Enteral Nutrition Support Therapy for Adults
Manual of Clinical Nutrition Management B- 36 Copyright © 2013 Compass Group, Inc.
potential for ileus (5). The clinical condition of the patient is an important consideration in the decision to
initiate enteral nutrition. A soft, nontender abdomen, adequate perfusion, and hemodynamic stability are
indicators of the potential for the safe administration of enteral nutrition (3,4). For most patients, lower
gastrointestinal bleeding does not affect the administration of enteral support (4,14).
Nutrition Intervention
Enteral feedings can be nutritionally adequate if an appropriate formula is selected with consideration of
each patient’s individual estimated requirements. Energy requirements may be calculated by predictive
equations or measured by indirect calorimetry (5). Predictive equations should be used with caution, as they
provide a less accurate measure of energy requirements than indirect calorimetry (5). In the obese patient,
the predictive equations are even less accurate (5). (Refer to Section II: Estimation of Energy Requirements.)
Tube feedings may be used as the sole source of nutrients or as a supplement to inadequate oral nutrition.
Enteral nutrition should be initiated within 24 to 48 hours of injury or admission to the ICU, and the average
intake delivered within the first week should be at least 60% of the total the estimated energy requirements,
as determined by the nutrition assessment (Grade II) (3). Provision of enteral nutrition within this time frame
and at this intake level is associated with fewer infectious complications (Grade II) (3). Guidelines for critically ill
patients from ASPEN and the SCCM include similar recommendations (5). These guidelines recommend the
provision of more than 50% to 65% of the estimated energy requirements during the first week of
hospitalization to achieve the clinical benefits of enteral nutrition (4,5). The impact of a specific threshold of
enteral nutrition delivery on mortality, hospital length of stay (LOS), and days on mechanical ventilation is
unclear due to inconsistent results produced by existing studies (Grade II) (3).
Based on limited evidence available, permissive underfeeding rather than overfeeding obese critically ill
patients may produce better medical outcomes. In obese, critically ill adults, the Registered Dietitian (RD)
may consider prescribing hypocaloric, high protein enteral feedings (Grade III) (3). According to the Academy of
Nutrition and Dietetics (AND) guidelines, very limited research in patients receiving enteral nutrition shows
that the effect of hypocaloric, high protein feeding (< 20 kcal per kg adjusted body weight (ABW) and 2 g
protein per kg ideal body weight (IBW) promoted shorter intensive care unit (ICU) stays, although total
hospital length of stay (LOS) did not differ (3). In the group receiving hypocaloric, high protein feedings,
nitrogen balance was not adversely affected (Grade III) (3). Guidelines from ASPEN and the SCCM recommends
permissive underfeeding or hypocaloric feeding with enteral nutrition in the critically ill obese patient (5). For
patients with a body mass index (BMI) greater than 30 kg/m^2 , the goal of the enteral nutrition regimen 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) (5).
In addition to the delivery of energy, the adequacy of protein provision should be assessed on an ongoing
basis (5). The use of additional modular protein supplements is a common practice, as standard enteral
formulations tend to have a high ratio of nonprotein energy to nitrogen (5). The protein requirements of
critically ill patients with a BMI less than 30 kg/m^2 are 1.2 to 2.0 g/kg actual body weight per day; these
requirements may be higher in burn patients or multiple-trauma patients (5). Critically ill patients who are obese
have higher protein requirements to maintain an adequate nitrogen balance and accommodate the needs for
wound healing. The protein requirement for class I and II patients (BMI, 30 to 40 kg/m^2 ) is greater than 2.0
g/kg ideal body weight per day, and the protein requirement for class III patients (BMI >40 kg/m^2 ) is greater
than 2.5 g/kg ideal body weight per day (5).
Antioxidant vitamins (including vitamin E and ascorbic acid) and trace minerals (including selenium, zinc,
and copper) may improve patient outcome, especially in burns, trauma, and critical illness requiring
mechanical ventilation (5). A combination of antioxidant vitamins and trace minerals (specifically selenium)
should be provided to all critically ill patients receiving specialized nutrition therapy (5).
How to Order the Diet
The physician in collaboration with the dietitian determines the appropriate prescription for the enteral
nutrition regimen, including the route and type of formula. A dietitian should facilitate the selection of the
formula type and goal rate for tube feeding. Once the goal rate is reached, a nutrient intake study may be
beneficial to verify that the total nutrient intake (oral plus enteral) is adequate.