# IV Math Problems HELP!!!!!

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Hi everyone!

These problems have me confused! If anyone has time to tackle them I'd be really appreciative! (I think the first one is 12 ml/hr) I have a pass/fail math exam in a few weeks and I'm stressed! Thanks alot for your time!

2. Your CCU patient is currently receiving heparin sodium 800units/hr/. The PTT is lower than expected so the physician orders heparin sodium to be increased to 1200units/hr. Your bag of solution is labeled 25,000 units in 250ml of D5W. What IV rate will set on the pump to deliver the correct dose of heparin? ___________ml/hr

5. Dopamine drip at 250mcg/min is ordered. You have the standardized hospital solution of 200mg in 250ml of D5W. You have micro drip tubing 60gtts/ml available. How many drops/min will deliver the correct dose?

112 Posts

Yes, #2 is 12mL/hr.

#5 is 19gtt/min. Using dimensional analysis, set up the problem with the data provided so that all units except those desired at the end (gtt/min) cancel out, then do the math: (dots added for formatting)

250mcg X .. 250mL ....... X ...... 60gtt ...=... 19gtt

1 min. .......200,000mcg ...........1mL ...........1min.

58 Posts

#2 I know there are several ways to do these, but here goes the way I use....(12,000 units / 100 units) X 1mL = 120 mL/hr OR you could do (12,000 units / 25,000 units) X 250 mL = 120 mL/hr

To me it is easier to get how many units there is in 1 mL before working the problem, but you end up doing it in the problem anyways if you dont. Also, dont let extra information mess you up. Just figure out what the order is by asking yourself "what are you going give the pt when you go in the room".

#5 This problem has a couple of steps going on so I like to organize the info without having a word problem. This is the setup I use and I also add in more stuff if the problem contains more stuff. Anyways, "order" means what the actual order is (what you will be administering), 'hand" means what you have on hand or available or in the med room, tubing is the drop factor of the tubing, and "??" is what the question is asking for or what your final labeling will be.

ORDER: 250 mcg/min

HAND: 200mg/250mL

TUBING: 60gtts/mL

??: gtts/min

Ok, so in order to get the gtts/min you need to know how much SOLUTION you are giving not how much medication that solution contains; however, you have to make sure that the amount of solution contains the right amount of med. So first you need to find out how many mL you are going to be administering. You need the ORDER and what you have on HAND to figure this out.

(250 mcg / 200 mg) X 250 mL

Also in order to finsih this problem you need to add in a conversion of mcg to mg. This can be done a million ways and this is not the best way to type this but here it goes

(250 mcg / 200 mg) X 250 mL X (1 mg / 1000 mcg)

Simplify and cancle and you get the answer of 0.31 mL/min

Now you have to use that to solve the rest of the problem

(0.31 mL / min) x 60gtts/mL which ends up equaling 19gtts/min

Hope this helps....Feel free to ask me to explain some things I might have done. Also if I typed this on word I could show things more acurately!!

112 Posts

#2 I know there are several ways to do these, but here goes the way I use....(12,000 units / 100 units) X 1mL = 120 mL/hr OR you could do (12,000 units / 25,000 units) X 250 mL = 120 mL/hr

amyb2684, note the order is for 1200units/hr, not 12,000.

Using dimensional analysis:

1200units...X... 250mL ....=..12mL

...1hr.............25,000units....1hr..

58 Posts

amyb2684, note the order is for 1200units/hr, not 12,000.

Using dimensional analysis:

1200units...X... 250mL ....=..12mL

...1hr.............25,000units....1hr..

OOPS!! I had it right when I wrote it down and I went back and checked it and.....I dont know what I did. Thanks!!

4 Articles; 14,603 Posts

Specializes in med/surg, telemetry, IV therapy, mgmt. Has 40 years experience.

your ccu patient is currently receiving heparin sodium 800units/hr/. the ptt is lower than expected so the physician orders heparin sodium to be increased to 1200units/hr. your bag of solution is labeled 25,000 units in 250ml of d5w. what iv rate will set on the pump to deliver the correct dose of heparin? ___________ml/hr

iv pumps are always set at
ml/hour
, so that's the final answer you are looking for must have those labels on the answer.

by dimensional analysis:
1,200 units/hour
(dose desired)
x 250 ml/25,000 units
(dose on hand)
=
12 ml/hour
(rate to set pump at)

you can also do this by
the dose desired divided by dose on hand multiplied by the amount the dose on hand comes in
formula and get the same answer:
(1,200)/(25,000) x 250 = 12

dopamine drip at 250mcg/min is ordered. you have the standardized hospital solution of 200mg in 250ml of d5w. you have micro drip tubing 60gtts/ml available. how many drops/min will deliver the correct dose?

by dimensional analysis:
250 mcg/minute
(dose desired)
x 250 ml/200 mg
(dose on hand)
x 1 mg/1000 mcg
(conversion factor)
x 60 gtts/ml
(drop factor of iv tubing)
= 18.75 gtts/minute
, round up to
19 gtts/minute

20 Posts

I don't want to sound totally clueless, but in the second problem why is there no dividing by 60 min to get gtt/min? Thanks for your help!

112 Posts

I don't want to sound totally clueless, but in the second problem why is there no dividing by 60 min to get gtt/min? Thanks for your help!

What is it that you would divide by 60 minutes?

The only units you would ever have to convert into minutes would be 'hours', as in problems that contain 'mL/hr' and that you need to result in 'gtt/min'. There are no 'mL/hr' in this problem. There are 'mcg/min', 'mL/mg', and 'gtt/mL', all of which are sufficient to end up with 'gtt/min' as dimensional analysis allows you to cancel undesired units.

4 Articles; 14,603 Posts

Specializes in med/surg, telemetry, IV therapy, mgmt. Has 40 years experience.
i don't want to sound totally clueless, but in the second problem why is there no dividing by 60 min to get gtt/min? thanks for your help!

dimensional analysis is also called the factor label method. there are two things going on that you are dealing with:

1. labels attached to the numbers, and
2. arithmetic (math)

in dimensional analysis numbers and labels are each operated on separately. however, the terms going into the equation you create are derived from the information you are given and from critical, rational thinking. the problem was set up:

250 mcg/minute
(dose desired)
x 250 ml/200 mg
(dose on hand)
x 1 mg/1000 mcg
(conversion factor)
x 60 gtts/ml
(drop factor of iv tubing)
= 18.75 gtts/minute

and you will see where the "minute" label was included in the problem as part of the term for the dose desired.

where did you come up with this "60 min"? it wasn't a term or part of the information given in the problem. "60" by itself doesn't mean anything. and, "60 min" wasn't a factor that was needed to compute the answer to this problem.

58 Posts

I don't want to sound totally clueless, but in the second problem why is there no dividing by 60 min to get gtt/min? Thanks for your help!

You only use 60 minutes if the time you are given is 1 hour. The bottom of the first part of the equation will always be "time that you are infusing in MINUTES". If you are given 1 min you use 1 min, if you are given 2 minutes you use 2 min, and if you are given 1 hour you use 60 min...and so on. Be thankful when you are given a breakdown to 1 min because you have less math. Also, remember that your tubing will not always be microdtrip (60gtts/min).

PS. No questions can make you sound clueless. You have the initiative to ask for help which makes you NOT clueless.

20 Posts

Thank you guys so much for explaining. My prior belief was dividing by 60 min to acquire per minute. Your explanations make perfect sense and thanks to everyone for your time and patience! I've never seen a problem like this before so thanks again!

4 Articles; 14,603 Posts

Specializes in med/surg, telemetry, IV therapy, mgmt. Has 40 years experience.

There has to be a reason you would be "dividing by 60 minutes".

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