Metabolic and nutritional support of the intensive care patient. Ascending the learning curve.

The learning curve of nutritional support in the critically ill began with the amelioration of the effects of starvation in patients with a disabled intestine. Next, there was an appreciation that feeding formulas could be tailored to support patients with specific organ insufficiencies. Then it was realized that feeding enterally has distinct advantages over feeding parenterally. In addition to a decrease in catheter-related sepsis, there was noted a distinct decrease in "remote site" sepsis. In fact, good scientific reasons have been identified to explain why this occurs, such as maintaining the competency of the intestine against a translocation of endotoxin and bacteria and "turn-on" of the stress response. Further, we now know that specific nutrients can produce desirable pharmacologic effects. In the future, feeding formulae will be devised that continue to modify the patient's response to illness favorably. Another important consideration is to begin nutritional support as soon as possible--i.e., on the day of admission, if appropriate. The critical care specialist should be expert in these techniques, with the goal of eliminating malnutrition as a confounding variable in the clinical course of the intensive care unit patient.