The role of the gut in critical illness.

The gastrointestinal tract is a major immunologic organ that must be maximally supported during critical illness. Gastrointestinal tissues require direct contact with nutrients to support their own rapid cellular turnover rate and carry out the multitude of metabolic and immunologic functions needed for successful adaptation to stress. Disruption in the ecologic equilibrium of the gastrointestinal tract often occurs during critical illness and the therapies provided. Problems encountered include stress ulcers, intestinal ischemia, bacterial overgrowth, aspiration pneumonia, bacterial translocation, sepsis, and the systemic inflammatory response syndrome. Early enteral nutrition has been shown to be a viable, economic, and physiologically beneficial way to support the gastrointestinal tract during critical illness. The fortification of enteral formulas with glutamine, arginine, or fiber is being studied to determine each one's unique role in the gut and immunologic changes that occur with severe stress.