Modern parenteral and enteral nutrition in critical care

With both enteral and parenteral feedings, the amount of nutrients required depends on the degree of nutritional depletion, level of hypermetabolism, and the phase of the patient's response to illness or injury. Protein requirements are significantly increased in the critically ill. In skeletal trauma, energy needs are increased approximately 25%, in sepsis, 50%, and in severe burns, 75-100%. Energy requirements increase also but in part are met by body fat reserves. While D5W solutions were once thought to spare body proteins by reducing gluconeogenesis, it is now known that such semi-starvation regimes are deficient by omitting protein intake. Enteral and parenteral feeding techniques have developed as precise methods for administering a balance of required protein and calories. A comprehensive nutritional assessment will determine patient nutrient requirements. The marasmic patient without significant stress will generally require 30-40 kcal/kg and 1.5 g protein/kg of ideal body weight. Such support should lead to a slow weight gain and positive nitrogen balance of 2-6 g nitrogen. In the hypoalbunemic patient with concomitant stress, nitrogen retention will be limited until the stress, i.e. acute injury or infection, is relieved. Nitrogen (g):calorie (kcal) intake will average 1:80. During therapy, nutritional assessment parameters must be measured periodically to evaluate the effectiveness of the nutritional regime.