Please help me with dosage calculations

[Bigbear71]

I am pretty much trying to teach myself how to do these calculations. I'm beginning my last semester in an ASN program and we have barely touched dosage calculations. They say we will hit it hard this upcoming semester..Critical care rotations..Anyway, I just received these problems in the mail from the school with a note to have them completed by the first class. I have Dosage Calculations Made Easy and many other pocket guides with formulas included. I'm still confused and don't know where to begin with these problems. If anyone could please explain them to me I will really appreciate the help!!!

1. The Dr. ordered Cordarone IV 900 mg to be added to 500 ml of D5W and run IV at a rate of 1mg/min for 6 hours. The manufacturer's directions agree with the Dr. order. The available 3 ml vials of Cordarone contain 50 mg per 1 ml. The infusion set delivers 60 drops per ml.

A. How many ml of Cordarone IV should the nurse add to the 500 ml D5W?

B. How many mg of drug are pesent in 1 ml of the Cordarone IV 900 mg in 500 ml of D5W solution?

C. How many ml per minute must infuse to deliver the prescribed amount of drug?

D.How mant ml per hour should the electronic infusion device be set to deliver?

2. The Dr. has ordered Intropin 200 mg to be added to 250 ml of D5W and run IV at a rate of 5 mcg/kg/min until the pt. systolic blood pressure is greater than 110 mmHg. The manufacturer directions agree with the Dr order. The available 5 ml vials of Intropin contain 200 mg. The IV set delivers 60 drops per 1 ml.

A. How many ml of Intropin should the nurse add to the 250 ml D5W?

B. Based on weight, how many mcg/min of Intropin should the pt. receive?

C. How many mg of drug are present in 1 ml of the Intropin 200 mg in 250 ml D5W?

D. How many ml per min must infuse to deliver prescribed amount?

E. How many ml per hour should the IV device be set to deliver?

Thank you

[crb613, BSN, RN]

Google Mary Bennett Indiana University for her nursing math website......can't recall it right now but it will teach you what you need to know. Good Luck

[Bigbear71]

Thank You

[iHeartNICU]

I have a question about #1B. It's asking how many mg of drug are in 1mL of the fluid. My question is, do you just use the 500 mL for your volume or do you add the amount (18mL) of drug to the 500 for a final volume of 518 mL? Thank you!

[moongirl]

I have a question about #1B. It's asking how many mg of drug are in 1mL of the fluid. My question is, do you just use the 500 mL for your volume or do you add the amount (18mL) of drug to the 500 for a final volume of 518 mL? Thank you!

the bag will total 500 ml.

there will be 1.8mg per ml

900/500

[iHeartNICU]

awesome, thank you!

[al7139, ASN, RN]

Get Dosage Calculations by Pickar (through your school or at Barnes and Noble). Worth every penny!

Amy

[Daytonite, BSN, RN]

the dr. ordered cordarone iv 900 mg to be added to 500 ml of d5w and run iv at a rate of 1mg/min for 6 hours. the manufacturer's directions agree with the dr. order. the available 3 ml vials of cordarone contain 50 mg per 1 ml. the infusion set delivers 60 drops per ml.

a. how many ml of cordarone iv should the nurse add to the 500 ml d5w?

b. how many mg of drug are pesent in 1 ml of the cordarone iv 900 mg in 500 ml of d5w solution?

c. how many ml per minute must infuse to deliver the prescribed amount of drug?

d.how mant ml per hour should the electronic infusion device be set to deliver?

a.

900 mg

(dose desired)

/1 x 1 ml/50 mg

(dose on hand)

=

18 ml of cordarone needs to be added to the 500 ml of d5w

b.

this is a situation of taking a ratio and simplifying it, like this:

900 mg/500 ml = x

mg/1 ml,

so that

900 mg/500 ml =

1.8 mg/1 ml

.

there are 1.8 mg of cordarone in each ml of this solution of d5w.

c.

you want to end up with ml/min, so you set up a "dose desired divided by dose on hand" equation in the form of fractions (ratios) manipulated so that you will end up with

ml's

in the numerator of the final answer and

minutes

in the denominator of the final answer, like this:

1 mg/1 minute

(dose desired)

x 500 ml/900 mg

(dose on hand)

=

0.555 ml/1 minute

to compute the drip rate using the 60 gtt/1 ml tubing you take

0.555 ml/1 minute

(dose to give)

x 60 gtts/1 ml

(drip factor)

= 33.3,

but you need toround this off because you can't get a 33.3 drop of anything unless you are god. so the answer is

33 gtts/1 minute

d.

all infusion pumps must be set at ml/hour. you already know the ml/minute, so you only need to apply a minute-to-hour conversion factor, like this:

0.555 ml/1 minute x 60 minutes/1 hour

(conversion factor)

=

33.3 ml/1 hour

.

again, you must round off to a whole number since the pump does not deal with decimals, so your final answer would be

33 ml/1 hour

.

the dr. has ordered intropin 200 mg to be added to 250 ml of d5w and run iv at a rate of 5 mcg/kg/min until the pt. systolic blood pressure is greater than 110 mmhg. the manufacturer directions agree with the dr order. the available 5 ml vials of intropin contain 200 mg. the iv set delivers 60 drops per 1 ml.

a. how many ml of intropin should the nurse add to the 250 ml d5w?

b. based on weight, how many mcg/min of intropin should the pt. receive?

c. how many mg of drug are present in 1 ml of the intropin 200 mg in 250 ml d5w?

d. how many ml per min must infuse to deliver prescribed amount?

e. how many ml per hour should the iv device be set to deliver?

be very careful with the labels attached to the numbers on these kinds of problems. mcg (micrograms) is very different from mg (milligrams). overlooking this will get you a wrong answer on a test and a dead patient in the bed.

a.

200 mg

(dose desired)

/200 mg

(dose on hand)

= 1 dose.

since each dose come in a 5 ml vial, you will add

one vial, or 5 ml

to the 250 ml of d5w.

b.

not clear what this question seeks. since no weight is given for the patient in question, then the obvious answer to this is that the patient should receive 5 mcg/minute for each kg of weight. this is information that is given in the problem.

c.

again, this is a matter of taking a ratio and simplifying it, like this:

200 mg/250 ml = x mg/1 ml

, so that

200 mg/250 ml =

0.8 mg/1 ml

.

there are 0.8 mg of intropin in each ml of d5w. there are 1000 mcg in a mg, so this is also equal to

800 mcg/1 ml

.

d.

since no patient weight is given, it seems to me that this question if asking for the

ml/min for 1 kg of body weight

. you were already told the 5 mcg (micrograms) per one minute in the problem, so it is a matter of converting the mcg to a ratio of the equivalent amount contained in a ml/min. you know from "c" above that there are 0.8 mg in a ml of this solution. using these two pieces of information, you set up a dimensional analysis equation to get the answer, like this:

5 mcg/1 minute

(dose desired)

x 1 mg/1000 mcg

(conversion factor)

x 1 ml/0.8 mg

(dose on hand)

=

0.00625 ml/1 minute

e.

all infusion pumps must be set at ml/hour. you already know the ml/minute, so you only need to apply a minute-to-hour conversion factor, like this:

0.00625 ml/1 minute x 60 minutes/1 hour

(conversion factor)

=

0.375 ml/1 hour. however, since the pump can only be programmed in whole numbers, you must round this number off. 0.375 must be rounded to

1 ml/1 hour

.

now, i have to confess that i am not accustomed to working with intropin and while i usually trust my math and dimensional analysis skills, i am not so sure i have correctly computed "d" and "e" here. so, if anyone else sees a flaw in my calculations, please correct me! you can check your conversions on

http://www.convert-me.com/en/convert/weight

there are also a number of these kind of mcg/kg/min drug problems that i have worked out by dimensional analysis in the posts of the dosage calculations thread on this forum which you should go back through and review (

https://allnurses.com/forums/f205/dosage-calculations-88867.html

)

good luck and happy calculating!