Enteral formulations enriched in arginine, omega-3 fatty acids, and glutamine nucleotides are considered to enhance the immune response, and treatments with these formulations are collectively referred to as immunonutrition. The formulations under consideration vary in composition. They are distinguished by high (12-15 g/l) or low (4-6 g/l) arginine, the presence or absence of glutamine and nucleotides, and the concentration of omega-3 fatty acids. The proceedings of the summit on immune-enhancing enteral therapy concluded that immuno-nutrition should be given to malnourished patients undergoing elective gastrointestinal surgery and trauma patients with an injury severity score of >18 or those with an abdominal trauma index of >20. Despite lack of evidence, it was recommended for patients undergoing head and neck surgery and aortic reconstruction, those with severe head injury and burns, and for ventilator-dependent nonseptic patients. The summit did not recommend it for patients with splanchnic hypoperfusion, bowel obstruction distal to the access site, and after major upper gastrointestinal hemorrhage.
In contrast to the conclusions of the summit, systematic reviews of the evidence have given mixed results. The reviews suggested that although immunonutrition did reduce septic complications, the reduction did not result in reduced mortality. In a meta-analysis of 22 randomized controlled trials performed in 2419 critically ill or surgical patients, it was concluded that the amount of argi-nine in the formulations influenced the results. Taken as a whole, in critically ill patients there were no treatment effects on mortality or rates of infectious complications. In fact, there was a suggestion that in critical illness these formulations may increase mortality. To support this possibility, a trial suspended the use of immunonutrition in seriously ill patients after an interim analysis showed increased mortality with immunonutrition in these patients. However, in elective surgical patients immunonutrition reduced complications and length of stay. Since many trauma and septic patients may be critically ill, the recommendations made in the two publications referred to previously are at variance. Other meta-analyses have not separated critically ill and nonseptic patients and have concluded that immunonutrition reduced septic complications and length of stay but criticized the component studies as being variable and overall not altering mortality.
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