Contemporary Rationale for Delivering Enteral Nutrition in Critically Ill Adults

OBJECTIVES: To review the rationale for and timing, dose, and monitoring of enteral nutrition and protein delivery in critically ill adults. DATA SOURCES: Medline searches to identify relevant studies, systematic reviews and meta-analyses, and guidelines informing the phases of critical illness, enteral nutrition and protein doses, and monitoring enteral nutrition. STUDY SELECTION: Preclinical and contemporary clinical literature informing the rationale for and timing, dose, and monitoring of enteral nutrition and protein dose in critically ill adults. DATA EXTRACTION: The evidence describing the rationale for and timing, dose, and monitoring of enteral nutrition and protein dose in critically ill adults is summarized. DATA SYNTHESIS: The early delivery of enteral nutrition remains a cornerstone of therapy for critically ill adults. Historically, critical care nutrition guidelines have recommended achieving full-dose enteral nutrition within the first 72 hours of ICU admission. The rationale for delivering early enteral nutrition depends on the phase of critical illness, and providing a restrictive dose during the acute phase preserves gut integrity, supports the microbiome, and modulates immune dysregulation. Contemporary randomized controlled trials comparing enteral nutrition doses during the acute phase of critical illness have found full-dose enteral nutrition, compared with restrictive dose, and may offset the benefit from enteral feeding, causing iatrogenic stresses to the system leading to worse outcomes. Even though critically ill adults have anabolic resistance and undergo skeletal muscle proteolysis, recent trials have found that high-dose protein, compared with standard, does not improve clinical outcomes and may be harmful in certain subsets of critically ill adults. CONCLUSIONS: Contemporary data support the use of restrictive dose enteral nutrition during the acute phase of critical illness. High-dose protein is not superior to lower and is associated with worse outcomes in critically ill adults with acute kidney injury and those with greater severity of illness.