anyone know how to work out this equation

Think it out in general terms before you go trying to jam numbers into an equation. What are you looking at? Break it down.

A patient (70kg) has been prescribed Dobutamine infusion of 5mcg/kg/min.

OK, then, that's seventy kilos, five mcg per kilo...That's, umm, 5 x 70 = 350 mcg. In a minute. Good.

You have prepared 250mg in 50mls. What rate should you set the infusion pump at, in mms/hr, to deliver this dose?

Not sure what mms/hr is; I'll assume you meant mls/hr. So now you have to figure out how many mcg there are in a ml, so you can figure out how many mls are going to give you that 350mcg you need for a minute.

How many mcg is in 1 mg? How many mcg in 250 mg? If you have that many in 50ml, how many are there in ONE?

Now, how many of those will give you the magic 350 mcg? That's in a minute, right? So How many cc will that be in an hour? X 60, right?

Yes, this is many small equations. Once you can see how that works and you have done a lot of them for practice, you can think about learning a bigger one.

I was really confused by these problems until I found a D over H formula. Here it is

Ord dose (mcg per min) X pt wt in kg X 60 min

---------------------------------------------

Amount of mcg per one ml

If you stick to this you will be fine. You always leave the 60 min in there unless the drug is calculated per hour. In that case, just leave the 60 minutes out. Same thing with the pt weight, if the weight is not provided just leave it out and it still comes out the same. Here is how the problem will be set up:

5 mcg X 70 kg X 60 min

---------------------------- = 4.2 ml/hr

5000 mcg/ ml

Just make sure to remember to always convert the available to mcg. Also double check to make sure if the ordered is per minute or per hour. Hope this helps