I have not a clue on this impossible math problem

macawake, MSN · Nov 22, 2016

A pint of blood (500 mL is hung at 1100 hrs. The flow rate is 42 gtt/min. The drop factor on the administration set is 10 gtt/min. When will the infusion be complete?

I'm guessing that the drop factor on the administration set is 10gtt/ml, not 10 gtt/min.

meanmaryjean, DNP, RN · Nov 22, 2016

Yup- typo! Drop factor is gtts/mL

bsnursing2018 · Nov 22, 2016

OH MY GOSH THANK YOU!!!! That makes perfect sense!! I was seriously driving myself mad trying to figure out what was wrong here, thank you guys so much!

NurseStorm, BSN, RN · Nov 22, 2016

I was about to say, this has to be a typo- otherwise makes no sense! lol. I feel bad you wasted so much time and effort due to someone's careless mistake! :X

AnnieOaklyRN, BSN, RN, EMT-P · Nov 23, 2016

If i did the math right the drip will be done at 12:11.

It's been a while though...

Annie

haunani, BSN, RN · Nov 23, 2016

If i did the math right the drip will be done at 12:11.
It's been a while though...
Annie

I got that it would take 119 minutes, so it'd be done at 1259.

(500 mL) * (10 gtt/mL) * (1/42 min/gtt) = 5000/42 = 119.05 minutes

macawake, MSN · Nov 23, 2016

I got that it would take 119 minutes, so it'd be done at 1259.
(500 mL) * (10 gtt/mL) * (1/42 min/gtt) = 5000/42 = 119.05 minutes

You're absolutely right.

In a perfect world where the bag contains exactly 500 ml (and delivered every last drop of it), 10 drops from the administration set is exactly 1 ml and the flow rate was exactly 42 drops per minute, it would take 119 minutes and 3 seconds to deliver the 500 ml :)

A pint of blood (500 mL is hung at 1100 hrs. The flow rate is 42 gtt/min. The drop factor on the administration set is 10 gtt/min. When will the infusion be complete?

If i did the math right the drip will be done at 12:11.

That's not correct. I don't know if this tip might help anyone out there or not, but I'll share it in case it does. Whenever calculating medication dosages, concentrations or flow rates I always double check my answer by looking at it and judging if it makes sense/seems reasonable.

In this case we know that the blood is administered at a rate of 4.2 ml/minute.

(drop factor: 10 gtts/ml and flow rate: 42 gtts/min).

Knowing that we also know that it will take slightly more than 100 minutes to administer the whole bag containing 500 ml. So it's reasonable to expect an answer that's over one and a half hours. 100 minutes would deliver 420 ml (a bit less than what's in the 500 ml bag), so we know that the answer should be more than 100 minutes, but not a whole lot more as we only have 80 more ml to administer at the 100 minute mark. We know that 100 mintues is the same as 1 hour and 40 minutes so at this point in our thought process we know it's reasonable to expect an answer somewhere around two hours.

By evaluating my answer using this process, and reaching a similar result from both methods (algebra and "logic double check"), I'd feel confident about my answer.

Been there,done that, ASN, RN · Nov 23, 2016

It is not a pint of blood...it is a unit of PRBC's. That is 480 cc's. Where are you going to school?

TheCommuter, BSN, RN · Nov 23, 2016

Moved to the Nursing Student Assistance forum.

AliNajaCat · Nov 23, 2016

Gtt factor means "drops in one cc." That should get you where you need to go. :)

And a unit of PRBCs is more like 250 cc. Hardly anybody gives whole blood anymore-- it's better to break it down into PRBCs, plasma, platelets, and whatever to get more bang for its buck, so to speak.

Shows you that this program is using old questions. The arithmetic (or at least basic algebra) is the important part, but I don't see why they couldn't update their word problems to reflect current clinical reality.

Agree c Macawake's eyeballing. I said, "Hmmm, if it were 4cc/min, that would be 125 minutes, and if it were 5cc/min, that would be 100 minutes, so the answer has to be in between there, closer to the 125."

Off soapbox.

Esme12, ASN, BSN, RN · Nov 23, 2016

It is not a pint of blood...it is a unit of PRBC's. That is 480 cc's. Where are you going to school?

Typically 1 unit of "blood" is considered a "pint"

Usually.....in one unit of whole blood there is 500mls. When only packed RBC's are being transfused the "unit" is usually 250 to 300mls. There is no real way to have a standard amount on every unit of packed cells because the removal of different blood/plasma varies with each individual. One unit of FFP varies bag to bag depending on the donors plasma concentration that is removed from the whole blood donation of around 200mls/unit. When platelets and precipitate are removed the volume varies around 25 to 50mls. Because of the varying amounts most labs label the bags.

http://www.ucsfcme.com/2009/slides/MEM09002/HREM%20Day%203%20Folder/20HendeyTransfusions.pdf

https://www.pathology.med.umich.edu/bloodbank/coi0809.pdf