Food and Nutrient Delivery

Nasogastric Route

Nasogastric tubes (NGTs) are the most common way to access the GIT. They are generally appropriate only for those requiring short-term EN, which is defined as 3 or 4 weeks. Typically, the tube is inserted at the bedside by a nurse or dietitian. The tube is passed through the nose into the stomach (Figure 14-2). Patients with normal gastrointestinal function tolerate this method, which takes advantage of normal digestive, hormonal, and bactericidal processes in the stomach. Rarely, complications can occur (Box 14-1).

NG feedings can be administered by bolus injection or by intermittent or continuous infusions (see “Administration” later in this chapter). Soft, flexible, and well-tolerated polyurethane or silicone tubes of various diameters, lengths, and design features may be used, depending on formula characteristics and feeding requirements. Tube placement is verified by aspirating gastric contents in combination with auscultation of air insufflation into the stomach or by radiographic confirmation of the tube tip location. Techniques for placing a tube are described by Metheny and Meert (2004).

Gastric versus Small-Bowel Feeding

The decision to use a small-bowel feeding tube versus a gastric tube is multifaceted. It is much easier to place tubes into the stomach; therefore gastric feedings generally result in a patient being fed sooner. However, ease of access is only one consideration. Gastric feedings may not be well tolerated, especially in critically ill patients (see Chapter 39). Signs and symptoms of intolerance to gastric feeding include abdominal distention and discomfort; vomiting; and persistent, high gastric residuals (defined as more than 400 mL). Patients receiving gastric feedings are often thought to be at higher risk of aspiration pneumonia, but this is debatable (Bankhead et al., 2009).

Nasoduodenal or Nasojejunal Route

For those patients unable to tolerate gastric feedings who require relatively short-term nutrition support, a nasoduodenal tube (NDT) or a nasojejunal tube (NJT) is indicated. This requires that the tip of the tube pass through the pylorus and into the duodenum or pass all the way through the duodenum and into the jejunum. Positioning of these tubes requires one of the following techniques: (1) intraoperative placement (generally not just for the purpose of placing a feeding tube), (2) endoscopic or fluoroscopic guidance, (3) spontaneous placement that depends on a gastric tube migrating into the duodenum by peristalsis, or (4) bedside placement using a computer guidance system (Figure 14-3). Spontaneous migration of a gastric tube cannot be used for an NJT. Confirmation that the tube has migrated to the correct position can take several days and requires x-ray confirmation. This can result in delayed feedings

Gastrostomy or Jejunostomy

When enteral feedings are necessary for more than 3-4 weeks, gastrostomy or jejunostomy should be considered to prevent some of the complications related to nasal and upper GIT irritation (see Box 14-1) and for the general comfort of the patient (Figure 14-4). These procedures can be done surgically and this may be the most efficient method if the patient is otherwise undergoing surgery (e.g., patients undergoing esophagectomies commonly have jejunal feeding tubes placed at the time of surgery). Nonoperative procedures are now far more common.

The percutaneous endoscopic gastrostomy (PEG) is a nonsurgical technique for placing a tube directly into the stomach through the abdominal wall; the technique is performed using an endoscope, with the patient under local anesthesia. Tubes are endoscopically guided from the mouth into the stomach or the jejunum and then brought out through the abdominal wall. The short procedural time required for insertion, limited need for anesthesia, and minimum wound complications also make it preferable for the physician and others caring for the patient.

PEG tubes used are generally large bore (feeding tubes are measured as french size), making clogging less likely. It is possible to convert a PEG to a gastrojejunostomy by threading a small-bore tube through the PEG tube into the jejunum using either fluoroscopy or endoscopy. PEGs may have a short piece of tubing that can be used to inject feedings with a syringe or to connect to a feeding bag. PEGs that are “low profile” are flush to the skin. These feeding tubes, also known as “buttons”, are a good choice for those patients prone to pulling on their tubes (e.g., children, older adults with dementia). They are also beneficial for those who are active and want to avoid the bulkiness of a feeding tube under their clothing.

Other Minimally Invasive Techniques

High-resolution video cameras have made percutaneous radiologic and laparoscopic gastrostomy and jejunostomy enteral access an option for patients in whom endoscopic procedures are contraindicated. Using fluoroscopy, a radiologic technique, tubes can be guided visually into the stomach or the jejunum and then brought out through the abdominal wall to provide the access route for enteral feedings. Laparoscopic or fluoroscopic techniques are used in some facilities and offer alternative options for enteral access (Nikolaidis, 2005).

Multiple Lumen Tubes

Gastrojejunal dual tubes are available for either endoscopic or surgical placement. These tubes are designed for patients in whom prolonged gastrointestinal decompression is anticipated. The multiple lumen tube has one lumen for decompression and one to feed into the small bowel. These tubes are used for early postoperative feeding.

Protein

The amount of protein in enteral formulas varies from 6% to 25% of total kilocalories. The protein is typically derived from casein, whey, or soy protein isolate. Standard formulas provide intact protein, whereas elemental or predigested formulas have protein as di- and tripeptides and amino acids. The latter require less digestion. Specialized formulas may have the protein as crystalline amino acids for conditions such as renal or hepatic failure. These truly elemental formulas may also be used in the case of severe allergies. (Gottschlich 2006), In some cases specific amino acids have been added to enteral formulas. For example, arginine is added to renal products and critical care products because it is considered to be a conditionally essential amino acid in those clinical situations. See Chapter 39 for further discussion.

Carbohydrate

The percentage of total calories provided as carbohydrates in enteral formulas varies from 30% to 85% of kilocalories. Corn syrup solids are usually the carbohydrate found in standard formulas. Sucrose is added to flavored formulas that are meant for oral consumption. Hydrolyzed formulas have carbohydrate from cornstarch or maltodextrin. A recent innovation in the carbohydrate component of enteral formulas is fructooligosaccharides (FOS). These oligosaccharides are fermented to short-chain fatty acids and used as fuel by colonocytes (Charney, 2006).

Formulas are lactose-free. Lactose is not used as a carbohydrate source in most formulas because lactase deficiency is common in acutely ill patients. Fiber or carbohydrate that cannot be digested by human enzymes, although digested by colonic microflora into short-chain fatty acids, is frequently added to enteral formulas. Fibers are classified as water soluble (pectins and gums) or water insoluble (cellulose or hemicellulose) (see Chapters 1 and 3). The effectiveness of different fibers in enteral formulas used to treat gastrointestinal symptoms in acutely ill patients is controversial (see Chapter 39).

Lipid

Lipid varies from 1.5% to 55% of the total kilocalories in enteral formulas; between 15% and 30% of the total kilocalories of standard formulas are provided by lipids, usually from corn, soy, sunflower, safflower, or canola oils. Elemental formulas usually have minimum amounts of long-chain fat. Approximately 2% to 4% of daily energy intake from linoleic and linolenic acid is necessary to prevent essential fatty acid deficiency (EFAD). The remainder of the fat in enteral formulas is in the form of long-chain and medium-chain triglycerides (MCTs). Formulas contain a combination of ω-3 fatty acids and ω-6 fatty acids. The ω-3 fatty acids include eicosapentaenoic acid and docosahexanoic acid. These are considered advantageous compared with ω-6 fatty acids because of their antiinflammatory effect; see Chapter 6.

MCTs can be added to enteral formulas because they do not require bile salts or pancreatic lipase for digestion and are absorbed directly into the portal circulation. Most formulas provide 0% to 85% of fat as MCTs. MCTs do not provide the essential linoleic or linolenic acids; they must therefore be provided in combination with long-chain triglycerides.

Vitamins, Minerals, and Electrolytes

Most, but not all available formulas are designed to meet the dietary reference intakes (DRIs) for vitamins and minerals if a sufficient volume is taken. However, DRIs are intended for healthy populations, not for acute or chronically ill people. Formulas intended for use in renal and hepatic failure are intentionally low in specific vitamins, minerals, and electrolytes. In contrast, disease-specific formulas often are supplemented with antioxidant vitamins and minerals with the intention of improving immune function and accelerating wound healing. Electrolytes are provided in relatively modest amounts compared with the oral diet and may require supplementation when diarrhea or drainage losses occur.

Fluid

Fluid needs for adults can be estimated at 1 mL of water per kilocalorie consumed, or 30 to 35 mL/kg of usual body weight (see Chapter 7). Without an additional source of fluid, tube-fed patients may not get enough free water to meet their needs, particularly when concentrated formulas are used. Standard (1 kcal/mL) formulas contain approximately 85% water by volume, but concentrated (2 kcal/mL) formulas contain only approximately 70% water by volume. All sources of fluid being given to a patient receiving EN, including feeding tube flushes, medications, and intravenous fluids, should be considered when determining and calculating a patient’s intake. Additional water can be provided through the feeding tube as needed.

Bolus

The feeding modality of choice when patients are clinically stable with a functional stomach is the syringe bolus method (see Figure 14-4). Syringe bolus feedings administered in 5 to 20 minutes are more convenient and less expensive than pump or gravity bolus feedings, and should be encouraged when tolerated. A 60-mL syringe is used to infuse the formula. If bloating or abdominal discomfort develops, the patient is encouraged to wait 10 to 15 minutes before proceeding with the remainder of formula allocated for that feeding. Patients with normal gastric function can usually tolerate 500 mL of formula at each feeding. People receiving home EN may tolerate greater volumes of formula over time. Three or four bolus feedings per day can provide the daily nutritional requirements for most patients. Feedings should be at room temperature because cold formula can cause gastric discomfort.

Intermittent Drip

Quality-of-life issues are often the reason for the initiation of intermittent drip feeding regimens, which allow mobile patients more free time and autonomy compared with continuous drip infusions. These feedings can be given by pump or gravity drip. Gravity feeding is done by pouring formula into a feeding bag with a roller clamp. The clamp is adjusted to the desired drips per minute. A schedule is based on four to six feedings per day administered for 20 to 60 minutes. Formula administration is initiated at 100 to 150 mL per feeding and increased incrementally as tolerated. Success with this method of feeding depends largely on the degree of mobility, alertness, and motivation of the patient to tolerate the regimen.

Continuous Drip

Continuous drip infusion of formula requires a pump. This method is appropriate for patients who do not tolerate large-volume infusions during a given feeding such as those occurring with bolus or intermittent methods. Patients with compromised gastrointestinal function because of disease, surgery, cancer therapy, or other physiologic impediments are candidates for continuous drip infusion. Patients that are being fed into the small intestine should be fed only by continuous drip infusion. The feeding rate goal, in milliliters per hour, is set by dividing the total daily volume by the number of hours per day of administration (usually 18 to 24 hours). Feeding is started at one quarter to one half of the goal rate and is advanced every 8 to 12 hours to the final volume.

Formulas can generally be started at full strength; however, high osmolality formulas may require more time to achieve tolerance and should be advanced conservatively. Dilution of formulas is not necessary and can lead to underfeeding.

Modern enteral pumps are small and easy to handle. Many pumps are battery operated for up to 8 hours in addition to being electrically powered, allowing flexibility and mobility for the patient. Most pumps have a complete delivery system available, including bags and tubing compatible with proper pump operation.

Monitoring for Complications

Abdominal leakage of gastric contents from a gastrostomy site can cause skin erosion and skin breakdown, leading to infection and peritonitis; however, fewer than 10% of patients experience serious complications. Other complications can be prevented or managed with careful patient monitoring. Box 14-3 provides a comprehensive list of complications associated with EN.

Aspiration is a concern for patients receiving EN and is also a controversial topic because many experts believe the issue is not aspiration of formula into the airway, but aspiration of throat contents and saliva. To minimize the risk of aspiration, patients should be positioned with their heads and shoulders above their chests during and immediately after feeding (ASPEN, 2010, Bankhead et al., 2009).

There is confusion in the literature as to the efficacy of checking gastric residuals, because procedures are not standardized and the practice of checking residuals does not protect the patient from aspiration. Stable patients, especially those who have been fed by tube for long periods, do not need residuals checked regularly. Also, it is difficult to aspirate the stomach contents, and the residuals may contain more secretions and gastric fluids than formula. In critically ill patients the best methods for decreasing the risk of aspiration are elevating the head of the bed, continuous subglottic suctioning, and oral decontamination (American Dietetic Association, 2010; Bankhead et al., 2009).

Diarrhea is a common complication, often from colonic bacterial overgrowth, antibiotic therapy, and gastrointestinal motility disorders associated with acute and critical illness. Hyperosmolar medications such as magnesium-containing antacids, sorbitol-containing elixirs, and electrolyte supplements can also contribute to diarrhea. Adjustment of medications or administration methods can frequently correct the diarrhea. The addition of FOS, pectin, and other fibers, bulking agents, and antidiarrheal medications can also be beneficial. Use of a predigested formula can also be considered when managing diarrhea in a tube-fed patient.

Among stable patients receiving EN, constipation can become a problem. Fiber-containing formulas or stool-bulking medication may be helpful, and adequate fluid must be provided. Again, medications should be reviewed. Narcotic pain relievers have the side effect of slowing GIT activity. Gastrointestinal motility should be assessed because diarrhea can coexist with constipation, usually when there is also a fecal impaction.

Monitoring for Tolerance and Nutritional Intake Goals

Monitoring the patient’s actual intake and tolerance is necessary to ensure that nutrition goals are achieved and maintained. Monitoring of metabolic and gastrointestinal tolerance, hydration status, and nutritional status is extremely important (Box 14-4). It is important to avoid use of blue dye to evaluate the contents of aspirate; the risks outweigh any perceived benefit (American Dietetic Association, 2010). Another concern is gastroparesis or high gastric residuals. In these cases, a promotility drug may be beneficial to increase gastrointestinal transit, improve EN delivery, and improve feeding tolerance (American Dietetic Association, 2010). The development and use of practice guidelines, institutional protocols, and standardized ordering procedures are helpful to ensure optimal, safe monitoring of EN (ASPEN, 2010).

It is important to monitor actual intake compared with prescribed intake. During routine patient care, feeding time is commonly lost from the prescribed feeding schedule as a result of (1) a dislodged tube, (2) gastrointestinal intolerance, (3) medical procedures requiring discontinuation of feeding, and (4) difficulties with the feeding tube position. When feedings must be turned off for long periods of time the result can be inadequate nutrition and adjustment in the tube feeding regimen should be made. For example, if tube feedings are being turned off for 2 hours every afternoon for physical therapy, the rate on the feeding should be turned up and the length of feeding time decreased to accommodate the therapy schedule.

Peripheral Access

Nutrient solutions not exceeding osmolalities of 800 to 900 mOsm/kg of solvent can be infused through a routine peripheral intravenous angiocatheter placed in a vein in good condition (Matarese and Steiger, 2006). Protocols for dressing changes and rotation of the site are used to prevent thrombophlebitis, the principal complication of peripheral catheters.

A beneficial development in peripheral catheter technology is the extended dwell catheter. These catheters are sometimes called midline or midclavicular catheters, depending on their position. Extended dwell catheters require a vein large enough to advance the catheter 5 to 7 inches into the vein. These catheters can remain at the original site for 3 to 6 weeks and make PPN a more feasible option in patients with veins large enough to tolerate the catheter (Krzywda et al., 2005).

Short-Term Central Access

Catheters used for CPN ideally consist of a single lumen. If central access is needed for other reasons, such as hemodynamic monitoring, drawing blood samples, or giving medications, multiple-lumen catheters are available. To reduce the risk of infection, the catheter lumen used to infuse CPN should be reserved for that purpose only. Catheters are most commonly inserted into the subclavian vein and advanced until the catheter tip is in the superior vena cava, using strict aseptic technique. Alternatively, an internal or external jugular vein catheter can be used with the same catheter tip placement. However, the motion of the neck makes this site much more difficult for maintaining the sterility of a dressing. Radiologic verification of the tip site is necessary before infusion of nutrients can begin. Strict infection control protocols should be used for catheter placement and maintenance (Krzywda et al., 2005). Figure 14-5 shows alternative venous access sites for CPN; femoral placement is also possible.

A peripherally inserted central catheter (PICC or PIC) may be used for short- or moderate-term infusion in the hospital or in the home. This catheter is inserted into a vein in the antecubital area of the arm and threaded into the subclavian vein with the catheter tip placed in the superior vena cava. Trained nonphysicians can insert a PICC, whereas placement of a tunneled catheter is a surgical procedure (Krzywda et al., 2005). All catheters must have radiologic confirmation of the placement of the catheter tip prior to initiating any infusion.

Long-Term Central Access

A commonly used long-term catheter is a “tunneled” catheter. This single- or multiple-lumen catheter is placed in the cephalic, subclavian, or internal jugular vein and fed into the superior vena cava. A subcutaneous tunnel is created so that the catheter exits the skin several inches from its venous entry site. This allows the patient to care for the catheter more easily as is necessary for long-term infusion. Another type of long-term catheter is a surgically implanted port under the skin where the catheter would normally exit at the end of the subcutaneous tunnel. A special needle must access the entrance port. Ports can be single or double; an individual port is equivalent to a lumen. Both tunneled catheters and PICCs can be used for extended therapy in the hospital or for home infusion therapy. Care of long-term catheters requires specialized handling and extensive patient education.

Protein

Commercially available standard PN solutions are composed of all the essential amino acids and only some of the nonessential crystalline amino acids. Nonessential nitrogen is provided principally by the amino acids alanine and glycine, usually without aspartate, glutamate, cysteine, and taurine. Specialized solutions with adjusted amino acid content that contain taurine are available for infants, for whom taurine is thought to be conditionally essential.

The concentration of amino acids in PN solutions ranges from 3% to 20% by volume. Thus a 10% solution of amino acids supplies 100 g of protein per liter (1000 mL). The percentage of a solution is usually expressed at its final concentration after dilution with other nutrient solutions. The caloric content of amino acid solutions is approximately 4 kcal/g of protein provided. Approximately 15% to 20% of total energy intake should come from protein (Kumpf et al., 2005).

Specialized solutions for patients with renal or liver disease are available, but are used infrequently because of their expense and the lack of conclusive research data supporting their efficacy. Recently, the amino acid glutamine has been suggested as an additive for patients requiring PN in the critical care setting (Martindale, 2009). Glutamine is not yet readily available in a commercial form and is therefore not routinely added to PN formulations.

Carbohydrates

Carbohydrates are supplied as dextrose monohydrate in concentrations ranging from 5% to 70% by volume. The dextrose monohydrate yields 3.4 calories per gram. As with amino acids, a 10% solution yields 100 g of carbohydrates per liter of solution. The use of carbohydrates (100 g daily for a 70-kg person) ensures that protein is not catabolized for energy during conditions of normal metabolism.

Maximum rates of carbohydrate administration should not exceed 5 to 6 mg/kg/min in critically ill patients. When PN solutions provide 15% to 20% of total calories as protein, 20% to 30% of total calories as lipid, and the balance from carbohydrate (dextrose), infusion of dextrose should not exceed this amount. Excessive administration can lead to hyperglycemia, hepatic abnormalities, or increased ventilatory drive (see Chapter 35).

Lipid

Lipid emulsions, available in 10%, 20%, and 30% concentrations, are composed of aqueous suspensions of soybean or safflower oil, with egg yolk phospholipid as the emulsifier. Lipid emulsions should not be used when a patient has an egg allergy. The three-carbon molecule, glycerol, which is water soluble, is added to the emulsion. Glycerol is oxidized and yields 4.3 kcal/g.

Dietitians may be asked to calculate what the patient is receiving. A 10% emulsion provides 1.1 kcal/mL, a 20% emulsion provides 2 kcal/mL, and 30% emulsion provides 2.9 kcal/mL. Providing 20% to 30% of total calories as lipid emulsion should result in a daily dosage of approximately 1 g of fat per kilogram of body weight. Administration should not exceed 2.5 g of lipid emulsion per kilogram of body weight per day. In the hospital lipid is infused during 24 hours when mixed with the dextrose and amino acids. Alternatively, lipids can be provided separately by infusion via an infusion pump. For adult patients receiving PN at home, the PN will most often be infused during 10-12 hours per day with the lipid as part of the PN solution.

Approximately 10% of calories per day from fat emulsions provide the 2% to 4% of calories from linoleic acid required to prevent EFAD. Soybean and safflower oils are rich sources of linoleic acid, providing approximately 40%. Linoleic acid alters prostaglandin metabolism, thereby producing both proinflammatory and immunosuppressive effects, particularly at high doses and at faster infusion rates (Mizock and DeMichele, 2004). Therefore it is important not to use high doses of linoleic acid in the solutions.

Electrolytes, Vitamins, Trace Elements

General guidelines for daily requirements for electrolytes are given in Table 14-3, for vitamins in Table 14-4, and for trace elements in Table 14-5. Parenteral solutions also represent a significant portion of total daily fluid and electrolyte intake. Once a solution is prescribed and initiated, adjustments for proper fluid and electrolyte balance may be necessary, depending on the stability of the patient. The choice of the salt form of electrolytes (e.g., chloride, acetate) affects acid-base balance.

Because parenterally administered vitamins and trace elements do not go through the digestive and absorptive processes, these recommendations are lower than the DRIs. Recently a review of the micronutrient needs of patients receiving PN, especially those receiving long-term home parenteral nutrition (HPN), has raised awareness of the need for careful review of patient requirements compared with the content of current trace element formulations. Monitoring of manganese and chromium status is recommended for patients receiving PN for longer than 6 months (Buchman, 2009). Iron is not normally part of parenteral infusions because it is not compatible with lipids and may enhance certain bacterial growth. Additionally, care must be taken to ensure that a patient can tolerate the separate iron infusion. When patients receive iron on an outpatient basis, the first dose should be done in a controlled setting (such as an outpatient infusion suite) to observe for any reactions that the patient might experience.

Fluid

Fluid needs for PN or EN are calculated similarly. Maximum volumes of CPN rarely exceed 3 L, with typical prescriptions of 1.5 to 3 L daily. In critically ill patients volumes of prescribed CPN should be closely coordinated with their overall care plan. The administration of other medical therapies requiring fluid administration, such as intravenous medications and blood products, necessitates careful monitoring. Patients with cardiopulmonary, renal, and hepatic failure are especially sensitive to fluid administration. For HPN, higher volumes may be best provided in separate infusions. For example, if additional fluid is required as a result of high output by the patient, then a liter bag of intravenous fluid containing minimal electrolytes may be infused during a short time during the day if the PN is infused over night. See Appendix 32 on calculating PN prescriptions.

Compounding Methods

PN prescriptions have historically required preparation or compounding by competent pharmacy personnel under laminar airflow hoods using aseptic techniques. Hospitals may have their own compounding pharmacy or may purchase PN solutions that have been compounded outside the hospital in a central location, and then returned to the hospital for distribution to individual patients. A third method of providing PN solutions is to utilize multichamber bag technology whereby solutions are manufactured in a quality-controlled environment using good manufacturing processes. These PN solutions are standardized but are available in multiple formulas with varying amounts of dextrose and amino acids, making them suitable for CPN or PPN infusion. They contain conservative amounts of electrolytes or may be electrolyte free. These products have a shelf life of 2 years and do not need to be refrigerated unless the product covering has been opened to reveal the infusion bag (Figure 14-6). Institutions frequently use standardized solutions, which are compounded in batches, thus saving labor and lowering costs; however, flexibility for individualized compounding should be available when warranted (Kumpf et al., 2005).

Prescriptions for PN are compounded in two general ways. One method compounds all components except the fat emulsion, which is infused separately. Solutions are usually mixed in one bag at a 1 : 1 dextrose-to-amino acid volume ratio. The second method combines the lipid emulsion with the dextrose and amino acid solution and is referred to as a total nutrient admixture or 3-in-1 solution. The PN Safe Practices Guidelines provide practitioners with information on many techniques and procedures that enhance safety and prevent mistakes in the preparation of PN (Seres, 2006).

A number of medications, including antibiotics, vasopressors, narcotics, diuretics, and many other commonly administered drugs, can be compounded with PN solutions. In practice this occurs infrequently because it requires specialized knowledge of physical compatibility or incompatibility of the solution contents. The most common drug additives are insulin for persistent hyperglycemia and histamine-2 antagonists to avoid gastroduodenal stress ulceration (Kumpf et al., 2005). One other consideration is that the PN usually is ordered 24 hours prior to its administration, and patient status may have changed.

Continuous Infusion

Parenteral solutions are usually initiated below the goal infusion rate via a volumetric pump and then increased incrementally over a 2- or 3-day period to attain the goal infusion rate. Some practitioners start PN based on the amount of dextrose, with initial prescriptions containing 100 to 200 g daily and advancing over a 2- or 3-day period to a final goal. With high dextrose concentrations, abrupt cessation of CPN should be avoided, particularly if the patient’s glucose tolerance is abnormal. If CPN is to be stopped, it is prudent to taper the rate of infusion in an unstable patient to prevent rebound hypoglycemia, low blood sugar levels resulting from abrupt cessation. For most stable patients this is not necessary.

Cyclic Infusion

Individuals who require PN at home will benefit from a cyclic infusion; this entails infusion of PN for 8- to 12-hour periods, usually at night. This allows the person to have a free period of 12 to 16 hours each day, which may improve quality of life. The goal cycle for infusion time is established incrementally when a higher rate of infusion or a more concentrated solution is required. Cycled infusions should not be attempted if glucose intolerance or fluid tolerance is a problem. The pumps used for home infusion of PN are small and convenient, allowing mobility during daytime infusions. Administration time may be decreased because of patient ambulation and bathing, tests or other treatments, intravenous administration of medications, or other therapies.

Monitoring and Evaluation

As with enteral feeding, routine monitoring of PN is necessary more frequently for the patient receiving PN in the hospital. For patients receiving HPN, initial monitoring is done on a weekly basis or less frequently as the patient becomes more stable on PN. Monitoring is done not only to evaluate response to therapy, but to ensure compliance with the treatment plan.

The primary complication associated with PN is infection (Box 14-6). Therefore strict adherence to protocols and monitoring for signs of infection such as chills, fever, tachycardia, sudden hyperglycemia, or elevated white blood cell count are necessary. Monitoring of metabolic tolerance is also critical. Electrolytes, acid-base balance, glucose tolerance, renal function, and cardiopulmonary and hemodynamic stability (maintenance of adequate blood pressure) can be affected by PN and should be monitored carefully. Table 14-6 lists parameters that should be monitored routinely.

The CPN catheter site is a potential source for introduction of microorganisms into a major vein. Protocols to prevent infection vary and should follow Centers for Disease Control Prevention guidelines (Centers for Disease Control and Prevention [CDC] and O’Grady, 2002). Catheter care and prevention of catheter-related bloodstream infections are of utmost importance in both the hospital and alternate settings. These infections are not only costly but may be life-threatening. Catheter care is dictated by the site of the catheter and the setting in which the patient receives care.