Math Calculations Help!!

[MarySnov]

Hi,

I need help setting up this math problem. I'm familiar with dimensional analysis, but I get confused on starting the problems. Can someone please help me with this? I don't need you to actually work the problem, just tell me how to set it up.

Mrs. H is a 56 y/o woman who is admitted w/ peritonitis. She is receiving fluids at 125 mL/hr. Her BP was 84/52 on admission. She was prescribed Drug D (400mg in 250 mL DSW) at 10 mcg/kg/min required to keep SBP higher then 90 mmHg. Mrs. H is 69kg.

Calculate the ml/hr the pump will run for 10/mcg/kg/min.

Thanks!!!

[203bravo, MSN, APRN]

before I tell you how I would tackle the problem... what ideas do you have or what have you attempted so far?

I would solve this using 3 steps.

[BeachsideRN, ASN]

First figure out which information is vital and which is not, get rid of the numbers that are unnecessary. Then work from there. Doing the math is the "easy" part so having someone else set up the problem for you is not going to help you learn.

[IVRUS, BSN, RN]

If you can plug in the variables of the order into this dimensional analysis formula,then it becomes a simple

matter of multplying and dividing.

_____kg X ____mcg/kg/min X 60min/1 hr X 250ml/ 400mg X 1mg/1000mcg

69kg X 10mcg/kg/min X 60min/hr X 250ml = 10,350,000

400mg X 1000mcg = 400,000 Take 400,000 into top number which is 10,350,000 and you'll come up

with 25.875 ml/hr. So, you have the known variables, of 60min=1hr, and 1mg is 1000 mcg.. the rest of the numbers comes from your order.

[nurseprnRN, BSN, RN]

We see people here all the time who see a bunch of numbers in a word problem (and in nursing they're ALL word problems) and rush to plug them into a formula (often dimensional analysis), and then they get confused and lost. As an aside, the people who write exam questions know this and put in distractors (the three wrong answers) in the choices knowing what numbers will result when the wrong numbers are plugged in.

So. When you get a problem like this, don't just do something, sit there! Think! Read it again. In this one, what is the final question? It is, "How many cc/hour do you set this IV to run?"

The pt's BP and baseline IV rate have nothing to do with that.

So you know you want to give her 10mcg / kg / min. You know she weighs 69kg, so you will be giving 690 mcg/minute, right? Do you see that? Now, how many mcg will that be in 60 minutes?

To know how many cc's that is (your IV pump is in cc/hour), you need to know how many mcg there are in one cc. Do you know how to figure that out? 400 mg in 250 cc, right? But wait! How many mcg in a mg?

These are the pieces of your problem you have to have in hand as you think about what you'll be doing for this patient.

And this is why we ask you to show us what you did before we give you the answer, so we can see where you went wrong. Someone has helpfully given you the answer but I'd like to see your thought processes first. Just asking us "how to set it up" isn't going to help with the next such problem you get if you don't know how to think about it first.