Drug Calculation help needed

[rhan101277]

I have some drug calculation practice questions. I have done 8 of them but the last two are tough and I am not sure what I am doing wrong. Any help would be appreciated.

The formula:

Dosage x (kg) x (min) x volume on hand
--------------------------------------
concentration on hand

8) A 150lb 25y/o patient has a blunt spinal cord injury with neurological deficits. The physician orders you to begin steroids to control edema around the cord. The bolus dose of Solu-medrol is 30mg/kg to be administered over 15 minutes. Solu-Medrol is available in 1g vials of powdered concentrate that should be diluted with 30cc sterile water or NS. What volume of medication should be administered?

My work:

30mg x 68kg x 15min x 30cc
---------------------------
1,000mg

Working above formula gives me 918cc; also the dosage comes out to about 2 grams over 15 minutes. So I know 918cc is way wrong. Should be around 60cc I think. Where did I go wrong on this?


9) 45 minutes after giving the bolus dose of Solu-medrol, you need to being an infusion of 5.4mg/kg/min. You have three vials of Solu-medrol 1g/30cc and a 250cc bag of NS. Describe how you would mix the infusion AND determine the rate to set the infusion pump.

My work:

5.4mg x 68kg x 60min x 250cc
-----------------------------
3,000 mg

This comes to 1,836cc again doesn't make since.

The rest of them I am comfortable with, but I don't know what I a missing on these. Any help at what I am missing is greatly appreciated.

[rhan101277]

I really need some pointers on this please.

[rhan101277]

This isn't homework, this is practice to prepare me for medication administration during clinicals. Surely there is at least one paramedic on the boards that can chime in. VentMedic, RidRyder can you help? someone? anyone?

[flhtci01]

Do you know how to double check your work using the units?

First look at what the question is asking for example is a dose or flow rate? A dose is usually in mg's and a flow rate might be cc's/hour. This will give you an idea of what your answer should be. If you need a dose and the answer is cc's/min then you are doing something wrong.

Example: Consider you are traveling in a car going 60 mph. How fast are you traveling in feet per second?

60 miles ..... 5280 feet ... hour ........ min
-------- x --------- x -------- x --------
.....hour ...... mile ...... 60 min ......60 sec

Consider the units divided by the same units as equal to one. They cancel and forget about them. So the miles, hour and min cancel each other.

You are left with

60 x 5280 feet
---------------
60 x 60 sec

The same principle can be applied to drug calcs.

You have to know what units your answer should be. If you are trying to calculate a dose and end up with a rate, either something was forgotten or too much information was used.

Does this make sense?

[DV_EMT]

just try to remember you decimal system and the conversions,

I was doing the calc earlier with the pharmacist, and the 1st one was around 2.2 grams total that needed to be given and then put it in a bolus. just trying to give you some help there.

[Melclin]

8)
Am I missing something?

Why are you bringing time into it? Time has nothing to do with the dose. If you had to administer 30mg/kg over 15 mins, you would draw up the same dose as if you had to administer is over 30 mins, you just give it slower.

Its a bolus dose given over a period of time.

(30 x 68) x 30____61,200
--------------- = -------- = 61.2 cc
____1000 ________1000

9)
Now I haven't done infusions yet. Why have you put down 60 mins? Is that the standard time that your infusions last?

[rhan101277]

Originally Posted by Melclin

8)
Am I missing something?

Why are you bringing time into it? Time has nothing to do with the dose. If you had to administer 30mg/kg over 15 mins, you would draw up the same dose as if you had to administer is over 30 mins, you just give it slower.

Its a bolus dose given over a period of time.

(30 x 68) x 30____61,200
--------------- = -------- = 61.2 cc
____1000 ________1000

9)
Now I haven't done infusions yet. Why have you put down 60 mins? Is that the standard time that your infusions last?

You are absolutely right, it doesn't say 30mg/kg/min, that 15 minutes threw me off. I feel like an idiot. The other questions were similar and those didn't get me like this one.

For number 9, I reworked it and came up with 66cc over 45 minutes. Again threw off by the three vials comment. According to the 30mg/kg bolus needed for solu-medrol, I need only administer 2 grams, so only need two vials . So mix up two different 30cc syringes, each with 1g of solu-medrol. Then connect to medication port on IV line, cut of one side of line so med will move up into bag.

For a 250cc bag it should run out in just under 4 hours.

[rjrobinson]

just curious. do you still use cc?

thought everyone was using mL now?

[thegreypilgrim]

IV and Drug Calculations for Busy Paramedics

This helped me out a bit.

[rhan101277]

Originally Posted by EMTRob

just curious. do you still use cc?

thought everyone was using mL now?

One instructor likes cc, the other like mL, go figure. I personally like mL because that is the way the medication is labeled. But both are the same.