CHAPTER 20 | Nutrition Support 311


intravenous multivitamin preparations now contain vitamin K. Although vitamin K administration may interfere with anticoagulation therapy, current rec- ommendations suggest managing this with consistent vitamin K intake and not avoidance of it, either in the oral diet or in the intravenous multivitamin. Multi- ple trace element preparations contain zinc, copper, selenium, and manganese. Some vitamins and trace elements can be ordered as single additives if needed.


Medications


The use of PN as a method of medication administra- tion is not recommended because of potential incom- patibility between the drug and other components of the solution, the inability to adjust or discontinue the dosage without discontinuing the solution, and the necessity to infuse PN continuously rather than intermittently. Medications added to PN solutions may include insulin to control blood glucose and H2 histamine blockers (eg, famotidine) to prevent gastric ulcer formation. A pharmacist should be consulted before adding any medication to a PN solution.31


Administering Parenteral Nutrition Formula Selection


Central PN solutions are usually categorized as either two-in-one (ie, dextrose plus protein) or three-in-one (ie, dextrose plus protein and lipids) solutions. A concentration of dextrose greater than approximately 10% requires central administration due to the high osmolality.30,31


The type of formula is determined by


the individual’s clinical and nutritional status and by the type of intravenous access. For two-in-one solu- tions, ILE can be infused separately by “piggybacking” into the intravenous line using a Y-set; however, this is most often used in home PN for young children, as providing a three-in-one bag with ILE daily is typi- cally used for adolescents and adults. Standardized, ready-to-use PN solutions in multi-


chambered bags are available in many institutions and may be appropriate for individuals who are medically stable. These standardized solutions may or may not include ILEs and usually have moderate levels of elec- trolytes. All contents of PN solutions should be labeled carefully. The RDN should be able (1) to calculate the


macronutrient content of the formula, (2) determine the dextrose, amino acid, and lipid content of solu- tions, and (3) make recommendations for vitamin, trace element, and electrolyte content as well. This requires specific expertise and additional training for competency in writing complete PN orders.2,22,31,32


Box


20.6 on page 312 demonstrates ways to determine the macronutrient component of the PN prescription.


Administration Techniques


PN is typically administered continuously over 24 hours in the hospital because it requires minimal manipulation of the intravenous lines and facilitates management of fluid and electrolytes. At home, PN is usually cycled over 8 to 12 hours to allow time away from the intravenous pump. This cycling can also be applied to older adults in nursing facilities. However, cycling PN may be more difficult with older adults because it requires increasing the infusion rate of fluid and dextrose in the face of potential age-related declines in kidney and cardiovascular function 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 carbohy- drate.2,22


For individuals receiving cyclic PN, the PN


usually needs to be tapered down at the end of the cycle to prevent rebound hypoglycemia. It may also be necessary to taper the PN up for 1 or 2 hours to avoid hyperglycemia at the start of a cyclic infusion. Infu- sion pumps are programmed to do this automatically. If the PN needs to be stopped unexpectedly, it should be replaced with an infusion of 10% dextrose solution (D10) for 1 hour to prevent rebound hypoglycemia. If time allows, PN should be decreased to half-rate for at least 1 to 2 hours before discontinuing.28


Monitoring Parenteral Nutrition


Careful monitoring and pristine catheter care help to prevent PN-associated complications. The following should be monitored routinely when PN is adminis- tered in a nursing facility or at home: serum levels of electrolytes, blood urea nitrogen, creatinine, and vis- ceral proteins as well as blood or urine sugars, weight, fluid intake and output, vital signs, and current


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