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Flow Rates

After completing this chapter, youshould be able to:

• Define flow rates.

• Illustrate the dimensionalanalysis for flow rates.

• Calculate flow rates todetermine drops/minute.

• Calculate flow rates inmilliliters/hour.

INTRODUCTIONFlow rates are calculated to determine at what rate, usuallystated in drops per minute, a medication will flow through IVtubing to the patient. Dimensional analysis is commonly usedto perform these calculations. Dimensional analysis useslogical sequencing and placement of units so that they can becanceled out to leave the desired terms for the final answer.

CHAPTER

8

68

L earning Objectives

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Chapter Eight Flow Rates 69

Basic Dimensional AnalysisIt is common for individuals to become overwhelmed and confused whenapproaching complex pharmacy calculations. The truth is, however, thatwhile many pharmacy calculations can appear to be complex, they are, inactuality, very simple.

Sterile product calculations and flow rates are typically viewed as amongthe most difficult, but each problem can be solved either by using basicdimensional analysis or ratios/proportions. We have covered ratios/propor-tions extensively in earlier chapters of this book, so now we will cover thebasics of dimensional analysis.

Before moving forward, however, let’s review several fundamental mathprinciples.

1. Any number multiplied by 1 retains the same value.

2. Any whole number can be expressed as a fraction by placing a 1 as thedenominator.

3. Any number divided by itself equals 1.

The first set of examples and practice problems in this chapter will notappear to have anything at all to do with sterile product calculations, but bepatient and realize that these early examples are laying a foundation for youto easily comprehend more “advanced” flow rate calculations.

EXAMPLE 8.1 How many hours are there in 6 days?In this problem we are working with days and hours. What

information, or facts, do we know about days and hours?

• There are 24 hours in 1 day.

This could be written as:

• 24 hours � 1 day

•

•

Using the principle of dimensional analysis, we can use thisinformation to solve the problem.

6 days =

6 days

1*

24 hours

1 day= ?

24 hours

1 day

1 day

24 hours

ex. 2>2 = 1

ex. 4 , 4 = 1

ex. 18 = 18>1

ex. 3 = 3>1

ex. 12 * 1 =12

ex. 4 * 1 = 4

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After setting the problem up, we can cancel out like units and/ornumbers.

which can now be written as:

Therefore, 6 days is equivalent to 144 hours.

EXAMPLE 8.2 How many minutes are there in 5 hours?In this problem we are working with minutes and hours. What

information, or facts, do we know about minutes and hours?

• There are 60 minutes in 1 hour.

This could be written as:

• 1 hour � 60 minutes

•

•

Using the principle of dimensional analysis, we can use this infor-mation to solve the problem.



Therefore, 5 hours is equivalent to 300 minutes.

EXAMPLE 8.3 45 minutes is equal to how many seconds?We know that there are 60 seconds in every 1 minute, this could

be written as:

•

•

•60 seconds

1 minute

1 minute

60 seconds

1 minute = 60 seconds

5 hours = 5 * 60 = 300

5 hours = 5 * 60 = ?

5 hours =

5 hours

1*

60 minutes

1 hour= ?

5 hours =

5 hours

1*

60 minutes

1 hour= ?

60 minutes

1 hour

1 hour

60 minutes

6 days = 6 * 24 = 144

6 days = 6 * 24 = ?

6 days =

6 days

1*

24 hours

1 day= ?

70 Chapter Eight Flow Rates

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Therefore, 45 minutes is equivalent to 2700 seconds.

EXAMPLE 8.4 How many seconds are there in 3 hours?We know that there are 60 seconds in every 1 minute and that

there are 60 minutes in every hour.Using the principle of dimensional analysis, we can use this

information to solve the problem, but to solve this problem we willnow have to add a third component.



Therefore, there are 10,800 seconds in 3 hours.

EXAMPLE 8.5 How many seconds are there in 4 days?We know that there are 60 seconds in every 1 minute,

60 minutes in every hour, and 24 hours in every 1 day.Using the principle of dimensional analysis, we can use this

information to solve the problem, but once again we will needto add another component compared to previous examples.

4 days =

4 days

1*

24 hours

1 day*

60 minutes

1 hour*

60 seconds

1 minute= ?

3 hours = 3 * 60 * 60 = 10,800

3 hours = 3 * 60 * 60 = ?

3 hours =

3 hours

1*

60 minutes

1 hour*

60 seconds

1 minute= ?

3 hours =

3 hours

1*

60 minutes

1 hour*

60 seconds

1 minute= ?

45 minutes = 45 * 60 = 2700

45 minutes = 45 * 60 = ?

45 minutes =

45 minutes

1*

60 seconds

1 minute= ?

45 minutes =

45 minutes

1*

60 seconds

1 minute= ?


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Now we know . . . there are 345,600 seconds in 4 days.

PRACTICE PROBLEMS 8.1

1. How many hours are there in 8 days? ________________

2. How many minutes are there in 14 hours? ________________

3. How many minutes are there in a day? ________________

4. Ten minutes is equivalent to how many seconds? ________________

5. How many seconds are there in 50 minutes? ________________

6. 1.5 days is equal to________________ hours.

7. There are ________________ minutes in 2.1 hours.

8. How many seconds are there in 8 hours? ________________

9. One hour is equal to ________________ seconds.

10. How many seconds make up a full day? ________________

Flow Rate DurationEXAMPLE 8.6 A 1-L IV bag is being administered at a rate of 200 mL per hour.

How long will this IV bag last?Do not get overwhelmed or confused now that the problems are

talking about IV bags instead of days, hours, and seconds. Just asbefore, we can use dimensional analysis to solve this problem. Inessence, the problem being asked is 1 L is equal to how many hours?

Again, we should start by looking at the information, or facts,that we know.

We know that there are 1000 mL in every 1 L, which could bewritten as:

•

•

•1000 mL

1 L

1 L

1000 mL

1 L = 1000 mL

4 days = 4 * 24 * 60 * 60 = 345,600

4 days = 4 * 24 * 60 * 60 = ?

*

60 seconds

1 minute= ?

4 days =

4 days

1*

24 hours

1 day*

60 minutes

1 hour


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We also know, according to the problem, that 200 mL are beingadministered per hour, which can be written as:

•

•

•




Therefore, the 1-L bag will last 5 hours

EXAMPLE 8.7 A 2-L IV is to be administered at 250 mL hr. How long will the IV last?Let’s start by looking at the information, or facts, that we know.We know that there are 1000 mL in every 1 L, which could be

written as:

•

•

• `

We also know, according to the problem, that 250 mL are being administered per hour, which can be written as:

•

•

•


2 L =

2 L

1*

1000 mL

1 L*

1 hr

250 mL= ?

250 mL

1 hr

1 hr

250 mL

1 hr = 250 mL

1000 mL

1 L

1 L

1000 mL

1 L = 1000 mL

>

1 L =

1000

200= 5 hr

1 L =

1 * 1000 * 1 hr

200= ?

1 L =

1 L

1*

1000 mL

1 L*

1 hr

200 mL= ?

1 L =

1 L

1*

1000 mL

1 L*

1 hr

200 mL= ?

200 mL

1 hr

1 hr

200 mL

1 hr = 200 mL


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Therefore, the 2-L bag will last 8 hours.

EXAMPLE 8.8 A patient is set to start a 500-mL infusion of cimetidine in lactatedringers 5% at 10:00 a.m. The bag is to be administered at a rate of125 mL per hour. At what time will the infusion be complete?

This example provides us with additional informationconcerning the drug name, solution strength, and administrationstart time. As always, let’s start by looking at the information thatwe know and that we will need to calculate the problem.

We know that:

• the bag contains a total of 500 mL

• 125 mL are being administered per hour

• the infusion is scheduled to start at 10:00 a.m.

Using the principle of dimensional analysis, we can use this infor-mation to determine how long the infusion will last.



Therefore, the 500 mL bag will last 4 hours.

The question being asked, however, is what time will the infu-sion be completed?

To answer this question simply take the start time (10:00 a.m.)and add the length of duration (4 hours).

10:00 a.m. + 4 hr = 14:00 hr, or 2:00 p.m.

500 mL =

500

250* 1 hr = 4

500 mL =

500

250* 1 hr = ?

500 mL =

500 mL

1*

1 hr

250 mL= ?

500 mL =

500 mL

1*

1 hr

250 mL= ?

2 L =

2000

250= 8 hrs

2 L =

2 * 1000 * 1 hr

250= ?

2 L =

2 L

1*

1000 mL

1 L*

1 hr

250 mL= ?


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EXAMPLE 8.9 Three 1 L IV bags are to be infused at a rate of 150 mL/hour. Howlong will these three bags last?

Let’s start by looking at the information, or facts, that we know.We know that:

• 1 IV bag contains 1 L

• there are 1000 mL in every 1 L





Therefore, the 3 bags will last 20 hours.

EXAMPLE 8.10 Two 2-L IV bags containing heparin sodium and NS are set to beadministered at a rate of 250 mL per hour at 7:00 a.m. When willboth bags be completely administered?








2 bags =

2 * 2 * 1000 * 1 hr

250= ?

2 bags =

2 bags

1*

2 L

1 bag*

1000 mL

1 L*

1 hr

250 mL= ?

2 bags =

2 bags

1*

2 L

1 bag*

1000 mL

1 L*

1 hr

250 mL= ?

3 bags = 3 * 1 * 1000 * 1 hr = 20

3 bags =

3 * 1 * 1000 * 1 hr

150= ?

3 bags =

3 bags

1*

1 L

1 bag*

1000 mL

1 L*

1 hr

150 mL= ?

3 bags =

3 bags

1*

1 L

1 bag*

1000 mL

1 L*

1 hr

150 mL= ?


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Therefore, the 3 bags will last 16 hours.

The question being asked, however, is what time will the infusion becompleted?

To answer this question simply take the start time (7:00 a.m.)and add the length of duration (16 hours).

PRACTICE PROBLEMS 8.21. A 250-mL bag is to be administered at 100 mL per hour. How long will

the IV bag last? ________________

2. A 1-L IV is running at 250 mL hr. How long will the infusion last?________________

3. 500 mL of NS is being infused at 150 mL per hour. What will be theduration of the infusion? ________________

4. 500-mg cefazolin in 100 mL D5W is being administered at 200 mL hr.How long will the IV last? ________________

5. A 500-mL bag with Diamox® is being infused at 250 mL per hour. Whatwill be the duration of the bag? ________________

6. 1 L is being infused at a rate of 200 mL hr. If the infusion began at8:15 a.m., when will it be finished? ________________

7. Two 1-L bags are being infused at 250 mL hr. How long will both bagslast? ________________

8. 750 mL of NS is set to be administered at 150 mL per hour, startingat 11:00 a.m. At what time will the infusion be finished?________________

9. Two 1-L IV bags with ascorbic acid are being administered at 200 mL hr.What will be the duration of both bags? ________________

10. A 250-mL bag with ranitidine is being administered at themaximum rate of 10.7 mL per hour. How long will the bag last?________________

Volume Per HourEXAMPLE 8.11 A patient is to receive 750 mL infused over 3 hours. What is the

rate of infusion in mL per hour?Unlike the previous IV flow rate problems, solving volume per

hour is easily done by setting up a ratio and proportion . . . thensolving for the unknown, as illustrated below.

Total mL

Total hr=

x

1 hr

>

>

>

>

>

7:00 a.m. + 16 hr = 23:00 hr, or 11:00 p.m.

2 bags = 2 * 2 * 1000 * 1 hr = 16


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Using the information provided in the problem, set up a ratio andproportion.

Now, we must cross-multiply.

Using basic algebra principles, isolate the unknown (x) to solve.In this example, both sides of the equation need to be divided by 3to isolate x.

So, .

This infusion will be administered at 250 mL per hour.

EXAMPLE 8.12 A 250-mL IV, containing 1 mg of Isuprel®, is to be given over 100 minutes. What is the rate of infusion in mL per hour?

Using the information provided in the problem, set up a ratioand proportion. Since the administration time is given in minutes,we can substitute the 1 hour beneath the unknown (X) with60 minutes.

Next, cross-multiply.

Now, solve for x.

So,

This infusion will be administered at 150 mL per hour (60 minutes).

EXAMPLE 8.13 500 mL of D5W containing 1 g of lidocaine hydrochloride is tobe given over 250 minutes. What is the infusion rate in mLper hour?

First, set up your ratio and proportion.

500 mL

250 min=

x

60 min

x = 150

100x

100=

15,000

100

100x = 15,000

100 * x = 250 * 60

250 mL

100 min=

x

60 min

x = 250

3x

3=

750

3

3x = 750

3 * x = 750 * 1

750 mL

3 hr=

x

1 hr


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Now, solve for x.

So, This infusion will be administered at 120 mL per hour

(60 minutes).

EXAMPLE 8.14 A 250-mL IV is to be administered over 50 minutes. What is theinfusion rate in mL hr?



Now, solve for x.

So, This infusion will be administered at 300 mL per hour (60 minutes).

Notice that the actual IV is being administered in less than anhour, so the rate per hour should logically contain more volumethan the actual IV.

EXAMPLE 8.15 1000-mL NS containing 50 mg nitroprusside sodium is to beadministered over 50 minutes. What is the infusion rate in mL hr?



Now, solve for x.

So, This infusion will be administered at 1200 mL or 1.2 L per hour(60 minutes).

x = 1200

50x

50=

60,000

50

50x = 60,000

50 * x = 1000 * 60

1000 mL

50 min=

x

60 min

>

x = 300

50x

50=

15,000

50

50x = 15,000

50 * x = 250 * 60

250 mL

50 min=

x

60 min

>

x = 120

250x

250=

30,000

250

250x = 30,000

250 * x = 500 * 60


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PRACTICE PROBLEMS 8.3

1. 1 L is being infused over 6 hours. What is the rate of infusion in mL perhour? ________________

2. 500 mL is being administered over 4 hours. What is the administrationrate per hour? ________________

3. 2 L is to be given via IV over 8 hours. What is the rate of infusion perhour? ________________

4. 480 mL of D5W containing dobutamine is being given over 8 hours.What is the administration rate per hour? ________________

5. 1 g of Gemzar® in 25 mL NS is to be administered over 30 minutes.What is the rate of infusion in mL per hour? ________________

6. 100 mL is being infused over 30 minutes. What is the rate of infusion inmL per hour? ________________

7. 250 mL is being given over 100 minutes. What is the administrationrate per hour? ________________

8. 500 mL NS is being administered over 6 hours. What is the rate in mL per hour? ________________

9. 50 mL SWFI containing folic acid is to be infused over 30 minutes.What is the infusion rate per hour? ________________

10. 100 mL Iveegam® is infused over 100 minutes. What is the rate ofinfusion per hour? ________________

Drug Per HourEXAMPLE 8.16 100 mg of medication is to be administered in 500 mL of LR over

2 hours. How much drug will be administered per hour?Similar to solving volume per hour, calculating the amount of

medication administered per hour is easily done by setting up aratio and proportion . . . then solving for the unknown, asillustrated below.

Using the information provided in the problem, set up a ratio andproportion.

Now, we must cross-multiply.

2x = 100

2 * x = 100 * 1

100 mg

2 hr=

x

1 hr

Total mg

Total hrs=

x

1 hr


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Using basic algebra principles, isolate the unknown (x) to solve. Inthis example, both sides of the equation need to be divided by 2 toisolate x.

So, This infusion will provide 50 mg per hour.

EXAMPLE 8.17 600 mg of fluorouracil is to be administered by continuousinfusion over 24 hours. How much drug will be administeredper hour?

Using the information provided in the problem, set up a ratioand proportion.

Now cross-multiply.

Using basic algebra principles, isolate the unknown (X) to solve. Inthis example, both sides of the equation need to be divided by 24 toisolate X.


EXAMPLE 8.18 200 mg of Vibramycin IV® is diluted in 400 mL LR to beadministered over 4 hours. How much drug will be administeredper hour?

First, set up a ratio and proportion.


Now, solve for x.


x = 50

4x

4=

200

4

4x = 200

4 * x = 200 * 1

200 mg

4 hr=

x

1 hr

x = 25

24X

24=

600

24

24x = 600 24 * x = 600 * 1

600 mg

24 hr=

x

1 hr

x = 50

2x

2=

100

2


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EXAMPLE 8.19 125 mg of Cardizem® is being infused in 125 mL over 12.5 hours.How much drug will be administered per hour?



Now, solve for x.


EXAMPLE 8.20 5 million units of Penicillin G Aqueous® is being delivered in 1 L ofD5W over 12 hours. How much drug will be administered perhour?



Now, solve for x.

So, Therefore, this infusion will provide 416,667 units per hour.

PRACTICE PROBLEMS 8.41. 250 mg of medication in 1 L is administered over 5 hours. How much

drug will be administered per hour? ________________

2. 800 mg of medication in 2 L is to be infused over 4 hours. How muchdrug will be administered per hour? ________________

3. 500 mg of medication in 500 mL is to be given over 4 hours. How muchdrug will be administered per hour? ________________

4. 250 mL of Plasmanate®, which contains 25 g of plasma protein, is to beadministered over 250 minutes. How much drug will be administeredper hour? ________________

x = 416,666.67

12x

12=

5,000,000

12

12x = 5,000,000

12 * x = 5,000,000 * 1

5,000,000 units

12 hr=

x

1 hr

x = 10

12.5x

12.5=

125

12.5

12.5x = 12512.5 * x = 125 * 1

125 mg

12.5 hr=

x

1 hr


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5. 500 mg of nafcillin sodium in 150 mL is to be infused over 30 minutes.How much drug will be administered per hour? ________________

6. A 100-mL bag contains 75 mg of medication to be given over30 minutes. How much drug will be administered per hour?________________

7. 25 mcg of medication in 250 mL is to be infused over 2 hours. Howmuch drug will be administered per hour? ________________

8. 250,000 units of medication in 1 L is administered over 8 hours. Howmuch drug will be administered per hour? ________________

9. 100 mg of tenposide in 500 mL is given over 45 minutes. How muchdrug will be administered per hour? ________________

10. 75 mg of Demadex® in D5W is to be administered over 24 hours. Howmuch drug will be administered per hour? ________________

Drop FactorsWhen preparing sterile products, pharmacy personnel are often responsiblefor calculating the rate of IV administration, expressed as drops per minute(gtts/min). Literally, this drip rate will determine how to calibrate the IVpump and the volume of medication to be administered minute by minute.

Various IV administration sets release specific drops per milliliter. Microdripsets are calibrated to deliver 60 drops per mL, whereas macrodrip sets mightbe calibrated to deliver 10, 15, or 20 drops per mL. The larger the number


microdrops

60 gtt/mL

20 gtt/mL

15 gtt/mL

10 gtt/mLmacrodrops

FIGURE 8.1 IV Drop Sets.

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of drops per milliliter, the smaller the drops will be—since clearly one milli-liter is one milliliter.

In pharmacy, you will work with four common IV drip rates–10 gtts/mL,15 gtts/mL, 20 gtts/mL and 60 gtts/mL. Drip rates can be expressed by theirdrop factor, which is just a simpler way of listing a drip rate.


Drop Factor Drip Rate

60 60 gtts/mL20 20 gtts/mL15 15 gtts/mL10 10 gtts/mL

The most commonly used drip rate is the microdrip—60 gtts/mL. Therefore,if a problem does not indicate a specific drip rate or drop factor, you should always assume 60 gtts/mL.

Drip RatesEXAMPLE 8.21 A 1-L bag of D5W is to be administered at a drop factor of 60 over

6 hours. What is the flow rate in gtts/min?Let’s start by looking at the information, or facts, that we know.We know that:



• the drop factor is 60, so there are 60 gtts/mL

• the duration of administration is 6 hours

• there are 60 minutes in 1 hour




So, the infusion rate is 167 gtts/min.

1 bag =

1000 * 1 gtts

6 min= 166.66

1 bag =

1000 * 1 gtts

6 min= ?

1 bag =

1000 mL

6 hr*

60 gtts

1 mL*

1 hr

60 min= ?

1 bag =

1000 mL

6 hr*

60 gtts

1 mL*

1 hr

60 min= ?

Table 8.1

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EXAMPLE 8.22 500 mL is to be administered to a patient over 5 hours, using a 15-drop factor. What is the flow rate in gtts/min?

Let’s start by looking at the information, or facts, thatwe know.

We know that:

• 1 IV bag contains 500 mL








EXAMPLE 8.23 Rx—Vancomycin® 250 mg/250 mLDisp. 500 mg over 3 hours q 8 hr.What is the flow rate in gtts/min?

Let’s start by looking at the information, or facts, thatwe know.

We know that:


• the drop factor is not stated, so we must assume 60 gtts/mL



Notice that the additional information provided is not necessary insolving this problem.


1 bag =

500 mL

3 hr*

60 gtts

1 mL*

1 hr

60 min= ?

1 bag =

7500 gtts

300 min= 25

1 bag =

500 * 15 gtts

300 min= ?

1 bag =

500 mL

5 hr*

15 gtts

1 mL*

1 hr

60 min= ?

1 bag =

500 mL

5 hr*

15 gtts

1 mL*

1 hr

60 min= ?


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So, the infusion rate is 167 gtts/min

EXAMPLE 8.24 A 100 mL bag containing 1 g of Zanosar® is to be infused, with adrop factor of 15, over 1 hour. What is the flow rate in gtts/min?

We know that:



• the duration of administration is 1 hour






EXAMPLE 8.25 Rx—2 g Mandol® in 1 L of D10W over 4 hours TIDWhat is the flow rate in gtts/min?


• 1 IV bag contains 1000 mL (1 L)

• the drop factor is not stated, so we must assume 60 gtts/mL

1 bag =

1500 gtts

60 min= 25

1 bag =

100 * 15 gtts

60 min= ?

1 bag =

100 mL

1 hr*

15 gtts

1 mL*

1 hr

60 min= ?

1 bag =

100 mL

1 hr*

15 gtts

1 mL*

1 hr

60 min= ?

1 bag =

500 gtts

3 min= 166.66

1 bag =

500 * 1 gtts

3 min= ?

1 bag =

500 mL

3 hr*

60 gtts

1 mL*

1 hr

60 min= ?


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Notice that the additional information provided is not necessary insolving this problem.


After setting the problem up, we can cancel out like unitsand/or numbers.



PRACTICE PROBLEMS 8.5Solve the following flow rate problems.

1. Rx Claforan (cefotaxime) 500 mg/50 mL IV 50 mg/kg/dose

The patient weighs 22 lb.

a. How many milligrams per dose should the patient receive?________________

b. How many minutes will it take to administer the IV if the administra-tion set is calibrated at 20 gtt/mL and the flow rate is set at 30 gtt/min?________________

2. Rx ampicillin 0.5 g/100 mL 50 mg/kg/day q8h over 90 min

The patient weighs 30 kg.

a. How many milligrams are needed for each dose? ________________

b. What is the flow rate in gtt/min? ________________

c. What is the flow rate in mL hr? ________________

3. Rx penicillin G potassium 20,000,000 U/1 L 25,000 U/kg/day up to20,000,000 U/day over 24 hours

The patient weighs 189 lb.

a. What is the patient’s weight in kilograms? ________________

b. How many units will be needed daily? ________________

c. What is the flow rate in mL hr? ________________

d. How many units will be administered per hour? ________________

>

>

1 bag =

1000 * 1 gtts

4 min= 250

1 bag =

1000 * 1 gtts

4 min= ?

1 bag =

1000 mL

4 hr*

60 gtts

1 mL*

1 hr

60 min= ?

1 bag =

1000 mL

4 hr*

60 gtts

1 mL*

1 hr

60 min= ?


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4. Rx dexamethasone sodium phosphate 0.25 mg/kg/dose q8h over 15 min

The patient weighs 14 lb. You have a stock vial containing 4 mg/mL in a10-mL vial. The IV bag holds 50 mL, and the IV administration setdelivers 30 gtt/mL.

a. What is the patient’s weight in kilograms? ________________

b. What is the dose in milligrams? ________________

c. How many milliliters will you need from the stock vial to provide thedose? ________________

d. What is the flow rate in gtt/min? ________________

5. Rx Ringer’s solution 500 mL

If the flow rate is set at 63 mL hr, how many hours will it take toadminister the solution? ________________

6. Rx D5W 60 mL hr

How many milliliters of D5W do you need for 24 hr? ________________

7. Rx electrolyte solution 500 mL

The IV administration set delivers 20 gtt/mL, and the flow rate is set at40 gtt/min. What is the infusion time in hours? ________________

8. Rx antibiotic 250 mL over 2 hr

The IV administration set delivers 15 gtt/mL.

a. What is the flow rate in gtt/min? ________________

b. What is the flow rate in mL hr? ________________

9. Rx Rocephin (ceftriaxone) 2 g/100 mL

The IV administration set delivers 30 gtt/mL, and the flow rate is set at60 gtt/min.

a. What is the infusion time in hours? ________________

b. How much drug will be delivered each minute in mg/min?________________

c. Determine mg/mL. ________________

10. Rx insulin 100 U/250 mL 100 U over 2.5 hr

The IV administration set delivers 30 gtt/mL.

a. What is the flow rate in gtt/min? ________________

b. How many units of insulin will be delivered per minute?________________

SUMMARYOften described as one of the most challenging calculations used in pharmacy,flow rates are simply a series of basic fundamental calculations. Using ratios and proportions, which you covered earlier in the book, you shouldnow be able to solve more complicated and in-depth calculations such asthose presented in this chapter.

>

>

>


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CHAPTER REVIEW QUESTIONS


CHAPTER

8

MULTIPLE CHOICE

1. You have a stock vial of cefataxime 500 mg /10 mL. The dose is 2 g over 30 min. How manymg/min will the patient receive?________________

a. 17 mg/min c. 47 mg/min

b. 27 mg/min d. 67 mg/min

2. You have a stock vial of cefataxime 500 mg /10 mL. The dose is 2 g over 30 min. What isthe flow rate in mL hr? ________________

a. 40 mL hr c. 80 mL hr

b. 60 mL hr d. 100 mL hr

3. You have a stock vial of cefataxime 500 mg/10 mL. The dose is 2 g over 30 min. What isthe flow rate in gtt/min if the IV administrationset is calibrated to deliver 20 gtt/mL?________________

a. 27 gtt/min c. 80 gtt/min

b. 67 gtt/min d. 87 gtt/min

4. What is the flow rate in gtt/min for a 1-L TPNover 12 hr if the IV administration set is cali-brated to deliver 30 gtt/mL? ________________



5. What is the flow rate in gtt/min for 50 mL of anantibiotic administered over 60 min?________________



6. You have an order for cefuroxime 1.5 g/50 mLwith a maximum dose of 1.5 g q8h. The patient

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weighs 200 lb. What is the flow rate in gtt/minif the dose is administered over 90 min?________________



7. You have a stock vial of product 30 mg/mL.How many milliliters will you need to preparean IV containing a dose of 150 mg/50 mL?________________

a. 5 mL c. 20 mL

b. 10 mL d. 30 mL

8. The recommended dose for a drug is 20 mg/kg/day qid. The patient weighs 220 lb.What is the dose for this patient?________________

a. 0.5 g c. 2.0 g

b. 1.0 g d. 4.0 g

9. You have a stock vial of product 25 mg/mL. Thedose is 250 mg. How many milliliters arerequired? ________________

a. 2.5 mL c. 10 mL

b. 5.0 mL d. 25 mL

10. What is the flow rate for a 250-mL IV to beadministered over 2 hr? ________________

a. 125 gtt/min c. 12.5 gtt/min


TRUE OR FALSE

11. Dimensional analysis is an efficient way to calculate flow rates. ________________

a. true b. false

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12. When setting up flow rate problems, alwaysassume that the IV administration set delivers60 gtt/min unless otherwise stated in the problem. ________________

a. true b. false

13. The formula to calculate a patient’s weight inkilograms is pounds/2.2 �kilograms. ________________

a. true b. false

14. The flow rate is usually stated as mg/min.________________

a. true b. false

15. Infusion time should be stated in hours.________________

a. true b. false

SHORT ANSWER

16. What is dimensional analysis?________________

17. Write out the formula for flow rates using dimensional analysis. ________________

18. Compare the doses needed for each of the following orders and indicate which one is thelarger dose for a 10-kg patient.________________

Order A � 50 mg/kg/dose

Order B � 150 mg/kg/day divided into threedoses

19. A standard IV administration set is calibrated todeliver how many gtt/mL? ________________

20. Describe the first segment of the flow rateformula. ________________


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