As a result, feeding becomes mechanical, rather than an expression of personal preference, social pleasure or cultural tradition. Parenteral nutrition therapy supplies all of the known essential nutrients intravenously, either partially or totally. Total parenteral nutrition, the most aggressive method of nutritional support, involves the infusion of a mixture of amino acids, carbohydrates, fats, vitamins, electrolytes and trace elements. Patients who are unable to be fed through the gastrointestinal tract are candidates for total parenteral nutrition. The large diameter of the superior vena cava, a blood vessel in the neck that leads to the heart and its high rate of blood flow allow concentrated parenteral solutions to be infused safely.
Enteral nutrition is always preferred to parenteral nutrition for many reasons.
First, enteral nutrition helps maintain normal gut function. If the gastrointestinal tract is not used for some time, the cells of the intestine shrink and enzyme activity in the gut is reduced. Second, enteral feeding usually results with fewer complications, since no surgery is involved and there is a decreased risk of infection in comparison to total parenteral nutrition. Finally, enteral nutrition is less costly than total parenteral nutrition. Other complications associated with total parenteral nutrition are related to catheter insertion and metabolic difficulties.