PCA pump math question HELP


A new PCA order for a post-surgical case pain control. Hydromophone demand dose 0.1 mg, lockout 10 minutes, basal rate 0.2 mg/hr. Maximum PCA dose is 4 hours. The medication is supplied in a 25 mL syringe that indicates 0.2 mg/mL. After 12 hours, the nurse found this client has pushed the PCA button about 10 times per hour. CAn you calculate how much medication is left in the syringe after 12 hours. _____mg and ______mL

PLEASE help, i have tried every possible way and still cannot figure out and does not make sense. I already submitted my answer but I just want to see how to do it for clarification. Thank you!

Specializes in NICU, ICU, PICU, Academia. Has 46 years experience.

You are missing the 4 hour lockout. You have it listed above as 4 hours- but a lockout does is expressed in mg.


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Specializes in Neuro, Telemetry. Has 8 years experience.

Put what you've done here so people can see where you went wrong and correct from there.

Start with what's easy first: the 12 hour basal amount. Deduct that from the 25 ml.

Then, find the demand amount. Also keep in mind that even though the client has pressed the demand button 10 times in an hour doesn't mean that they received the demand dose because of the 10 minute lockout. They can receive 6 demand doses in 60 minutes.


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Specializes in Hospital medicine; NP precepting; staff education. Has 22 years experience.

I loved doing dimensional analysis. It was like a puzzle, putting the pieces together and voila!


3,951 Posts

You can't calculate delivered dose with the information provided.

In addition to number of PCA attempts, every PCA pump I'm familiar with also provides doses delivered. Without this information, there is no to determine what the patient received.