Dosage Calc -- PCA Pump -- not finding how to calculate sample prob for test -- HELP

[chamrob]

Hi -- I have been struggling since Friday to study for Dosage Calc in the AM and find probs matching the sample we were given. We are using the Pickar 8th Editon, only PCA reference is on page 369. The online site practice questions contained nothing and have been working them from Chapter 15 - 17. My instructor just said she does not know the answer to the sample and I am lost on it.... This is exactly what she gave us to study:

Patient weighs XXX kg

Begin on XXX med PCA 10 mg/mL

Rate of __ mg (she put 8 in parenthesis) q 15 min with lockout of 24 mg/hr

Bag has 150 mL

Started at 0800, if patient receives 3 doses/hr how long will bag last?

I have worked it:

150mL / 10mg/mL = 15 mg/mL

8 mg / 15 mg = 0.533 = 0.5 mg/mL q 15 min x 3doses/hr =

You see -- I am confusing myself horribly.... I usually make 100% on these Dosage Calc Quizzes -- I need every point I can get -- Thanks in advance for your help - I am truely stumped... thinking I am over thinking it....

[anonymousstudent]

ok. you have to find a way to keep dose and volume in perspective.

the bag has 150 ml of solution.

there are 10 mg of medication per ml of solution.

150 ml * 10 mg/ml = 1,500 mg of total medication in the bag.

there are 2 ways to go from here, use the one that makes the most sense to you...same answer both ways.

considering volume:

the patient receives 8 mg per dose, which is 0.8 ml each dose. the max per hour is 3 doses, so 0.8 ml * 3 = 2.4 ml per hour maximum.

150 total ml in the bag / 2.4 ml/hr = 62.5 hours

or, consider dose (this is probably a better way to do it, because then you have a perspective of how much medication your patient is getting, not just how much fluid...jmo)

the patient receives 8 mg per dose, at 3 doses max per hour = 24 mg per hour.

1,500 mg total in the bag / 24 mg/hr = 62.5 hours

[chamrob]

anonymousstudent -- thanks for taking time to help me -- that makes sense -- and simplified!! i knew i was working it wrong... i can do that ....