drug calculation help!

allthingsbright · Dec 4, 2004

Well, 1 mg=1000mcg, so you should be able to convert from that and do what you normally do.

Maybe posting a problem will help? I HATE math-LOL! :rotfl:

:)Amy

janetrette · Dec 4, 2004

i figure it would be 1000mcg however i needed to make sure if it's correct. i dont have any problems dealing with mcg/kg/min because i heard that for my final this professor loves math like this and calories. so sad because i don't think nurses really do figure out calories and such...

but thank you so much. i could do the math however once in nursing they love to make math stories meaning taking out only those numbers thats important or figure out a number to solve that problem. :balloons:

Kudra · Dec 4, 2004

edited: nevermind :)

kathy_79 · Dec 4, 2004

1kg = 1000g

1g= 1000mg

1mg = 1000mcg

so if you want to know how much mcg is in 1kg, you need to multiply by

1x1000x1000= 100000mcg

going backward:

1mcg = 0.001mg

1mg = 0.001g

at my school we use

15 min = 1ml

8 min = 0.5ml

hope it helps

you can email me if any more question, :)

Pediatric Critical Care Columnist · Dec 4, 2004

we run a lot of our infusions at x mcg/kg/min. we mix our infusions such that 1ml/hr will give us anywhere between 0.05 mcg/kg/min to 100 or more mcg/kg/hr (usually morphine... some of our kids are on a truckload of it). let's pretend we have a pt who weighs 16 kg and who needs dopamine at 5 mcg/kg/min. i'd mix my infusion so that 1 ml/hr will give me 5 mcg/kg/min. i do my calculation like this:

16 (pt's wt) x 5 (mcg/kg/min desired) x 50 (# mls total volume in syringe) x 60 (minutes in an hour) / 1000 (conversion from mcgs to mgs) to find out how many mg i need for my infusion.

16 x 5 x 50 x 60 / 1000 = 240 mg

so now i know how many mg i need to mix into a total volume of 50 mls to deliver the desired dose at 1 ml/hr. dopamine comes as 1 ml = 40 mg, so i'd need 6 ml of drug and 44 ml of d5w. once you do it a few times it's easy. you can tell at a glance how much of a drug the pt is getting by looking at the rate on the pump and the concentration listed on the label. piece of cake.

if you simply need to know how many mg per hour a pt will receive at x mcg/kg/min, the equation looks like this:

x x wt x 60 / 1000. our example would give a result of 4.8 mg.

help?

aruray · Dec 12, 2004

we run a lot of our infusions at x mcg/kg/min. we mix our infusions such that 1ml/hr will give us anywhere between 0.05 mcg/kg/min to 100 or more mcg/kg/hr (usually morphine... some of our kids are on a truckload of it). let's pretend we have a pt who weighs 16 kg and who needs dopamine at 5 mcg/kg/min. i'd mix my infusion so that 1 ml/hr will give me 5 mcg/kg/min. i do my calculation like this:
16 (pt's wt) x 5 (mcg/kg/min desired) x 50 (# mls total volume in syringe) x 60 (minutes in an hour) / 1000 (conversion from mcgs to mgs) to find out how many mg i need for my infusion.
16 x 5 x 50 x 60 / 1000 = 240 mg
so now i know how many mg i need to mix into a total volume of 50 mls to deliver the desired dose at 1 ml/hr. dopamine comes as 1 ml = 40 mg, so i'd need 6 ml of drug and 44 ml of d5w. once you do it a few times it's easy. you can tell at a glance how much of a drug the pt is getting by looking at the rate on the pump and the concentration listed on the label. piece of cake.
if you simply need to know how many mg per hour a pt will receive at x mcg/kg/min, the equation looks like this:
x x wt x 60 / 1000. our example would give a result of 4.8 mg.
help?

piece of cake? im not even sure what were figuring out here. ive been staring at it for at least 10min and still not sure i get it. its unlike any calculation problem ive seen but im intrested to learn. where did u get 1ml/hr? howd u get 50ml and 60min? is it because kids always get their iv's at 50mls and never over an hour? (sorry did my peds rotation too long ago, last semester lol) im so used to figuring out a math problem but feel like i cant figure out calculating a real order. i must sound like a total dumbass but this just confuses me somehow.

Pediatric Critical Care Columnist · Dec 12, 2004

piece of cake? im not even sure what were figuring out here. ive been staring at it for at least 10min and still not sure i get it. its unlike any calculation problem ive seen but im intrested to learn. where did u get 1ml/hr? howd u get 50ml and 60min? is it because kids always get their iv's at 50mls and never over an hour? (sorry did my peds rotation too long ago, last semester lol) im so used to figuring out a math problem but feel like i cant figure out calculating a real order. i must sound like a total dumbass but this just confuses me somehow.

let me see if i can clarify this for you. we run our drug infusions on a syringe pump. the volume we usually use is 50 ml, just because it's easier and a standard number. we mix our meds so that the concentration will be whatever gives us the 1 ml/hr = x mcg/kg/min (or hr). my patient is 12 kg. i need a dopamine infusion to run at 5 mcg/kg/min. i'm mixing it in a total volume of 50 ml of fluid and i want the concentration to be such that if i run it at 1 ml/hr it will give me 5 mcg/kg/min. so i use the equation i gave in my previous example...

12 (kg, the pt's wt) x 5 (# mcgs/kg i need) x 60 (# min in an hour) x 50 (total volume i want to mix up) = 180000mcg / 1000 (mcg per mg)= 180 mg. so i need 180 mg of dopamine to mix into a total volume of 50 ml of fluid. dopamine comes as 40 mg/ml so i need 4.5 ml of dopamine and 45.5 ml of d5w to mix it into. my final volume will be 50 ml, and the concentration will be 3600 mcg/ ml and that will give me an infusion i can run at 1 ml/hr to give me 5 mcg/kg/min. if my order changes and i need 7.5 mcg/kg/min, i would run it at 1.5 ml. if i needed 12.5 mcg/kg/min i'd run it at 2.5 ml/hr.

let's do one for morphine, which would be ordered as x mcg/kg/hr. same pt, concentration to give an infusion that would give me 1 ml/hr = 20 mcg/kg/hr...

12 (pt's wt) x 20 (# mcg/kg i need) x 50 (total volume of fluid desired) = 12000 / 1000 (mcg per mg) = 12 mg in total volume of 50 ml. if i use a 10 mg/ml and a 2 mg/ml amp, i'll have 12 mg in 2 ml total volume of drug, added to 48 ml of d5w to get the desired volume of 50 ml. if the order says "morphine 20 mcg/kg/hr" i will run it at 1 ml/hr. if the order is 50 mcg/kg/hr, it goes at 2.5 ml/hr.

peds meds are always customized to the pt's wt. tylenol's usual dose is 15 mg/kg per dose, so this pt would get 180 mg/ dose. ancef is usually 30 mg/kg/dose, so this pt would get 360 mg.

i too was confused when i first started doing meds this way, but now that i'm doing it, it's the easiest and most readily understood method i've ever seen. anyone coming to my pt's bedside can see at a glance what the epi is running at, because the label on the pump will say, "1 ml/hr = 0.1 mcg/kg/min" and they can see that the pump is running at say, 2 ml/hr, so the pt is getting epi at 0.2 mcg/kg/hr. (sick kid, needs a lot of epi.) has this made any better sense? (hope so, i wrote this after a bottle of wine and a relly nice dinner!)

aruray · Dec 12, 2004

i got the calculation but i still dont understand 1ml/hr. u used 1ml/hr because thats the smallest infusion rate in the pump? does that 1ml/hr true for adults too?

wonderbee, BSN, RN · Dec 12, 2004

I think that what she's saying is that we want ml/hr to run on the pump. I don't mean to answer for the poster, I'm trying to figure this out too.

Kudra · Dec 12, 2004

if you want practice with titration problems (like janfrn posted), i suggest going to this page... besides the quizzes, there are tutorial pages as well...

a few things to clear up: the 1 ml/h sounds like it's for convenience sake in a peds setting... but by far not the standard in all clinical areas...

60 min/h is a constant in the equation...

so the basic equation looks like this:

rate (ml/h) x concentration (mcg/ml) = mcg/Kg/min

time (min/h) x wt (Kg)

krissypoo · Dec 12, 2004

where were you'all in aug.?

I am just finishing up pharm and i have to say that i am just now really starting to understand the math...............especially the recalculation times for IV's........uck!!!!!

Its very frustrating at times!----especially when you start to talk to RN's whom are all,"I don't know why they require you to know all of the conversions. We have chrts to look them up when we need to."

Plus in my state there are colleges where pharm is not required, at all.

'I am a stronger person for it, i am a stronger person for it, i am a stronger person for it'............................................

good luck to all whom still have finals to get through!!!!!!!!!!!!!!!!!!!!