Help with a drug calculation problem

  1. Hi everyone!
    Well we're having another drug calculations exam next week and fortunately, we were given a practice test to help prepare.

    I am having difficulty understanding one problem in particular:

    Order: Heparin 7500 units IVPB in 500cc N/S to run @ 50 units per hour.

    Set the IV pump at ____ cc/hr to deliver 50 units/hr.

    Now, I do know that the correct answer is 3.33 cc/hr per the key that was provided, but I can not understand why this is. Can someone please be so kind as to explain? :trout:

    Thanks so much in advance!
    Janet
    Last edit by imanubee on Nov 11, '07
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  2. 3 Comments

  3. by   Jw1724
    hey there.

    you want to do a proportion pretty much (well.. this is how i like to do it)

    it's 7500 units/500cc
    sooo.. since you want 50units/hr


    7500units 50units
    500cc x
    ----------------->cross multiply to get:
    7500x=25000

    Divide each side by 7500
    You get 3.33

    Make sense?
  4. by   Daytonite
    order: heparin 7500 units ivpb in 500cc n/s to run @ 50 units per hour.

    set the iv pump at ____ cc/hr to deliver 50 units/hr.
    dose desired: 50 units of heparin/1 hour
    dose on hand: 7500 units in 500cc of normal saline

    you want to get the dose to give expressed as cc/hour.
    50 units/1 hour (dose desired) x 500cc/7500 units (dose on hand) = 3.33 cc/hour (dose to give). however, you would actually set the pump at 3cc/hour since most pumps, except some of the very new and sophisticated ones, can only be programmed with whole numbers.
  5. by   imanubee
    Aha--that makes sense! I could plug in the numbers to get the answer as was provided on the key, but just needed it explained for clarity. Thanks!!!

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