Help with math problem

[ChronicUpset]

Can someone please help me to understand how to do the following problem?

Dopamine 400 mg in 250 cc D5W to infuse at 5 mcg/kg/min. The patient’s weight is 200 pounds. How many cc/hour would this be on an infusion pump?

The first thing I did was covert lbs to kg and got 90.909.... I then rounded it to the nearest hundredth and ended up with 90.91.

Secondly, I tried to calculate the desired dose by multiplying 5 mcg by 90.91 and got 454.55 mcg (this doesn't seem right for some reason). I think I then need to calculate the amount to administer which I know how to do but I am confused because I think my previous step is wrong. It also looks like I need to convert mg to mcg as well before I can continue. Can someone please explain this to me and not just give me the answer. Providing an explanation of how you got your answer will help me to understand and complete future problems. Any assistance will be greatly appreciated. Thanks!!

[Hygiene Queen]

dopamine 400 mg in 250 cc d5w to infuse at 5 mcg/kg/min. the patient’s weight is 200 pounds. how many cc/hour would this be on an infusion pump?

1) pt wt: 200 lbs= 90.91 kg

2) 5 mcg x 90.91 kg x 60 (because there are 60 min. in 1 hr.) = 27273

3) concentration: 400 mg ÷ 250 cc = 1.6 mg = 1600 mcg

4) 27273 ÷ 1600 = 17.045 = 17 cc/hr

i think that's right.

that's the simplest way to go about it, imo.

think in steps.

[ChronicUpset]

Thank You very much for responding. No wonder I was stuck, I did not even think to multiply by 60 min "duh". You made it seem so simple. Thanks again.

[Hygiene Queen]

You're welcome.

Glad to help :)

[ChronicUpset]

Two Questions for you Hygiene Queen.

If the problem is asking to calculate the infusion drip rate cc/hr and mentions the patient weight in lbs in the problem. Does the weight have to be included in setting up the problem to solve it.

Secondly, If the question is asking for the mg/min and includes the weight in kg, does the the weight have to be included in setting up the problem to solve it.

I guess I am confused because some questions will ask for all three such find the mg/kg/min and others will ask for just mg/min or cc/hr but may or may not include the pt weight in the question. Not sure if that is a distraction or not. I now know how to solve the problem but just not sure if I am to include the weight in solving the problem unless it specifically ask for it such solve for mcg/kg/min, etc. I hope this is clear and can receive some feedback.

Disregard, I figured it out.

[smart99guy]

The IV flow rate is volume/time, unless it's asking for drips per minute. In that case, you would use the drop factor. If it's asking for volume only, then you have to use a little algebra. The same goes for time, etc. Hope this helps. I don't want to confuse you more.

[Double-Helix, BSN, RN]

The only time that a patient's weight matters is if the dose is based on their weight (such as mcg/kg/min or mg/kg/day, etc)

So if the question reads like: A patient is receiving epinephrine at 0.5 mcg/kg/min. The patient's weight is 120 pounds. Calculate the infusion rate if the concentration is 5000 mcg in 1000 mls. Then you need the patient's weight in the question.

But if the question reads: A patient is receiving epinephrine at 3mcg/min. The patient's weight is 120 pounds. Calculate the infusion rate if the concentration is 5000 mch in 1000mls. In this question, since the doseage is set and not based on the weight, the patient's weight is irrelavent.