Enteral nutrition in the critically ill patient: a critical review of the evidence.

OBJECTIVE: To examine the relationship between enteral nutrition (EN) and infection in the critically ill.

SETTING: Computerized search of published research and review of relevant reference lists.

STUDY SELECTION: 151 citations were reviewed and 39 articles met selection criteria. Primary studies were included if they evaluated EN in critically ill humans and its effect on infectious morbidity and mortality.

MEASUREMENTS AND RESULTS: Relevant data were abstracted on the timing and impact of EN on morbidity, the optimal route of administration, composition and pH of EN, and bacterial contamination of EN. The evidence from human studies that EN, particularly early EN, results in reduced septic morbidity as compared to parenteral nutrition is limited to small, unblinded studies with non-rigorous definitions of pneumonia. There is no evidence to support a preference of feeding into the stomach versus the small bowel. The addition of fish oil, arginine, glutamine and fiber to enteral feeds has a variable impact on survival in animal models; there are no trials in critically ill patients that demonstrate a reduction in infectious morbidity and mortality. Acidification of enteral nutrition results in decreased bacterial colonization of the stomach in critically ill patients. Bacterial contamination of enteral nutrition is an important source of infection.

CONCLUSIONS: Evidence from experimental data in critically ill patients suggests that enteral nutrition may have a favourable impact on gastrointestinal immunological function and infectious morbidity.