Evolution of Nutrition in Critical Care: How Much, How Soon?

Abstract

The intensive care unit (ICU) patient presents a number of nutritional challenges. The case mix of patients admitted to ICUs may range from those admitted electively after major elective surgery to those admitted as emergencies after some surgical catastrophe, major trauma, sepsis, or respiratory failure. The variation in age range and prior health status may be extreme and nowadays ICUs are admitting increasingly more elderly, frail, or malnourished patients whose nutritional reserve may be severely compromised. Critically ill patients requiring vital organ support in ICU commonly have anorexia and may be unable to feed volitionally by mouth for periods ranging from days to months. Unless such patients are provided with macronutrients in the form of enteral or parenteral nutrition, they accumulate an energy deficit that rapidly reaches proportions that contribute to lean-tissue wasting and that are associated with adverse outcomes. Nutritional support has gained importance with better understanding of the pathophysiology of protein energy malnutrition (PEM) in ICU patients and optimal modalities in administration of nutritional therapy. The degree of energy deficit accumulating in critically ill patients is strongly associated with the duration of stay in the ICU, which, in turn, is associated with an increased incidence of infectious complications and risk of death.