# Drug Calculations/IV GTT Rates for EMT Advanced



## 78mfire (Apr 5, 2016)

This is my first post, even though I have been "browsing" for some time. I am currently about 4 weeks out from NREMT and well into the clinical portion of the class. My question is this, I am having a rough time nailing down the dosage rate calculations. Its coming to me at a frustratingly slow pace. I always considered myself able to handle conversions but this is a little confusing to me. Would anybody have any hints or suggestions that would help me grasp this a little better. Thanks in advance and I really enjoy this website!!


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## Aprz (Apr 6, 2016)

Not sure how we can help. It's basic arithmetic. What are you having trouble with exactly? Drips? Do you have any examples? Where are you getting stuck or lost?

I've written some stuff about it before.

http://emtlife.com/threads/drug-calculation.35378/#post-504817

I know I've written more on it before, but can't find it. I think it was in the 100% directionless. XD Good luck with anyone finding that.

The way I do it can be confusing, but I just stay systematic like with my assessments and ECG interpretation.


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## 78mfire (Apr 6, 2016)

Thanks for the reply. Converting grams to milligrams, etc is causing me some trouble.


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## Akulahawk (Apr 6, 2016)

I do that stuff all the time and it's starting to become easier. The drugs that drive me nuts are the ones that are weight based... but I use a simple ratio/proportion formula and it's pretty easy to get the right dose. After that, you just simply have to figure out the drip rate and even that's not too difficult. I do, however, have a trick up my sleeve if I need it: an app that calculates drip rates.


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## StCEMT (Apr 6, 2016)

That's the beauty of the metric system, its all based on 10's. 1g=1000mg. All you have to do is move the decimal place over 3 spots.


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## 78mfire (Apr 6, 2016)

The advice is much appreciated, I'm 98.9% sure it's just me over thinking it but I really want to nail this down so I don't second guess myself when it counts!


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## StCEMT (Apr 6, 2016)

If g<-->mg<-->mcg is really your biggest issue, yea, you are overthinking things and are fine.


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## Aprz (Apr 6, 2016)

Ah, it was actually easy enough to find using the search, searched by poster, and put med math or something, lol. This was on dopamine and the difference between 10 gtt drip set, 15 gtt drip set, 20 gtt drip set, and 60 gtt drip set.

http://emtlife.com/threads/the-100-directionless-thread.9773/page-2277#post-164731


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## Gurby (Apr 6, 2016)

I had a eureka moment in the shower a few weeks ago... If you are using a 60 gtts set, the number of drops per second = the number of ml's per minute.

So, 1 drop/sec = 1 mL/min.  0.5 drop/sec (ie 1 drop every 2 seconds) = 0.5 mL/min.


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## chaz90 (Apr 6, 2016)

Gurby said:


> I had a eureka moment in the shower a few weeks ago... If you are using a 60 gtts set, the number of drops per second = the number of ml's per minute.
> 
> So, 1 drop/sec = 1 mL/min.  0.5 drop/sec (ie 1 drop every 2 seconds) = 0.5 mL/min.


It's like there was a reason they chose 60 as the base rather than 50...


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## Gurby (Apr 6, 2016)

chaz90 said:


> It's like there was a reason they chose 60 as the base rather than 50...



My face when I made this discovery:


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## 78mfire (Apr 7, 2016)

Gurby said:


> I had a eureka moment in the shower a few weeks ago... If you are using a 60 gtts set, the number of drops per second = the number of ml's per minute.
> 
> So, 1 drop/sec = 1 mL/min.  0.5 drop/sec (ie 1 drop every 2 seconds) = 0.5 mL/min.


Excellent!! That seems too easy......


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## medichopeful (Apr 7, 2016)

Disregard


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## medichopeful (Apr 7, 2016)

Learn dimensional analysis (https://en.wikipedia.org/wiki/Dimensional_analysis). It's truly the most useful mathematical strategy you'll ever learn.  You can use it for anything: drip rates, unit conversion, weight-based drugs, how much of a drug to give, etc.  

Plus, it has it's own checks and balances system.  If you set it up wrong, as long as you keep track of the unit labels and plug in the right numbers/conversion factors, it will tell you that something is off.  



Akulahawk said:


> I do that stuff all the time and it's starting to become easier. The drugs that drive me nuts are the ones that are weight based... but I use a simple ratio/proportion formula and it's pretty easy to get the right dose. After that, you just simply have to figure out the drip rate and even that's not too difficult. I do, however, have a trick up my sleeve if I need it: an app that calculates drip rates.



The pumps we use in the hospital do drip rates for us.  I'm totally spoiled.  Select the drug, weight, and desired rate, and it automatically plugs it all in for you and sets the ml/hr.  There's also the option to enter a volume and an amount of time to infuse it over and it will calculate that out too.  Hopefully similar pumps come out for ems in the near future.


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## Aprz (Apr 8, 2016)

Gurby said:


> I had a eureka moment in the shower a few weeks ago... If you are using a 60 gtts set, the number of drops per second = the number of ml's per minute.
> 
> So, 1 drop/sec = 1 mL/min.  0.5 drop/sec (ie 1 drop every 2 seconds) = 0.5 mL/min.


If you had read my post carefully, you would've figured it out sooner. 



Aprz said:


> If you can convert any other drip set into a 60 gtt drip set, you can easily figure out mL/hr too because whatever gtt/min with a 60 gtt drip set equals the same as mL/hr eg 13 gtt/min with a 60 gtt drip


http://emtlife.com/threads/the-100-directionless-thread.9773/page-2277#post-164731

Edit: Oh, you are talking about gtt/sec = mL/min. I was thinking of gtt/min = mL/hr. Thinking about mL/min is actually probably more useful. Never thought of this.


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## Akulahawk (Apr 9, 2016)

medichopeful said:


> Learn dimensional analysis (https://en.wikipedia.org/wiki/Dimensional_analysis). It's truly the most useful mathematical strategy you'll ever learn.  You can use it for anything: drip rates, unit conversion, weight-based drugs, how much of a drug to give, etc.
> 
> Plus, it has it's own checks and balances system.  If you set it up wrong, as long as you keep track of the unit labels and plug in the right numbers/conversion factors, it will tell you that something is off.
> 
> The pumps we use in the hospital do drip rates for us.  I'm totally spoiled.  Select the drug, weight, and desired rate, and it automatically plugs it all in for you and sets the ml/hr.  There's also the option to enter a volume and an amount of time to infuse it over and it will calculate that out too.  Hopefully similar pumps come out for ems in the near future.


If you're able to get the hang of dimensional analysis, it really _is_ a great tool for doing medical calculations. While I can do it, I'm much more familiar with ratio/proportion formulas so I go with what's easier for me. Also, I'm getting spoiled too... our pumps do the same things for us. Sometimes when we've got a question about drip rates for a given drug, we sometimes defer to the pump because that's pre-programmed into the device. That's useful when the drug references are a little fuzzy about specific rates.


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## medichopeful (Apr 9, 2016)

Akulahawk said:


> If you're able to get the hang of dimensional analysis, it really _is_ a great tool for doing medical calculations. While I can do it, I'm much more familiar with ratio/proportion formulas so I go with what's easier for me. Also, I'm getting spoiled too... our pumps do the same things for us. Sometimes when we've got a question about drip rates for a given drug, we sometimes defer to the pump because that's pre-programmed into the device. That's useful when the drug references are a little fuzzy about specific rates.



It's funny, dimensional analysis is really the only one I can wrap my head around.  People have tried to teach me other ways, and I just can't do them.  Whatever is easiest and gives the correct answer is the best way to do it! What pumps do you use?


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## Carlos Danger (Apr 9, 2016)

There are only 2 simple steps to calculate a drug given by IVP:

*First, figure out how much drug you need to administer.* This is simply the known dose x the patients weight in kg. For example, the ped dose of Ancef is 25 mg/kg. So if you have a 10 kg kid, you just multiply 25x10. 250 mg is your total dose to give. 

*Second, convert the amount of drug you are need to give (in mcg or mg) to a volume (number of cc's) to give.* This is simply the dose of the drug you are going to give divided by the concentration you have on hand. So if your Ancef comes in a concentration of 100mg/ml. you divide your dose (250) by your concentration (100). 250/100 =  2.5. That the number of cc to give.
Another one: you need to give 1 mcg/kg of fentanyl to a 75kg patient. First, calculate the total dose: 1mcg x 75kg = 75 mcg. Now, you need to covert 75mcg to a volume to give. Your fentanyl is 50mcg/ml. So now divide your dose by your concentration: 75 / 50 = 1.5 ml to give.

That's all there is to it: multiply the ordered dose by the patient's weight, and then divide that number by the concentration on hand. Done.


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## medichopeful (Apr 10, 2016)

Remi said:


> There are only 2 simple steps to calculate a drug given by IVP:
> 
> *First, figure out how much drug you need to administer.* This is simply the known dose x the patients weight in kg. For example, the ped dose of Ancef is 25 mg/kg. So if you have a 10 kg kid, you just multiply 25x10. 250 mg is your total dose to give.
> 
> ...



Similar to (ordered/available)*(vehicle).

So if you need to give 2mg of Zofran (4mg/2ml):
(2mg/4mg)*(2ml)=1ml.  Therefore, give 1ml.

I like this method because it works for any concentration, you don't have to get it down to blank/1ml.  In addition, it's nice because you can use it for pills too:
You need to give 4mg of Zofran ODT.  You have 8mg tabs.  How many do you give?
(4mg/8mg)*(1 tab)=0.5 tabs.


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## Akulahawk (Apr 10, 2016)

medichopeful said:


> It's funny, dimensional analysis is really the only one I can wrap my head around.  People have tried to teach me other ways, and I just can't do them.  Whatever is easiest and gives the correct answer is the best way to do it! *What pumps do you use*?


We use Baxter Sigma Spectrum infusion pumps. They're not too complicated in that all you're really doing is controlling a gravity drip setup with a pump. That's nice if you're used to doing gravity IVPB infusions and you really want to control the rate... but if you need to do concurrent infusions, you need 2 pumps. Personally I'd prefer pumps that have at least 2 channels or a single cartridge that allows an A (primary) and B (secondary) channel within the cartridge. Then you can run a concurrent secondary drip on a single channel.


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## Akulahawk (Apr 10, 2016)

Remi said:


> There are only 2 simple steps to calculate a drug given by IVP:
> 
> *First, figure out how much drug you need to administer.* This is simply the known dose x the patients weight in kg. For example, the ped dose of Ancef is 25 mg/kg. So if you have a 10 kg kid, you just multiply 25x10. 250 mg is your total dose to give.
> 
> ...


The above is GREAT if you're giving weight-based medications. Very handy and basically what I do if I must make those calculations myself. 


medichopeful said:


> Similar to (ordered/available)*(vehicle).
> 
> So if you need to give 2mg of Zofran (4mg/2ml):
> (2mg/4mg)*(2ml)=1ml.  Therefore, give 1ml.
> ...


This is good for those times when you know you need to give a drug dose that's different from unit dose that you have on hand. A couple weeks ago I had to give an antibiotic that we didn't have the particular dose in stock anywhere in the hospital but we did have it available in another dose. I used this formula to determine how much of the antibiotic to give. 

Fortunately a lot of the time you only need to give full unit doses...


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## Carlos Danger (Apr 10, 2016)

I explain it the way I do in order to make the procedure of volume calculation appear to be as "math-less" as possible. 

This is because I've found people who have a hard time with drug calculations often do so because for whatever reason, they just have some sort of mental block about math and equations. Show them an example of dimensional analysis and they get anxious. And maybe they understand it when you explain it, but then have a hard time remembering how to apply it much later when they need to use it.  

I think once people understand that it really only breaks down to 2 steps that each require a single, simple calculation, it makes sense in their minds and is easy to remember because once you understand it what you are doing, it becomes quite obvious in a way that dimensional analysis just isn't to many people.

Of course infusions are a little different, but I really don't think anyone should be running infusions without a pump, in any case.


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## NomadicMedic (Apr 10, 2016)

Remi said:


> Of course infusions are a little different, but I really don't think anyone should be running infusions without a pump, in any case.



Yet we do, all the time. Dopamine, epi, and lido are the ones that I seem to use most frequently. Why is it that EMS will buy all kids of goofy toys for the trucks, but hardly anyone carries pumps?


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## gotbeerz001 (Apr 10, 2016)

I understand math and have no problem finding answers; however, in the field I prefer a systems such as the Handtevy method for peds and dosing/drip charts since everything seems to go down at 3 am when I am borderline brain-dead. 


Sent from my iPhone using Tapatalk


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## medichopeful (Apr 10, 2016)

Akulahawk said:


> We use Baxter Sigma Spectrum infusion pumps.



When I was doing nursing clinicals, one of the hospitals I was at was switching over to those.  I really like how small they are and how the display is laid out.  Easy to see the exact rate from across the room.



Akulahawk said:


> Personally I'd prefer pumps that have at least 2 channels or a single cartridge that allows an A (primary) and B (secondary) channel within the cartridge. Then you can run a concurrent secondary drip on a single channel.



The pumps we currently use allow that (Abbott Plum A+3 infusion pumps), but the problem is the setup is huge.  Perfect for ICU, not so great for ER (where there's more patient movement).  Even so, they're the best pumps I've ever used.


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## Ethan (Apr 21, 2016)

dd x wt. in kg x ds divided by concentration x time in min


dunkin donuts was dripping sugar over their coffee and tea


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## Mantis Toboggan (Apr 21, 2016)

Dimensional analysis practice (if you enjoy that sort of thing):

A jewelry manufacturer is provided 50 lb blocks of silver.  One of these blocks will be drawn into a silver wire that is 2.25mm in diameter.  If its density measures 10.49 g/cm³, how many feet of wire can be obtained from the silver block?


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## 78mfire (Apr 26, 2016)

I would like to thank all of you for the replies. I will have more time after NREMT to figure out what really works best for me but in the mean time I just need a hard and fast way to do it for registry. After that, I'm not going to rely on an app and will work it a lot more but I know our rigs have basic drip rates/calculations cheat sheets. As a Intermediate service, we usually establish an IV TKO or saline lock, depending on if we have a ALS rig intercepting us or transport time. Thanks to all of you again. 
I am always open to new and different procedures, within my scope anyway!


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## Gurby (Apr 26, 2016)

Mantis Toboggan said:


> Dimensional analysis practice (if you enjoy that sort of thing):
> 
> A jewelry manufacturer is provided 50 lb blocks of silver.  One of these blocks will be drawn into a silver wire that is 2.25mm in diameter.  If its density measures 10.49 g/cm³, how many feet of wire can be obtained from the silver block?



8652.6 feet?


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## Tigger (Apr 28, 2016)

DEmedic said:


> Yet we do, all the time. Dopamine, epi, and lido are the ones that I seem to use most frequently. Why is it that EMS will buy all kids of goofy toys for the trucks, but hardly anyone carries pumps?


Even though our MiniMeds are a pain, they are waaaay better than any sort of gravity infusion. WE buy refurbished models that are two grand plus the yearly service. In the scheme of biomedical devices, that's a good deal.


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