# Drug Calculations

Posted
MaureenF (New)

I just returned to ICU nursing after being away from it for 5 years. Most everything has come back to me, however I'm still struggling with calculating drip rates. Our educator is useless, and I'm somewhat embarrassed to ask other nurses for help on this. Hoping someone hear can make it easy for me to understand. Thanks

Drip Rate per minute =

(Amount to infuse in mL) x (Drop Factor of IV set)

-------------------------------------------------------------

(No. of hrs to infuse) x 60

Basic formula ^.^

Do you not have IV pumps that do the calculations for you?

Specializes in Not too many areas I haven't dipped into.

Do you not have IV pumps that do the calculations for you?

at one major hospital here in Cincinnati, they will not allow you to use the pumps to calculate...you have to do the math each titrationa dn double check with another nurse

Besides, it's always important to know how to do the math, not solely relying on infusion pumps to do the calculations.

Specializes in CTICU, PICU, L & D. Has 10 years experience.

I feel your pain after being away from the bedside for 3 months on a family leave.

I think it is sad that your educator is useless, and there has to be one colleague that you

can turn to for a drip review? Better to be a bit embarrassed now then make a life altering mistake later though.

I work in a PICU and will give you some examples of how I calculate my drips. I also agree that we should never rely on the pump to do the calculations.

Dopamine (800mg in 250 cc bag) = a concentration of 32 mg/cc or 3200 mcg/cc. Dopamine runs in mcg/kg/min

so to calculate the drip multiply the patients weight x dose x 60 and divide by the concentration in mcgs to get the cc/hour to set the pump.

The order reads 20mcg/kg/min and my patient weighs 58 kg Sooooooooo here we go

20(dose) x 58(wt) x 60(min)

________________________ = 21.75 cc/hr

3200(mcgs)

Epinephrine (6 mg in 50 cc bag) = 0.12 mg/cc or 120 mcgs/cc Order read Epi drip 0.15 mcg/kg/min

0.12 x 58 x 60

____________ = 4.35 cc/hr

120

Milrinone (20 mg in 100 cc bag) = 0.2 mg/cc or 200 mcgs/cc Order read Milrinone 0.5 mcg/kg/min

0.5 x 58 x 60 = 8.7 cc/hr

____________

200

Morphine (5 mg per cc) Order read 0.18 mg/kg/hr

0.18 x 58 = 10.44 and then divide by 5 (the concentration ) to get 2.09 cc/hr

Nimbex (2 mg per cc or 2000 mcg per cc) Order read Nimbex 2.2 mcg/kg/min

2.2 x 58 x 60

_____________ = 3.82 cc/hr

2000

I hope this helps and just give another should out if you need more practice.

My first week back to work was nuts. Patient on Epi, dopa, vaso, morphine, versed, nimbex, calcium, mg, nexium

and CVVHDF. I completely leaned on my neighbors for both help and a confidence boost and that is o.k.

Good luck to you

Specializes in ICU, Education. Has 25 years experience.

Always figure out concentration first--figure out the mg, mcg, or unit you want to deliver per ml to start. If the dosage is not weight based, and is only to be delivered per hour rather than per minute--you are done-you have your constant (constant X ml/hour = dose). However, if it is to be delivered per minute, divide that number by 60. Then, if it is to be weight based, divide that number by the patient's dry weight in Kg. This is your constant (never changes). Then you just multiply your constatn by the rate (ml/hour), so you always know what your dosage is with every rate change.

Specializes in Sub acute rehab, ICU.

The facility I am at uses this "K Constant" formula for drip calculations for verifying the pump is set correctly. I struggled with learning this formula because I am a bit of a math/science purest and this "K" really isn't a constant. I have not found or seen the source documentation for this formula or an article that discusses the theory, rationale and application. Can someone cite a link?

Specializes in geriatrics.

mark~~~~~~~~~~~~~~~~~~

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