HI everyone, I am having some real problems with one sort of IV math problems. These are practice math problems. I have been nearly stuck on them for about 2 hours trying to figure out how to solve them, unfortunately I still don't know how. I really need help, please any assistance truly appreciated! The problems are:
1. The physician orders dopamine at 5 MG/Kg/min. The concentration is dopamine 2 g in 250 mL of 0.9% NS. The patient's weight is 80 kg. How many mL/ h should the IV pump be programmed for? The answer is 3 mL.
5x80x60 over 8000. But where does 8000 come from???
2. The physican orders dobutamine at 12 MG/KG/min for a patient weighing 75 kg. The concentration is dobutamine 1 g in 250 mL of D5W. How many mL/h should the IV pump be programmed for? The answer is 13.5 mL.
12x75x60 over 4000. But where does 4000 come again from?
you multiply dose x kg x min == your total dose ordered
You look at the concentration of the drug dose. In this case it is 2 g per 250 ML.
You need to see how much dose would be in one liter, in this case 4x250=1000 which will be 8 grams in one liter.
Now from the calculation on the first line, you have to have 24000 mg which is 24 g total ordered. You need to have three bags to deliver the order given. You divide the three bags in one day.
Punch it in on the Baxter-It'll figure it out for you. No, really, the only way to get good at the equations is to do a ton of them-I used to spend hours doing problems until I could do them in my head. The key is to see the big picture, which really comes with experience. If you get a number and it doesn't look right, you have to be able to stop, think, and question it-if not, you can overdose a pt-it's not just about math. Also, always double check with another nurse to make sure you're looking at the same thing. Be Safe!!!!!!!!!!
The doses, as ordered, are wrong. In the first case, it should be 5mcg/kg/min, and the in the seconds case, it should be 12mcg/kg/min.
Where does the 8000 come from? In the bottom equation you want to know the concentation per ml. Therefore, you have 2gm (or 2000mg) diluted in 250ml. So, the concentration of mg/ml is 2000mg divided by 250ml = 8mg per ml. Now, you have to convert this to mcg/ml, so you multiply the 8 by 1000 ( since there are 1000 mcg in a mg) giving you the 8000mcg/ml!
Good call on the problem being mcg's instead of mg's! I was taught solving math problems using dimensional analysis, where all the factors cancel out except the end label needed. I did the problems, but my answers were 1000 more! When done in mcg, the answers were correct. Thanks, I'm taking my boards in Feb. and I thought I was losing my mind! I've been out of school for 1 month and studying questions upon questions.
Typical concentrations of dopamine are 400 mg /250 ml unless double concentrated, then is 800 mg/250 ml, these are standard for the manufacturer. Dobutrex in standard formula is 250 mg/250 ml unless double concentrated then is 500 mg/250 ml. If you where working with the concentration you put down that would be both irresponsible and dangerous, might let your instructors know this. Standard deviation is I think easiest way to solve such problems.
Even though math came easy to me in nursing school, one of my second semester nursing instructors gave us all a wonderful tidbit of information. If you know what the answer -in units- is, then that should help. For example if your answer is ml/hr, then you know you will need to cancel out any other units of measurements in the problem...kg, mg, or mcg.
Hello. I'm a student nurse as well. I first tried to work your first problem (I use Dimensional Analysis) but like you, I was not getting a correct answer. So, I next went to my Davis drug book because I figured that the dose might be too high for Dopamine. And it looks like what is normally ordered for IV is between 0.5 to 10 mcg/kg/min, not MG. Thus, if you change the dosage in your calculation to 5 mcg/kg/min, you will get the answer 3 ML (6,000,000 / 2,000,000 = 3). So you can hopefully go back to your instructor and tell them the doctor ordered a dose that may cause adverse effects like mydriasis and arrhythmias! Good luck.
No, really, the only way to get good at the equations is to do a ton of them-I used to spend hours doing problems until I could do them in my head. The key is to see the big picture, which really comes with experience. If you get a number and it doesn't look right, you have to be able to stop, think, and question it-if not, you can overdose a pt-it's not just about math. Also, always double check with another nurse to make sure you're looking at the same thing. Be Safe!!!!!!!!!!
Good luck.
Silverdragon102, BSN
1 Article; 39,477 Posts
You are welcome