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Nutrient Needs and Total Parenteral Nutrition
1. When is it advisable/acceptable to use TPN?
The decision to recommend TPN rather than PPN is based on the number of calories
needed.
Inability to absorb nutrients via the GI tract owing to massive small bowel
resection, diseases of the small intestine, radiation enteritis, severe diarrhea, or
intractable vomiting.
High-dose chemotherapy, radiation, and bone marrow transplantation.
Moderate to severe pancreatitis.
Severe malnutrition in the face of a nonfunctional GI tract.
Severe catabolism with or without malnutrition when the GI tract is not usable
within 5 to 7 days.
Examples: major surgery, moderate stress, enterocutaneous fistulae,
inflammatory bowel disease, hyperemesis gravidarum, moderate malnutrition
requiring intensive medical or surgical intervention.
Inability to establish adequate enteral nutrition w/I a 7-10 day period of
hospitalization.
Inflammatory adhesions with small bowel obstruction.
Intensive cancer chemotherapy.
2. What are the difference between TPN (Central) and PPN (Peripheral) and the factors
associated with appropriate use of each, such as osmolality of solution, etc.?
Central access refers to catheter tip placement in a large, high blood flow vein such as the
superior vena cava. Peripheral access refers to catheter tip placement in a small vein
typically in the arm. Peripheral veins cannot tolerate concentrated solutions; therefore,
diluted larger volume infusions are often necessary to meet nutritional requirements.
Volume-sensitive patients such as those with cardiopulmonary, renal, or hepatic failure
are not good candidates for PPN. Concentrated calories in the form of CHO are
hypertonic solutions. Hypertonic solutions cannot be given in peripheral veins, which
have low blood flow. If a hypertonic solution is given, the area can become infiltrated
and then inflamed, or a thrombosis can occur. This means that it is difficult to administer
a large number of CHO or protein calories with PPN. Fat calories are provided as
isotonic emulsions that can be administered peripherally. Concentrated calories or
hypertonic solutions can be administered directly into the superior vena cava because the
solution is quickly diluted in the blood due to the rapid blood flow. This decreases the
risk of inflammation and venous thrombosis.
3. How to calculate the total calories, grams of protein, grams dextrose, grams fat provided in a
mixed TPN solution?
See sample calculations.
4. How to calculate the total kcal: g N ratio and interpret what it means? Is it the
