TPN Calculations for a 2/1
When you have to calculate the nutrients in a given solution:
REMEMBER:
gm
%
vol
Example: D15%A5% @ 75cc/hr + 10% IL @20cc/hr
Patient wt = 65 kg
1. Calculate the dextrose/AA volume infused in 24 hrs.
75cc/hr x 24 hrs = 1800cc
2. Calculate the grams of dextrose by multiplying the total volume by the concentration
(%) of dextrose.
1800cc x 15% = 270 gms
3. Calculate the GUR (mg/kg/min) by multiplying the gm of dextrose by 1000, then
divide by the patient’s weight in kg, then divide by 24 (hrs), then divide by 60 (min).
270 x 1000 = 270,000 – 65 = 4154 – 24 = 173 – 60 = 2.9 mg/kg/min
4. Calculate the grams of AA (protein) by multiplying the total volume by the
concentration (%) of AA.
1800cc x 0.05 = 90 gms
5. Calculate total calories provided by TPN solution by multiplying the grams of
dextrose and AA by their respective cal/gm. (dextrose = 3.4 cal/gm, AA = 4.0
cal/gm) Then add calories from fat by multiplying the ml infused in 24 hrs by 1.1
cal/ml of 10% IL or 2.0 cal/ml of 20% IL
Dextrose: 270 gm x 3.4 = 918 calories
AA: 90 gm x 4.0 = 360 calories
IL: 480 ml (20ml x 24hrs) x 1.1 cal/ml (10% IL) = 528 calories
918 + 360 + 528 = 1806 total calories
6. Calculate % of calories from fat by multiplying the ml of IL by 10% or 20% to get the
gm of fat, then multiply the number of gm by 9 cal/gm to get fat calories. Then divide
fat calories by the total TPN calories and then multiply by 100 to get %.
480 ml IL x 10% = 48 gm fat x 9 cal/gm = 432 fat calories
432 fat calories – 1806 total calories = 0.239 x 100 = 24% calories from fat
When you have to recommend a TPN order based on a patient’s nutrient needs:
Example: Use Parenteral Case Study and fill in the steps.