So...I am in my 3rd semester (just started last week), and I am trying to stay ahead of the game. I'm pretty good with the math, but I'll tell you, I have been sitting here trying to figure out how the heck they get these answers to the PCA pump questions. Is there something I'm missing? Here is an example problem:
Morphine Sulfate: basal rate=2mg/hr
PCA dose=2mg with a lock-out of 6 minutes
(possible dose every 6 minutes for 4 hours)
2mg/hr x 4 hours=8 mg in 4 hrs. from IV
2 mg every 6 minutes (a dose every 6 minutes=60 minutes divided by 6=10 doses/hr)= 2mg x 10 doses=20 mg in 60 min. x 4 hrs=80 mg in 4 hrs
8 mg + 80 mg= 88 mg maximum in 4 hours
This is exactly how the sample problem is presented. Where are they getting 88 mg in 4 hours, if it is 2 mg/hr? I am lost! I am used to dimensional analysis (if it can be figured out that way). Please tell me what I am missing. I've tried finding some web-sites to help, but I can't find anything like this. Thanks again, I appreciate the help.
Correct! Just remember that if a patient is receiving a basal rate, they are receiving that amount regardless of if they press the button. The basal rate is like a continuous infusion...no matter what, they will receive that amount per hour.
So, for example, if the order is: 4mg/hour basal rate, 1mg with a lock-out time of 6 minutes...
Total amount = Basal rate (4mg) + patient demand (60minutes/6minutes=10 demands; 10 demands x 1mg= 10mg)
Thank you so much for posting this. I am having an exit math test and we never learned PCA calculations and now we are tested on it and this helped out so much and i dont even have to pay you as much as i am paying for my school that is supposed to teach me all this. thank you so much!
PCA problems usually scare students for that reason-- they don't know the terminology. That, and so many of them are programmed to use a particular formula for all their med math problems, and they don't learn to look at the patient, the med, and the clock to figure it out.
If somebody says, PCA pumps have two functions:
1) to deliver a steady rate of a drug, usually prescribed for an amt/hour
2) to give extra doses on demand when the patient pushes a button, usually prescribed for an amt/per dose, so many doses allowed/hour
...does that help?
So, when you add those two up, how much can the patient get in an hour (max)?
If he doesn't push the button at all, what's the least he can get in an hour?
If you can think about it like that, it makes a lot more sense and it's a lot easier to figure out.
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Java Mama
183 Posts
Thank you :)