1Your ordered to administer dopamine to a 178 lb. pt by mixing 400 mg of dopamine into a 250 mL bag of D5W. Dopamine is supplied in ampules containing 200mg/5mL. The order is to deliver the dopamine at 5 ug/kg/min. At how many drops per min will you adjust your microdrip (60 gtt/min) admin. set to drip?
#2 The Dr. orders you to start an iv of 0.9 NS to run at 100ml per hour. you have a macrodrip set that delivers 15gtt/mL. At how many drops per min will you set your adminstration set to drip?
#3 You are ordered to administer lidocaine drip at 4mg/min in a post arrest pt. The vial supplied reads "1% lidocaine, 5g/20ml." Your supervisor instructs you to add 2g. of lidocaine to a 250 mL bag. What is the concentration in the bag?
#2 The Dr. orders you to start an iv of 0.9 NS to run at 100ml per hour. you have a macrodrip set that delivers 15gtt/mL. At how many drops per min will you set your adminstration set to drip?
#3 You are ordered to administer lidocaine drip at 4mg/min in a post arrest pt. The vial supplied reads "1% lidocaine, 5g/20ml." Your supervisor instructs you to add 2g. of lidocaine to a 250 mL bag. What is the concentration in the bag?
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1) 178 lbs = about 80 kg. at 5ug/kg/min, that gives a total of 400ug/min. The 400mg in the 250 bag is 1000 times the volume that you want to give, meaning you'll want to five .25mL/min. Using a microdrip, this is 15 drops per min.
2) 100 mL/hr = 1 2/3 mL/min. at 15gtt/mL, you'll want to give 25gtt/min.
3) 2g in a 250 bag is the same as 8g in a 1000 bag. Thus the concentration in the bag is 8g/L.
2) 100 mL/hr = 1 2/3 mL/min. at 15gtt/mL, you'll want to give 25gtt/min.
3) 2g in a 250 bag is the same as 8g in a 1000 bag. Thus the concentration in the bag is 8g/L.
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I'm not going to do your homework for you, but I always set up these kinds of problems as a linear equation where I can cancel the unneeded forms of measurement along the way.
So in your first example, you are starting with an amount in mg/mL and you need one in gtt/min. What you want to do is start with 400mg/250mL and multiply across, using conversions where needed, until you end up with the units of measurement that you want. My first step would be to change the mg to ug. Then multiply by the patient's weight with the denominator correcting for the metric weight. And so on. You see where it's going. If you write out every unit and every conversion, it's hard to go wrong, and when you get better at it you can condense steps (like assuming that your dopamine will be given as 400mg/250 mL/hr so your time unit is built into your initial equation).
You can also do it as separate steps where you get each part of the problem separately: You need to know how many drops delivers 5 ug/kg. So first you need to know how many kg the patient is. Figure that out. Then figure how many drops give 5 ug. That number multiplied by the first gives you the gtt/kg. You can then figure how many drops are needed per minute. That first one you might want to do in steps anyway because it's pretty convoluted. (I think you also need to remember to correct for the additional mLs of fluid in the ampoules.) The thing is, they're all conversion problems, so if you write out all the conversions you can't mess up.
One caveat: I don't happen to know what a drop (ggt) is considered to be but in your second example you list something as gtt/mL. That doesn't make sense to me--aren't both of those units of volume?
So in your first example, you are starting with an amount in mg/mL and you need one in gtt/min. What you want to do is start with 400mg/250mL and multiply across, using conversions where needed, until you end up with the units of measurement that you want. My first step would be to change the mg to ug. Then multiply by the patient's weight with the denominator correcting for the metric weight. And so on. You see where it's going. If you write out every unit and every conversion, it's hard to go wrong, and when you get better at it you can condense steps (like assuming that your dopamine will be given as 400mg/250 mL/hr so your time unit is built into your initial equation).
You can also do it as separate steps where you get each part of the problem separately: You need to know how many drops delivers 5 ug/kg. So first you need to know how many kg the patient is. Figure that out. Then figure how many drops give 5 ug. That number multiplied by the first gives you the gtt/kg. You can then figure how many drops are needed per minute. That first one you might want to do in steps anyway because it's pretty convoluted. (I think you also need to remember to correct for the additional mLs of fluid in the ampoules.) The thing is, they're all conversion problems, so if you write out all the conversions you can't mess up.
One caveat: I don't happen to know what a drop (ggt) is considered to be but in your second example you list something as gtt/mL. That doesn't make sense to me--aren't both of those units of volume?