# Dimensional Analysis Calculation Help

1. good day all:

i need help calculating the problem below using dimensional anlaysis:

dopamine 800 mg in 250 ml d5w is infusing at 12 ml/h in a patient weighing 195 lbs. you would document that the patient is receiving _______ mcg / kg / min.

i understand that i need to factor the mg to mcg, the lbs to kg, and the h to min.

i tried to solve the problem but i am not coming up with the same answer the book has of 7.22 mcg/kg/min?

thanks!

Joined: Feb '09; Posts: 7
from US

3. Quote from iamruthann
good day all:

i need help calculating the problem below using dimensional anlaysis:

dopamine 800 mg in 250 ml d5w is infusing at 12 ml/h in a patient weighing 195 lbs. you would document that the patient is receiving _______ mcg / kg / min.

i understand that i need to factor the mg to mcg, the lbs to kg, and the h to min.

i tried to solve the problem but i am not coming up with the same answer the book has of 7.22 mcg/kg/min?

thanks!
aren't these sorts of problems fun (not)? nearly as much fun as word problems..."if a train leaves tokepa heading east at 7am, and a roller derby queen leaves boston at 2pm,blahblahblah"

i've set this up as a bunch of sequential multiply/divides. hope it gets formatted ok when you view it.

(800 mg/250 ml) * (1000 mcg/1 mg) * (12 ml/1 hr) * (1 hr/60 min) * (1/195 lb) * (2.2 lb/1 kg)

= 7.2205 mcg/kg/min
4. Thanks! I figured out from your post what I was doing wrong. I had the weight as 195/1 instead of 1/195.
5. Quote from Iamruthann
Thanks! I figured out from your post what I was doing wrong. I had the weight as 195/1 instead of 1/195.
The "wrong" answer of 1407 mikes/kilo/min would be a LOT more exciting! It would probably result in impressively high BP & heart rates, until something bad happened.:uhoh21: