Dimensional Analysis Question

crb613, BSN, RN · Mar 29, 2005

Hi all ~
We had our Nursing Care of the Child Rearing Family final today, and one of the questions was a cc/hr question.
Basically, it said " Pedi pt weighs 20 lb. Order is 1000ml/1st10kg/day. How many cc's per hour should the IV be running?"
Everyone in our class came up with either 38cc/hr or 42cc/hr - but no one is certain that they were right!
If you can give us the correct answer, we'd ALL appreciate it. (waiting for the instructor to inform us will take awhile)
Thanks! Now on to Psych rotation...

I got 37.87cc/hr rounded 38cc/hr. We are not allowed to round but must truncate(sp) at the hundreds.

landonsles · Mar 29, 2005

I don't use dimensional analysis, but working it out my way, I got 38cc/hr.

20lbs/2.2lbs per kg=9.1kg

9.1kg = 10kg

X 1000ml

Then you cross mulitply, and you get 910 ml. Divide that by 24 hours and you get 37.9 cc/hr or 38cc/hr

Hope that helps.

Iluvhospice · Mar 29, 2005

Good! That's what I got.

Thanks for your help!

wonderbee, BSN, RN · Mar 29, 2005

Using DA:

mL/hr = 1000 mL/10 kg x 1 kg/2.2 lbs x 20 lbs/24 hrs x 1 hr = 20000/528 = 37.87

Altra, BSN, RN · Mar 29, 2005

Hang on guys ...

20 lb. = 9.09kg (relevant info is that pt. weighs

so: 1000ml/day = 1000/24 hours = 42ml per hour

Enjoy your psych rotation! :)

wonderbee, BSN, RN · Mar 29, 2005

Hang on guys ...
20 lb. = 9.09kg (relevant info is that pt. weighs
so: 1000ml/day = 1000/24 hours = 42ml per hour
Enjoy your psych rotation! :)

Yep, I stand corrected.

Iluvhospice · Mar 29, 2005

That makes perfect sense... but leads me to another question,

if the order is for 1000ml/1st 10kg/day - if the patient weighed more than 10kg - it would still be 42ml/hr? I've just never seen an order like this (not too surprising considering that we only had 5 weeks in Peds!)

Thanks for everyone's input on this!

Sarah

Altra, BSN, RN · Mar 29, 2005

That makes perfect sense... but leads me to another question,
if the order is for 1000ml/1st 10kg/day - if the patient weighed more than 10kg - it would still be 42ml/hr? I've just never seen an order like this (not too surprising considering that we only had 5 weeks in Peds!)

In the "real world" this order would probably have been written in that format to comply with a facility's policy that all med orders be written as __mg/kg/day in an attempt to prevent errors in pediatric dosages. Especially when docs enter their own orders in an electronic system, there can be some strangely worded, choppy orders as various phrases are selected and "cut & pasted" together.

HTH :)