CONTROVERSIES

20. Does preoperative TPN enhance surgical outcome?

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It is well documented that malnourished patients are at an increased risk for septic complications, problems with wound healing, longer hospital stays, and increased mortality. However, nutritional status may be a reflection of the severity of disease. Results of studies evaluating preoperative TPN and outcome are variable. Preoperative TPN may decrease the rate of postoperative complications, but not mortality, in moderately malnourished patients with GI cancers. When malnourished GI cancer patients were fed high-kilocalorie TPN only after surgery, complication rates increased. Perioperative enteral nutrition may lower postoperative complications in patients with a variety of cancers. Provision of immune-enhancing diets, when adequately tolerated, may decrease complications and reduce length of hospital stays after surgical resection of upper GI cancer. In elderly, underweight women with hip fractures, supplemental enteral feedings increase functional status, reduce complications, and decrease length of stay. After major abdominal surgery, early enteral nutrition reduces complications, especially wound infection. Further research is needed in homogenous patient populations using current level of feeding practice and glycemic control in order to determine the impact on outcome of perioperative nutritional support.

21. Should TPN solutions contain the same percentage of fat kilocalories that are recommended in the diet of healthy Americans (i.e., 30% of total kilocalories)?

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The American Heart Association’s (AHA) recommendations for 30% of total kilocalories as fat are geared toward cardiovascular disease prevention in healthy people and were never intended for IV feeding in critically ill individuals. Furthermore, the AHA suggests that those kilocalories should be divided almost equally between saturated; monounsaturated; and polyunsaturated fat, including omega-3 series fatty acids. Current lipid formulations available in the United States are made from either soybean oil or a mixture of soybean and safflower oil; thus, they are predominately polyunsaturated (i.e., omega-6) fat. Glucose kilocalories are the most cost-effective kilocalories, followed by standard amino acid kilocalories, and then lipid calories. Lipid infusions 1 g/kg of body weight have been associated with decreased immunocompetence and oxygenation in critically ill patients.

22. Does supplemental glutamine enhance outcome in surgical patients?

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Glutamine is the amino acid found in greatest concentration in muscle and plasma; it decreases after surgery and injury and with stress. Thus, it is considered a conditionally essential amino acid. It plays a role as a metabolic substrate for rapidly replicating cells, is thought to maintain the integrity and function of the intestinal barrier, and protects against free radical damage because of its role in maintaining GSH levels.

Glutamine is not included in standard amino acid solutions because of limited solubility and stability; in its dipeptide form bound to alanine or glycine, glutamine is more stable and soluble. Supplementation may reduce infectious complication rates and decrease length of hospital stays in surgical patients.

References
WEB SITE
http://www.acssurgery.com/abstracts/acs/acs0623.htm
BIBLIOGRAPHY
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