The most important question upon initiation of enteral feeding is whether the disease process warrants the use of an immune-modulating formula. A recent US Summit on Immunonutrition helped identify those patients who were candidates for an immune-modulating formula . Candidates were designated based on literature showing that use of an immune formula in that particular disease process would favorably impact outcome (compared to use of a standard enteral formula alone). Such candidates would include patients undergoing elective major GI surgery such as esophagectomy, gastrectomy, or pancreatotomy. Trauma with injury severity scores >18 or abdominal trauma index scores >20 (especially if severe head injury is involved) would be candidates for an immune formula. Patients with burns over a total body surface area of >30% would be candidates, as would patients with head and neck cancer. Critically ill patients on mechanical ventilation would also be considered a candidate for an immune-modulating formula, with the exception of those with ongoing sepsis. In any of these patients, an immune arginine-containing formula should be utilized and should be provided for at least 10-14 days before switching back to a standard formula .
Caution is indicated in those patients who are critically ill who have ongoing sepsis, with the concern related to the possibility that arginine would stimulate inducible nitric oxide synthetase leading to production of nitric oxide and worsening hypotension. Such concern is based primarily on two studies in the literature by Bower  and Bertilini  and a third unpublished study by Ross/Abbott Laboratories . In two of the studies, the Bower study and the unpublished study by Ross, mortality was 2-21/2 times greater in patients receiving the immune-enhanced formula compared to controls receiving standard formula [55, 57]. In the third study by Bertilini mortality was higher in the group receiving an immune-enhanced enteral formula compared to controls receiving PN . In all three of these studies, less than 25-30% of patients had sepsis, and only in the Bower study was a truly high arginine-containing formula utilized [55-57]. In contrast, in a different study by Galban in which 100% of the patients were septic, use of a high-arginine formula improved mortality compared to controls receiving a standard formula . Not surprisingly, in animal models with sepsis, supplementation with arginine in most studies improved survival .
Until more studies are available, the consensus opinion indicates that there is probably no evidence of a deleterious effect of arginine-containing immune formulas in a systemic inflammatory response syndrome alone. Use of arginine-containing immune formulas should be initiated if patients are not septic and meet the criteria for candidacy for use of an immune formula. Once started, such formulas may be continued if the patient becomes septic. However, if the patient is septic at initiation of enteral feeding, use of a non-arginine immune formula or standard formula is probably indicated.
If patients are not candidates for an immune formula, a standard enteral formula (at 1 cal/cc) should be utilized (Table 10.3). The only other decision upon initiating enteral feeding with regard to formula selection pertains to whether or not there is possible malassimilation (either maldigestion from pancreatic insufficiency or malabsorption because of abnormalities in small bowel physiology). In these situations, use of a small peptide formula fortified with medium-chain triglyceride oil or a fiber-containing formula may improve assimilation. Specialty formulas designed for chronic liver disease, respiratory failure, diabetes, stress, or renal failure are rarely indicated (because of increased cost and the fact that no data exist to show an impact from their use on patient outcome).
Once feeding has been initiated, monitoring for tolerance is important. The clinician should evaluate segmental contractility. Evidence that the stomach is functioning is indicated by a nasogastric output < 1, 200ml/day (in light of the fact that over 5,000ml/day are produced
Table 10.3 Categorization of Enteral Formulas
• Oral supplements
Rationale - Carbohydrate added to facilitate taste
Examples - Carnation Instant Breakfast, Boost, Ensure, Resource
• Enteral formulas (primarily for tube only; exceptions* are palatable and may be used orally)
Standard - 1 kcal/ml, standard protein (35-45 g/l)
Examples - Osmolite, Isocal, Nutren*, Isosource High protein - Higher protein content (45-65 g/l), 1.5 kcal/ml
Examples - Osmolite HN, Isocal HN, Replete*, Promote High caloric density - 2 kcal/ml
Examples - 2Cal HN*, Nutrin 2.0, Resource 2.0 Fiber containing - Fiber added to reduce diarrhea
Examples - Fibersource, Jevity, Ultracal, Probalance Elemental - Protein as individual amino acids, nearly fat free
Examples - Vivonex TEN, Free Amino Acid (FAA), Vital HN Semi-elemental - Protein as small chain peptides, fat mostly as MCT oil Examples - Peptamen*, Subdue*, Peptinex, Perative, Alitraq
• Specialty formulas
Pulmonary - Higher fat:carbohydrate ratio to reduce CO2 production
Examples - Pulmocare, Nutren Pulmonary Hepatic - Higher branch chain:aromatic AA ratio to I encephalopathy
Examples - Nutrihep, Hepaticaid Renal - Higher essential AA to t nitrogen cycling, better electrolyte profile
Examples (PreDialysis) - Renal Cal, Suplena (Dialysis) - Nepro, Novasource Renal Diabetic - Lower nonprotein calorie:nitrogen ratio, alternate carb sources
Examples - Glucerna, Resource Diabetic, Glytrol Inflammatory bowel - Transforming Growth Factor Beta added to I inflammation
Example - Modulin Immune modulating - Arginine to t immunity, omega-3 fish oil to I inflammation Examples - Crucial, Impact, Resource Arginaid through salivary and gastric secretion). Small bowel contractility may be evaluated by abdominal distention, presence of bowel sounds, and air-fluid levels on abdominal radiograph. Contractility in the colon may be indicated by passage of flatus and stool. Use of gastric residual volume is a very poor, inaccurate measure of gastric emptying and overall tolerance of enteral feeding. Identification and correction of electrolyte abnormalities and reassessment of the need for sedation and analgesia may help improve tolerance and minimize ileus. Naloxone (Narcan; Endo Pharmaceuticals, Inc., Chadds Ford, PA) may be given through the feeding tube into the small bowel to remove the effects of opioid narcotics at the level of the bowel without disturbing central nervous system analgesia. Minimizing the period that the patients are NPO helps improve tolerance. Clinicians should be encouraged to "feed an ileus" as long as there is no evidence of septic hypotension or need for pressor agents.
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WHAT IT IS A three-phase plan that has been likened to the low-carbohydrate Atkins program because during the first two weeks, South Beach eliminates most carbs, including bread, pasta, potatoes, fruit and most dairy products. In PHASE 2, healthy carbs, including most fruits, whole grains and dairy products are gradually reintroduced, but processed carbs such as bagels, cookies, cornflakes, regular pasta and rice cakes remain on the list of foods to avoid or eat rarely.