Math calculation. Help!

[sashaq]

This is a two-step ml/hr flow rate problem. I need help please.

Medicaton is ordered at the rate of 3mcg/kg/min for an adult weighing 95.9 kg. The solution strength is 400 mg in 250mL D5W. Calculate flow rate to the nearest tenth mL.

Is there a formula that can be applied here.

[Wuzzie]

What have you tried so far?

[sashaq]

There was this formula that I saw online (ATI website): (dose/kg/time) (time converted to hourly) (weight in kg)/ (drug concentration per ml)

I started plugging the numbers in according to the formula. (3mcg/kg/min) (95.9 kg)/250 ml. My hunch is I have to multiple 3mcg by 95.9 kg this equals 287.7 kg/mcg then convert to mg.which is 0.287 mg. I converted to mg because the solution is in mg. But my answer is not matching the answer sheet.

[Wuzzie]

How many total mcgs of the drug in 250ml? How many mcgs/ml? And you've got the very first step right (mcgs/kg) but look at the rate.

[sashaq]

The total mcg in 250 ml is 250,000mcg. I divided 250/0.001

[Wuzzie]

Try again. You used the volume not the concentration. You cannot convert ml to mcg. You CAN convert mg to mcg. What factor in the question is written in mg and how many mg are there?

[sashaq]

Well we have 400 mg if we convert to mcg we have 400,000 mcg

[Wuzzie]

Very good. So we have 400,000 mcg in 250 ml. Using these numbers how would you solve to find out how many mcg are in each ml.

[sashaq]

400,000/250=1600

[Wuzzie]

400,000/250=1600

Super. So you know the patient needs 3mcg/kg which totals 287.7 mcg (you figured this out earlier, yay for you) but that's ordered per minute and the pump will be set per hour so with the information you have can you figure out how many ml/hr you need to set the pump. Remember your concentration is 1600mcg/ml.

[sashaq]

I solved it and did the the other problems that were similar. 287.7 mcg X 1 MG/400 MG X 250ML/400 MG X 60/1 hour =4315500/400000=10.78

Now, I'm stuck on another problem. lol But thank you for your help with this.

[Wuzzie]

Yay for you sashaq. You're doing a great job. Now you know you can figure it out in mg and then convert to mcg or what I do which is convert first. Both ways are correct and just reflect how our individual brains work. I'm very proud of you for sticking with it. Bring on the next problem.