Math Calculations for last semester of Nursing Program

jmdRN · Jan 8, 2012

The patient has an order to receive Lidocaine (xylocaine) for PVC's. The pharmacy has sent you Lidocaine 2 grams IV in 1000 ml D5W at 4mg/min. What is the pump setting to deliver the desired dosage?

For the 1st one, you need to figure out how many gr (or mg) are in each ml, then do the conversions to get to your desired rate of 4mg/min to x ml/min. And I'm not sure about your pumps, but our pumps are in x ml/hr increments, so you'll need to convert your 4mg/min to x ml/min to x ml/hr for your pump rate.

WantingtheBest · Jan 8, 2012

So 2mg/ml.

1000/2=500

2ml/min

2x60min= 120ml/hr

So the answers is 120ml/hr??

VickyRN, MSN, DNP, RN · Jan 8, 2012

Moved to Nursing Student Assistance Forum as more appropriate forum :)

NCRNMDM, ASN, RN · Jan 9, 2012

I am only going to answer (or attempt to answer) some of these. If my answers are wrong, I hope that someone will correct me.

Okay, let's start with the first one. Here's how I understand it: 2 grams of Lidocaine in 1000 ml of fluid. 2 grams is 2000 mg, and you have it in 1000 ml of IV fluid. 2000 mg/1000 ml= 2 mg/1 ml. Since the patient needs 4 mg/min, you would set the pump to deliver 2 ml/minute because 2 times 2 equals four.

To do micrograms, you need two formulas. The first is micrograms x kilograms/1000 x 60. Let's take the second problem, for example, and apply the formula to it. A patient weighing 154 pounds is ordered to have Dopamine at 15 mcg/kg/min. The pharmacy has sent you Dopamine 800 mg in 500 ml NS. What is the rate of infusion?

Let's get the kilogram weight first. Divide 154 by 2.2 and you get 70 kilograms. Now, let's multiply 15 micrograms by the 70 kilograms. When we do that, we get 1050. Now, let's divide that by 1000. When we do that, we get 1.05. Now, let's multiply that by 60. When we do that, we get 63. 63 is the dose in milligrams per hour that we want to give the patient. Now we must use a second formula in order to figure out milliliters per hour. To figure this out, we will use the formula: desired/what you have on hand x the volume. In this situation, we would say 63/800 x 500. This gives us an answer of 39.375, or 39.4 ml/hr. This dose will deliver the proper dose of medication to the patient.

Let's move on to the micrograms per minute Nitroglycerine problem. This is another two step problem. First, we are going to convert mcg/min to mg/hr. To do this, we are going to take the 5 micrograms, divide by 1000, and multiply by 60. 5 mcg/1000 x 60= 0.3 mg/hr. Next we are going to use the desired/have x volume equation again. This time we are going to say 0.3/50 x 500. This gives us an answer of 3 ml per hour.

I hope that these are correct, and I hope that someone will set me straight if they aren't. I also hope that this helps you out a little bit. nursing calculators

Try that link, it has a ton of calculators on it, and it describes how to go about the calculations directly underneath the calculator. Good luck!

momtojosh · Jan 9, 2012

question......do nurses have to figure this out for real?....

nurses that i talk to say it comes all set...the dosage....all you have to do is plug in the numbers in the machine?..is this true?

i am so very afraid of this math....i passed it in LPN school.....i dont even come close to doing this....or knowing how...and i am trying to get into a RN program.....maybe i should rethink? as this scares the poop out of me......i am haivng some sort of panic attack now just thinking about it..... :bluecry1:

please let me know...

NCRNMDM, ASN, RN · Jan 9, 2012

In most hospitals, the IV pumps are very sophisticated, and you can just input your information into the machine. However, when you are an ICU RN and your patient is receiving three pressors, two sedatives, a paralytic, an insulin drip, an antibiotic, lidocaine, potassium, and IV fluids are you going to be content to simply trust everything the machine says? When your patient is on the verge of death, and in such critical condition that you are afraid to turn them, are you going to be satisfied that the numbers the IV pump produced are totally accurate? I know I'm not, and I want to work the math out before I input my information into the IV pump as a double check. In some facilities, like smaller community hospitals, the technology isn't as advanced, and, yes, nurses do this type of math everyday.

However, don't let it scare you away from nursing school. You are there to learn, and you will be taught all about this kind of math.

Esme12, ASN, BSN, RN · Jan 9, 2012

question......do nurses have to figure this out for real?....
nurses that i talk to say it comes all set...the dosage....all you have to do is plug in the numbers in the machine?..is this true?
i am so very afraid of this math....i passed it in lpn school.....i don't even come close to doing this....or knowing how...and i am trying to get into a rn program.....maybe i should rethink? as this scares the poop out of me......i am having some sort of panic attack now just thinking about it.....
please let me know...

you may find these site very helpful. they are simple effective tools to iv/med calculations. don't be afraid you will learn.

dosagehelp.com - helping nursing students learn dosage calculations

http://www.davesems.com/files/drug_d...lculations.pdf

but....yes you do. you are responsible for all the meds you give.

you are the final safety check before the meds are administered to the patient. you should always double check the administration rates when using dose mode pumps for safety's sake......maybe you input the wrong concentration when programming the pump and need to correct it before hitting start. nurses who truly believe that all you need to do is plug in the information and everything's good are deluding themselves that they are practicing safe. machines have made mistakes with fatal outcomes.

https://allnurses.com/nursing-news/babys-death-spotlights-584283.html

https://allnurses.com/nursing-news/nurse-suicide-follows-556477.html

case in point. supervising in a small community hospital i went to start an iv on a seven year old girl that was receiving a antibiotic that can be toxic to the liver. i saw the iv bag and noticed the bag was 10 times the amount that a child of 70 lbs should receive. when i left the room the nurse caring for her came up to me and asked if i had started the antibiotic and i said no.....she was relieved because she was checking the dose and realized it was too much for a child. this dosage had been given every eight hours for 3 days because it was checked by pharmacy, in the pyxis, and matched the order.

when i called the pharmacy at home he remembered the name and was shocked it was a child of 70 pounds not an adult of 70 kilos. the information was correct in the computer and clearly stated 70 pounds. had that nurse not checked that massive dosage would have continued for who knows how long. the md was po'd because he had spoken to the pharmacy himself and wrote for the dosage he was told to give. the liver enzymes were only slightly elevated and disaster was averted.

always check your math.

KelRN215, BSN, RN · Jan 9, 2012

question......do nurses have to figure this out for real?....
nurses that i talk to say it comes all set...the dosage....all you have to do is plug in the numbers in the machine?..is this true?
i am so very afraid of this math....i passed it in LPN school.....i dont even come close to doing this....or knowing how...and i am trying to get into a RN program.....maybe i should rethink? as this scares the poop out of me......i am haivng some sort of panic attack now just thinking about it.....
please let me know...

YES, nurses do have to figure this out for real. Our pumps are quite sophisticated and for drips (for example a heparin drip), it will ask for the concentration of heparin, the patient's weight in kilograms and the intended rate in units/kg/hr and convert that to mL/hr. HOWEVER, it is still ultimately your responsibility to ensure that the right dose is delivered to the patient. So yes, you should calculate the math beforehand to ensure that the rate the pump is delivering is correct.

SCSTxRN · Jan 10, 2012

I was taught - and I teach - to do this by "dimensional analysis"

Assuming you know that 1kg = 2.2 lbs, 60 minutes = 1 hour, and 1000mcg = 1mg and 1g = 1000 mg

To use 'dimensional analysis' you have to have everything equal to something else in the problem, so for #1, the order is 4mg / minute and the concentration is 2 grams in 1000mL

1. 4mg 1g 1000mL 60 min

min 1000 mg 2g 1 hour

2.

154lbs 1kg 15mcg 1mg 500mL =

pt. 2.2 lbs kg min 1000mcg 800 mg

gives answer in ml/ hour (which is a pump rate)

lbs on top cancels lbs on bottom, etc - all thats left is ml/hour, multiply across the top and bottom, divide,

3.

5mcg 1mg 500mL 60 minutes

minute 1000mcg 50 mg 1 hour

again leaves answers in mL/ hour

4.

6mL 2g 1000 mg

hour 500 mL 1g

This will give you mg/hour if you want mg/min, multiply by 1 hour

60 min

5. Weight is thrown in there to make you NUTS - it doesn't matter in this problem.

25mL 900 mg

hour 500 ML

again, this gives you mg / hour - if you want it per minute, see above.

6. Your patient is to start a dopamine drip due to severe hyptotension. The pharmacy has sent you a 250ml bag of NS with 400mg dopamine. What is the rate of infusion if the physician has ordered the following: 8mcg/kg for your client that weighs 186 pounds?

186 lbs 1kg 8mcg 1mg 250mL

patient 2.2lb kg (per hour?) 1000mcg 400mg

=0.42 mL/(hour?)

7. How much would the patient be receiving if his pump was running at 11ml/hr?

I got 17.6/hr???

11mL 400mg

hour 250 mL = 17.6 mg/hour if you want to take that all the way to weight dosage, though

11mL 400mg 1000mcg patient 2.2lb

hour 250 mL 1 mg 186lbs 1kg

then the patient is receiving 208 mcg/kg, so it kind of depends on exactly what the teacher is asking.

My head hurts, and all this formatting is making it worse. If you would like me to check your answers, send me a message so I get an email. It seems like you're on the right track, though. :)

And YES - nurses really do have to do this kind of math. You do get to use a calculator, usually, but the set up is all you.

LadyinScrubs, ASN, RN · Jan 10, 2012

question......do nurses have to figure this out for real?....
nurses that i talk to say it comes all set...the dosage....all you have to do is plug in the numbers in the machine?..is this true?
i am so very afraid of this math....i passed it in LPN school.....i dont even come close to doing this....or knowing how...and i am trying to get into a RN program.....maybe i should rethink? as this scares the poop out of me......i am haivng some sort of panic attack now just thinking about it.....
please let me know...

MomtoJosh - I had the same attitude as you until I got a rude awakening--we ran out of pumps. I had to do the IV calculation the old fashioned way and apply it to a drip. That was a teaching moment.

Don't count on technology doing your job. What happens if there is a problem. What did those nurses who stayed on the job during Katrina do? They had no power, but they had patients, and the patients needed meds. You need to learn the basics. You never know when you will need them.

As far as the math that we do, it is simple math. I would say what we are doing is probably elementary or middle school math--ratios/porportions; adding, subtracting, and multiplying; and solving for a missing number. Math is a tool just like every thing else we learn in nursing school.

If math frightens you, it is because you do not understand math's rules and have not done enough problems. There are only so many ways questions can be asked. Once you undersand this and understand how to solve these questions, you won't be afraid. I was in your shoes and was an adult before I took my first algebra class. Now I love the challenge math presents.

nurseprnRN, BSN, RN · Jan 11, 2012

this isn't math, it's basic algebra, multiplication, and division. you learned how to solve for x in sophomore (high school) algebra. this is why high school math is a prerequisite to nursing school....and it's also illustrative of why you should remember stuff you learned in your first-year pharmacy calculations class. because, well, you need it to be a nurse.:doh: