Dosage Calculations - pt Factor ?

Tony35NYC · Aug 20, 2005

I've never heard of the term "patient factor". Sounds like a hifalootin' way of saying 'flow rate' to me. Since your medication is available in mls, its logical to assume that what they want to know is how many mls of the dopamine you're going to give. I have no idea how they came up with 0.59 for that answer, though.

I worked the problem in two steps. First step is to determine the concentration of the dopamine. To do that, I converted the miligrams to micrograms (x 1000), then divided it by the 250ml (ans=3200mcg/ml)

Second step is to determine the rate per minute. To do this, I multiply the ordered number of micrograms by the patient's weight in kilograms (2mcg x90kg=180mcg) then I divide that number by the concentration of the dopamine (3200mcg/ml). Which gives a rate of 0.056ml/min or approximately 3ml/hr.

Since the physician ordered a range of 2 to 5 mcg, you would have to repeat step 2, substituting the 2mcg for 5mcg to determine what the maximum dose is for the patient. But with 5mcg you're going to have a rate of about 8ml/hr.

I don't have a clue how they got 0.59 ????

Anyone else wanna take this on? I think I understand these math problems pretty well, but I just don't see the 0.59:)

mauser · Aug 20, 2005

Thanks for trying Tony. I usually have no problem with the tests - but never was asked this "factor" question before. When I was observing in Trauma Neuro the RN talked about using the "factor," but I just figured out the dosage/rate my usual way - I end up with the same answer she does. But if the question specifically asks me what the factor number is - I will be lost.

crb613, BSN, RN · Aug 20, 2005

I've never heard of the term "patient factor". Sounds like a hifalootin' way of saying 'flow rate' to me. Since your medication is available in mls, its logical to assume that what they want to know is how many mls of the dopamine you're going to give. I have no idea how they came up with 0.59 for that answer, though.
I worked the problem in two steps. First step is to determine the concentration of the dopamine. To do that, I converted the miligrams to micrograms (x 1000), then divided it by the 250ml (ans=3200mcg/ml)
Second step is to determine the rate per minute. To do this, I multiply the ordered number of micrograms by the patient's weight in kilograms (2mcg x90kg=180mcg) then I divide that number by the concentration of the dopamine (3200mcg/ml). Which gives a rate of 0.056ml/min or approximately 3ml/hr.
Since the physician ordered a range of 2 to 5 mcg, you would have to repeat step 2, substituting the 2mcg for 5mcg to determine what the maximum dose is for the patient. But with 5mcg you're going to have a rate of about 8ml/hr.
I don't have a clue how they got 0.59 ????
Anyone else wanna take this on? I think I understand these math problems pretty well, but I just don't see the 0.59:)

Beats the heck outta me! I worked it several times like you & did/could not get their answer. I also thought they meant flow rate. So mauser are you saying you figured out how to get the 0.59 for an answer? If so will you please post how you did it!

suzy253, RN · Aug 20, 2005

whew! I'm not losing it then. I tried to do this calculation a few times and gave up thinking I better brush up on my dosage calcs (which I'll do anyway) but this was making me nervous.

Nrs_angie, BSN, RN · Aug 24, 2005

I came up with the same as Tony... 3 ml/hr and 8 ml/hr... I have no idea what they mean by patient factor... could they possibly mean Drip Factor??

CritterLover, BSN, RN · Aug 24, 2005

i start class on monday with the dreaded drug calc test. while working as an extern, one of the facilitators gave us a worksheet to help get ready for the test. however, she is asking what the patient's factor is. i am not even sure what this is.
ex: dr. orders dopamine drip at 2 to 5 mcg/kg/min and you have dopamine 800 mg in 250 ml. pt weighs 90 kg. calculate the factor.
answer: 0.59.
help! i am really feeling stupid right now.

i think that they are referring to the relationship between mcg and ml per hr for this patient. when you calculate the ml per hour for 2 mcg, you get 3.375 ml per hour (which we all round to 3 ml/hr). divide 2 by 3.375, and you get 0.59. once you determine this factor, you don't have to do the whole calculation each time. if you want 10 mcg/kg/min, you would divide it by your "patient factor" and you get the correct rate.... 16.9 ml/hr. does that make sense? it is a "constant" .... remember from chemistry and physics?

hollyster · Aug 24, 2005

i think that they are referring to the relationship between mcg and ml per hr for this patient. when you calculate the ml per hour for 2 mcg, you get 3.375 ml per hour (which we all round to 3 ml/hr). divide 2 by 3.375, and you get 0.59. once you determine this factor, you don't have to do the whole calculation each time. if you want 10 mcg/kg/min, you would divide it by your "patient factor" and you get the correct rate.... 16.9 ml/hr. does that make sense? it is a "constant" .... remember from chemistry and physics?

it is called the cal factor or star factor. as critter lover has stated it is a quick way to calculate rate or mcgs. mcgs x kilograms x 60. you find out how many mcgs are in a fluid by finding out how many milligrams are in 1000 cc. say pt is on dopamine and weighs 75kg. (400mlligrams in 250cc = 1600mcg. 1600mcgs/75/60= cal factor .36

to get mcg per kilo per minute multiple cal factor x ccs .36 x 35cc =12.6mcgs/min.

to get cc/hr divide mcgs per minute by cal factor 12.6mcgs/.36 = 35cc/hour