Dimensional Analysis problem

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  • by ICAN!
    Specializes in Dialysis.

KCl 5 mEq is to be added to 500 mL's of D5W and infused at 40 ml. per hour. KCl is supplied in a 10 ml. ampule containing 20 mEq per ml. How many mL's of KCl should be added to the IV bag?

Would someone please show me how to set this up. I know the answer is .3 but I'm trying to figure out how to get the answer.

Thanks!

Specializes in Med-Surg/Tele, ER.

I got .25 for an answer, using 5 mEq as your starting factor x 20mEq on the bottom and 1 ml on the top but I could be wrong

EymieICURN

44 Posts

Specializes in Adult ICU (All over), NICU, Education.

I agree with kimmie

kfarinato

139 Posts

Specializes in LTC.

ml= 1ml x 5meq

____ = 0.25ml

20meq

ok it didn't stay formatted. but you get the general idea i hope

ml = 1ml/20meq x 5 meq= 0.25ml

Daytonite, BSN, RN

1 Article; 14,603 Posts

Specializes in med/surg, telemetry, IV therapy, mgmt.

kcl 5 meq is to be added to 500 ml's of d5w and infused at 40 ml. per hour. kcl is supplied in a 10 ml. ampule containing 20 meq per ml. how many ml's of kcl should be added to the iv bag?

dimensional analysis is also called
factor labeling
. it is called that because you set up an equation along with the labels on the numbers with the express purpose of manipulating the labels and factoring them out so that the answer will contain specific labels on them. for this problem, you will want to use this formula:
dose desired divided by the dose on hand multiplied by the amount that the dose on hand comes in to get the amount to use. . .

dose desired:
5 meq kcl

dose on hand:
10 ml ampules of
20 meq/ml

set up the equation and calculate:
5 meq
(dose desired)
/20 meq
(dose on hand)
x 1 ml
(amount that the dose on hand comes in)
= 0.25 ml
, rounded up to
0.3 ml
.

the reason the answer is rounded up to 0.3 ml is because most syringes are not calibrated to be able to precisely draw up 0.25 ml. most syringes can only draw up amounts in increments as small as 0.1 ml. this is the kind of answer that is based in real world application. it may also be because of rounding rules. since the dose desired is only one digit, the answer needs to be presented as one place past the decimal point (one digit) which requires rounding up the answer.

ICAN!

127 Posts

Specializes in Dialysis.

Thanks for the drawn out explanation (that is exactly what I needed); it made the problem more clear to me. I guess all the other numbers in the problem were confusing me. I really appreciate your help.

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