Dosage Calc Confusion

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I thought I understood dosage calculations, and I normally do well on exams. We had a practice test and there was an IV question that has me super confused.

Pt is to receive Dopamine at 5mcg/kg/min. Pt weighs 80 kg. You have 1.6 Gm/250ml. What should the nurse set the ml/hr too.

So here is what I did (please correct me):

5mcg x 80kg = 400 mcg/min

400 x 60= 24000 mcg/hr 1.6 x 1000 = 1600 mg/250ml

24000/1000= 24 mg/hr

24mg/hr

________ X 250 ml = 3.75 ml/hr

1600 mg

The correct answer is 15 ml/hr. I have no clue how this answer was reached. Thank you for any help.

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I tried to do it and I didn't get 15 either. I did find this, however:

http://www.globalrph.com/dopamine_dilution.htm

About halfway down, they show the calculation as:

Calculation of drip rate (ml/hr) 400mg/250 ml: wt(kg) x mcg/min x 0.0375.

When I plug the numbers into that calculation, the answer is 15. 80 x 5mcg/min x 0.0375

I still don't understand it, so I'll check back to see if someone explains it! ?

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Specializes in Med Surg, PCU, Travel.

was 15 a textbook answer? Your calculations are correct, text is wrong. final step round it up to 4 ml/hr.

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I agree with man-nurse2b regarding your answer, 3.75 mL/hour is correct.

In solving this type of problem I use the following formula: (dose × weight × 60) ÷ concentration.

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Specializes in Critical Care, ED, Cath lab, CTPAC,Trauma.

I have looked at this something is wrong. If the answer is 15 in the book......that is 20mcgs/kg/min Your answer of 3.75 is correct for 5mcg/kg/min of an 80 kg patient

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Thank you all. It is always a terrible feeling when you have no IDE where an answer came from. I appreciate y'all checking my work. My teacher said it must have been a typo, but I couldn't get a hold of her prior to panicking.

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We used to mix Dopamine 400mg/500cc. 1600mg/250cc is eight times more concentrated, and so there is actually a significant dose difference between 3.75cc and 4cc. Weird example.

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Specializes in Critical Care, ED, Cath lab, CTPAC,Trauma.
We used to mix Dopamine 400mg/500cc. 1600mg/250cc is eight times more concentrated, and so there is actually a significant dose difference between 3.75cc and 4cc. Weird example.
but we never had pumps that infused 3,75 cc's. I would start with 3cc if the MAP was close to or above 60...if it dipped frequently I would start at 4.

but the answer key said the answer for 5mcg/kg/min was 15ml/hr or actually 20mcg/kg/min...they question was wrong.

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