New student with math problem

[fostersgirl69]

I am a first year RN nursing student and I am having problems with a math calculation. If anyone can please show me step by step how to figure it out, I would be very greatful. Thank you so much for your time.

1. The physician has prescribed 500 ml of D5W with 150 mg of Ritodrine HCL to be infused at a rate of 100 mcg/min. Using an IV administration set that delivers 60 microdrops/ml, how many microdrops/min will you infuse the IV?

[SummitRN, BSN, RN]

(500ml/150mg)*(100mcg/min)*(1mg/1000mcg)*(60gtts/1ml)

added units

[SummitRN, BSN, RN]

Wow...

So * is multiplication.

[LadyinScrubs, ASN, RN]

the physician has prescribed 500 ml of d5w with 150 mg of ritodrine hcl to be infused at a rate of 100mcg/min.

using an iv administration set that delivers 60 microdrops/ml,

how many microdrops/min will you infuse the iv?

a. there are two ways to infuse an iv. the iv pump (which will give you ml/hr) and the drip system (which will give you drops per minute).

b. the question is asking you for drops/min -- dead giveaway that you are not using an iv pump. the drip set this question is using is

micro gtts/ml

c. the question is giving two similar terms. mcg and micro gtts. it is easy to confuse the two. don’t

d. there are two ways to solve the problem and i will show both

1.a. you need to convert the 150 mg to mcg. remember there are 1000 mcg in 1 ml = 150,000 mcg

1.b. now you need to determine how many minutes 150,000 mcg will infuse at the rate the physician ordered, 100 mcg/min

150,000 mcg/ 100 mcg per min = 150 minutes

1.c. this is the formula for obtaining drops per minute

amount of ml/# minutes * 60 micro gtts/1 ml

500 ml/150 min * 60 micro gtts/1 ml = 3000/150 = 200 micro gtts/min

or some solve it this way

(the way summitap did)

2.a.

500ml/150mg * 1000 mcg/1 min * 1 mg/1000 * 60 micro gtts/1 ml = 200 micro gtt/ min

the way you solve the problem will determine how you were taught to do the med math.

[fostersgirl69]

The teacher's answer sheet said the answer was 20 gtts/min. That's where I keep messing up!

[fostersgirl69]

To LadyinScrubs,

thanks for taking the time to break this question down for me. I can't understand it when people just give me the answer, or just plug the numbers for me. I need to know what to ask myself when trying to figure out a calculation problem. The teacher's answer to this question is 20 gtts/min not 200gtts/min. That's what was confusing to me.

[SummitRN, BSN, RN]

ladyinscrubs your solution is wrong. the answer is 20gtt/min.

this solution is correct:

(500ml/150mg)*(100mcg/min)*(1mg/1000mcg)*(60gtts/1ml)=20gtt/min

150,000 mcg/ 100 mcg per min = 150 minutes

this is where you made your error. it should be 1500minutes. also, you somehow inserted an extra zero in to your version of my solution which gave you the same erroneous answer of 200.

[LadyinScrubs, ASN, RN]

ladyinscrubs your solution is wrong. the answer is 20gtt/min.

this solution is correct:

(500ml/150mg)*(100mcg/min)*(1mg/1000mcg)*(60gtts/1ml)=20gtt/min

this is where you made your error. it should be 1500minutes. also, you somehow inserted an extra zero in to your version of my solution which gave you the same erroneous answer of 200.

ah...dyslexic.....or lack of sleep.

[trudiegrl]

(60 gtts/1mL)*(500mL/150 mg)*(1mg/1000mcg)*(1000mcg/1min)

= 3,000,000/150,000

= 20 gtts/min

I agree with SummitAp. I had to try the problem it's good practice :)

[Bob_N_VA]

I got 20gtt/min as well. One thing to keep in mind is that when you get one of these problems that is looking for gtt/min, the answer is going to be somewhere in the range of say 20-60gtt/min since you really would have a hard time counting anything slower or faster. So an answer of 200 immediately rings bells in my head as out of range. Usually its one simple math error that screws everything up.