Malnutrition is a common and serious problem in intensive care units. Negative energy balance has been associated with increased morbidity and mortality in critically ill patients. The increased incidence of complications related to malnutrition correlates with increased length of hospital stay and overall health care costs. Although early enteral nutrition is the preferred method of feeding critically ill patients, enteral nutrition alone often fails to supply adequate calories and nutrients to critically ill patients, who are frequently hypermetabolic.~Artificial nutrition support has evolved into a primary therapeutic intervention to prevent metabolic deterioration and loss of lean body mass with the aim to improve the outcome of critically ill patients. Apart from the timing of initiation and the targeted amount of macronutrients, the route of delivery is viewed as an important determinant of the effect of the nutritional intervention.~Using the enteral route is considered to be more physiologic, providing nutritional and various non-nutritional benefits including maintenance of structural and functional gut integrity as well as preserving intestinal microbial diversity.~The disadvantage of enteral nutrition is related to a potential lower nutritional adequacy particularly in the acute disease phase and in the presence of gastrointestinal dysfunction.~In contrast, parenteral nutrition may better secure the intended nutritional intake but is associated with more infectious complications, most likely due to hyperalimentation and hyperglycemia.~Supplementation of insufficient enteral nutrition with parenteral nutrition may optimize nutritional support and avert negative energy balance in critically ill patients, thereby improving outcome.~Combining parenteral nutrition with enteral nutrition constitutes a strategy to prevent nutritional deficit but may increase risk of overfeeding, which has been associated with liver dysfunction, infection, and prolonged ventilatory support.
Supplementation of insufficient enteral nutrition with parenteral nutrition may optimize nutritional support and avert negative energy balance in critically ill patients, thereby improving outcome.