Parenteral nutrition in critical illness: can it safely improve outcomes?

Total parenteral nutrition was developed in the 1960s and has since been implemented commonly in the intensive care unit (ICU). Studies published in the 1980s and early 1990s indicate that the use of total parenteral nutrition is associated with increased mortality and infectious morbidity. These detrimental effects were related to hyperglycemia and overnutrition at a period when parenteral nutrition was not administered according to the all-in-one principle. Because of its beneficial effects on the gastrointestinal tract, enteral nutrition alone replaced parenteral nutrition as the gold standard of nutritional care in the ICU in the 1980s. However, enteral nutrition alone is frequently associated with insufficient coverage of the energy requirements, and subsequent protein-energy deficit is correlated with a worse clinical outcome. Recent evidence suggests that all-in-one parenteral nutrition has no significant effect on mortality and infectious morbidity in patients in the ICU if a glycemic control is obtained and hyperalimentation avoided. Thus, the time has come to reconsider the use of parenteral nutrition in the ICU. Supplemental parenteral nutrition could prevent onset of nutritional deficiencies when enteral nutrition is insufficient in meeting energy requirements. Clinical studies are warranted to show that the combination of parenteral and enteral nutrition could improve the clinical outcome of patients in the ICU.