# Pharm math and Syringes

Posted

Hi,

I'm in my 4th month of LPN school so please bear with me. What are the most common types of syringes used on a day to day basis by LPNs? I'm asking because I'm struggling with this on my Pharm math quizzes and I need to get this down before I take my actual Pharm math Exams.

For example:

Question 1

Physician orders Diphenhydramine hydrochloride 30mg IM stat, the pharmacy has sent Diphenhydramine hydrochloride 40mg/ml

My answer which I calculated was 0.75ml.... my instructor marked this question wrong because I didn't specify "0.75ml in a TB syringe"

Question 2

Physician orders Epinephrine 0.4mg sq stat, the pharmacy sends Epinephrine ampule labeled 1mg/2ml

My answer which i calculated was 0.8ml... but i rounded up to 1ml. my instructor marked this wrong because she said I can admin 0.8ml in a 3cc syringe or in a TB syringe.

I know the rule more than 5 rounds up and 4 or less rounds down... so i guess my question is how do you know when its appropriate with meds to round up or down and which syringe to use to draw?

Thanks,

~UB~

Specializes in Critical Care, ED, Cath lab, CTPAC,Trauma. Has 41 years experience.

Anything you give that is less the 1ml should be in a TB/1cc syringe for accuracy.

Epinephrine is like insulin no rounding....it changes the dosage.

Anything that is 1ml or less there isn't rounding.

This may help...http://www.aultmancollege.edu/Files/Calculations%20and%20Rounding%20Rules.pdf

What I have learned is, if it's less than 1 mL or mg, then you round to the hundredths decimal place, if it's 1 mL or mg and higher, then you round to the tenths decimal place. The only time that you round to a whole number is when it's gtts.

Specializes in Hospice, Palliative Care. Has 3 years experience.

Good day,

Check if your school has published rounding rules. Ours is as follows:

]When rounding final answers…If the answer is less than 1 such as 0.456 calculate to the thousandth place and use that last number to round to the hundredth place….so 0.456 would round to 0.46. If your final answer is greater than 1 such as 1.78….calculate to the hundredth place and use that last number to round to the tenth place….so 1.78 would round to 1.8.

Thank you.

Specializes in NICU, PICU, PACU. Has 30 years experience.

And when you get to peds you don't round, you use 1ml syringes.

As Esme stated:

Never ever round insulin. Ever. You have no need to. Insulin comes in 30 unit syringes. 10 units syringes. Even 100 unit syringes. Let's use some common sense.

You get an order for 7 units novolog... which syringe is best?

What if the order calls for 10 units of scheduled novolog and 5 units of sliding scale novolog? That's 15 units. So which syringe would you use?

It'll get better when you get some practice behind it. I didn't understand squat about syringes to be completely honest until I started working!

Lasix 40 mg IV Push.

The ampule says: 20mg/2mL

You'll need two ampules and what type of syringe would you use?

5 mL? 10 mL?

Hope this makes sense =)

Edit: Idk if you'll give Lasix IVP as a LPN! Just giving examples off the top of my head. Sorry c:

Edited by StudentOfHealing

Has 6 years experience.

Anything you give that is less the 1ml should be in a TB/1cc syringe for accuracy.

Epinephrine is like insulin no rounding....it changes the dosage.

Anything that is 1ml or less there isn't rounding.

I'm not sure I agree with this. I don't feel the gauge of a TB needle is appropriate for many IM injections. I have used bigger syringes for less than 1 mL as long as they had proper demarcations on the syringe. Of course, in my facility we only have 1 mL syringes that actually are TB syringes with a non-detachable needle, so most of the time a 3 cc syringe is the most appropriate under those circumstances.

Thank you all for your feedback... when we had practice the instructor gave us a 50 unit Insulin syringe, a 3cc syringe, and a 1cc TB syringe. She has us do math problems then draw our syringes to the the amount for our answers to demonstrate what is measurable and what isn't measurable.... BUT when it came time to take the quiz I totally spaced out because I forgot to indicate which type of syringe and rounded when I shouldn't have, etc.

Thanks

UB

Specializes in Neuro, Telemetry. Has 6 years experience.

I would first be questioning your instructor why they would use a TB syringe for an IM injection. The needle is neither long enough (in most cases for adults) nor is it the correct gauge. You would need a 1-1.5 in needle that is 22-25g and a 1 or 3 mL(or cc if you guys use that measure) syringe. A TB syringe would imply the instructor means the all in one TB syringe that already has a needle and those have a 5/8" length needle and are usually 26 gauge. They are quite far off the mark on that one.

For medication NEVER round to a whole number unless specifically told to do so or if you are measuring gtt (which you wouldnt as an LPN anyway). Each program gives its own guidelines for rounding. In general for adult medication you would round to the tenths and for pedi you would round to the hundredths place. Syringe have markings so that you can draw up medications in more specific measurements than whole numbers. 1mL syringes can measure up to hundredths place and 3mL and larger can do tenths place most of the time.

As for what needle to use, that has not much to do with the med and more to do with location and type of injection. Learn the needle sizes and lengths required for SC, IM, and ID. This will be very important. Than when you do a med math calc asking for needles, you will automatically know what needle based on what type of injection it is.

Also knowing some pharmacology will help. If you understand how epinephrine works and its mode of action, you would know why you would want to be very acurate with that med.Same with some high alert meds like heparin and insulin. All meds are important to be accurate with, but some meds are just more dangerous than others.

Specializes in Neuro, Telemetry. Has 6 years experience.

And i just realized that not all facilitie use the all in one TB syringe/needle combo, so my comment about needle size may be irrelevant. Some just have the tb needles separate from the tb syringes. But why not just say a "1mL syringe" you dont specifically have to use a TB syringe for less than 1mL of medication.

Has 6 years experience.

And i just realized that not all facilitie use the all in one TB syringe/needle combo, so my comment about needle size may be irrelevant. Some just have the tb needles separate from the tb syringes. But why not just say a "1mL syringe" you dont specifically have to use a TB syringe for less than 1mL of medication.

There's a school of thought that says 1 mL and a TB syringe are one and the same. In my opinion, a TB syringe is one that already has a non-detachable needle (I think it's a 27 gauge, but I'm not sure - regardless, it's NOT appropriate for an IM injection but for some rare circumstances) although there are 1 cc syringes with detachable needles. In those cases, the 1 mL would be the best choice, but really in the real world nobody gives a crap which one you use as long as you draw up and administer the correct dose