262

Part II Nutrition Assessment, Consequences, and Implications

routinely added to PN solutions include heparin to prevent catheter occlusion, insulin to control blood sugars, and H2 blockers (eg, famotidine) to prevent gastric ulcer formation. Other medications that have been added to PN include antibiotics, aminophylline, metoclopramide, octreotide, and steroids. A pharmacist should be consulted before adding any medication to a PN solution.

Administering Parenteral Nutrition Formula Selection

Central PN solutions are usually categorized as either two-in-one (ie, dextrose + protein) or three-in-one (ie, dextrose + protein + lipids). The concentration of dex- trose above approximately 10% requires central admin- istration due to the high osmolality (31). The type of formula is determined by the individual’s clinical and nutritional status and by the type of IV access. Three- in-one solutions provide all macronutrients daily, while two-in-one dextrose-based PN eliminates the lipids. PN solutions or “bags” can be alternated based on the lipid need, giving a three-in-one bag two to three times per week and the two-in-one bags on the other days. Lipids can be infused separately by “piggybacking” into the IV line using a Y-set; however, this is most often utilized in home PN for the very young, as pro- viding a three-in-one bag with lipids is usually used in adolescents and adults.

Standardized, ready-to-use PN solutions in multi- chamber bags are available in many institutions and may be appropriate for individuals who are medically stable. These standardized solutions may or may not include lipids and usually have moderate levels of elec- trolytes. The RDN should be able to calculate the mac- ronutrient content of the formula, determining the dextrose, amino acid, and lipid content of solutions and making recommendations for vitamin, trace element, and electrolyte content as well. This requires specific expertise and additional training for competency in writing complete PN orders. Boxes 18.5 and 18.6 demonstrate ways to determine the PN prescription (see pages 266–267).

Administration Techniques

PN is usually administered continuously over 24 hours in the hospital because it requires minimal effort and manipulation of the IV lines and facilitates manage- ment of fluid and electrolytes. At home, PN is usually cycled over 8 to 12 hours to allow time away from the IV pump. This can be applied to older adults in nursing facilities. Cycling PN may be more difficult in older adults because it requires increasing the infusion rate of fluid and dextrose in the face of potential

age-related declines in renal and cardiovascular func- tion and carbohydrate metabolism. Tapering (ie, gradually increasing or decreasing the infusion rate at the beginning or end of a cycle) is used to prevent severe changes in blood glucose due to the abrupt infusion or discontinuation of carbohydrate (13). Individuals receiving cyclic parenteral nutrition usually need to be tapered down at the end of the cycle to prevent rebound hypoglycemia. It may also be nec- essary to taper the PN for up to one or two hours, to avoid hyperglycemia at the start of infusion. Infusion pumps are programmed to do this automatically. If the PN needs to be stopped unexpectedly, it should be replaced by D10

for one hour to prevent rebound hypo-

glycemia. If time allows, PN should be decreased to half-rate for at least one hour before discontinuing.

Monitoring Parenteral Nutrition Careful monitoring and pristine catheter care will help to prevent PN-associated complications. Serum levels of electrolytes, BUN, creatinine, visceral proteins, blood or urine sugars, weight, fluid intake and output, vital signs, and current medications should be moni- tored routinely when PN is administered in a nursing facility or at home (21). Table 18.3 provides a sug- gested plan for monitoring home PN. Older adults may need to be monitored more closely than would younger adults because of age-related decreases in compensa- tory mechanisms.

Complications

Complications of PN are typically either mechanical/ catheter related or metabolic. When complications occur, it is important to understand the cause and the treatment. Mechanical/catheter complications relate to the IV access site, catheter, and catheter care (13,21,30). Meticulous catheter care is required to avoid infectious complications, as this can be a very serious, life-threatening complication. Mechanical complications may include development of thrombo- sis, which can be avoided with proper catheter care and an appropriate flushing protocol. Catheter occlu- sion and catheter breakage are serious complications that require a professional experienced with manag- ing that specific catheter. In some cases, the catheter may have to be replaced, but the goal is always to maintain it if possible. Metabolic complications include hyper- or hypoglycemia, electrolyte abnor- malities, and nutrition-related complications such as vitamin or mineral deficiencies as well as essential fatty acid deficiency (13,21). These complications can be mitigated through careful attention to the development and compounding of the PN formula as well as close clinical monitoring (13,21,31). The