Drug calculation

[Sharktooth]

Can someone help me figure this one out?

Lidocaine:
100mg mixed in a 100cc bag D5w
Concentration is 1000mcg/cc
Drip at 20 mcg/kg/min

Its our pedi drip for Lido. How would I apply that to our select a drip setting? We have a 60 drop per cc min setting and a 10 drop per cc setting?

:blink:
Thanks!

 

[chaz90]

We don't do homework problems for you, but we will help with the math itself. If the concentration of lidocaine you have is 1000 mcg/mL and you want 20 mcg/kg/min, first calculate how much you want based on the weight of the kid. Let's say 20 kg, so 400 mcg/minute. I typically set up a proportion at this point. 400/1000=x/60, with x being how many drips/minute from a 60 gtt set. Calculating this out gives you 24 drops/minute. To check your math, think about the general range you should be in. If you were to give 30 drops/min, you'd be at half a mL a minute, which would be 500 mcg/minute. You want slightly less than that, so 24 drops/minute seems right.

 

[Aprz]

I don't think it's a homework problem. The OP didn't provide the patient's weight in kg so there is no math problem for us to solve anyway. It looks like the OP has figured out the concentration, but doesn't know where to go next. Also asked how to do it for a 60 (micro) and 10 (macro) gtt drip set.

OP, you need to find out how much cc you want to administer per minute, and then convert that to how much gtt you want to administer per minute.

Find out the concentration

100 mg Lidocaine / 100 cc D5W

1 mg = 1,000 mcg

(100 mg Lidocaine / 100 cc D5W) x (1,000 mcg / 1 mcg) Convert to mcg

100,000 mcg / 100 cc D5W

1,000 mcg Lidocaine / 1 cc D5W Simplified

Find out how much cc I want to administer per minute

1,000 mcg Lidocaine / 1 cc D5W = mcg Lidocaine I want to administer per min/ cc I want to administer per min

mcg Lidocaine I want to administer per min = 20 mcg x pt's weight in kg

1,000 mcg Lidocaine / 1 cc D5W = (20 mcg x pt's weight in kg) / cc I want to administer per min

1,000 mcg Lidocaine x cc I want to administer per min = (20 mcg x pt's weight in kg) x 1 cc D5W Cross multiplied

(1,000 mcg Lidocaine x cc I want to administer per min) / 1,000 mcg = ((20 mcg x pt's weight in kg) x 1 cc D5W) / 1,000 mcg Isolate "cc I want to administer per min"

cc I want to administer per min = ((20 mcg x pt's weight in kg) x 1 cc D5W) / 1,000 mcg

1000 = 20 x 50

cc I want to administer per min = ((20 mcg x pt's weight in kg) x 1 cc D5W) / (20 x 50) mcg

cc I want to administer per min = ((20 x pt's weight in kg) x 1 cc D5W) / 50 Simplified

Convert cc/min I want to administer to gtt/min I want to administer, gtt = drop

cc I want to administer per min x (drip set / 1 cc) = (((20 x pt's weight in kg) x 1 cc D5W) / 50) x (drip set / 1 cc)

cc I want to administer per min x (drip set / 1 cc) = ((20 x pt's weight in kg) x 1 cc D5W x drip set) / 50 cc

x gtt/min = (pt's weight in kg x drip set) / 50 Simplified <-- This can only be used for 100 mg Lidocaine in 100 cc D5W

Example 1

pt's weight in kg = 20 kg, drip set = 60 gtt drip set (a.k.a micro drip set)

x gtt/min = (pt's weight in kg x drip set) / 50

x gtt/min = (20 x 60) / 50

50 = 5 x 10

60 = 6 x 10

20 = 5 x 4

x gtt/min = (5 x 4 x 6 x 10) / (5 x 10)

x gtt/min = 4 x 6 Simplified, got rid of 5 and 10

x gtt/min = 24

24 gtt/min for a 20 kg pt

Example 2

pt's weight in kg = 68 kg (about 150 lbs by the way), drip set = 60 gtt drip set

x gtt/min = (pt's weight in kg x drip set) / 50

x gtt/min = (68 x 60) / 50

60 = 6 x 5 x 2

50 = 5 x 5 x 2

68 = 17 x 2 x 2

x gtt/min = (68 x 6 x 5 x 2) / (5 x 5 x 2)

x gtt/min = (68 x 6) / 5 Simplified, got rid of 5 and 2

x gtt/min = 408 / 5

x gtt/min = 81.6

81.6 gtt/min for a 68 kg pt

Round Down

81 gtt/min for a 68 kg pt

You can always multiply or divide to the drip set you want to use.

For example, if you did the math to find out how much gtt/min you want to administer with a 60 gtt drip set, but you decided to use a 10 gtt drip set for some odd reason, to go from 60 to 10, you divide by 6. The same for the gtt/min. Same thing.

Example 1

You want to use a 10 gtt drip set (a.k.a a macro drip set)

24 gtt/min with a 60 gtt drip set

60 drip set / 10 gtt drip set = 6

24/6 = 4 gtt/min with a 10 gtt drip set

Example 2

You want to use a 15 gtt drip set (a.k.a another macro drip set I see).

24 gtt/min with a 60 gtt drip set

60 drip set / 15 gtt drip set = 4

24/4 = 6 gtt/min with a 15 gtt drip set

Example 3

You want to use a 20 gtt drip set (a.k.a another macro drip set I see).

24 gtt/min with a 60 gtt drip set

60 drip set / 20 gtt drip set = 3

24/3 = 8 gtt/min with a 20 gtt drip set

 

[kaisardog]

WOW, I am learning so much just reading this forum. as an EMT B in my state we don't do these sorts of calculations.. thanks.

 

[VirginiaEMT]

WOW, I am learning so much just reading this forum. as an EMT B in my state we don't do these sorts of calculations.. thanks.

Amount per kilogram per minute

mcg/mg. per min x kg x drip set
amount of drug(in mcg/mg)/amount of fluid it was placed into

=gtts. (drops per minute)


Amount of fluid over a certain amount of time:

ml. in bag X drip set
number of minutes

= gtts.

 

[MSDeltaFlt]

This is my universal drug calculation that includes drops per minutes regardless of drip set.

Dose X weight in kg X drip set
______________________________ = drops per minute
Concentration

If using a 60 drop set or a pump the drops per minute become cc/hr.

If the drug is not weight based, take out the pt weight from the equation. If it is an IV push dose, take out the drip set.