Injection example 2 ....

In this example we're ordered to give 75mg Lidocaine IV push stat for for a patient experiencing arrhythmia's (also know as FLB's - funny little beats). For this purpose Lidocaine, a class 1b antiarrhythmic, can be found in the emergency med tray or the crash cart. It's usually in pre-measured syringes intended for an injection device such as a carpojet. We open a box containing a 4 cc syringe labeled Lidocaine 20mg per cc. What we are actually going to give the patient is a liquid - liquids are measured in volume (cc or ml) so start with:

 

 

We know our 3 necessary pieces of information:

Ordered  dose - 75mg

Available dose - 20mg

Available form - per cc

Or first factor is something we know that has the unit corresponding to what we want to know, orienting it  in the same position :

 

 

 

And then multiply by the ordered dose, orienting it so the unit is opposite :

 

 

We can see we aren't going to have any left over units, so we can cancel and solve :

 

 

Remember we have a 4cc syringe - each cc has 5 hash marks. We know we're going to give 3 whole cc's, but how many hash marks does the 0.75 ml correspond to ?

You might think it's silly to go through all the trouble to "figure" this out using the factor label method. What I'm trying to demonstrate is that this method is useful for figuring out a lot of different things - and for making sure a problem was thought all the way through. Sometimes under pressure, even simple things have a way of escaping - having a sure way of checking can be useful...

We have an "ordered dose" - 0.75 ml

And we have an available dose - 5 hash marks

And an available form - per cc

So .... we want to know marks :

 

 

 

Next add what we know that has the same unit as what we want to know, orienting it so the unit is in the same position:

 

 

Multiply by our dose, orienting the units opposite:

 

 

And cancel and solve :

 

 

We'll give 3cc and then almost 4 marks worth of the next cc.

Lidocaine IV is given as a slow push - 25-50 mg per minute. Over what period of time  do we give this 75 mg? We want to know minutes :

 

 

We multiply by what we know that has the same unit as what we want to know, writing it so the unit's position corresponds :

 

 

Multiply by our 75 mg dose, orienting it so the units are opposite :

 

 

And cancel & solve :

 

 

Being as prepared as we are, we also had the "stuff" ready to begin the Lidocaine drip that will have to start following the bolus ......

  As you have seen, this factor-label method can be used to solve a whole array of problems nurses commonly encounter.

 

©1997-2006 Dale Sampson, RN