Drug Calc Help!

chare · Aug 5, 2013

To solve this problem you need to determine the following:

How many mL of dopamine is the patient receiving each minute?
What is the concentration of dopamine per mL (mcg/mL)?
What is the patients weight in kg?

After you determine the answers above, you can use the following formula to solve your problem.

mL per minute × (mcg dopamine / mL) ÷ patients weight

miamiabean · Aug 5, 2013

I don't understand how to figure out the mcg/ml. I have a number with like 6 0's. Should I be converting the 800mg into mcg? I feel like I'm missing something blatantly obvious, but I'm not sure what. :nailbiting:

I have 330ml/min for the dopamine... and the kg as 100.

Thank you so much for your help!

chare · Aug 5, 2013

I will work a similar problem and show the steps involved.

Order: Dobutamine 45 gtts/minute

Available: 1000 mg/500 mL

Patient weight: 220 lbs

Drop factor: 60 gtts/mL

What is the dose being deliverd? _____ mcg/kg/minute.

1. How many mL of dobutamine is the patient receiving each minute?

45 gtts min × (1 mL / 60 gtts) = 0.75 mL

2. What is the concentration of dobutamine per mL (mcg/mL)?

(1000 mg / 500 mL) × (1000 mcg / 1 mg) = 2000 mcg/mL

3. What is the patients weight in kg?

220 lb × (1 kg / 2.2 lb) = 100 kg

0.75 mL × 2000 mcg / mL ÷ 100 kg = 15 mcg/kg/minute

miamiabean · Aug 5, 2013

I have a dumb question. Before I attempt to work out my order, I saw you had a drop factor in your example problem. Should I assume that drop factor is in my problem even though it's not stated?

chare · Aug 5, 2013

No, the drop factor should be provided in the information that you are given. However, as the information that you provided included the answer, the drop factor was able to be determined.

miamiabean · Aug 5, 2013

Ohh, the answer was on the answer sheet. So, I wouldn't have had it otherwise, like if I was taking a test. Is there any other way to figure out what the drop factor is if it's not stated?

I'm sorry to be asking so many questions. My brain is just not computing this problem for some strange reason.

Esme12, ASN, BSN, RN · Aug 5, 2013

DosageHelp.com - Helping Nursing Students Learn Dosage Calculations

is a great site

chare · Aug 5, 2013

The drop factor should always be provided. It is likely that you are not going to be given all of the information necessary to determine the drop factor; I was only able to do so because you provided the answer.

miamiabean · Aug 5, 2013

Oh. I'm not sure what to do then... if left to my own devices for the gtt/min conversion to mL, I would wind up w/ 1.7mL (which is probably wrong)...

For the gtt/min I did a ratio of 15gtt/1ml = 26gtts/x and solved for x... which was 1.7mL

For the concentration I did 800mg/500ml x 1000mcg/1mg = 1600mcg/mL

and for the weight of 220kg, I converted it to 100kg.

Then I did 1.7mL x 1600mcg/ml divided by 100kg= 27.2mcg/kg/min. Which is wrong. Again. :confused:

nurseprnRN, BSN, RN · Aug 5, 2013

Hey. So, I failed my Drug Calc Level 2 proficiency exam. Sigh.
We were given a packet to study for the retest in a few weeks. I'm looking it over and I have NO idea how to figure one of the calculations. I'm not looking at allnurses.com for the answer, as I have it already. I'm looking to understand how to get it.
Order: Dopamine 26gtts/min
Available: 800mg/500mL
Patient weight: 220lbs
I have 330ml/min for the dopamine... and the kg as 100.
What is the dose being delivered? _____mcg/kg/min
Should I be converting the 800mg into mcg?

Whoa. 330 cc per MINUTE? If you had a 500cc bag, you'd give most of it in a MINUTE? That's a clue right there that something is wrong.

Chare has given you a great way to think about what you are looking at.

nurseprnRN, BSN, RN · Aug 5, 2013

I have a dumb question. Before I attempt to work out my order, I saw you had a drop factor in your example problem. Should I assume that drop factor is in my problem even though it's not stated?

Two things:

1) in most problems like this they do give you a drop factor

2) you ought to have learned in pharmacology or in clinical that hemodynamically-active IV meds (like dobutamine) are given with microdrop sets, where 1 cc = 60 gtts

The reason you're not able to wrap your head around this question is because you aren't given all the information you need to solve it. I know this will make you crazy....but sometimes, questions are wrong. if you are normally proficient at med calculations, when you run into one, your best bet is to do your best and move on.