# math question (medical related)

Status
Not open for further replies.

#### mjrand

##### Senior member
Have a friend studying to be a nurse, and she's having some trouble understanding some math concepts regarding IV rates and such. I tried to figure it out as well, but never end up with the correct answer. Any help you guys could offer would be much appreciated.

Here's the question.

240cc of 0.9 percent sodium chloride needs to be given within 6 hours at a rate of 40gtt/min. Which other IV set can be used?

According to her teacher, a rate of 60gtt can be used as well, but for the life of me, I can't figure out how to come to 60gtt. Any ideas guys?

Last edited:

#### F1N3ST

##### Diamond Member
????? gtt? But taking the numbers 40*6 is 240? I don't know. Seriously.

40/minute 60 minutes / hour? Just a thought.

#### Itchrelief

##### Golden Member
(240cc)/(360min)=(0.66667 ml/min) * (1min)/(40gtt) = 0.016666667 ml/gtt

(0.01666667 ml/gtt)^(-1)=60 gtt/ml

I aint a nurse, but it appears your friend forgot to give you some critical information. From googling, it appears that the gtt is NOT a fixed volume. I am guessing it's something akin to a drop or something, but the size of the drop depends on the equipment, and the equipment will have a gtt/ml rating assigned to it.

The question is probably asking you which gtt/ml rating would you want your equipment to be in order to be able to infuse this patient.

The answer the instructor gave is 60 gtt/ml, NOT 60 gtt/min. That's the best I can do.

Better hope a nurse pops in if you want the real answer.

[stupid paragraphs better be in this time or i'm going to...]

[edit #bazillion and one: cc and ml are pretty much interchangeable in case that was confusing. the volumes are identical in one cubic centimeter and one milliliter]

Last edited:

what

#### dighn

##### Lifer
(240cc)/(360min)=(0.66667 ml/min) * (1min)/(40gtt) = 0.016666667 ml/gtt (0.01666667 ml/gtt)^(-1)=60 gtt/ml I aint a nurse, but it appears your friend forgot to give you some critical information. From googling, it appears that the gtt is NOT a fixed volume. I am guessing it's something akin to a drop or something, but the size of the drop depends on the equipment, and the equipment will have a gtt/ml rating assigned to it. The question is probably asking you which gtt/ml rating would you want your equipment to be in order to be able to infuse this patient? The answer the instructor gave is 60 gtt/ml, NOT 60 gtt/min. That's the best I can do. Better hope a nurse pops in if you want the real answer.

yep. question didn't make sense to me even after googling the meaning of gtt/min and gtt/ml, but then I'm not a nurse.

#### Matthiasa

##### Diamond Member

To calculate rate using hours
(volume x calibration) /(hours x 60) = gtt/min

so 240x/(6*60)=40
240x=40*360
x=40*360/240
x=60

which gives it a unit of gtt/c^3 as mentioned.

Last edited:

#### 911paramedic

##### Diamond Member
240cc of 0.9 percent sodium chloride needs to be given within 6 hours at a rate of 40gtt/min. Which other IV set can be used?

According to her teacher, a rate of 60gtt can be used as well, but for the life of me, I can't figure out how to come to 60gtt. Any ideas guys?

That question is a mess. I think the instructor is asking the different drip rates for a micro/macro set, at least that's how we come up with fluid rates.

For those that don't know: Micro = 60gtt/ml and Macro = 15gtt/ml

I think the question was meant to be: If 240cc of a 0.9% normal saline needs to be infused over 6 hours, what are the drip rates/min for the different IV sets?

240ml in 6 hours = 40ml/hr (240ml/6hr)
40ml/hr = 0.666...ml/min (40ml/60min)

Now you simply multiply how many ml/min you need by the drip rates per set.

Macro: 15gtt/ml * 0.666...ml/min = 10gtt/min
Micro: 60gtt/ml * 0.666...ml/min = 40gtt/min

Correction: Now that I have done the calculations I see what the question was meaning to ask. It should read: 240cc of 0.9 percent sodium chloride needs to be given within 6 hours at a rate of 40gtt/min with a micro set. Which other IV set can be used and what would the rate per minute be?

I hope that helps.

Status
Not open for further replies.