An update on nutrition support in the critically ill.

Nutrition support in the critically ill patient has shifted from adjunctive toward fundamental therapy with the publication of high-grade evidence. Early enteral nutrition (EN) is recommended because it is associated with decreased infectious complications and use of EN is associated with decreased mortality and infections compared with parenteral nutrition (PN). EN is not without risks, such as diarrhea or aspiration, but use of prokinetic agents, head of bed elevation, and use of feeding protocols can maximize benefits and minimize risks. Although recently high-grade evidence on nutrition support in the critically ill population has been published, many controversies still exist. In obese patients, use of hypocaloric feedings with increased protein has been demonstrated to promote weight loss and improved glucose management. In nonobese patients, small studies have demonstrated that providing more than 70% or less than 30% of goal caloric intake may be associated with worse outcomes, but more studies are needed. Additional research is also needed to conclude whether withholding intravenous fat emulsions for the first 7 to 10 days of PN reduces infectious complications. Finally, more high-quality studies are needed to define the role of immune-enhancing nutrients such as arginine, glutamine, omega-3 fatty acids, zinc, and selenium.