I.V. Calculation HELP

Hello everyone, I need some help figuring out this calculation problem. I just cant figure it out.

4 grams of lidocaine in dextrose 5% in water has been prescribed for IV infusion at a rate of 1mg per minute. The IV solution has a total volume of 500 ml. The IV should be infused at how many mL per hour?

The answer given was 7.5 mL per hour.

Can any one please just give me an idea on how to pursue this:D?

Thanks a bunch.

I like the Ratio and Proportion method so I do it like this.

First I convert the 4 grams of Lidocaine to mg's since that is what the rate is specified in.

4 grams = 4000 mg

4000 mg : 500 ml = 60 mg : x ml

So we have 4000 mg in 500 ml of solution and we need to to infuse 60 mg is one hour (1 mg per min x 60 min)

So lets solve this,

4000 mg : 500 ml = 60 mg : x ml

4000X = 500 x 60

(500 x 60 = 30,000)

Now we know that 4000 X is equal to 30,000 so to solve for X we divide 30,000 by 4000 ( 30,000 / 4000 = 7.5 )

x = 7.5 ml / hr

Hope that helped.

The ratio will work...or you can do it in 2 simple steps

you want ml/hr. you set up your units ahead of time to where they will cancel..mult. the top, and the bottom..divide top by bottom. =)

ml 60 min`x`1mg`x`1g`x`500ml=30000====30000= 7.5 ml/hr

hr......1hr```1min` 1000mg`4g```4000====4000