Does the formulation of enteral feeding products influence infectious morbidity and mortality rates in the critically ill patient? A critical review of the evidence

OBJECTIVE: To examine the relationship between the formulation of enteral nutrition and nosocomial infection in critical illness. DATA SOURCES: Computerized search of published research and reference list review. STUDY SELECTION: Review of 151 citations. Included are 31 primary studies in which the authors described the formulation of enteral nutrition and its effect on infectious morbidity and mortality rates in critically ill humans or animals. DATA EXTRACTION: Abstraction of the methods of primary studies and the impact of the composition of enteral nutrition on infectious morbidity and mortality rates. DATA SYNTHESIS: There is no evidence that the addition of branch-chain amino acids or nucleotides to enteral nutrition reduces infectious morbidity in animals or humans. Supplementation with fish oil, arginine, or glutamine has a variable impact on survival in animal models; there are no clinical trials in critically ill patients that demonstrate reduced infectious morbidity or mortality rates. Some animal studies suggest that intestinal overgrowth and bacterial translocation may be related to the type of fiber used, or elemental or polymeric formulas. Preliminary evidence suggests that Modular Tube Feeds (an enteral formula developed at the Shriner's Burn Institute, Cincinnati, OH), and a commercially available enteral formula (enhanced with omega-3-fatty acids, arginine, and yeast RNA; Impact, Sandoz Nutrition, Minneapolis, MN) may result in decreased infections in burn and postoperative cancer patients, respectively, but not in critically ill patients. Acidification of enteral feeding results in decreased bacterial colonization of the stomach in critically ill patients. CONCLUSIONS: Insufficient experimental data exist to permit conclusions that enteral nutrition formulations or supplements reduce infectious morbidity and mortality rates, but results are promising enough to warrant further research.