TPN
Meaning of TPN: The word total is the whole point: nothing is expected of the gut, so every nutrient has to be in the bag.
Definition of TPN
TPN stands for total parenteral nutrition, a complete feeding formula delivered into a vein rather than through the gut. It supplies all the protein, calories, fat, vitamins, minerals and fluid a person needs, usually through a catheter whose tip sits in a large vein near the heart. The word total marks it as the sole source of nourishment.
Why does TPN need a central line?
The formula is far more concentrated than blood, mainly because of the sugar dissolved in it. Pushed into a small vein in the arm, that concentration irritates the vessel wall and inflames it within days. A catheter threaded so its tip lies in a large vein close to the heart puts the formula straight into a fast, high-volume stream that dilutes it immediately. Weaker mixtures can run into an arm vein for a short course, an arrangement called peripheral parenteral nutrition, but they cannot carry enough calories to meet full needs for long.
What does the word total exclude?
| Term | What it supplies | Does the gut contribute? |
|---|---|---|
| Total parenteral nutrition | Everything the person requires | No |
| Partial parenteral nutrition | Part of the requirement | Yes, some intake by mouth or tube |
| Enteral nutrition | All or part, delivered by tube | Yes, absorption is still required |
The distinction is not academic. A formula intended to be the only source has to contain trace elements and vitamins that a partial formula can leave to the diet, and it is built to a fuller specification for that reason.
When is it used?
TPN is started when the digestive system cannot be relied on at all: a blocked or leaking bowel, an intestine too short after surgery to absorb what is put into it, severe inflammatory disease, or vomiting and diarrhea that will not stop. It is also used through intensive treatment such as high-dose chemotherapy, radiation to the abdomen, or a bone marrow transplant, when the lining of the gut is damaged and feeding through it is neither tolerated nor absorbed. Once running, it is monitored closely, since blood sugar, salts, kidney and liver tests all shift in response to it, and the mixture is recalculated rather than repeated unchanged. The older word hyperalimentation means the same thing and survives in some records. Stopping abruptly is avoided because the body has adapted to a steady sugar load, and the rate is usually stepped down instead.
Also known as
Used in a sentence
TPN was initiated through a central line after the patient was unable to tolerate oral or tube feeding.
Good to know
TPN specifically denotes a complete nutritional formula given by vein, as distinguished from partial parenteral nutrition, which supplements rather than replaces some intake through the digestive tract.