Page 428 - Nutrition Essentials for Nursing Practice

416 U N I T 3 Nutrition in Clinical Practice

production, which may complicate weaning from mechanical ventilation. The trend toward
less aggressive feeding has decreased the incidence of this complication.

Fat

Lipid emulsions, made from soybean oil or safflower plus soybean oil with egg phospholipid
as an emulsifier, are isotonic. They are available in 10%, 20%, and 30% concentrations, sup-
plying 1.1, 2.0, and 2.9 cal/mL, respectively. Lipids are a significant source of calories and
so are useful when volume must be restricted or when dextrose must be lowered because
of persistent hyperglycemia. Because all lipid emulsions in the United States are composed
of mostly proinflammatory omega-6 fatty acids, most experts recommend limiting intra-
venous lipids to less than 30% of total calories in noncritical patients and that they should
be used sparingly in critically ill patients (Academy of Nutrition and Dietetics Evidence
Analysis Library, 2012). When PN is used long term, 500 mL of 10% lipids two to three
times a week is recommended to prevent fatty acid deficiency (Academy of Nutrition and
Dietetics Evidence Analysis Library, 2012). Patients with egg allergies may not tolerate lipid
emulsions because they contain egg phospholipids as emulsifiers.

Electrolytes, Vitamins, and Trace Elements

Sodium, potassium, chloride, calcium, magnesium, and phosphorus are the electrolytes
added to parenteral solutions. The amounts of these nutrients infused parenterally are
lower than Dietary Reference Intake (DRI) recommendations because DRI values take into
account the efficiency of intestinal absorption when nutrients are consumed orally. Daily
blood tests are used to monitor electrolyte values until the patient is stable.

Standard adult and pediatric preparations exist for vitamins and trace elements. Paren-
teral multivitamin preparations usually contain all of the vitamins, although a preparation
without vitamin K is available for patients on warfarin therapy.

Trace element preparations contain four trace elements (copper, manganese, selenium,
and zinc) or seven trace elements (iodine, zinc, manganese, molybdenum, selenium, chro-
mium, and copper). Because iron destabilizes other ingredients in parenteral solutions,
a special form of iron must be injected separately as needed.

Medications

Medications are sometimes added to intravenous solutions by the pharmacist or infused
into them through a separate port. Patients receiving PN may have insulin ordered if glu-
cose levels are greater than 150 to 200 mg/dL (levels higher than normal are considered
acceptable because there is no fasting state with continuous infusions). Heparin may be
added to reduce fibrin buildup on the catheter tip. In general, medications should not be
added to PN solutions because of the potential incompatibilities of the medication and
nutrients in the solution.

Initiation and Administration

PN is initiated and administered according to facility protocol, typically as a 24-hour
infusion in critically ill patients. One approach is to initiate PN slowly (i.e., 1 L in the first
24 hours) to give the body time to adapt to the high concentration of glucose and the
hyperosmolality of the solution. After the first 24 hours, the rate of delivery is gradually
increased by 1 L/day until the optimal volume is achieved. Another approach is to initiate
PN at the full volume but with diluted concentrations of macronutrients that are advanced
to full concentration as tolerated.