Dosage Calculation Question

  1. Ok.. tomorrow we have our exit dosage calculation test which we have to make a 100 on and I am stumped on a couple of practice questions.. So here they are:

    Order: IV of 1000cc of Lactate Ringers with KCL 40 mEq at 100 cc/hr... IV tubing delivers 20gtts/cc

    How many drops per minute should this IV infuse to deliver the correct amount...

    Another one:

    Order: 300cc LR with 10U Pitocin to be completed in 2hrs... What Rate should be set on the infusion pump to complete this IV as ordered??

    Thanks for any help..
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    About Ortho_RN

    Joined: Nov '01; Posts: 1,616; Likes: 37
    New RN Grad... Just passed NCLEX.. Working on a Ortho floor


  3. by   aus nurse
    Great website someone posted here once is:

    For the first question you need your formula to calculate drops per minute.

    Volume............. x Drop factor
    Time in minutes......... 1

    So your equation would look like this:
    1000 .......... x 20
    600 .............. 1

    (You gotta imagine those division lines, coz I can't do them here!!Ignore the fullstops)

    It tells you it is infusing at 100 mls/hour, so this will take 10 hours to infuse. Convert that to minutes by mutiplying by 60 therefore getting 600 minutes

    Answer is 33.33 drops/minute.

    Second is just asking you to set rate on pump. To infuse 300 mls over 2 hours you would set pump at 150 mls/hour

    Hope this helps. Good luck
    Last edit by aus nurse on Nov 3, '02
  4. by   boggle
    nurse 2b, these really aren't tooooo hard. Try thinking of them as problems you would work out when cooking or when budgeting at home. Math always looks scarier when medical terms are involved......but it's the same math!

    The first problem require you to determine the number of cc per minute:

    so divide the 100cc by 60 (minutes)= 1.67

    then multiply the number of cc per minute by your drop factor:

    1.67 x 20= 33.4 or 33 gtts per minute.

    That second one you can do in your head....just relax.....

    300cc in 2 hours= 150 in one hour. (2 x 150 = 300).

    Good luck on your test. Eat something before your test, bring your calculator, and try some relaxation techniques!!! :kiss
  5. by   jnette
    nurs2b :

    I found a really EASY way to memorize these calculations.. maybe they'll help you, too. One is for a gravity flow frip, the other for an ICD (pump).

    Gravity Flow Drip:

    "Volume x Volume divided by Minutes"

    in other words the volume to be admin. (in this case 100ml/hr.) times the gtt factor of the tubing, which is always "so many gtts. per ML...(that's how I remember my formula as volume x VOLUME...the second "volume" is really the drop factor...)
    Then divide the answer by MINUTES, or "run time"... how long it is ordered to run. In this case it was one hour, or 60 minutes.

    Disregard the 1000ml LR part, 'cuz that's just a distraction.. look for the "meat" of the problem.. it was hidden right in there ...100ml/hr.

    SO: volume 100ml x "volume" 20 (drop factor) =2000
    2000 divided by60 minutes(prescribed runtime) =33.3 or 33gtts./min.

    Just remember the above: Vol.xVol. divided by minutes
    (just remember teh second "vol" is really the tubing gtt.factor) That's your Gravity drip.

    The second is just as simple, and it's practically my head, I remember an ICD pump is "opposite" of the gravity flow's how I remember it:

    I always start with 60 !!! (minutes)

    Minutes DIVIDED by Minutes x Volume

    SO: 60 min. divided by 120 minutes (2hours prescribed run time)=0.5... TIMES the Volume to be infused (300ml) = 150. That's the setting reqired. ICD pumps are always looking for ml/hr.

    So once you understand the "components" of my little "memory help formula", it's really simple to go from there in any problem you may be given. I jotted these down all over my books, my notes, anytime, anywhere, just to memorize these two. Now you can wake me from a deep sleep and I can rattle them off.

    Grav. Flow: Vol.xVol. Divided by Min.(run time)

    ICD Pump: Min.(60) Divided by Min.(runtime) xVol. (to be admin.)

    Hope this helps.... everybody has their own little way of remembering these things.. this was mine.
  6. by   Ortho_RN
    Thanks everyone.. I knew these weren't difficult.. But I have worked so many problems that I am making them more difficult than they are...

    But thanks again..
  7. by   dstudent
  8. by   Cindy_A
    20gtts/cc X 100cc/hr X 1hr/60min = 33.3 gtts/min

    300cc/2hrs = 150 cc/hr

    That's the way I do mine. Good Luck!