Dosage calc

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:

• • 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

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.