The Nursing Math Thread

[Tweety]

A member pm'd me the following question highlighted below. We created this thread for you guys to talk about math, solve math problems, and post math websites that you have found helpful.

I was wondering, is there a sticky or a special site that can be coordinated for "math sufferers". Perhaps, beginning calculations or shall i say the basics..simple to complex...step by step on how to calculate. I'm a visual learner, numbers and I don't work well. I am trying, but I've got a block!

[jorgegarcia]

haha sometimes computing iv fluids is hard ..specially on toxic hours LOL

[JillFRN]

Ok, I need help with a problem. My SIL asked me to help her and I am stumped. I guess this is what happens when you leave nursing school! Amoxicillin 100mg/m2 ( I think this is supposed to be mg/ml?) in 2000ml NS over 90 min. Pt ht is 68 inches and weighs 81.8 kg. Available as Amox 2mg/ml.

a. What is pt's BSA...I have this

What is the total dose of amoxicillin...I am assuming 50mg...am I correct? I don't want to sound like a dummy, but this seems to simple for the complexity of her problem.

Thank you in advance!

[murphyle, BSN, RN]

Right idea, but you lost it when calculating the dose. Did you divide by 1.98, perhaps? :)

So, our patient is 172.7 cm tall and weighs 81.8 kg. Using the Mosteller BSA formula,

_

\/ (Ht x Wt) / 3600

we get: 14126.9 / 3600 = 3.92

of which the square root is: 1.98

The amoxicillin is dosed at 100 mg/m2, so taking (dose/m2 x BSA), the square meters cancel, leaving:

100 x 1.98 = 198 mg total dose.

Divide by 2 mg/mL to get the volume for admixture: 99 mL. This will be added to your 2000 mL of .9, giving a final infusion volume of 2099 mL.

Hope this helps! :)

[CaptScrubs13]

I need some help with pedi fluid calculations ...

In class, we just practiced 24 hr fluid maintenance. In clinical, our instructor gave us a packet of problems to solve. These ones are different though:

1. Your 33kg child will need 1 1/2 maintenance for the next 8 hours. What should the hourly pump rate be set for?

We've been given:

100mL/kg for the first 10kg

50mL/kg for the second 10kg

20mL/kg for the remainder of the weight

so I came up with 1760mL for the 33kg child. This should be the 24 hours maintenance though. Do I multiple this by 1.5 for the "1 1/2" maintenance? Divide it by 8 hours?

Some of the other problems are:

Your child is 28kg. The physician has ordered the child to receive 2/3 maintenance. She ordered the hourly rate to be 69 mL /hour. Is this correct?

What is the hourly rate on the pump for a child weighing 39kg receiving 2/3 maintenance?

Anyone able to help? Thanks!

[AOX4RN, MSN, RN, NP]

I'm sure I have done this before but it's been a while and I can't remember how to set it up!

Order: Acetaminophen 1 tsp PO q 4 hours

Available: 80 mg/ 0.5 tsp

How many milligrams will you administer?

How many milliliters will you administer?

Duh. Please help.

[Suethestudent]

Order: Acetaminophen 1 tsp PO q 4 hours

Available: 80 mg/ 0.5 tsp

How many milligrams will you administer?

How many milliliters will you administer?

I am a bit puzzled by this question because an order would never be for a tsp. A doctor would not prescribe in this way, as it does not specify the dose to be administered. Remember an order has to have the pt,drug,dose, route,frequency and this order is missing the dose.

[AOX4RN, MSN, RN, NP]

Order: Acetaminophen 1 tsp PO q 4 hours

Available: 80 mg/ 0.5 tsp

How many milligrams will you administer?

How many milliliters will you administer?

I am a bit puzzled by this question because an order would never be for a tsp. A doctor would not prescribe in this way, as it does not specify the dose to be administered. Remember an order has to have the pt,drug,dose, route,frequency and this order is missing the dose.

It appears this imaginary doctor has prescribed 1 tsp [dose] acetaminophen [drug] PO [route] every 4 hours [frequency]. The only thing that's missing is the imaginary patient's name, but this is just a math problem (that was so obvious I'm embarrassed but keeping up for humility's sake ).

[Suethestudent]

I'm sorry to labor a point but a tsp is NOT a dose it is a volume (5ml) and is thus not acceptable.

It would be the same as ordering 1 capsule, 2 pills or 5 buckets BUT OF WHAT CONCENTRATION??????

It isn't done, so I don't agree with problems that are not real life. It confuses people that are starting out and trying to learn. Once again, a tsp is not a dose. Period.

[AOX4RN, MSN, RN, NP]

I will let my teacher know. What would you like me to do? Sheesh.

[live&love&heal]

i need some help trying to understand why the following calculation does not take into consideration frequency of when the medication should be administered and the weight:

medication problem:

the order if for digoxin 100 mcg iv q12h for a 2 year old child weighing 40 kg.

the dose available is digoxin 200 mcg in 1 ml ampules. how much do you administer?

i understand the set up using dimensional analysis is:

vehicle = ml

desired = 25 mcg

on hand = 50 mcg

equation set up is ml = 1ml/200 mcg x 100 mcg/ dose. answer is 0.5 ml

my question is...why would you not take into consideration the other values i mentioned (q12h = 2 doses and 40 kg)?

when i read medication calculation questions, i tend to over analyze, second guess myself, and get nervous that my answer is incorrect.

thanks in advance everyone!

[beth66335, BSN, RN]

i need some help trying to understand why the following calculation does not take into consideration frequency of when the medication should be administered and the weight:

medication problem:

the order if for digoxin 100 mcg iv q12h for a 2 year old child weighing 40 kg.

the dose available is digoxin 200 mcg in 1 ml ampules. how much do you administer?

i understand the set up using dimensional analysis is:

vehicle = ml

desired = 25 mcg

on hand = 50 mcg

equation set up is ml = 1ml/200 mcg x 100 mcg/ dose. answer is 0.5 ml

my question is...why would you not take into consideration the other values i mentioned (q12h = 2 doses and 40 kg)?

when i read medication calculation questions, i tend to over analyze, second guess myself, and get nervous that my answer is incorrect.

thanks in advance everyone!

the order is established in the question as 100mcg every 12 hours iv already, so the person that wrote the question is letting you know that they have calculated the dose based on the child's wt and age. the question has just done some of the work for you. if they needed to know how much in 24 hours they would ask about both daily doses but the question is only asking about the amount of medicine in this one dose. does that help? it is easy to add information into a question like that but just read it literally and straight forwardly to glean out only what info they want you to provide as an answer.

[live&love&heal]

Thanks beth66335 for the response. After reading it again and again and AGAIN. I now can see how it's straight forward. It's asking, this is the order. This is what you have on hand. How much are you going to give.

I guess it takes awhile to train your eye and just read the med math questions for what they are just asking for. I will keep practicing. Thanks again!