Paramedic Math – The basics

To begin with I want to define the variables I will be using in the upcoming formulas.

We are going to use the all of the following variables in our equations – most equations only need some of them… but lets define them all at once

  • DD – desired dose
  • C – Concentration
  • V – Volume
  • gtt – Drip set
  • T – time
  • WT – Weight in pounds or kg

DD – is the amount of medication or fluid we want to administer

  • examples give 5 mg of…
  • administer 1000 ml
  • infuse 10 mcg/kg/min

Whatever we want to give to our patient is the desired dose or DD

C – the concentration of medication in the vial we have on hand – (see photos below) the sample problems here will give you the amount of drug and the amount of fluid it is in, the photos show how to determine that for yourself on an actual vial. For our purposes C is always a weight based measurement – in other words some fraction of a gram

  • 5 mg  in 10 ml
  • 25 g in 50 cc
  • 100 mcg in 1 ml

V – The volume our medication is contained in in its vial  – (see photos below) the sample problems will also give you the volume – for our purposes the volume will always be a volume based measurement in other words some fraction of a liter

  • 5 ml  in 10 ml
  • 25 g in 50 cc
  • 100 mcg in 1 ml

C and V defined on package of Atropine

C and V defined on a box of D-50

What are the values for C & V on this vial?

If your answer is C=50 mg and V=1 ml You are correct

gtt – the number of drops in 1 ml of fluid based on the administration set you are using, it is usually found on the packaging, sometimes inside a drop shape  – this number will be provided for you in the problems

This particular set is a 15 gtt/ml set - the gtt value would be 15

T – The time specified for your infusion in the order, if no time is specified the value here is 1 min

WT – The patients weight – if the weight is in pounds we have to convert it to kg for our formulas

Which brings me to my next topic – medical math conversions


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