Nurse Calclations

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I been doing this problem over and over again, I come up with the same answer but is wrong any feedbacks please is appreciate it

The physician has ordered an IV medication to infuse at 5 mcg/kg/minute. The patient weighs 175 lbs. The medication is available in the following concentration - 400 mg/250 mL. The rate should be ____ mL/hr.(record your answer using one decimal place)

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175 divided by 2.2 is 79.5 multiply by 5 is 397.5 divided by 400 is 0.99 multiplied by 250 is 248.4 divided by 1000 answer is 0.2 ml/hr

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Specializes in OR, Nursing Professional Development.

You missed a conversion in there with mcg to mg- look at your concentration vs. your prescribed dose.

At least, I think you did. It's hard to follow your calculations since you didn't include units and threw it all together. Perhaps you would also be helped if you broke it down step by step.

Do you know what the correct answer is?

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175 divided by 2.2 is 79.5 multiply by 5 is 397.5 divided by 400 is 0.99 multiplied by 250 is 248.4 divided by 1000 answer is 0.2 ml/hr

Okay, I see what you have done here, and what is missing. What you have done here is to solve. correctly, a 5 mcg/kg infusion. There is one additional step that you need to complete to solve for a 5 mccg/kg/minute infusion. What do you think that would be.

The formula that I would have used to solve the problem that you did would be:

(dose x weight) / concentration

When I solve this type problem I convert the weight and determine the concentration outside of the equation and then insert the values. What you've done isn't wrong, but I find I am less likely miscalculate if each step is done distinctly. Regardless of which method you use, take care to ensure that you are using like units throughout. I also will wait until I have completed all calculations prior to rounding.

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You missed a conversion in there with mcg to mg- look at your concentration vs. your prescribed dose.

[...]

No, she didn't. What she did was solve for 5 mcg/kg, not 5 mcg/kg/minute. When incorporate that step into what she has here, it is correct.

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Specializes in OR, Nursing Professional Development.
No, she didn't. What she did was solve for 5 mcg/kg, not 5 mcg/kg/minute. When incorporate that step into what she has here, it is correct.

Thanks. I couldn't tell for sure without the units being included but knew there was a step missed somewhere.

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Thanks. I couldn't tell for sure without the units being included but knew there was a step missed somewhere.

Yes, that was my first thought as well.

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Specializes in Emergency.

Remember how many minutes are in an hour. 175 lbs = 79.55. Multiply this by 5, then multiply that by 60. Then you can do your easy "Want over have to get your rate.

5 mcg/kg/minute. The patient weighs 175 lbs. The medication is available in the following concentration - 400 mg/250 mL

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Specializes in Med-Tele; ED; ICU.
175 divided by 2.2 is 79.5 multiply by 5 is 397.5 divided by 400 is 0.99 multiplied by 250 is 248.4 divided by 1000 answer is 0.2 ml/hr
The problem is that you have no units of measure, just a bunch of numbers.

(175 lb) / (2.2 lb/kg) = 79.5 kg

79.5 kg x 5 mcg/kg/min = 397.7 mcg/min... that is, the mass flow rate of the medication

Of course, your pump doesn't think in terms of the mass of the medication, only in terms of a volume of medication.

The concentration of the solution allows you to relate the mass of medication to a volume.

400 mg / 250 mL is the concentration but it is in mass units of milligrams rather than micrograms as is your dosage order.

(400 mg / 250 mL) x (1000 mcg / 1 mg) = (1600 mcg / 1 mL)

(397.7 mcg/min) x (1 mL / 1600 mcg) = 0.249 mL/min

(0.249 mL/min) x (60 min / 1 hr) = 14.9 mL/hr

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