Dosage Calculations

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I am in a desperate situation. I thought I was getting my calculations correctly and today I got back my math results and i got a 70% I am so disappointed I dont know what to do. On my first exam I received an 80%.

My professor said that if i get above 95% on my final (which is next week) I may be able to average a b+ or a- , but it will all depend on the overall average, if he curves grades or not. I went and bought 2 self help books on calculations .... My question is ..... do you think it is humanly possible to ingest all this info by next week (exactly a week from today)! I am having problems with the drips and the three step conversions. Is there a website that can help me? To top it off my professor sucks, so what I have learned, I have learned on my own. I am so frustrated, so much so, that it is getting harder and harder for me to pick up a book .....sorry for venting

Specializes in Gerontological, cardiac, med-surg, peds.

Free Dosage Calculation Study Ware from Delmar Publishing (interactive - great study tool!):

http://www.delmarlearning.com/companions/content/1418015636/studyware/index.asp?isbn=1418015636

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Specializes in Observation Unit, ACLS, BLS.

Hi can anyone help have an upcoming exam and I'm practicing problems according to my schools study guide that was posted. I've been able to work out all of them except this one even though I think this requires the same formula. The IV is infusing at 20ml/hr and contains 50mg. Nipride in 250ml D5W. The client weighs 185lbs.

___kgs. (tenth)

___mcg/kg/min to (tenth). I've worked the kgs to 84.1 but can't seem to figure the other half. Thanks in advance for your help..

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Specializes in med/surg, telemetry, IV therapy, mgmt.
nmb107 said:
the iv is infusing at 20ml/hr and contains 50mg. nipride in 250ml d5w. the client weighs 185lbs.

___kgs. (tenth)

___mcg/kg/min to (tenth). i've worked the kgs to 84.1 but can't seem to figure the other half. thanks in advance for your help..

To convert pounds to killograms:

185 pounds x 1 kg/2.2 pounds = 84.090909=
84.1 killograms
(rounded off to tenths)

To work the problem by dimensional analysis and using the formula dose desired divided by dose on hand to give you the dose to give:

dose desired:
20 ml/hour (this already has the patient's weight of 84.1 kg calculated into it)
dose on hand:
50mg of nipride in 250 ml of d5w
dose to give: x
mcg/kg/minute
conversion factor:
1 mg = 1000 mcg
conversion factor:
1 hour = 60 minutes
Plug all figures into the equation and compute. You do not need to figure in the patient's weight since it is already part of the calculation for the dose desired . You must know how to work with fractions and ratios to do this:
20 ml/1 hour
(dose desired)
x 50 mg/250 ml
(dose on hand)
x 1000 mcg/1 mg
(conversion factor)
x 1 hour/60 minutes
(conversion factor)
= 66.7 mcg/minute
, or
67 mcg/minute
, rounded off to a whole number.

Another way to figure this out is to determine how many milligrams of the nipride the patient is getting every hour. That is 4 mg. That figure is determined by taking the 50 mg and dividing it by the total amount in the iv bag (250 mls) to get 0.2 mg/ml. Since the infusion is running at 20 ml/hour, you multiply the 0.2 mg/ml times the 20 ml/hour to get that the patient is receiving 4 mg/hour of the nipride. 4 mg converted to mcg is 4,000 mcg/hour (1mg = 1,000 mcg). To figure out how much the patient is getting in one minute, simply divide the 4,000 mcg by 60 (1 hour = 60 minute) and you will still get 66.6666 mcg which you will have to round off to either one decimal or a whole number, whichever your instructor prefers.

1
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Hello everybody,

This was a question that was gnawing at me since I finished my dosage exam a couple hours ago.

Available: Tylenol 325mg/tab

Order: gr X

How many tablets are you gonna administer?

Hmmm, is this right:

325mg : 1 tab :: 600mg : x tab

325x/325 = 600/325

x = 1.8 tablets (can you have 1.8 tablets?!)

-___- that doesn't seem right... Are my grains correct D:?

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Specializes in med/surg, telemetry, IV therapy, mgmt.
gopherguts said:
Hello everybody,

This was a question that was gnawing at me since I finished my dosage exam a couple hours ago.

Available: Tylenol 325mg/tab

Order: gr X

How many tablets are you gonna administer?

Hmmm, is this right:

325mg : 1 tab :: 600mg : x tab

325x/325 = 600/325

x = 1.8 tablets (can you have 1.8 tablets?!)

-___- that doesn't seem right... Are my grains correct D:?

There are two acceptable conversion factors for grains to milligrams:

1 grain = 60 milligrams
1 grain = 65 milligrams

This is how I would have done that problem by dimensional analysis:

Dose Desired
: grain x (10 grains)
Dose on Hand
: 325 mg/1 tablet
Conversion factor:
1 grain = 65 milligrams
You want to end up with the number of tablets to give in the numerator of the answer. . .
10 grains/1
(dose desired)
x 1 tablet/325 mg
(dose on hand)
x 65 mg/1 grain
(conversion factor)
=
2 tablets
(amount to administer)

The answer to your question is: no, you cannot give 1.8 tablets. You would have to round off the answer to a whole number of 2. However, using the other conversion factor of 1 grain = 65 mg would have given you the whole number answer. This, by the way, is a very common order that doctors wrote (and probably some of the older guys still write) for Tylenol, so it is grounded in real practice.

1
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Once you get your kilograms. 185 pounds divided by 2.2. It should equal 84.1 when you round to the tenth. Next, you say (50,000/250ml/84.1). Then multiply times 20 to get 47.56... You divide by 60 to get 0.792...mcg/kg/min. And you know how our school is when it comes to rounding. Either to the tenth or to the hundredths place depends on how they feel that day(inside joke). Hoped you passed this last one.

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I have not had to do drips yet - just regular conversions. All I can say about converting is focus on the known and unknown and keep them separate. good luck.

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Specializes in Observation Unit, ACLS, BLS.

Thanks everyone for your help with my dosage and calculation question. God Bless

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I posted these questions in the main forum but could still use some help with the formula set up:

My main problem is how do I exclude extra information? Like if the question asks:

Heparin drip of D5W 250cc with Heparin 25,000 units infusing at 8cc/hour How many units per hour is the patient recieving? And If the MD increased the dosage to 1100 units/hr how many cc/hr will this be?

What is the best way formula wise to set these up without including unneeded number info into the equation?

Another one is: KVO with D5W what hourly volume will you give? and What is the drop rate/min?

Don't you still need some info besides just KVO? What type of IV set would you use for KVO?

Can you use the formula below for ALL IV problems?

total # of milliliters (volume)

_________

total # of minutes (time) x Tubing Factor

I know DA is supposed to be the gold standard for all math problems but I just don't follow DA very well. But formulas I get. Pls help.

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Specializes in med/surg, telemetry, IV therapy, mgmt.
nurse2b allbetta said:
heparin drip of d5w 250cc with heparin 25,000 units infusing at 8cc/hour how many units per hour is the patient receiving? and if the md increased the dosage to 1100 units/hr how many cc/hr will this be?

With dimensional analysis you set up an equation so that you will end up with an answer that has a label of units in the numerator and hours in the denominator of the answer. You still use the dose desired divided by the dose on hand gives you the dose to give formula. It will end up being in the form of fractions (or ratios). These fractions are relationships that must be kept together--that's why i also say they are ratios. You must also know how to work with fractions to do these kinds of problems.

how many units per hour is the patient receiving?
25,000 units/250cc
(dose on hand)
x 8 cc/1 hour
(dose to give) =
800 units/hour
(dose desired)
and if the md increased the dosage to 1100 units/hr how many cc/hr will this be?
1100 units/1 hour
(dose desired) x
250cc/25,000 units
(dose on hand)
=
11cc/hour
(dose to give)
nurse2b allbetta said:
another one is: kvo with d5w what hourly volume will you give? and what is the drop rate/min?

don't you still need some info besides just kvo? what type of iv set would you use for kvo?

Yes. You need to know what the kvo rate is. Facilities have policies that tell the nurses exactly what the kvo rate is supposed to be unless the doctor specifically states it. In most facilities that i worked the kvo rate was 50cc/hour. Iv pumps default to 1cc/hour as their kvo rate. If this problem is coming from a textbook or workbook, re-read your text to see what it has to say about kvo rates.

Also a drop rate will depend on the type of iv tubing being used. There are iv administration tubings that deliver drops at 10, 12, 15, 20 and 60 drops per ml so, depending on which of these tubings is used, the drip rate will be different. The problem should tell you which tubing type is being used. Standard tubing is 15 drops per ml. Pediatric or microdrip tubing is 60 drops per ml.

For example, a 50cc/hour kvo drip rate for a standard 15 drop administration set. . .
50 ml/1 hour
(kvo dose to give)
x 15 gtts/1 ml
(drop rate)
x 1 hour/60 minute
(conversion factor)
= 12.5 gtts/minute
, rounded off to
13 gtts/minute
drip rate
1
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Thank you Daytonite. :)

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Hello everyone... I am having a problem figuring out IV flow rate question, It states:

Your patient has an order to receive 800 units of Heparin per hour by continuous intravenous infusion. If the pharmacy mixes the IV bag to contain a total of 5,000 units of Heparin in 500mL of D5W, how many cc's per minute should the patient receive?, am I using the correct formula? Rate/ml available X dose available...

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