7.1 Interpreting LabelsLabel Info Meaning

25 mg/ml This ratio tells the amount of medication in each ml of solution

1:4 Ratios written this way always mean grams per milliliter

30% Amount of medication (in grams) in every 100 ml of solution

40 mg = 2 cc Equation tells the amount of medication in the given volume

U-100 Units per ml (100 units per ml in this case)

20 mEq/ml This ratio tells the number of milli-equivalents per milliliter of solution

7.2 Dosage Calculation for Prepared Solutions

• Four ways of calculating solution dosages:

1. Dosage formula2. DQA (Desired Quantity Available)

proportion3. DHQ (Desired Have Quantity) formula4. Label proportion

7.2 Dosage Calculation for Prepared Solutions

• Ordered: 15 mg IM q.a..m.Label info: 20 mg per mlPatient dosage __________

• Using dosage formula : Doctors orders label info = patient dosage

mlmlmg

mlmg

ml

mgmg 75.0

4

3

20

115

1

2015

7.2 Dosage Calculation for Prepared Solutions

• Using DQA (Desired Quantity Available) proportion :

handonquantity

givetoquantity

amountavailable

amountdesired

mlmlXml

mlX

mg

mg75.0

4

3

120

15

7.2 Dosage Calculation for Prepared Solutions

• DHQ (Desired Have Quantity) formula:

mlmlXmlXmlmg

mg75.0

4

31

20

15

unknownquantityhave

desiredXQ

H

D

7.2 Dosage Calculation for Prepared Solutions

• Label proportion:

volumeSolution

weightMedication

givetoAmount

OrdersDoctor

mlmlX

Xml

mg

mlX

mg

75.04

3

15201

2015

7.3 Dosage Calculations from Medications in Powdered Form

• Medications may be unstable when stored in solution. They are packed in powder or granular form.

• You will be told:a. Doctor’s orders (charted amount)b. Label information

• You will need to calculate:a. How much to give per doseb. How often to give itc. How to relabel the vial if it is multidose

7.3 Dosage Calculations from Medications in Powdered Form

• Ordered: 250 mg IM q.i.d.• Label info: 500 mg medication – inject 1.2 ml

SW to yield 2 ml solution. Must be used within one hour.How much do you give and how often?Using dosage formula

mlg

mlg

ml

gg 2

4

8

4

80.1

8

40.1

7.3 Dosage Calculations from Medications in Powdered Form

• Complete answer:Give 2 ml IM every 6 hours.Relabel the vial 1.0 g = 2 ml, with the date and time of preparation, and your initials.

7.4 Finding the Amount of Medication in a Solution

• To determine the amount of pure medication by weight, in a solution with a specified strength, use one of the dosage calculation formulas (section 7.2) with the medication weight as the unknown.

7.4 Finding the Amount of Medication in a Solution

• How many grams of potassium citrate (crystals) are contained in 50 ml of 7% potassium citrate solutionUsing dosage formula :

Using DQA Proportion

ggml

gml

g

mlml 5.3

2

7

100

750

7

10050

gXXml

ml

Xg

g5.3350100

50

1007

7.4 Finding the Amount of Medication in a Solution

• How many grams of potassium citrate (crystals) are contained in 50 ml of 7% potassium citrate solutionUsing DHQ formula :

Using Label Proportion

gggml

ml5.3

2

77

100

50

gXXml

g

ml

Xg5.3350100

100

7

50

7.5 Diluting Solutions

• Inverse Proportion method:

volume

volumesmallersmaller

or

maketoamount

usetoamount

strengthavailable

strengthdesired

larger%larger

%

7.5 Diluting Solutions

• Example: How many ml of a 20% solution are needed to prepare 50 ml of a 5% solution?

Answer: Take 12.5 ml of a 20% solution and add 37.5 ml of sterile water to make 50 ml of 5% solution

mlX

Xml

mlX

5.1220

250

250)50(52005%02

%5

7.5 Diluting Solutions

• Dilution equation

%%

volumefinalvolumegiven

solutionweaksolutionstrong

or

strengthdesiredvolumedosage

strengthlabelstrengthavailable

7.5 Diluting Solutions

• Example: How many ml of a 20% solution are needed to prepare 50 ml of a 5% solution?

Answer: Take 12.5 ml of a 20% solution and add 37.5 ml of sterile water to make 50 ml of 5% solution

mlX

XmlmlX

5.1220

250

250)50(52005%5%02

7.6 Calculating Pediatric Dosages by Body Weight

• To calculate children’s dosage using body weight

1. if the medication is per kg (or lb.), child’s weight is in kg or lb.) rounded to tenths

2. Multiply the label my the child’s weight

..

lblb

mgorkg

kg

mg

7.6 Calculating Pediatric Dosages by Body Weight

• Ordered: antibiotic q.4h. For a 5 kg infantLabel: antibiotic 60 mg/kg/dayHow many mg per day?How many mg per dose?

dosemgdaydoses

daymgkgkg

mg

/50/6300

/300560

7.7 Dosage Calculation using a Nomogram

• Another way to calculate patient dosage is by finding the patient’s body surface area (BSA) using a nomogram (pg 209)

To get BSA read both the height and weight on the left and right scales, then use a straightedge to connect the points and read the BSA from the middle scale

• Example: Height = 56” and weight = 46kg, find the patient’s BSA. (Try this now)

7.7 Dosage Calculation using a Nomogram

• Once you get the BSA, the proportion or factor-label method to get the dosage.

• In previous example, the BSA = 132 m2. If the label says what is the patient dosage?Using the proportion method:

mgXm

X

m

mg4.92

32.11

7022

270

m

mg

7.7 Dosage Calculation using a Nomogram

• Using the factor-label method:

mgmm

mg4.92)32.1(7032.1

1

70 22

8.1 Rate of Flow – Formula Method

• Formula Method

• Factor-Label Method (equivalent)

)()minutes(

)()(min.gtts.ml

gtts.

RateFlowTime

nCalibratiomlVolume

)(

min. 60

.1)()(

min.gtts.

mlgtts.

hr.ml

RateFlow

hrnCalibratioVolume

8.1 Rate of Flow – Formula Method

• Ordered: IV 5% D/W 100 ml/hr.Tubing calibration: 15 gtts./mlFind the rate of flow using both methods

min.gtts.ml

gtts.

2560

1500

minutes06

15100

ml

min.gtts.

mlgtts.

hr.ml 25

60

1500

min. 60

.115100

hr

8.2 Rate of Flow –Division Factor Method

• Division Factor Method

)()(

min.gtts.FlowofRate

FactorDivision

mlVolume

factordivisionfactordrop )(.min60 mlgtts.

8.2 Rate of Flow –Division Factor Method

• Example:Ordered: IV rate at 200 ml/hr.Drop factor: 15 gtts./mlWhat is the flow rate?

min.gtts.

mlgtts.

504

200

415.min60

ml

8.3 Total Time

• Adjusted formula method

• Adjusted factor-label method

)minutes()(

)()(

min.gtts.

mlgtts.

TimeRateFlow

nCalibratiomlVolume

)minutes(

)()()ml( gtts.min.

mlgtts.

Time

RateFlowInvertednCalibratioVolume

8.3 Total Time

• Example:Ordered: 1200 ml IVDrop factor: 15 gtts./mlRate of flow: 50 gtts./min.How long will the IV run?

minutes360

50

151200

.min/.50

/.151200

gtts

mlgttsml

8.4 Pediatric IV’s

• To calculate flow rate of an IV

1. Read label to get volume that contains the correct dosage

2. Find amount of IV fluid to be added

3. Add diluted volume and flush volume to get total infusion volume

4. Calculate rate of flow

rateflowtime

factordropvolumetotal

.)(min

infusion

8.4 Pediatric IV’s

• Medication of 50 mg is ordered diluted to 50 ml. Infuse over 30 minutes and follow with a 15 ml flush. The label reads 25 mg/ml. Calculate the amount of IV fluid needed to mix the medication and the flow rate for administration.

1. 2 ml contains 50 mg

2. 50 ml – 2 ml = 48 ml

3. 50 ml + 15 ml = 65 ml total infusion volume

4. Rate of flowmin

.g130

min30

/.6065 ttsmlgttsml

8.5 Piggyback IV Solutions

• IV solutions are frequently ordered to run piggyback with IV fluids (see picture at beginning of this section)

When the piggyback is running, the main IV bag is either clamped shut or hung down lower than the piggyback to allow the secondary fluid to infuse

8.5 Piggyback IV Solutions

• To calculate rate of flow for the piggyback and the IV between piggybacks:

1. Calculate the rate of flow for each piggyback

2. Calculate the number of piggybacks to be given.

3. Determine the total time and total fluid volume for all piggybacks.

8.5 Piggyback IV Solutions

• To calculate rate of flow for the piggyback and the IV between piggybacks (continued)

4. Determine the amount of time and volume of fluid remaining.

5. Calculate the rate of flow of the IV between piggybacks, using the amounts from step 4.

8.5 Piggyback IV Solutions• Ordered: 3000 ml IV fluids in 24 hours

Piggyback med. in 100 ml to run 30 min. q.12h.Drop factor for all tubing is 15 gtts. per ml

1. Rate of flow:

2. # piggybacks in 24 hours

3. Total time and volume for piggybacks:

mingtts.ml

gtts.

50min30

15100

ml

piggybacks21224

mlml 2001002

.min60.min302

8.5 Piggyback IV Solutions• Ordered: 3000 ml IV fluids in 24 hours

Piggyback med. in 100 ml to run 30 min. q.12h.Drop factor for all tubing is 15 gtts. per ml

4. Time in minutes and volume in ml remaining:

5. Rate of flow between piggybacksml

remaining

hr

28002003000

min1380601440

min14406024 hrmin

mingtts.ml

gtts.

43.30min1380

152800

ml

8.6 Drug Infusion Rate of Flow

• Many critical care medications are added to the IV solution and infused at the rate of a specified concentration of medication per unit of time. This is called drug infusion rate, and is expressed in ml/min. or ml/hr.

8.6 Drug Infusion Rate of Flow

• To calculate the drug infusion rate:

a. Determine the solution strength

b. Determine what has been ordered

c. Calculate the patient dosage, calculate the drug infusion rate in ml/min.

d. Calculate the drug infusion rate in ml/hr.

8.6 Drug Infusion Rate of Flow• Order: ISUPREL 2 mg IV in 500 ml 5% D/W to

run at 5 g/min. Calculate the infusion rate in ml/min. and ml/hr.

a. solution strength: 2mg/500ml

b. dosage ordered: 5 g/min

c. Calculate the patient dosage, calculate the drug infusion rate in ml/min.

d. Calculate the drug infusion rate in ml/hr.

minml25.1

2000

500

min1

5

500

2

min1

5

g

mlg

ml

mgg

hrml

hrmin

minml 756025.1

8.7 Monitoring Flow Rates

• No problems from this section.