there is generally no math to be done that i know of. the syringes containing the medication are standardized and the doctors orders are usually on a pre-written form where the docs merely fill in the numbers. the pump computes the dosage for you. i would use the dose desired divided by dose on hand multiplied by the amount you have on hand (which is going to be the total amount of solution in the syringe) formula for any computations you would want to do. the first link below might give you more of an idea of how a pca is set up in it's pump. i found an example of a standing order as well. although this may not be exactly what you were looking for, i hope you find it helpful. your best information is going to come from being able to get your hands on one of these pumps and being able to play around with it. they are an odd animal--a bit different from iv pumps.
- pictorial on how to set up a pca pump. also includes a movie you can watch
- this article talks some about dosage, but not a lot
- this is an example of pre-printed standing orders for pca analgesia. you will note that the concentration of the morphine and dilaudid are given as 1mg/ml. i was unable to find operating instructions for the abbott lifecare pca pump, but i believe that the pump is already programmed with the concentration of the medication in the syringe, or the nurse can input this information so the computer in the pump calculates dosages for you.
- information on this particular pca pump states that it's bar code reader automatically identifies the drug name and drug concentration
- patient-controlled analgesia: making it safer for patients. a continuing education program for pharmacists and nurses from the institute for safe medication practices. good discussion about pca. includes a very nice chart of the commonly used medications for pca, their side effects, advantages, disadvantages, precautions and contraindications as well as the range of the loading dose, pca dose, lockout interval and four hour limit for morphine and dilaudid.
- a powerpoint slide show presentation on pca
- pain control after surgery - patient-controlled analgesia (pca)