IV Infusion Problem

18G

18G

Paramedic
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I am pretty comfortable with med math.. parenteral and IV infusions... except... mg/hr. I am very frustrated and can't seem to be certain if I am doing it right.

Here is what I am trying to understand. Some protocols call for a diltiazem drip which is administered 5-15mg/hr.

Say you have diltiazem (125mg/25mL) and mix it in a 100mL solution of D5W. You now have a 1:1 ratio where 1mL = 1mg of diltiazem since its 125mg of drug to 125mL of D5W.

Now say the order is to start the drip at 5mg/hr... I'm used to figuring everything else in mg/min or mL/hr for fluid over time.

Is this formula correct...

Dose x Volume
Concentration = drops/min

5mg/hr x 125mL
125mg = 5gtts/min ??

Every 12mins (60 drops) the patient would be getting 1mg. 12 x 5 = 60mins.

I know this is 1:1 and intuitive... I just want to make sure if I have concentrations other than 1:1 that they will be correct.

I guess I am confused because the drip factor is not included in the formula.
 
So if you're going for 5mg/hr...

Drug Concentration = 1mg/cc

Drop Set = 60gtt/cc

5mg*60gtt=(300gtt/60min)

gtt/min=5gtt/min

So that works for ya! Nicely done.

Easier way to look at it instead of 5mg/hr is 5mg/60min...that way it helps reduce it down a bit!
 
Thanks for the reply... so the formula I mentioned in my opening post is a correct formula?

Here is a problem I found online:

Protocol states to mix 20mg of diltiazem in a 150mL bag of D5W and deliver at a rate of 5mg/hr.

How many gtts/min to achieve this dose?

Concentration:125mg/25mL (5mg/mL)

Here is how I figured it out:

Inject 4mL (20mg) of diltiazem into the 150mL bag = 0.13mg/mL

5mg/hr x 154mL
20mg = 38.5 gtts/min ....... is this the correct flow rate?

What if all you had was a 15 dropper set instead of a 60?
 
Med math? What's that?


*goes back to his calculator, iv pump, and pre measured drugs*
 
Hahaha I'm in COMPLETE agreement man. Charts are wonderful things. So is titrating to effect...

So if you've got a 154ml bag with 20mg in it, and you want to give 5 mg of that, you want to give 1/4 of that bag over an hour right? So you want to give 38.5cc over the course of 60minutes ^_^

So....38.5cc*60gtt=2310

2310/60mins= 38.5gtt/min!

There are a couple different ways of getting to the answer, your formula is the way we learned in school, I go a little Rainman on it sometimes hahaha
 
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