Total Parenteral Nutrition

Overview :

TPN is normally given through a large central vein. A catheter is inserted into the vein in the chest area under local anesthesia and sterile conditions. Often the placement is done in an operating room to decrease the chance of infection. Several different types catheters are used based on the reason TPN is needed and the expected length of treatment. Catheters are made of silicone. Once the catheter is in place, a chest x ray is done to make sure the placement is correct.

Normally TPN is administered in a hospital, but under certain conditions and with proper patient and caregiver education, it may also be used at home for long-term therapy. TPN solution is mixed daily under sterile conditions. Maintaining sterility is essential for preventing infection. For this reason, the outside tubing leading from the bag of solution to the catheter is changed daily, and special dressings covering the catheter are changed every other day.

The contents of the TPN solution are determined based on the age, weight, height, and the medical condition of the individual. All solutions contain sugar (dextrose) for energy and protein (amino acids). Fats (lipids) may also be added to the solution. Electrolytes such as potassium, sodium, calcium, magnesium, chloride, and phosphate are also included, as these are essential to the normal functioning of the body. Trace elements such as zinc, copper, manganese and chromium are also needed. Vitamins can be included in the TPN solution, and insulin, a hormone that helps the body use sugar, may need to be added. The TPN catheter is used only for nutrients; medications are not added to the solution. Adults need approximately 2 liters of TPN solution daily, although this amount varies with the age, size, and health of the individual. Special solutions have been developed for individuals with reduced liver and kidney function. The solution is infused slowly at first to prevent fluid imbalances, then the rate is gradually increased. The infusion process takes several hours.

Successful TPN requires frequent, often daily monitoring of the individual's weight, glucose (blood sugar) level, blood count, blood gasses, fluid balance, urine output, waste products in the blood (plasma urea) and electrolytes. Liver and kidney function tests may also be performed. The contents of the solution are individualized based on the results of these tests.