Question

Can someone please tell me if these calculations are correct! I'm reviewing my notes, and my professor said to always multiply the lipids by 3 and then divide by 7 to get the total amount of cals of lipids per day... I'm not completely sure why you do that? Can someone explain. Why don't you just stop at 700 cals for lipids?

1. Calculate the number of calories and grams protein for the following TPN solution:
D50W in 500cc
10% AA in 500cc
20% lipids in 350cc (given piggy back 3 times a week)
Flow rate: 75cc/h x 24h

The total number of calories is 2,190 kcals on Monday, Wednesday, and Friday (lipids) and 1,890 on the days with no lipids, and the total grams of protein is 90 grams.

Total Formula Volume: 75 ml/ hr x 24 hours = 1800 mL (1.8 L)

            Dextrose: 500 mL x 1.8 L = 900 mL

            AA: 500 mL x 1.8 L = 900 mL

Dex: 900 mL x 0.5 g/mL = 450 g x 3.4 kcal/g = 1,530 kcal dextrose

AA: 900 mL x .10 g/mL = 90 grams protein x 4 kcal/g = 360 kcal protein

Lipids: 350 mL x 2 cal/mL = 700 kcal x 3 days = 2100 kcal / 7 days = 300 kcals

Total kcals: 1,530 + 360 + 300 = 2,190 kcals (MWF- 3 days with lipids)

                    2,190 – 300 = 1,890 (calories for days without lipids)

Answer 1

Three is the multiplication factor (it is number of days where lipid is given) for lipid and if you want to know about daily requirement then you have to divide the lipid value from the week which is seven day in a week that's why you have to multiply lipid by three and to get the daily dose, divide by seven as they are not providing daily. Seven hundred Cal from lipids are given only for three day, not for whole week, that's why if 700 Cal/ day given, so its would be 2100 Cal for 3 days only and if you want to evaluate its daily content then divide by 7 that will tell you 300 Cal per day.

All the calculations are correct but please make uniformity in the unit, like if you are using litre then use litre through out. Example

Dex 0.5 lit x 1.8 = 0.9 litre (900 mL)

Protein (AA)= 0.5 x 1.8 L= 0.9 L (900mL) and since its 10% so amount would be 900/10=90 mL or 90 gm (if specific gravity is 1). Remaining calculations are also correct.