Parenteral Nutrition Support for AdultsManual of Clinical Nutrition Management B- 51 Copyright © 2013 Compass Group, Inc.
considered when the output is less than 200 mL/day or when enteral access may be placed distal to the
fistula.) (1)
acute exacerbations of inflammatory bowel disease (eg, Crohn disease) complicated by fistulas
radiation therapy or allogeneic bone marrow transplantation
hemodynamic instability with mean arterial pressure < 70 mm Hg
increased doses of vasopressors
increased need for mechanical ventilation
worsening signs of GI intolerance
Contraindications (1,3,6,7)
Parenteral nutrition is not indicated for patients:
who have a fully functional and accessible gastrointestinal tract
for whom venous access cannot be obtained
whose prognosis does not warrant aggressive nutrition support
whose need for parenteral nutrition is expected to be less than 7 days (6)
for whom the risks of parenteral nutrition exceed the potential benefits, such as in cases of severe
hyperglycemia (>300 mg/dL), azotemia, encephalopathy, hyperosmolality (>350 mOsm/kg), and severe
fluid and electrolyte disturbances (3)
Nutrition Intervention
Parenteral Feeding Formulations
The osmolarity of a parenteral formula depends on the energy substrate mixture, primarily the dextrose (5
mOsm/g), amino acid (10 mOsm/g), and electrolyte (1 mOsm/mEq) content (3). For example, the estimated
osmolarity of a parenteral feeding formula that provides 150 g/L of dextrose, 50 g/L of amino acids, and 150
mEq/L of electrolyte additives is 1,400 mOsm/L (3). The maximum osmolarity tolerated by a peripheral vein
is 900 mOsm/L (10,11). Formulas for peripheral vein administration usually require more fluid and a higher
content of fat as an energy source than formulas for central access, as lipids are isotonic (3). Midline catheters
can be used to improve peripheral vein tolerance to the nutrition infusion because these catheters can access
larger veins where the blood flow may dilute the parenteral feeding formulations to a more tolerable
concentration (3). Fluid-restricted, energy-dense formulations should be considered for patients with acute
respiratory failure (6).
Nutrient Sources and Indications
Energy requirements: Mildly permissive underfeeding should be considered, at least initially, for all adult
critically ill intensive care unit (ICU) patients receiving parenteral nutrition (6). The ultimate goal or dose of
parenteral feeding should be 80% of the patient’s energy requirements (6). This strategy avoids the potential
for insulin resistance, greater infectious morbidity, prolonged duration of mechanical ventilation, and
increased length of hospitalization that is associated with excessive energy intake (6). As the patient
stabilizes, parenteral nutrition may be increased to meet energy requirements (6). For obese patients (body
mass index (BMI) >30 kg/m^2 ), the dose of parenteral nutrition with regard to protein and energy provision
should follow the same recommendations given for enteral nutrition (6). Guidelines for critically ill adult
patients from ASPEN and the Society of Critical Care Medicine recommend permissive underfeeding or
hypocaloric feeding with enteral nutrition for obese patients (6). The goal of the enteral nutrition regimen for
obese patients should not exceed 60% to 70% of target energy requirements or 11 to 14 kcal/kg actual body
weight per day (or 22 to 25 kcal/kg ideal body weight per day) (6).
Carbohydrate sources: The most commonly used source of carbohydrate is dextrose. Dextrose in its
monohydrate form provides 3.4 kcal/g. Commercial dextrose solutions are available in concentrations
ranging from 2.5% to 70% (11). These solutions are acidic, with a pH ranging from 3.5 to 6.5 (11). Formulas
with final dextrose concentrations greater than 10% are reserved for central venous access (11). Sugar alcohol
glycerol is a less frequently used carbohydrate source, and it provides 4.3 kcal/g. Parenteral formulas
containing sugar alcohol glycerol are protein sparing and induce a smaller insulin response as compared to
dextrose-based solutions (12-14). More research is needed to determine the efficacy of the routine use of
parenteral formulas that contain sugar alcohol glycerol.
Carbohydrate requirements: The minimum requirements for dextrose are 1 mg/kg per minute
(approximately 100 g/day for a 70-kg person). The maximum amount of carbohydrate tolerated is
approximately 5 to 7 mg/kg per minute (1,15). Hyperglycemia, which is caused by various factors including
stress, is the most common complication of parenteral nutrition (11). When carbohydrate is provided in