Drug Calculation Help

[summertx]

The question is:

1000 mL NS with 30,000 Units heparin prescribed to run at 1200 Units/ hr. The drop factor is 30 gtt/mL.   What's the flow rate in gtts/min?

What I did was do volume over time x the drop factor.

1000ml/60min x 30 = 500gtt/min (this seemed to be alot so..)

The other way I did was 

30,000/1000= 30units/ml

1200units/hr /30ml = 40

40/60min =  0.667

.667 x 30gtt/ml =  20 gtts

I don't understand why we're using the 1200 units in the calculation if the second way is the right answer and why not the first way with the volume only.

[Rose_Queen, BSN, MSN, RN]

In the first way, you just gave your patient the entire liter of heparin in one hour. That’s 30,000 units per hour, 25x the dose they are to receive. 

This is a 2 step problem where first you must determine the volume you need to give in one hour, then use that volume to calculate the gtt rate. 

[BostonFNP, APRN]

 

7 hours ago, summertx said:

The question is:

1000 mL NS with 30,000 Units heparin prescribed to run at 1200 Units/ hr. The drop factor is 30 gtt/mL.   What's the flow rate in gtts/min?

What I did was do volume over time x the drop factor.

1000ml/60min x 30 = 500gtt/min (this seemed to be alot so..)

The other way I did was 

30,000/1000= 30units/ml

1200units/hr /30ml = 40

40/60min =  0.667

.667 x 30gtt/ml =  20 gtts

I don't understand why we're using the 1200 units in the calculation if the second way is the right answer and why not the first way with the volume only.

The heparin was prescribed to run at 1,200 units/hour. In your first calculation you ran it at 30,000 units/hour (1000ml/hr). This mistake could be fatal to the patient which is why these calculations are critically important to understand. 

You added your own information of 1000mL/hr instead of using the provided 1200u/hr (or 40mL/hour).