Help! The teacher's answers are different from mine?

[Beaue]

Erythromysin 250 mg in 100 ccD5W to infuse over 1 hour. The I.V. tubing delivers 20 gtt/ml. Calculate gtt/min? I got 83.3 but her answer that she gave us was 33.

I am so afraid of failing drug cal tomorrow. We had only 2 days of class where she went over chapter 7 and 8, which is on Monday and Tuesday. Friday she handed out calculation worksheet to us while we were in fundamentals. The test is on Tuesday (tomorrow). We actually were in Fundamentals, not her class so barely got to ask questions. This seems unfair. we needed another day to review.

[chare]

4 minutes ago, Beaue said:

250mg in 100cc to infuse in over 1 hour and the 20 gtt/ml.

Do you need the 250 mg to calculate the drip rate?

[RoundAbout33, BSN, RN]

Try using dimensional analysis. Like a previous poster said, always start on top with what you're looking for - in this case, gtts. The question says there are 20gtts in 1ml, so that is what you write first. Next, think about what you're trying to get to - gtt/min, so what helps you get rid of the mL? Well, the question gives you 100ml needs to be infused in 1hr, so you have 100mL/1hr. This helps you get rid of the mL and now you have gtt/hr. Since you what gtt/min, you need to get rid of the hr. 1hr is 60 min, so you put that last and see that your remaining units are gtt/min. Multipy through and solve.

20gtt/ 1mL * 100mL/ 1hr * 1hr / 60min = 2000/60 = 33.3gtt/min

I've found that approaching all med calc questions this way has helped. Start with what you need to find, see what the question gives you that you can use for conversion, and solve. Make sure you know your conversion values in general.

Hope this helps!

[cameron5575, BSN, RN]

The formula for these types of problems are ((volume in ml) x (gtt/ml))/time in minutes.

Remember, the ml in the volume and the ml in the “gtt/ml” cancel out leaving you with gtt/min.

[Beaue]

thank you. You were very helpful. I added some stuff I didn't need to use. Hugs

[Chazzie_Made_It, ADN]

I got 33.33gtt/min.

There are 20gtt/ml

The volume you have is 100mL which has to infuse over 1 hour.

So, there are 2000gtt/100mL.

Next we need to calculate gtt/min. There are 60mins/hour. We will infuse the 2,000gtt over 60mins (2,000/60)

This comes out to 33.33gtt/min.

[Rose_Queen, BSN, MSN, RN]

16 hours ago, RoundAbout33 said:

Try using dimensional analysis. Like a previous poster said, always start on top with what you're looking for - in this case, gtts. The question says there are 20gtts in 1ml, so that is what you write first. Next, think about what you're trying to get to - gtt/min, so what helps you get rid of the mL? Well, the question gives you 100ml needs to be infused in 1hr, so you have 100mL/1hr. This helps you get rid of the mL and now you have gtt/hr. Since you what gtt/min, you need to get rid of the hr. 1hr is 60 min, so you put that last and see that your remaining units are gtt/min. Multipy through and solve.

20gtt/ 1mL * 100mL/ 1hr * 1hr / 60min = 2000/60 = 33.3gtt/min

I've found that approaching all med calc questions this way has helped. Start with what you need to find, see what the question gives you that you can use for conversion, and solve. Make sure you know your conversion values in general.

Hope this helps!

While I’m sure OP appreciates the answer, doing the work for them doesn’t help in the long run. Students need to learn how to solve these problems, including relevant information and distractors.

[RoundAbout33, BSN, RN]

@Rose_Queen Per OP's initial post, she already had the answer. She listed the answer she got and the answer that her professor provided. I was showing one way to get this answer because she was having difficulty understanding how to get to the correct answer of 33 - which was the reason I explained the steps. I agree, we need to learn how to solve these problems ourselves (I am a student as well), but it often helps if we can see the process of how to get to that answer. My professor who taught dimensional analysis had multiple voice-over ppts that worked through numerous med calc questions to show us how to set them up and get the correct answer. Repeatedly seeing the process and then doing is what helped me learn so I thought I would provide one to OP as well.

[BostonFNP, APRN]

17 hours ago, Beaue said:

thank you. You were very helpful. I added some stuff I didn't need to use. Hugs

Have you considered sitting down with your professor in office hours and getting some extra help with this? I am glad you got some help here, but this is a basic skill that you will need to be able to use both frequently and confidently all through your career. Understanding the basics of dimensional analysis will allow you to answer this question or any other of the thousands/millions of variants of this type of question you will see through school and your career. Getting help now will make your like much easier and your career much safer.

[JenMH88RN, BSN, RN]

Let your units guide you. If they’re looking for drops/min, then you know that you need to calculate the 20 drops/ml. Also, you need to calculate the 100ml/hr. There also needs to be a conversion in between, such as the hour into minutes. Disregard the 250 mg because that has nothing to do with anything. Using the dimensional analysis method makes it more easy for you to see what you’re doing. Also, round your drops to the whole number because you can’t have a half of a drop of something or 0.3 of a drop. Here’s an attachment of what I just explained.

[LvANrse80, ASN, BSN, CNA, LPN, RN]

Hi, 250mg is the amount of medication. Next 100cc * 20 gtt/60( time in minutes) is how the instructor got the answer. 33.33 rounded is 33ml/hr. The 250mg is a distractor.

[Wuzzie]

So let’s see if you have the concept down. You need to give 1gm of Rocephin over an hour. It comes mixed in a 250 ml bag and your tubing drop factor is 20gtts/ml. How many gtts/min will get the medication infused in the time allowed.

Also wanted to add that I wish they would have you do med math that is actually applicable to the real world. I haven’t had to titrate fluids by drop factor since the 80s and it’s unlikely you ever will. Same goes for calculations in grains and drams.

[kaylee.]

Just making sure u knew that cc MEANS ml, cc (cubic centiliters) is an old school unit of measurement that is still used in speech. They should have clarified this...

So if 20 gtt in 1 ml, then how many are in 100 ml? —> 100x20 = 2000 gtt

you want to give this over 1h, or 60 min, so 2000 gtt / 60 min = 33 gtt / min