The precise indications for nutritional support remain controversial. Most authorities agree that nutritional support is indicated for at least four groups of adult patients: (1) those with inadequate bowel syndromes, (2) those with severe prolonged hypercatabolic states (eg, due to extensive burns, multiple trauma, mechanical ventilation), (3) those requiring prolonged therapeutic bowel rest, and (4) those with severe protein–calorie undernutrition with a treatable disease who have sustained a loss of over 25% of body weight.
It has been difficult to prove the efficacy of nutritional support in the treatment of most other conditions. In most cases it has not been possible to show a clear advantage of treatment by means of nutritional support over treatment without such support.
The American Society for Parenteral and Enteral Nutrition (ASPEN) has published recommendations for the rational use of nutritional support. The recommendations emphasize the need to individualize the decision to begin nutritional support, weighing the risks and costs against the benefits to each patient. They also reinforce the need to identify high-risk malnourished patients by nutritional assessment.
NUTRITIONAL SUPPORT METHODS
Selection of the most appropriate nutritional support method involves consideration of gastrointestinal function, the anticipated duration of nutritional support, and the ability of each method to meet the patient’s nutritional requirements. The method chosen should meet the patient’s nutritional needs with the lowest risk and lowest cost possible. For most patients, enteral feeding is safer and cheaper and offers significant physiologic advantages. An algorithm for selection of the most appropriate nutritional support method is presented in Figure 29–1.
Nutritional support method decision tree.
Prior to initiating specialized enteral nutritional support, efforts should be made to supplement food intake. Attention to patient food preferences, timing of meals in relation to diagnostic procedures and required medications, and the use of foods brought to the hospital by family and friends can often increase oral intake. Patients unable to eat enough at regular mealtimes to meet nutritional requirements can be given oral supplements as snacks or to replace low-calorie beverages. Oral supplements of differing nutritional composition are available for the purpose of individualizing the diet in accordance with specific clinical requirements. Fiber and lactose content, caloric density, protein level, amino acid profiles, vitamin K, and calcium can all be modified as necessary.
Patients unable to take adequate oral nutrients who have functioning gastrointestinal tracts and who meet the criteria for nutritional support are candidates for liquid artificial nutrition (“tube feedings”). Small-bore feeding tubes are placed via the nose into the stomach or duodenum. Patients able to sit up in bed who can protect their airways can be fed into the stomach. Because of the increased risk of aspiration, patients who cannot adequately protect their airways should be fed nasoduodenally (though, as noted below, this may not ...