title: Parenteral nutrition in the critically ill.
abstract: OBJECTIVE
  Feeding guidelines have recommended early, full nutritional support in critically ill patients to prevent hypercatabolism and muscle weakness. Early enteral nutrition was suggested to be superior to early parenteral nutrition. When enteral nutrition fails to meet nutritional target, it was recommended to administer supplemental parenteral nutrition, albeit with a varying starting point. Sufficient amounts of amino acids were recommended, with addition of glutamine in subgroups. Recently, several large randomized controlled trials (RCTs) have yielded important new insights. This review summarizes recent evidence with regard to the indication, timing, and dosing of parenteral nutrition in critically ill patients.
  
  
  RESULTS
  One large RCT revealed no difference between early enteral nutrition and early parenteral nutrition. Two large multicenter RCTs showed harm by early supplementation of insufficient enteral nutrition with parenteral nutrition, which could be explained by feeding-induced suppression of autophagy. Several RCTs found either no benefit or harm with a higher amino acid or caloric intake, as well as harm by administration of glutamine.
  
  
  CONCLUSIONS
  Although unanswered questions remain, current evidence supports accepting low macronutrient intake during the acute phase of critical illness and does not support use of early parenteral nutrition. The timing when parenteral nutrition can be initiated safely and effectively is unclear.
authors.affiliation: Clinical Division and Laboratory of Intensive Care Medicine, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Gunst
authors.forename: Greet
authors.initials: G
authors.lastname: Van den Berghe
mesh_terms: D003422:Critical Care / Q000379:methods*; D016638:Critical Illness; D002149:Energy Intake; D004750:Enteral Nutrition; D006801:Humans; D018529:Nutritional Support; D010288:Parenteral Nutrition; D016032:Randomized Controlled Trials as Topic