Yet another math problem...

[Quidam]

An IV bag contains heparin 25,000 units/500 mL NaCl%. THe current flow rate is 20 mL/hr. You are to increase the infusion rate by 200 units/hr. What is the new IV flow rate? In mL/hr.

I use dimensional analysis and would appreciate any info. on how to set this problem up in that format. I am stumped.

Thanks so much.

Quidam

[Daytonite, BSN, RN]

an iv bag contains heparin 25,000 units/500 ml nacl%. the current flow rate is 20 ml/hr. you are to increase the infusion rate by 200 units/hr. what is the new iv flow rate? in ml/hr.

determine what the current units/hour that the patient is getting. . .

25,000 units/500 ml

(dose on hand)

x 20 ml/hour

(flow rate)

= 1000 units/hour

(dose being given)

you will increase the infusion rate by 200 units/hour, so

1000 units + 200 units = 1200 units

(dose to give)

determine the new iv flow rate. . .

1200 units

/hour

(new dose desired)

x 500 ml/25,000 units

(amount the dose on hand comes in)

=

24 ml/hour

(new flow rate)

[Quidam]

Thank you. Simple now that it's written out for me. I appreciate you taking the time to help.

Quidam

[Daytonite, BSN, RN]

they just played with one of the terms of the problem to have some fun with you guys. in actuality, heparin is often ordered as ____ units/hour. what your instructors did was play around with the flow rate to see if you could get the missing term. if you work with the formula, dose desired (ordered) divided by dose on hand multiplied by the amount the dose on hand comes in to get the amount to give and are able to identify at least two of these three terms--and it doesn't matter which two--you can always calculate the third. in the real world you will almost always know dose desired (ordered) and dose on hand. instructors, however, like to throw you monkey wrenches.

the above situation might occur when you get a patient after coming on your shift at work, ptt were just reported to the doc who says "increase the heparin drip by 200 units and hour" and you realize that all you have is a patient with a bag of heparin that originally had 500 ml of nacl and 25,000 units of heparin in it now dripping at 20 ml an hour. your first thought is to strangle the rn who didn't give you a better report on this iv and tell you how many units per hour of the heparin were infusing. your second is to do the calculations i just did. third, you will be kinder to the rn who follows you and report to them the units/hour that the patient has infusing. when you actually see this in action in clinical areas you will understand the practicality of this.