[The role of nutrition in the intensive care unit]

Clinical (artificial) nutrition in patients in a surgical intensive care unit (ICU) is a supportive, and not a therapeutic, measure. However, it is as necessary as medical or surgical treatment, because nutrition can prolong life, so that time is bought during which the clinician can start adequate treatment. Studies on the effectiveness of clinical nutrition are rare and difficult, but there is a huge amount of indirect evidence supporting the following basic concept. The caloric requirement of an ICU patient is clearly higher than that of a normal person. However, it seldom exceeds 2500 kcal (about 35 kcal kg-1 day-1) and can be satisfied with a standardized regimen. Fat and carbohydrates should be given, with fat amounting to 10% at least and 50% at most of total calories. Glucose administration should be limited to about 500 g day-1. As with calories, the demand for amino acids (100-150 g day-1) is increased in ICU patients due to catabolic illness and nitrogen loss, e.g., via drains, wound. The successful creation of different kinds of a stable and safe access to the gastrointestinal tract for enteral nutrition has opened a true alternative to the well-known practice of parenteral delivery of food to a critically ill patient. Today it is possible to nourish nearly all patients enterally via the stomach or small bowel with commercially available fluid diets. This kind of clinical nutrition obviates the need for concern about the optimal substrate composition. Moreover, enteral nutrition appears to be much simpler and more logical than parenteral nutrition. There is evidence suggesting that there are even clinical advantages of enteral nutrition.