Chapter 073. Enteral and Parenteral Nutrition (Part 2) Decision-making for the implementation of specialized nutrition support (SNS). CVC, central venous catheter; PICC, peripherally inserted central catheter. (Adapted from previous chapter by Lyn Howard, MD.) The first step in deciding to administer SNS is to consider the nutritional implications of the disease process. Is the condition or its treatment likely to impair food intake and absorption for a prolonged period of time? For example, a well-nourished individual can tolerate approximately 7 days of starvation while experiencing a systemic response to inflammation (SRI). The second step is to determine if the patient is already significantly malnourished to the degree that critical functions such as wound healing, immune function, or ventilatory function are impaired (Chap. 72). An unintentional weight loss of >10% during the previous 6 months or a weight/height <90% of standard, when associated with physiologic impairment, represents significant PCM. Weight loss >20% of usual or <80% of standard reflects severe PCM. The presence or absence of SRI should be noted, since inflammation, injury, and infection increase the rate of lean tissue loss. SRI also has pathophysiologic effects that influence nutritional responses such as fluid retention and hyperglycemia, as well as impairment of anabolic responses to nutritional support. Once it is determined that a patient is already or at risk of becoming malnourished, the next step is to decide whether SNS will impact positively on the patient's response to disease. In the end stages of many chronic illnesses with accompanying PCM, particularly those due to cancer or terminal neurologic disorders, nutrition may not reverse the PCM or improve quality of life. While the provision of food and water is part of basic medical care, nutrition delivered by tube or catheter, either enterally or parenterally, is associated with risk and discomfort. Thus, SNS should be recommended only when potential benefits exceed risks, and should be undertaken with the consent of the patient. Like other life support measures, enteral or parenteral therapy is difficult to withdraw once started. Initiating nutrition support may be appropriate before a final prognosis can be determined, but this should not preclude its subsequent withdrawal. If preventing or treating PCM with SNS is appropriate, nutritional requirements and the method of delivery should be determined. The optimal route depends on the degree of gut function and somewhat on the available technical resources. The timing of nutritional support is based on evaluation of the preexisting nutritional status, the presence and extent of SRI, and the anticipated clinical course. SRI is identified by the standard clinical signs of leukocytosis, tachycardia, tachypnea, and/or temperature elevation or depression. Although the degree of hypoalbuminemia provides an estimate of SRI severity, normal serum albumin levels will not be restored by adequate nutritional support until the SRI remits, even though nutritional benefits can be achieved by adequate feeding. The SRI can be graded as severe, moderate, or mild. Examples of severe SRI include sepsis or other inflammatory conditions like pancreatitis requiring ICU care, multiple trauma with an Injury Severity Score > 20–25 or APACHE II > 25, closed head injury with a Glasgow Coma Scale < 8, or major third-degree burns of >40% of body surface area. Moderate SRI includes less severe infections, injuries, or inflammatory conditions like pneumonia, major surgery, acute hepatic or renal insufficiency, and exacerbations of ulcerative colitis or regional enteritis requiring hospitalization. PCM should also be defined as severe, moderate, or minimal as assessed by weight/height, percent recent weight loss, and body mass index. The body mass index in relation to nutritional status is listed in Table 73-1. A patient with a severe SRI requires early feeding within the first several days of care because the condition is likely to produce inadequate spontaneous intake over the next 7 days. A moderate SRI, as commonly seen during a postoperative period without oral intake that exceeds 5 days, benefits from adequate feeding by day 5–7 if the patient was initially well nourished. If severely malnourished, candidates for elective major surgery benefit from preoperative nutritional repletion for 5–7 days. However, this is not often possible. Thus, early postoperative feeding is indicated. Patients with a moderate SRI and moderate PCM also benefit from earlier feeding within the first several days. Table 73-1 Body Mass Index (BMI) and Nutritional Status BMI Nutritional Status >30 kg/m 2 Obese >25–30 kg/m 2 Overweight 20–25 kg/m 2 Normal <18.5 kg/m 2 Moderate malnutrition <16 kg/m 2 Severe malnutrition <13 kg/m 2 Lethal in males <11 kg/m 2 Lethal in females From D Driscoll, B Bistrian: Parenteral and enteral nutrition in the intensive care unit, in Intensive Care Medicine , R Irwin, J Rippe (eds). Lippincott Williams & Wilkins, Philadelphia, 2003. . Chapter 073. Enteral and Parenteral Nutrition (Part 2) Decision-making for the implementation of specialized nutrition support (SNS). CVC, central. Moderate malnutrition <16 kg/m 2 Severe malnutrition <13 kg/m 2 Lethal in males <11 kg/m 2 Lethal in females From D Driscoll, B Bistrian: Parenteral and enteral nutrition. timing of nutritional support is based on evaluation of the preexisting nutritional status, the presence and extent of SRI, and the anticipated clinical course. SRI is identified by the standard