Nutrition enterale a visee immunomodulatrice en situation d'agression aigue

Currently there is no conclusive evidence that new formulations of enteral feeding products combining << immunonutrients >> are able to reduce infectious complications or mortality rate in the critically ill patient. The administration of a basic amount of enteral nutrition very early in the course of illness, ideally before the 12th hour, is probably more important than the type of enteral nutrition administered. Early enteral nutrition has been shown to decrease infectious complications in trauma patients and in severe burns, but the efficacy of the method remains to be demonstrated in critically ill patients, especially in cases of severe sepsis. The reduction of intestinal << bacterial translocation >> may partly explain the effects obtained: in this respect polymeric diets, supplemented or not with insoluble fibres, should be preferred to elemental diets which promote bacterial over- growth. No clinical trials in critical care have examined the effect of adding individual immunonutrients to enteral nutrition on outcomes such as infectious morbidity and mortality rates. Experiments in animal models clearly failed to show any improvement with enteral administration of branched-chain amino acids or nucleotides. A body of data from animal experiments, and some recent clinical studies, suggest that constitutive omega-3 fatty acids in fish oil could modulate the inflammatory response of trauma, and that arginine, glutamine and ornithine alpha-ketoglutarate may possess an immunomodulatory potential. Finally, the antioxidant properties of some vitamins (and trace elements) are under investigation and cannot be advocated for clinical practice. Combining immunonutrients to enrich enteral nutrition was the rational underlying the concept of specific nutrition for critically ill patients. This led to three immunologically designed feeding formulas that were recently evaluated in prospective randomized controlled trials, either after major surgery or in critically ill patients. In the majority of cases the immune status of patients was significantly improved compared with that of patients on standard nutrition, although the variability of the methods used to evaluate the immune status should be underscored. These preliminary results have not provided conclusive evidence that combined nutrients reduce infectious complications or mortality rate. However, the length of hospitalization and/or the stay in ICU could be reduced for subgroups of patients, especially in cases of severe sepsis. We should not be discouraged by these relatively disappointing results. On the contrary, they should exert an impact on the design of future studies. We should aim at evaluating individual immunonutrients in rigorously designed randomized trials focused on relevant patient populations instead of conducting wide-ranging, complex multicentric studies in heterogeneous patient populations. Obviously, certain marketing contraints, the excessive duration, and the huge cost of such studies (whose results are not necessarily favourable to the new diets) impose practical limitations which are almost impossible to overcome.