HELP With Med Math Problem

CametoitlateTexan · Jan 25, 2008

First problem

ml/hr = 250ml X 6 mcg X 1mg X 72.4 kg X 60 min = 130 ml

50mg kg/min 1000 mcg 1 1 hr hr

Second problem

ml/hr = 50ml X 60 min = 150 ml/hr

20 min 1 hr

CametoitlateTexan · Jan 25, 2008

Try again

ml/hr = 250 ml/50 mg X 6 mcg/kg/min X 1 mg/1000mcg X 72.4 kg/1 X 60 min/hr = 130 ml/hr

ml/hr = 50 ml/20min X 60 min/1hr = 150 ml/hr

kpyers32! · Jan 25, 2008

Thank you very much CAMETOITLATE for your help.

I'm feeling like a ding bat. Maybe I'm tired but I am not getting how you worked out the first problem from begining to end....also, are you plugging into a formula that you memorized? Thank you so much if you could possibly attempt to explain any more I would be very appreciative!! Thanks again! I'm just waiting for a lightening bolt to hit me!!! :idea: Thanks for your time!!

beachbum3 · Jan 25, 2008

Hi there all you smart nurses! I need your help please I have to take a quiz tomorrow!
Wow - It feels like i've been out of school forever (it's been 7mos), I have these a quiz for a new job....Can someone pretty please help me with these? Thanks soo much!!
Your pt. (weight 72.4kg) has been ordered to have an infusion of Lasix
(50 mg/250 ml) titrated btwn. 3-6 mcg/kg/mn. What is the max. mcg/min the pt. would would receive?
***this part I understand****
prt. 2 of this question. Calculate the flow rate for the above infusion.
Next question:
A pt. is being admitted to your unit wiht a diagnosis of bilateral lower extremity cellulitis. The physician orders Ancef 1 GM IV every 6 hours.
The pharmacy dispenses a piggyback with the medication in 50 ml labeled for the drug to infuse in over 20 min. What rate would you set the IV pump.

1. 130 ml/hr (edited to show work:

6 mcg x 72.4 kg/min= 434.4 mcg / min

434.4mcg x 1mg/1000mcg = 0.4344 mg (converts mcg to mg)

0.4344 mg/min x 60min/1hr= 26.064 mg/hr (convert min to hour)

26.064mg/50mg x 250 ml = 130ml/hr

2. 150ml/hr

60min in 1 hr

60/20= 3

50 ml x 3= 150ml/hr

Edited again, its 130 ml, not 13- i only hit 25 on my calc.! lol

CametoitlateTexan · Jan 25, 2008

The way I learned it was to determine what you are looking for (in this case ml/hr), then set up your problem to find that result.

ml/hr = 250 ml/50 mg X 6 mcg/kg/min X 1 mg/1000mcg X 72.4 kg/1 X 60 min/hr = 130 ml/hr

I started with 250ml/50 mg because the first thiing I want to find is ml

Next I put in 6mcg/kg/min and put in a conversion (1 mg/1000 mcg) leaving kg/min in the denominator after crossing out the mg and mcg.

Next the 72.4 kg to get rid of the kg. Then 60 min/1hr to eliminate minutes.

Once you cancel everything, you are left with ml/hr. Do the math and voila!

kpyers32! · Jan 25, 2008

Thanks for helping too. I should of said I have the answers I just don't know how to get them CAMETOITLATE is correct: 1) is 130 mL/hr and 2) is 150 mL/hr. Any additional pointers are very appreciated!!

CametoitlateTexan · Jan 25, 2008

1. I got 13 ml/hr (edited to show work:
6 mcg x 72.4 kg/min= 434.4 mcg / min
434.4mcg x 1mg/1000mcg = 0.4344 mg (converts mcg to mg)
0.4344 mg/min x 60min/1hr= 26.064 mg/hr (convert min to hour)
26.064mg/50mg x 250 ml = 13ml/hr
2. 150ml/hr
60min in 1 hr
60/20= 3
50 ml x 3= 150ml/hr

I stand by my work, thanks!

CametoitlateTexan · Jan 25, 2008

Thanks for helping too. I should of said I have the answers I just don't know how to get them CAMETOITLATE is correct: 1) is 130 mL/hr and 2) is 150 mL/hr. Any additional pointers are very appreciated!!

It's really a matter of just setting up the problem to get whatever units you want in the numerator and the denominator, then manipulate the information you have to get that result.

I apologize for not being a very good tutor! Good luck on the quiz, however.

beachbum3 · Jan 25, 2008

I stand by my work, thanks!

I edited- I'd only hit 25, not 250 when I multiplied it out. :bugeyes:

CametoitlateTexan · Jan 25, 2008

I edited- I'd only hit 25, not 250 when I multiplied it out.

I know what you mean. That's how my mistakes are usually made.

beachbum3 · Jan 25, 2008

Forgive my first error in my first post- I've gotten 100s on all math tests in my progam and just took the final competency. See what I get for posting before I review my answer? lol

The main formula for all problems is dose desired over (/) dose on hand, x your unit (or what it comes in) i.e.:

order is for 400 mg of ibuprofen. you have on hand 200 mg per tablet

400mg x 1 tab = 2 tabs

200mg

mg cancels each other out in the problem so you are left with tab for your final unit

so in more complex problems I like to do all the conversions first so I can always end up with the dose desired divided by dose on hand multiplied by what it comes in .

in a problem like the first one- I figured out what the dose ordered was first according to the weight. Then I did the conversions, mcg to mg, mins to hours. Then the last step was the dose desired divided by dose on hand x what it comes in

Remember that IV pump calculations are always ml/hr, (in most cases) so you want to end up with ml/hr. Also, its always a whole numer, so you have to round.

also (and I should follow my own advice) look at your answer and make sure it makes sense. Thats how I realized I'd gone wrong, because I knew the pt was supposed to get 26 mg per hour, and there was 50 mg in the 250 ml. So then roughly around half of the 250 should have been set to infuse per hour, yet I'd come up with 13..... It didn't make sense.