-pan/commode next to the bed for nighttime voiding (Henninger, 2004). TPN will alter a person's social life, because feeding schedules must be maintained, no matter what. The patient must also adapt to not eating regular food in a society where most social gatherings revolve around food (Henninger, 2004).

TPN is an important tool in maintaining nutrition for patients for which oral or enteral nutrition is not possible. However, it has a high risk of complications and requires close monitoring.

Collins, N. & Navarre, A. (2003). Managing nutrition in an acutely ill patient. Nursing. 33(6), 32H6. Retrieved July 27, 2004 from ProQuest.

Deshpande, K. (2003). Total parenteral nutrition and infections associated with use of central venous catheters. American Journal of Critical Care. 12(4). 326. Retrieved July 27, 2004 from ProQuest.

Henninger, M. (2004). An introduction to enteral and parenteral nutrition. The Exceptional Parent. 34(6). 68-70. Retrieved July 27, 2004 from ProQuest.

Marinella, M. (2003). The refeeding syndrome and hypophosphatemia. Nutrition Reviews. 61(9), 320. Retrieved July 27, 2004 from ProQuest.

MedAU. (n.d.). ICU a procedure manual. Retrieved July 27, 2004 from www.medicineau.net.au/clinical

Nettina, S. (2001). The Lippincott Manual of Nursing Practice (7th ed.). Lippincott, Philadelphia.

The Merck Manual. (n.d.). Nutritional support. Retrieved July 27, 2004 from http://www.merck.com/mrkshared/mmanual/section1/chapter1/1c.jsp.