Route of Administration After the decision is made that nutritional support is required, the appropriate route of administration must be determined. Enteral nutrition should be considered primarily because it is easy to deliver, associated with the fewest complications, linked to enhanced wound healing, and relatively inexpensive (21). Contraindications to this route of delivery include intestinal obstruction, gastrointestinal bleeding, and diarrhea. Many types of preparations are commercially available and can be chosen based on their caloric content, fat content, protein content, osmolality, viscosity, and price. Depending on the patient’s problem, the route of delivery may be through a Dobhoff feeding tube, a gastrostomy tube, or a feeding jejunostomy tube (22). If the gastrointestinal tract is unusable for more than 7 days postoperatively, TPN should be implemented.
Total parenteral nutrition must be delivered through a central vein and has wide acceptance as a means of providing nutritional support for surgically ill patients. It must be delivered through a subclavian or internal jugular vein, and the catheter must be placed using meticulous sterile surgical technique. Only intravenous access lines in the right atrium, superior vena cava, or inferior vena cava can be truly deemed central lines (23). Proper daily care is required to avoid infectious complications. When managed by an experienced team, the most frequent complication, infection, can be minimized (24).
maximal rate of glucose oxygenation in adults is approximately 7 g/kg/day, and glucose administration in excess of the caloric requirements can lead to fatty infiltration of the liver and other metabolic complications. When given by TPN infusion, the dextrose tolerance in critically ill patients is 5 mg/kg/min (24). Insulin should be used to maintain serum glucose concentration between 150 and 250 mg/dL, and it may be added directly to the TPN solution.
4.
Fats. Lipids in a 10% to 20% emulsion can be given as further caloric supplement and supply the essential fatty acids, linoleic acid, and α-linoleic acids. More calories can be given in the form of free fatty acids, which are the major source of energy for most peripheral tissues. When lipids are used as a major source of calories, a minimum of 50 to 150 g per day of glucose should also be given to provide a substrate for the central nervous system. Most patients can tolerate up to 2 g of fat per kilogram of weight per day, and daily dosages should not exceed4goffatper kilogram of weight per day. In critically ill patients, the lipid content should not exceed 1 g/kg/day. These lipid emulsions are isotonic and can be delivered simultaneously with the protein and carbohydrate mixture in a 3-L bag over a 24-hour infusion. In general, 30% to 50% of nonprotein calories should be supplied in lipid form. Serum triglyceride levels should be monitored to ensure that the patient can metabolize the fat.
5.
Electrolytes, vitamins, and minerals. In addition to calories and protein, nutritional support should be maintained in terms of electrolytes, vitamins, and trace elements. Daily maintenance requirements for electrolytes are as follows: sodium, 40 to 50 mEq; potassium, 30 to 40 mEq; magnesium, 8 to 10 mEq; calcium, 2 to 5 mEq; and phosphate, 13 to 25 mmol (24). A number of vitamins and trace elements must also be supplied to ensure that the patient is eumetabolic.
Fluid and Electrolytes Water constitutes approximately 50% to 55% of the body weight of the average woman. Two-thirds of this water is contained in the intracellular compartment. One-third is contained in the extracellular compartment, of which one-fourth is contained in plasma, and the remaining three-fourths is in the interstitium.