Basic Med-Math formulas

Paramedic Med-Math:

There is actually a surprisingly small amount of math required in paramedicine, as many of our medications are set doses. Some, however, are based on weight and require a bit of calculation. We also need to know how to calculate for IV fluid volume and drip rate over time. I will provide a quick discussion on the basics of paramedic me-math.

Calculating for dose:

The most commonly used math is that of dosage based upon available quantity of medication. The basic formula is:

(Dose required / Dose available) x quantity = Dose given

In simplified terms:

(Want / Have) x quantity = Dose

So if I want to give 0.5mg of epinephrine and I have epinephrine available in a quantity of 1mg/ml:

(Want: 0.5mg / Have: 1mg) x 1ml = 0.5ml

This is the basic medication formula for any type of medication administration you may perform.

IV drip rate:

IV calculations are a bit more complicated at face value, but in reality we are performing relatively simple math. The formula to determine drip rate (gtt/min) is as follows:

(Volume of fluid / Time in minutes) x Drip factor of the tubing

So, if I want to give 250ml of fluid over 30 minutes with a 15 drop set:

(250ml / 30min) x 15gtt/min

=125 gtt/min

To determine how many drips er second that is, we divide by 60 seconds.

125 gtt/min / 60 seconds

= 2

Medication infusion rate:

If we are giving medications by IV infusion we use the formula:

(Desired dose in mg/min x 60 min/hr) / Drug concentration mg/ml

This formula is less commonly used by PCPs, but may be used by ACP providers.

Thats pretty much it. Not as complicated as it seems.