Total parenteral nutrition (TPN), also known as parenteral nutrition (PN) is a form of nutritional support given completely via the bloodstream, intravenously with an IV pump. TPN administers proteins, carbohydrates, fats, vitamins, and minerals. It aims to prevent and restore nutritional deficits, allowing bowel rest while supplying adequate caloric intake and essential nutrients, and removing antigenic mucosal stimuli (Perry et al., 2014). TPN may be short-term or long-term nutritional therapy, and may be administered on acute medical floors as well as in critical care areas. The caloric requirements of each patient are individualized according to the degree of stress, organ failure, and percentage of ideal body weight. TPN is used with patients who cannot orally ingest or digest nutrition (Triantafillidis & Papalois, 2014). TPN may be administered as peripheral parenteral nutrition (PPN) or via a central line, depending on the components and osmolality. Central veins are usually the veins of choice because there is less risk of thrombophlebitis and vessel damage (Chowdary & Reddy, 2010). According to Chowdary & Reddy (2010), candidates for TPN are:
TPN is made up of two components: amino acid/dextrose solution and a lipid emulsion solution (see Figure 8.9). It is ordered by a physician, in consultation with a dietitian, depending on the patient’s metabolic needs, clinical history, and blood work. The amino acid/dextrose solution is usually in a large volume bag (1,000 to 2,000 ml), and can be standard or custom-made. It is often yellow in colour due to the multivitamins it contains. The ingredients listed on the bag must be confirmed by the health care provider hanging the IV bag. The solution may also include medication, such as insulin and heparin. The amino acid/dextrose solution is reviewed and adjusted each day based on the patient’s blood work. Lipid emulsions are prepared in 100 to 250 ml bags or glass bottles and contain the essential fatty acids that are milky in appearance. At times, the lipid emulsion may be added to the amino acid/dextrose solution. It is then called 3 in 1 or total nutrition admixture (Perry et al., 2014). TPN is prepared by a pharmacy, where the calories are calculated using a formula, and is usually mixed for a 24-hour continuous infusion to prevent vascular trauma and metabolic instability (North York Hospital, 2013). TPN orders should be reviewed each day, so that changes in electrolytes or the acid-base balance can be addressed appropriately without wasting costly TPN solutions (Chowdary & Reddy, 2010). Figure 8.9 Types of TPN (amino acids and lipids) Figure 8.10 TPN tubing with special filterTPN is not compatible with any other type of IV solution or medication and must be administered by itself. TPN must be administered using an EID (IV pump), and requires special IV filter tubing (see Figure 8.10) for the amino acids and lipid emulsion to reduce the risk of particles entering the patient. Agency policy may allow amino acids and lipid emulsions to be infused together above the filters. TPN tubing will not have any access ports and must be changed according to agency policy. Always review agency policy on setup and equipment required to infuse TPN. A physician may order a total fluid intake (TFI) for the amount of fluid to be infused per hour to prevent fluid overload in patients receiving TPN. It is important to keep track of all the fluids infusing (IV fluids, IV medications, and TPN) in order to avoid fluid overload (Perry et al., 2014). Do not abruptly discontinue TPN (especially in patients who are on insulin) because this may lead to hypoglycemia. If for whatever reason the TPN solution runs out while awaiting another bag, hang D5W at the same rate of infusion while waiting for the new TPN bag to arrive (North York Hospital, 2013). Do not obtain blood samples or central venous pressure readings from the same port as TPN infusions. To prevent severe electrolyte and other metabolic abnormalities, the infusion rate of TPN is increased gradually, starting at a rate of no more than 50% of the energy requirements (Mehanna, Nankivell, Moledina, & Travis, 2009). Complications Related to TPNThere are many complications related to the administration of TPN (Perry et al., 2014). Table 8.8 lists potential complications, rationale, and interventions.
A patient on TPN must have blood work monitored closely to prevent the complications of refeeding syndrome. Blood work may be ordered as often as every six hours upon initiation of TPN. Most hospitals will have a TPN protocol to follow for blood work. Common blood work includes CBC (complete blood count), electrolytes (with special attention to magnesium, potassium, and phosphate), liver enzymes (total and direct bilirubin, alanine aminotransferase [ALT], aspartate aminotransferase [AST], alkaline phosphatase [ALP], gamma-glutamyl transferase [GGT], total protein, albumin), and renal function tests (creatinine and urea). Compare daily values to baseline values, and investigate and report any rapid changes in any values (Chowdary & Reddy, 2010; Perry et al., 2014). Table 8.9 outlines a plan of care when a patient is receiving TPN.
TPN may be administered in the hospital or in a home setting. Generally, patients receiving TPN are quite ill and may require a lengthy stay in the hospital. The administration of TPN must follow strict adherence to aseptic technique, and includes being alert for complications, as many of the patients will have altered defence mechanisms and complex conditions (Perry et al., 2014). To administer TPN, follow the steps in Checklist 76.
Video 8.7Video 8.8 |