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!

[wondergirlhere]

Question

Keflex 400 mg po q8hr is ordered. Keflex oral suspension is supplied at a concentration of 125mg/mL. How many mL of suspension do we need to give? I calculated 3.2mL

How much Keflex does this patient get per day? (total dose per day)

I calculated 1200 mg/day

Your patient is a toddler with otitis media who weighs 16 kg. Would this dose be safe?

I think "yes" when given in 4 divided doses per day as therapy for otitis media requires dosage of 75 to 100 mg/kg/day in 4 divided dose for medication to be therapeutic.

16 kg child x 100mg/kg/day = 1600 mg/day

Question #2

Your patient is ordered vancomycin 1 gm IV q12hr. the pharmacy has supplied your medication in a 250 mL minibag. Your concentration is 1 gm/250 mL.

a) What is the concentration in mg per mL?

b) Pharmacy advises you ot run this medication over at least 90 minutes. What is your hourly rate for the pump?

c) What would your drip factor be on macro drip tubing (10 gtts/mL)?

[wondergirlhere]

So, I've completed some IV questions.

Let me know please if I did this correctly.

Question:

Your patient had orde for metoclopramide 10mg IV q4-6 hrs prn. The metoclopramid supplied to our is in theconcentation of 5mg/mL. Your are adding metoclopramide 10 mg IV to a minibag of 50 mL of NS.

a) How much total volume will your IV bag have after you add your metoclopramide? I think it's 52 mL

b) you want to administer this over 15 minutes. Your drip rate is micro drip (60 gtts/mL) what is your drip rate for this med? I think it's 208 gtts/minute

c) your tubing is macro drip (10 gtts/mL) What is your drip rate for this med? I think it's 35 gtts/minute

d) your tubing is the Alaris pump tubing (drip rate is 20 gtts/mL) and you need to run it by gravity. What is the driprate for this med? I think it's 69 gtts/minute.

[Daytonite, BSN, RN]

question

keflex 400 mg po q8hr is ordered. keflex oral suspension is supplied at a concentration of 125mg/ml. how many ml of suspension do we need to give? i calculated 3.2ml

how much keflex does this patient get per day? (total dose per day)

i calculated 1200 mg/day

your patient is a toddler with otitis media who weighs 16 kg. would this dose be safe?

i think "yes" when given in 4 divided doses per day as therapy for otitis media requires dosage of 75 to 100 mg/kg/day in 4 divided dose for medication to be therapeutic.

16 kg child x 100mg/kg/day = 1600 mg/day

question #2

your patient is ordered vancomycin 1 gm iv q12hr. the pharmacy has supplied your medication in a 250 ml minibag. your concentration is 1 gm/250 ml.

a) what is the concentration in mg per ml?

b) pharmacy advises you ot run this medication over at least 90 minutes. what is your hourly rate for the pump?

c) what would your drip factor be on macro drip tubing (10 gtts/ml)?

your answers to the questions about keflex are all correct. for "would this dose be safe?" be decisive in saying "yes this is a safe dose" or "no this is not a safe dose". work out the calculations to show the range of doses. my drug information on cephalexin (keflex) for a child indicates that the safe dose range is 25-50 mg/kg/day in 4 equal doses (page 234, mosby's nursing drug reference and http://www.drugs.com/pro/keflex.html), but i will use your parameters. i would show work like this:

safe dose range for a child: 75 to 100 mg/kg/day

• low dose: 75 mg x 16 kg = 1200 mg/day
  
  
• high dose: 100 mg x 16 kg = 1600 mg/day
  
  

the safe range is 1200 to 1600 mg per day. 1200 mg per day has been ordered (400 mg q8h), so this would fall within the safe range. yes, this is a safe dose.

however, based on the information i found. . .

safe dose range for a child: 25-50 mg/kg/day in 4 equal doses

• low dose: 25 mg x 16 kg = 400 mg/day
  
  
• high dose: 50 mg x 16 kg = 800 mg/day
  
  

the safe range is 400 to 800 mg per day. 1200 mg per day has been ordered (400 mg q8h), so this would fall above the safe range. no, this is not a safe dose.

the correct answer to this problem is dependent on where the information for the safe dosage came from. if it was given to you in the problem then work with that. if you had to find it, then re-check your references because i found the 25-50 mg/kg/day figure in two different places.

your patient is ordered vancomycin 1 gm iv q12hr. the pharmacy has supplied your medication in a 250 ml minibag. your concentration is 1 gm/250 ml.

a) what is the concentration in mg per ml?

1 gram/250 ml x 1000 mg/1 gram (conversion factor) =

4 mg/ml

b) pharmacy advises you not run this medication over at least 90 minutes. what is your hourly rate for the pump?

iv pumps are always set in

mls/hour

. you need to program in the mls you will be infusing and the hourly rate.

250 ml/90 minutes

(amount to infuse and time to infuse it over)

x 60 minutes/1 hour

(conversion factor)

= 166.666 ml/hour

, rounded up to

167 ml/hour

(hour rate to set the pump)

note:

pump rates must be set in whole numbers.

c) what would your drip factor be on macro drip tubing (10 gtts/ml)?

you know the infusion rate will be 167 ml/hour and that will be with 10 gtt/ml tubing. now, you need to calculate how many drops per minute that will be since in the clinical area this is how the nurse would monitor this iv infusion. . .

167 ml/1 hour

(infusion rate)

x 10 gtts/ml

(drop factor of iv tubing)

x 1 hour/60 minutes

(conversion factor)

= 27.833 gtts/minute

, round up to

28 gtts/minute

.

note:

drops must be expressed as whole numbers.

[Daytonite, BSN, RN]

So, I've completed some IV questions.

Let me know please if I did this correctly.

Question:

Your patient had order for metoclopramide 10mg IV q4-6 hrs prn. The metoclopramid supplied to our is in theconcentation of 5mg/mL. Your are adding metoclopramide 10 mg IV to a minibag of 50 mL of NS.

a) How much total volume will your IV bag have after you add your metoclopramide? I think it's 52 mL

b) you want to administer this over 15 minutes. Your drip rate is micro drip (60 gtts/mL) what is your drip rate for this med? I think it's 208 gtts/minute

c) your tubing is macro drip (10 gtts/mL) What is your drip rate for this med? I think it's 35 gtts/minute

d) your tubing is the Alaris pump tubing (drip rate is 20 gtts/mL) and you need to run it by gravity. What is the driprate for this med? I think it's 69 gtts/minute.

Yes, your answers are correct, but I don't know how you did the calculations or if you set them up correctly.

[moncj66]

Im practicing some questions and Im still having problems on a few others:

1.) Propofol (1000mg/100ml) is infusing at 90mcg/kg/min. Your patient weighs 175 pounds. Calculate the rate of infusion?

2.)Ordered: Dopamine 10mcg/kg/min. Patient weighs 150lbs.

Available: Dopamine 400mg in 500ml D52

Administer via IV pump: ??

[beth66335, BSN, RN]

question

keflex 400 mg po q8hr is ordered. keflex oral suspension is supplied at a concentration of 125mg/ml. how many ml of suspension do we need to give? i calculated 3.2ml

how much keflex does this patient get per day? (total dose per day)

i calculated 1200 mg/day

your patient is a toddler with otitis media who weighs 16 kg. would this dose be safe?

i think "yes" when given in 4 divided doses per day as therapy for otitis media requires dosage of 75 to 100 mg/kg/day in 4 divided dose for medication to be therapeutic.

16 kg child x 100mg/kg/day = 1600 mg/day

on this question always calculate both doses of mg/kg/day (75 and 100) to get your range because if the dose given is too low that is also not safe or therapeutic. the dose for 75 is 1200 which makes this dose right on the edge of the safe range.

question #2

your patient is ordered vancomycin 1 gm iv q12hr. the pharmacy has supplied your medication in a 250 ml minibag. your concentration is 1 gm/250 ml.

a) what is the concentration in mg per ml?

250ml / 1000mg= .25mg/ml

b) pharmacy advises you to run this medication over at least 90 minutes. what is your hourly rate for the pump?

250ml x 60min =15000 = 167ml/ hour

90min.....1hour....90

c) what would your drip factor be on macro drip tubing (10 gtts/ml)?

250ml x 10gtts =2500 = 28gtts/min

90min.....1ml......90

hope this helps!

[Daytonite, BSN, RN]

im practicing some questions and im still having problems on a few others:

1.) propofol (1000mg/100ml) is infusing at 90mcg/kg/min. your patient weighs 175 pounds. calculate the rate of infusion?

2.)ordered: dopamine 10mcg/kg/min. patient weighs 150lbs.

available: dopamine 400mg in 500ml d52

administer via iv pump: ??

these drugs would be infusing on iv pumps. iv pumps are always set at mls/hour.

propofol (1000mg/100ml) is infusing at 90mcg/kg/min. your patient weighs 175 pounds. calculate the rate of infusion?

by dimensional analysis (factor label method)

:

90 mcg/minute

(dose desired)

x 175 pounds

(patients weight in pounds)

/2.2 pounds

(to convert patients weight to kilograms)

x 100 ml/1000 mg

(dose on hand)

x 1 mg/1000 mcg

(conversion factor)

x 60 minutes/1 hour

(conversion factor)

= 42.9545 ml/hour

rounded off to

43 ml/hour

note

:

pumps rates must be set in whole numbers.

ordered: dopamine 10mcg/kg/min. patient weighs 150lbs.

available: dopamine 400mg in 500ml d5w

administer via iv pump

by dimensional analysis (factor label method)

:

10 mcg/minute

(dose desired)

x 150 pounds

(patients weight in pounds)

/2.2 pounds

(to convert patients weight to kilograms)

x 500 ml/400 mg

(dose on hand)

x 1 mg/1000 mcg

(conversion factor)

x 60 minutes/1 hour

(conversion factor)

= 51.136363 ml/hour

rounded off to

51 ml/hour

note

:

pumps rates must be set in whole numbers.

[mb1949]

Ok this was on my last pharm exam, and I got it wrong, unforetunately no one can or will explain why could someone enlighten me

order 500mg acetaminophen 500mg po prn for fever over 100.2

available 375mg per 10.15mL

I solved this way:

500mg x 10.15mg= xmg

375mg

x=375mg into 5075=13.53mg

x=13.53mg

marked wrong should have rounded up to 13.5mg what is rationale for this if I was giving 375mg would I draw up 10.15 or 10.2 I am so confused, and the pharm commitee chairman just blew me off when I questioned this

[Daytonite, BSN, RN]

ok this was on my last pharm exam, and i got it wrong, unforetunately no one can or will explain why could someone enlighten me

order 500mg acetaminophen 500mg po prn for fever over 100.2

available 375mg per 10.15ml

i solved this way:

500mg x 10.15mg= xmg

375mg

x=375mg into 5075=13.53mg

x=13.53mg

marked wrong should have rounded up to 13.5mg what is rationale for this if i was giving 375mg would i draw up 10.15 or 10.2 i am so confused, and the pharm commitee chairman just blew me off when i questioned this

you have the wrong label on your answer. the answer is 13.53 ml not 13.53 mg. the problem tells you the dose desired is 500 mg.

order 500mg acetaminophen 500mg po prn for fever over 100.2. available 375mg per 10.15ml

500 mg

(dose desired)/

375 mg

(dose on hand) x

10.15 ml

(amount the dose on hand comes in) =

13.5333 ml

, rounded to

13.5 ml

[mb1949]

The label is just my stinky typing skills, I still don't understand why you would round, and in real life if I was to give 375mg would i draw up 10.15 or 10.2

[Daytonite, BSN, RN]

The label is just my stinky typing skills, I still don't understand why you would round, and in real life if I was to give 375mg would i draw up 10.15 or 10.2

If I were to give 375 mg I would draw up 10.2 mL. Rounding rules are that you round up for 5 or over.

[mb1949]

Ok so then I will never say never, but in most cases you run up to the tenths for po med, I think I understand, thanks for your help, more helpful than my professors