In such cases, the enteral route is preferable to the parenteral route because it causes fewer complications, costs less, and may have a trophic effect on the intestine. Total parenteral nutrition is used when intestinal motility or absorption is abnormal. A total daily caloric requirement of 1.2 to 2 times the basal metabolic rate is generally adequate. The appropriate mixture of substrates, carbohydrates, proteins, and fats to meet the patient's metabolic needs to produce a positive nitrogen balance must be given. This infusion rate also approximates the maximum rate of glucose oxidation for a bedridden patient.
Any additional glucose is converted to fat.
Fats supply essential fatty acids and enough calories to minimize the mobilization of endogenous proteins for energy and gluconeogenesis. Antibiotics may alter the balance in normal gut flora, allowing overgrowth of Clostridium difficile. Diarrhea usually develops within 1 to 10 days after antibiotics are started. In one study of elderly patients, diarrhea developed an average of 2.7 days after antibiotics were started. Sigmoidoscopy may also help make the diagnosis.