Help: Difficulty understanding medication dosage question

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Specializes in General adult inpatient psychiatry.

I'm working on reviewing my math skills in preparation for the obligatory medication dosages exam on day 1 of med-surg and I've hit a bump upon coming across a few of the practice questions my professor sent the class.

The first problem reads as follows: "The physician has ordered KCL 10mEq in 1000 D5 NS to infuse at 100 mL/hr. How many milliliters will the nurse add to the IV?"

This is followed by a medication label that says "Potassium Chloride, 40 mEq (2 mEq/mL), 20 mL single dose vial."

The second problem reads as follows: "The physician has ordered Humulin NPH 20 units plus Humulin R 11 units SQ every evening. The medication is supplied in 100 units/mL. How many units will the nurse administer?"

For this one, can I just add the 20 + 11 and put it in a proportion to figure out the answer, like

31 units 100 mL

_______ = ____

x units 1 mL

and cross multiply, or am I missing something.

Can someone walk me through this? I feel like the answer is right in front of me but I'm never sure how to start problems like this.

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Specializes in Utilization Management.

Daytonite is much better at this than I am, but the real problem is trying to pick out the information that you need to use and knowing how to use it. I will give you some hints.

In the first one, what you need is 10 mEq's of KCL. The label tells you what you have, (KCL 2 mEq in each milliliter).

In the second one, you have 20 units + 11 units and your medicine already comes in units, so you don't have to convert anything.

I hope that helped. I'll confirm your answers after you post them, if you like.

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For the second problem the question is just about units so you just add 20 units + 11 units= 31 units. You just worry about the units and not the ml in this problem. I'm not sure for the first problem but I guess 10 mEq * 1 mEq/ 2 ml = 5 ml added. I'm confused about the first problem too. I hope that helps a little bit.

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Specializes in Telemetry/Cardiac Floor.

i got what they did..

5ml

31units

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It's pretty hard to explain in writing but I hope I can help.

I use the other formula D/A x Q instead of the proportion depending on what the problem asks for.

I don't want to confuse you but first things first...always read the problem then sift out the distractors. My instructor taught me to always look at the stem of the question first and figure out "what is the question asking you for?" I'll just try demonstrating what I'm talking about for the first question.

In the first problem it could ask you for many things (ie. mL/hr, etc.) but in the stem it asks you for "how many mL's" of KCl you'll have to add to your IV bag. So you now know your strictly looking for mL's - and this eliminates looking at that distracting '100 mL/hr' - the question has nothing to do with that.

In any case, this becomes a simple problem of:

dose ordered

------------- x Quantity (per amount in bottle)

Amount on hand

So...doc ordered 10meq. Your bottle of KCl is 40 meq in 20mL

Plug it in and you'll end up with 5 mL.

*edit* After looking at the second problem the stem only asks for units so you'd just add the two insulins together.

I'm not much of a teacher :specs: but I hope this helps a bit.

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Specializes in Utilization Management.
It's pretty hard to explain in writing but I hope I can help.

I use the other formula D/A x Q instead of the proportion depending on what the problem asks for.

I don't want to confuse you but first things first...always read the problem then sift out the distractors. My instructor taught me to always look at the stem of the question first and figure out "what is the question asking you for?" I'll just try demonstrating what I'm talking about for the first question.

In the first problem it could ask you for many things (ie. mL/hr, etc.) but in the stem it asks you for "how many mL's" of KCl you'll have to add to your IV bag. So you now know your strictly looking for mL's - and this eliminates looking at that distracting '100 mL/hr' - the question has nothing to do with that.

In any case, this becomes a simple problem of:

dose ordered

------------- x Quantity (per amount in bottle)

Amount on hand

So...doc ordered 10meq. Your bottle of KCl is 40 meq in 20mL

Plug it in and you'll end up with 5 mL.

After looking at your second problem it is similar to this problem and you could use the same formula above. Only thing is you must add those insulins together first and then plug it in: 31 units/100 units x 1 mL= 0.31 mL (*your probably aware you must cancel out your like units and in this case you'd be left with only mL's).

Knowing what the problem is speaking of could very well become confusing and tricky since it says the insulin is supplied in 100 units/mL. You must read the problem and understand it because this is speaking of the syringe and not an actual insulin bottle. This shows you must figure out how many mL's you'll be drawing up in the syringe.

I'm not much of a teacher :specs: but I hope this helps a bit.

The second problem reads as follows: "The physician has ordered Humulin NPH 20 units plus Humulin R 11 units SQ every evening. The medication is supplied in 100 units/mL. How many units will the nurse administer?"

I think you did very well on the first one, but the second one is asking for units, not milliliters, so that 31 units would be the correct answer.

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Specializes in Utilization Management.

This is what the actual vials and insulin syringes will look like once you get to clinicals. N is for NPH, R for regular. The syringes measure in units. You can mix NPH and Regular, so you'll be adding them together pretty frequently. I'm posting these because the insulin question is a very common calculation that you'll see a lot.

insulinbottlesKC.jpg

Insulin_Syringe.jpg

220070405112320.jpg

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I think you did very well on the first one, but the second one is asking for units, not milliliters, so that 31 units would be the correct answer.

Yeah, I caught that LOL! Hey, it would've been right if it was mL's! :D

I posted the picture of the vial label because I wanted you students to see that each of those bottles contains 10 milliliters. :thnkg:

However, there are 1000 UNITS in this bottle. I'm guessing that the confusion between mls and units was probably why ONLY insulin can be used in the orange-topped syringes and NO OTHER TYPE of syringe is to be used to give insulin.

So there you have your first online mini-clinical.....I knew it'd make you jump for joy...:hpygrp:

regular6602.jpg

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Specializes in med/surg, telemetry, IV therapy, mgmt.
"the physician has ordered kcl 10meq in 1000 d5 ns to infuse at 100 ml/hr. how many milliliters will the nurse add to the iv?"

this is followed by a medication label that says "potassium chloride, 40 meq (2 meq/ml), 20 ml single dose vial."

use the formula:
dose desired divided by dose on hand multiplied by the amount the dose on hand comes in to give you the amount you need.

dose desired: 10 meq

dose on hand: 40 meq in 20 ml

10 meq
(dose desired)
/ 40 meq
(dose on hand)
x 20 ml
(the amount the dose on hand is in)
=
5 ml
(amount ot potassium to add to the iv)

"the physician has ordered humulin nph 20 units plus humulin r 11 units sq every evening. the medication is supplied in 100 units/ml. how many units will the nurse administer?"

this is a simple addition problem:

20 units
(of humulin nph)
+ 11 units
(of humulin r)
=
31 units
(total)

all the pictures are nice to look at, but have nothing to do with the medication calculations. if a math problem is seeming to get very complicated--stop--start again--and try to keep it simple. most problems are simple rather than complicated. some instructors are fond of adding a lot of extraneous information which ends up tripping you up. why they do this, i don't know. keep the basic dose desired divided by dose on hand to give you the dose to give formula in your mind and look for the terms to plug into it.

there are two thread on the student forums that have medication calculation problems for you to check out:

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Specializes in Utilization Management.

I included the pictures so that the students could visualize the difference between a unit and a milliliter. One student's answer (before it was edited) was in milliliters instead of units.

I was taught that the last step of any drug calculation was to ask yourself, "Does this answer make sense?"

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I am just beginning to do medication calculation also, you guy I am really going to need you all help if you can help me.

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