Nutritional Assessment & Enteral Nutrition. Controversies
CONTROVERSIES
23. How fat is fat?
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Lean body mass is three times more metabolically active than adipose tissue. Multiple definitions of clinical obesity exist: > 120% ideal body weight (IBW), > 130% IBW, body mass index (BMI) > 30, body fat > 24-28% of body weight in men and > 30-35% in women. Measured weight is a poor indicator of relative adiposity. Self-reported weights or weights reported by family members are often erroneous in the ICU setting. Fluid resuscitation and edema make visual assessment challenging and limit the usefulness of noninvasive technology such as bioelectrical impedance (BIA) for measuring body composition. Although measured energy expenditure in kcal/kg of actual weight may sometimes approach that of normal-weight patients, feeding at the measured body weight level may be associated with profound hyperglycemia, hypercapnea, and the inability to clear triglycerides.
24. Should actual, ideal, or adjusted body weight be used in nutrition calculations for obese patients?
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Studies using an obesity-adjusted weight in kilocalorie calculations (IBW + 0.25 [actual IBW]) report greater correlation with measured energy expenditure than when using actual weight.
25. Which is more important, nitrogen or caloric balance?
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Ultimately, maintaining a positive nitrogen balance may be more important than achieving a positive kilocaloric balance.
26. Are postpyloric feedings superior to gastric feedings?
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After major surgery or injury, the stomach exhibits decreased motility for several days. Early enteral feeding, with its known benefits, may not be accomplished through a gastric feeding in the early stages of injury. Jejunostomy feedings have been associated with higher kilocalorie intake, more timely return to anabolism, and a lower pneumonia (aspiration) rate than continuous gastric feeding.
27. When should immune-enhancing formulas be used?
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Rarely. PRCTs have demonstrated that immune-enhancing diets (IEDs) improve outcome and reduce septic morbidity in patients prone to intraabdominal sepsis after major torso trauma and after major operative resection of upper GI cancers. The use of IEDs should be restricted to these patients, and the duration of use should be limited because of the increased expense. The IEDs have not been adequately tested in other types of patients and, when tested in mixed ICU patients, some evidence suggests that they might even be harmful in addition to being expensive.
28. Are arginine-containing formulas contraindicated in patients with sepsis?
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Arginine is thought to be a semi-essential amino acid in critically ill patients. It is a metabolic fuel for lymphocytes and fibroblasts. It is also a secretagogue for a variety of hormones (most notably growth hormone). PRTs have shown that supplemental arginine improves wound healing and immune responsiveness in high-risk surgical patients. Arginine is also one of the key ingredients of the newer IEDs. The other key ingredients include glutamine, omega-3 fatty acids, and nucleotides. A large number of PRTs have compared IEDs with standard enteral formula and have shown that IEDs reduce infections and decrease hospital length of stay. The most convincing data come from PRTs that have enrolled patients undergoing major upper GI cancer resections. PRTs that have enrolled less homogenous ICU patients have had a difficult time demonstrating improved outcome, and subset analysis suggest that IEDs may be harmful in ICU patients with sepsis. Reviewing the potential immunomodulating effects of the key ingredients in IEDs has led some authorities to hypothesize that arginine supplementation is harmful in the patients with sepsis. These patients exhibit increased levels of inducible nitric oxide synthase (iNOS). Arginine is a substrate for iNOS and, in its presence, arginine combines the molecular oxygen to produce citrulline and nitric oxide (NO). The resulting NO may have numerous adverse effects in sepsis, including vasodilation, cardiac dysfunction, and direct cytotoxic injury by generating potent reactive oxygen (peroxynitrite) species. Unfortunately, little data support or refute this hypothesis.
29. Should formula with increased fish oil be used in patients at risk for acute respiratory distress syndrome (ARDS)?
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One industry-funded PRCT demonstrated superior outcome in patients with ARDS when provided a high omega-3 fatty acid enteral product versus a high-omega-6 “pulmonary” formula. Unfortunately, the control diet is not the standard of care and may worsen ARDS. High omega-6 fatty acids increase inflammation and production of lipid mediators, which worsen V/Q mismatch in the lung, which worsen oxygenation in ARDS. Duplication of the results and comparison with standard, moderate-fat polymeric formula is needed.
References
WEB SITE
http://www.gpnotebook.co.uk/simplepage.cfm?ID=516948028
BIBLIOGRAPHY
1. ASPEN Board of Directors and the Clinical Guidelines Task Force: Guidelines for the use of enteral and parenteral nutrition in adult and pediatric patients. J Parent Enter Nutr 26(suppl 1):1SA-138SA, 2002.
2. Cutts ME, Dowdy RP, Ellersieck MR, Edes TE: Predicting energy needs in ventilator dependent critically ill patients: Effect of adjusting weight for edema or adiposity. Am J Clin Nutr 66:1250-1256, 1997.
3. Gadek JE, DeMichele SJ, Karlstad MD, et al: Effect of enteral feeding with eicopentaenoic acid, gamma-linolenic acid, and antioxidants in patients with acute respiratory distress syndrome. Crit Care Med 27:1409-1420, 1999. Medline Full article
4. Konstantinides FN, Konstantinides NN, Li JC, et al: Urinary urea nitrogen: Too sensitive for calculating nitrogen balance studies in surgical clinical nutrition. J Parent Ent Nutr 15:189-193, 1991.
5. Kozar R, McQuiggan M, Moore F: Nutritional support of trauma patients. In Shikora S, Martindale RG, Schwaitzburg S (eds): Nutritional Considerations in the Intensive Care Unit. Silver Spring, MD, Aspen, 2002, pp 229-244.
6. Malone AM: Is a pulmonary formula warranted for patients with pulmonary dysfunction? Nutr Clin Practice 11:189-191, 1997.
7. McClave SA, Snider HL: Understanding the metabolic response to critical illness: Factors that cause patients to deviate from the expected pattern of hypermetabolism. New Horizons 2:139-146, 1994. Medline Similar articles
8. Montecalvo MA, Steger KA, Farber HW, et al: Nutritional outcome and pneumonia in critical care patients randomized to gastric versus jejunal tube feedings. Crit Care Med 20:1377-1387, 1992. Medline Similar articles
9. Moore FA, Feliciano DV, Andrassy R, et al: Enteral feeding reduces post operative septic complications: A meta analysis. Ann Surg 216:62-71, 1992.
10. Talpers SS, Romberger DJ, Pingleton SK: Nutritionally associated increased carbon dioxide production: Excess total kilocalories vs high proportion of carbohydrate kilocalories. Chest 102:551-555. 1992. Medline Similar articles
11. Van den Berghe G, Wouters P, Weekers F, et al: Intensive insulin therapy in critically ill patients. N Engl J Med 345:1359-1367, 2001. Medline Similar articles
Comments
Abernathy’s Surgical Secrets, Updated Edition (Book w / Student Consult)
Author / s: Harken Alden H., Abernathy Charles, Moore Ernest Eugene
Year: 2004
Pages: 473
Publishers: Elsevier Mosby; 5th Bk & Acc edition
ISBN: 0323034160
