med formulas revisited

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medic44life

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Over the years, I have noticed many different ways for calculating med doses and infusions. I was thought one way however seem to Always encounter a easier way to simplified these calculations. Med math being my most difficult subject in school, and seeing a wave of new medics, I thought it be cool to discuss what formula do you use and do you have any trick\street math that facilitate the process during patient care? I seen different styles and some are more complex than others...thanks in advance.
 
dose/concentration = volume to give

That's all the med math I know.
 
Its not rocket science, if you can't do it in your head scratch it out on paper.
 
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Dopamine and lidocane clocks. I usually draw up meds in a 10cc flush and it makes it easier for me to do calculations (especially for PEDs) or if I do a drip either in a 100ml or 1,000ml bag to make it easier for myself. Its easy for me to do things in units of 10/rather than figure it from a 2-3ml dose. Your just changing the concentration part of the "dose/concentration" equation to better simplify it for yourself which sets yourself up for success rather than a potential mistake, I think
 
Dimensional analysis for the win...

Learn the principle behind the math and the conversion of units, and then it will all fall into place.

I am not a fan of tricks for med math, as they always seem to have a limit to their usefulness. I agree with the earlier poster who said "get better at math." I don't mean it in a crummy way, but it is one of those things.

And always use a calculator.
 
TXmed said:
Dopamine and lidocane clocks. I usually draw up meds in a 10cc flush and it makes it easier for me to do calculations (especially for PEDs) or if I do a drip either in a 100ml or 1,000ml bag to make it easier for myself. Its easy for me to do things in units of 10/rather than figure it from a 2-3ml dose. Your just changing the concentration part of the "dose/concentration" equation to better simplify it for yourself which sets yourself up for success rather than a potential mistake, I think
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I hope in this day and age people aren't still mixing their own drips. Everything should be pre-packaged with standardized doses. This takes the guesswork out of things and eliminates the potential for pushing syringes full of drugs that were meant to be put in a bag for infusion.
 
jwk said:
I hope in this day and age people aren't still mixing their own drips. Everything should be pre-packaged with standardized doses. This takes the guesswork out of things and eliminates the potential for pushing syringes full of drugs that were meant to be put in a bag for infusion.
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We have to mix our own drips for amiodarone, epinephrine (not like it's used often), and magnesium sulfate. Also diluting down D50 of course, but that's more personal preference when I do it than anything else. I don't think our ordering people are being cheap, but I don't really know a way around a few uncommon drips like that when all of our gear is restricted to two StatPacks and we have no ambulance to store excess supplies.
 
chaz90 said:
We have to mix our own drips for amiodarone, epinephrine (not like it's used often), and magnesium sulfate. Also diluting down D50 of course, but that's more personal preference when I do it than anything else. I don't think our ordering people are being cheap, but I don't really know a way around a few uncommon drips like that when all of our gear is restricted to two StatPacks and we have no ambulance to store excess supplies.
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Surprised that this still happens. Maybe you already do this - but if you're going to mix your own, take the correct bag of fluid, put it with the correct amount of drug, pre-print a little label to go with it all, and put it all in a ziploc bag. You should never have to take time to think about how much drug should go in what size bag of what type of fluid. Take the guesswork out of it. The best thing about doing it this way is it's almost free except for the cost of the bags. But honestly, epi, amio, and Mag are all commercially available in pre-mixed drips.
 
jwk said:
Surprised that this still happens. Maybe you already do this - but if you're going to mix your own, take the correct bag of fluid, put it with the correct amount of drug, pre-print a little label to go with it all, and put it all in a ziploc bag. You should never have to take time to think about how much drug should go in what size bag of what type of fluid. Take the guesswork out of it. The best thing about doing it this way is it's almost free except for the cost of the bags. But honestly, epi, amio, and Mag are all commercially available in pre-mixed drips.
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Right, but we don't have room in our gear bags to add three additional pre-mixed bags of meds. Every piece of our equipment (excepting monitor, vents, LUCAS, and suction) has to fit in two backpack sized StatPacks that can be carried by an individual. With everything else we carry, we simply don't have enough space to add three more bags of meds.
 
And, in DE, the Mag, Ami and Labetelol are all infusions, not really drips. You just put it in a bag and run it wide open. The Epi on the other hand... if you're running an Epi drip, you're down the road a bit and you can take the minute to do the math. :)
 
jwk said:
Surprised that this still happens. Maybe you already do this - but if you're going to mix your own, take the correct bag of fluid, put it with the correct amount of drug, pre-print a little label to go with it all, and put it all in a ziploc bag. You should never have to take time to think about how much drug should go in what size bag of what type of fluid. Take the guesswork out of it. The best thing about doing it this way is it's almost free except for the cost of the bags. But honestly, epi, amio, and Mag are all commercially available in pre-mixed drips.
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We didn't have premixes, either. I always just kept a note card stapled to my ACLS/PALS/NRP reference card in my pocket. The note cards had simple instructions for how to mix and start all the drips. For example "Epi: add 1ml of 1:1000 to 250 bag for 4 mcg/ml concentration. Start at 60 ml per hour (1 drop per sec) for 4 mcg/min dose. Titrate up or down".

It is important to take all the thinking out of mixing and starting these.


DEmedic said:
And, in DE, the Mag, Ami and Labetelol are all infusions, not really drips. You just put it in a bag and run it wide open. The Epi on the other hand... if you're running an Epi drip, you're down the road a bit and you can take the minute to do the math. :)
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How does that work? How do you know what dose you are giving?
 
Remi said:

How does that work? How do you know what dose you are giving?
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We know the total dose fine, but the rate we're administering it is the challenge. When using mag, we mix 2 g mag sulfate into a 100 mL bag then run it using a macro drip set. It's supposed to be administered somewhere over 5-10 minutes, so we try to target that based on flow rates. Again, no pumps of course, so there is an element of estimation there. Amiodarone is similarly targeted to administer 150 mg/100 mL over ~10 minutes.
 
chaz90 said:
We know the total dose fine, but the rate we're administering it is the challenge. When using mag, we mix 2 g mag sulfate into a 100 mL bag then run it using a macro drip set. It's supposed to be administered somewhere over 5-10 minutes, so we try to target that based on flow rates. Again, no pumps of course, so there is an element of estimation there. Amiodarone is similarly targeted to administer 150 mg/100 mL over ~10 minutes.
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So you are just talking loading doses here. Gotcha.
 
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