Dosage calc

[lylega]

Hello fellow health care workers,

I am in the last semester of an ADN program and I'm looking for a book that will help me with advanced IV calculations. I'm looking for something I might find online or in a bookstore, I have textbooks and I find their teaching methods worthless. Anybody have any suggestions?

Also, while I'm here, can anybody help me get through this particular dosage question:

One of your patients has an IV that is flowing at a rate of 10 gtt/min. The IV bag contains a solution of 500 ml of NS with 20,000 units of heparin. The drop factor is 15 gtt/ml. How many units of Heparin is the patient receiving in 24 hours?

The answer is 38,400 units of heparin every 24 hrs.

I understand the basics and have had no trouble up till now, and I can do drip rates, ml/hr, all the core stuff just fine. Anybody got any sensible ideas how to get from A to B on this one? I would certainly appreciate some help!

[Daytonite, BSN, RN]

this is still a dose desired divided by dose on hand to get the dose you want to give kind of problem. the difference is that they have already given you the dose desired, so you need to do a little algebra (if you do it the hard way) to get the answer. i like dimensional analysis. all you need to know for dimensional analysis is that you are looking for units/hour in the final answer. that's units, in the numerator and hours in the denominator of the final answer. the other thing that you need to keep in mind with dimensional analysis is relationships. the dose on hand (20,000 units of heparin in 500 ml if ns) is a relationship that can be expressed as a ratio/fraction and you must always keep these figures together. however, the heparin or the ns can be the numerator or denominator--doesn't matter--it only matters that they are kept together in the same ratio. got that? so, we set up a dimensional analysis equation that utilizes the necessary relationships to come out with units/hour like this:

the relationships:

• • dose on hand: 20,000 units/500 ml
    
    
  • dose to give: 10 gtts/minute
    
    
  • drop factor: 1 ml/15 gtts
    
    
  • conversion of minutes to hours: 60 minutes/1 hour

the equation and answer:

20,000 units/500 ml

(dose on hand)

x 10 gtts/minute

(dose to give)

x 1 ml/15 gtts

(drop factor)

x 60 minutes/1 hour

(conversion factor)

=

1,600 units/hour

then, let's do a little algebra. . .1,600 units/1 hour =

x

units/24 hours. cross multiply. (

x

units)(1 hour) = (1600 units)(24 hours). the labels all cancel out and you are left with

x

=

38,400

which is the answer you were looking for.

you can see problems worked out in the dosage calculations thread on this forum here (https://allnurses.com/forums/f205/dosage-calculations-88867.html). if someone started a thread asking for help with a drug calculation and i responded to it, i usually write the words dimensional analysis in my post somewhere. you can use the advanced search to find these threads by using the search word "dimensional" or "analysis" and my screen name to find them to see these examples.