Need help with a math problem.

[gabriellegoss]

I am doing math problems an am seeming to have a duh moment..

This is an IV Heparin Infusion problem.. Keeping in mind that the normal adult heparinizing dose is 20,000-40,000 U/24hr.

"The patient is receiving 500 ml D5W IV with 40,000U Heparin. The IV is infusing at 24 gtt/minute with and infusion set calibrated for 15 gtt/mL. Is the hourly dose of heparin safe?"

I have so far figured out that there are 80U heparin in each ml of D5W. Not sure what to do with the gtt/min or gtt/mL. Thought maybe to multiply 500mL x 15 gtt/mL which would give me 7500 gtt/500 mL. Then I tried multiplying that by 24 gtt/min.. I know this problem is probably super easy but I am totally blanking.

[SunshineDaisy, ASN, RN]

The answer I came up with is 7680 u of heparin. I first found out how many mL/hr there are... 1 mL/15 gtt X 24 gtt/min x 60 min/hr = 96 mL/hr. Then found out the units with that answer... 40,000u/500 mL x 96 mL/hr = 7680 u/hr

[SunshineDaisy, ASN, RN]

I hope I'm right :/

[nurseprnRN, BSN, RN]

OK, let's think about this.

So you know you have 80 units on one cc.

(Always write it out-- I know it's easy to read in typed fonts but get in the habit of writing it out because u is often misread as a zero in handwriting, with disastrous possibilities. This is why hospitals require the word "units" in all documentation. Ahem.)

And you have 15 gtts in one cc.

And your IV is running at 24gtts/minute. if 15gtts is one cc, how many cc's is 24 gtts?

if 80 units = 15 gtts = 1 cc, how many units is in 24 gtts?

That gives you units per minute, doesn't it?

So how may units per hour (and then per 24 hours) is that?

[furelite]

Which is the same answer that SunshineDaisy came up with, isn't it? If you multiply that by 24 hrs it appears to be waaaaay too much according the the normal dose cited?

[furelite]

I am figuring it out now by dimensional analysis, can you tell me if this is right (I get the same answers as above)

Units/hr = 40,000 units/500 mL x 1 ml/15gtt x 24 gtt/1minute x 60 min/1 hr = 7680 units/hr

[SunshineDaisy, ASN, RN]

I tend to do the long version of dimensional analysis, which helps me! I do the first problem, get that answer, then the second problem and get that answer.

[nurseprnRN, BSN, RN]

You are correct that the IV as set is giving 128 units per minute, which is 7680 units per hour, which is 184,320 units per 24 hours.

Which is waaaay out of your stated normal range.

15 gtts = 80 units

24 gtts = ? units

24 x 80

______ = 128 units /minute

15

60 x 128 = 7680 units per hour

7680 x 24 = 184,320 units per 24 hours