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Discussion

Help With Math Problem

Hello,

I am brushing up on some math problems before I start clinicals in Jan. I can't figure out theses to problems. Can you please help?

Thanks In Adavance,

Fox

If the order reads, "give .3 mgms. of Drug Z and 65 mgms of Drug N" how much fluid will you have in your syringe? The labels read Drug Z, 110.4 mgms 1/2 cc and Drug N, 0.075 g in 1 cc.

An IV was started at 9:00am with orders to infuse 500mL1 over 6 hrs. At 12 noon the IV infiltrate with 350mL left in the bag. At 1pm the IV was restarted. The set calibration is 20 gtt/mL. Calculate the new flow rate to deliver the fluid on time.

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  • Experts

if the order reads, "give .3 mgms. of drug z and 65 mgms of drug n" how much fluid will you have in your syringe? the labels read drug z, 110.4 mgms 1/2 cc and drug n, 0.075 g in 1 cc.

dose #1 (drug z) desired:
0.3 milligrams (mgm)

dose #2 (drug n) desired:
65 milligrams (mgm)

dose #1 (drug z) on hand:
110.4 milligrams (mgms) per 1/2 cubic centimeters (cc) (0.5 cc)

dose #2 (drug n) on hand:
0.75 grams (g) in 1 cubic centimeter (cc)

conversion factor:
1 gram = 1000 milligrams

the set up, by dimensional analysis is:

(
0.3 mgms/1
[dose desired of drug z]
x 0.5 cc/110.4 mgms
[dose on hand of drug z]
)
+
(
650 mg
[dose desired of drug n]
x 1 cc/0.075 g
[dose on hand of drug n]
x 1 g/1000 mg
[conversion factor]
)
=
0.15cc/110.4 + 8.67cc/75

now, there are a couple of things you can do with this answer. you can divide each term out into an answer and then add the result together. you could find the common denominator of the two terms and add them together to get the final answer. the difference between getting the two answers each way may or may not make a difference.
0.15cc/110.4 + 8.67cc/75 = .00135cc + 0.1156cc = 0.11695cc =
0.1cc
(final answer rounded off to tenths)

or

0.15cc/110.4 + 8.67cc/75 = 11.25 + 957.168/8280cc = 968.418/82875cc = 0.1168cc =
0.1cc
(final answer rounded off to tenths)

i have to say, however, that these dosages would be almost impossible to draw up in clinical practice. are you sure you copied the problem correctly?

an iv was started at 9:00am with orders to infuse 500ml1 over 6 hrs. at 12 noon the iv infiltrated with 350ml left in the bag. at 1pm the iv was restarted. the set calibration is 20 gtt/ml. calculate the new flow rate to deliver the fluid on time.

ok, first off, you need to calculate how many ml of solution were delivered from 9am to noon, and then how much of the 500 ml need to be infused if you want to finish the infusion before 6 hours have elapsed since 9am (9am + 6 hours = 3pm)
500ml - 350ml =
150ml
left to infuse

from 1pm to 3pm = 2 hours, so you have 2 hours to infuse 150ml with an infusion set that delivers at 20gtts (drops) per ml. the new flow rate at
ml/min
will be. . .
dose desired:
150ml/2 hours

drip factor of iv tubing:
20gtts/1 ml

conversion factor:
1 hour/60 minutes

150ml/2 hours
(dose desired)
x 1 hour/60 minutes
(conversion factor)
x 20 gtts/1 ml
(drip factor of iv tubing)
=
25 gtts/minute
(new iv flow rate)

there are more examples of dosage calculation problems worked out on this sticky thread that you can study:

ok, first off, you need to calculate how many ml of solution were delivered from 9am to noon, and then how much of the 500 ml need to be infused if you want to finish the infusion before 6 hours have elapsed since 9am (9am + 6 hours = 3pm)

500ml -
150ml
=
350ml
left to infuse

from 1pm to 3pm = 2 hours, so you have 2 hours to infuse 150ml with an infusion set that delivers at 20gtts (drops) per ml. the new flow rate at
ml/min
will be. . .
dose desired: 350
ml/2 hours

drip factor of iv tubing:
20gtts/1 ml

conversion factor:
1 hour/60 minutes
350ml/2 hours
(dose desired)
x 1 hour/60 minutes
(conversion factor)
x 20 gtts/1 ml
(drip factor of iv tubing)
=
58.3333333
gtts/minute
(new iv flow rate)

there are more examples of dosage calculation problems worked out on this sticky thread that you can study:

fixed! 350ml was lib, not amount infused. pt only got 150ml in the 4 hours (i don't know how because he was originally supposed to be getting ~82ml/hr)

  • Experts
fixed! 350ml was lib, not amount infused. pt only got 150ml in the 4 hours (i don't know how because he was originally supposed to be getting ~82ml/hr)

recalculate, my dear. 58.333 gtts/min is wrong! 25 gtts/minute is the correct answer. i calculated two different ways to confirm it was the correct answer before i posted it the other day.

recalculate, my dear. 58.333 gtts/min is wrong! 25 gtts/minute is the correct answer. i calculated two different ways to confirm it was the correct answer before i posted it the other day.

if the order reads to infuse 500ml over 6 hours and there is 350ml left in the bag and those 350ml need to be administered over the next 2 hours, how is that wrong?

  • Experts

OK, I see where I made my mistake. However, there is no such thing as a 58.33 drop. You have to round that up to 58 drops/minute.

OK, I see where I made my mistake. However, there is no such thing as a 58.33 drop. You have to round that up to 58 drops/minute.

Sometimes it's the simplest things

You're a great poster. You put a lot of time and effort into your posts and I thank you for that. I always read your posts and learn from them, but we all do make mistakes.

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