There are times when a patient can not eat, will not eat or
should not eat. There are also times
when a patient is taking in an insufficient number of calories. Examples of these situations are chronic
illness, short term illness or post surgery.
Patients in these situations have to be fed because no matter what our
physical state is, in order to sustain life, our bodies require a certain
amount of calories each day. We need
these calories in order to maintain our weight and nourish our cells.
The abbreviation TPN actually stands for Total Parenteral
Nutrition and depending on the practice setting, the term can be used to
describe all IV feedings or it can be used specifically to say that only IV
feedings that are administered through a central line are called TPN. It depends on the institution. Your institution may use terms such as PPN
which tands for Partial or Peripheral Parenteral Nutrition. Your institution may even use terms like 3 in
1 solution or Total Nutrient Admixture
abbreviated, TNA.
For purposes of this discussion, we are going to consider
all of these to be fundamentally the same.
The difference between TPN and PPN are the concentration of dextrose and
as a result the site of administration.
The difference between TPN and TNA is that the total nutrient admixture
has an extra base solution, etc. As far
as the calculations are concerned, they are basically the same. In other words, once you can do the
calculations for one, you can do the calculations for the others.
So let’s break this topic down into its elemental parts. There are two major components of these
formulations. They are Base solutions
and then Additives.
The base solutions for TPN are Dextrose and Amino
Acids. The base solutions for TNA are
Dextrose, Amino Acids and Lipids. Think
about it, in order to sustain life, our diets must have carbohydrates, fats and
protein. Dextrose is a crbohydrate;
Amino acids are the building blocks of protein and Lipids are fats. These base solutions are stated as
percentages for the most part. The only
exception is the TNA where there is a percentage of Lipid Emulsion (either 10%
or 20%) followed by a volume.
When we are calculating for the amount of base solution to
add, we can use either quantity times strength or the alligation method. So to calculate for each base solution, we
would set up an independent quantity times strength problem or allegation
problem to solve for the volume to be added.
Then there are the additives. Examples of additives are as follows:
Electrolytes
(ex: KCl, NaCl, KPO4, etc)
Insulin
(Regular only)
MVI
(Multivitamins)
Trace
minerals
H2
antagonist (ex: ranitidine, famotadine)
Vitamin
K
Heparin
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