Transcript Chapter 9 - Wolters Kluwer Health

Chapter 9:
Special Types
of Intravenous Calculations
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Intravenous Calculations
• These are very potent medications.
• Small changes infusion rate can greatly affect body’s
physiologic response.
• Pharmacy usually prepares medications and IV solutions.
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Dosage Calculations
• D = Desired dose or order
• H = On hand or have
• S = Supply
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Three Methods of Dosage Calculation
• Proportion expressed as two fractions
• Proportion expressed as two ratios
• Formula method
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Proportion Expressed as Two Fractions
• SUPPLY = X
HAVE
DESIRE
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Proportion Expressed As Two Ratios
• SUPPLY : HAVE :: X : DESIRE
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Formula Method
• DESIRE x SUPPLY = X
HAVE
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Infusion Rates Formulas
• Amount of Drug
=
Amount of Fluid (mL)
Amount of Drug in 1 mL
• Total number of units/hour x X mL= mL/hour
Number of units to run
• Total number of mg/hour x X mL= mL/hour
Number of mg to run
• Total number of milliters ordered = hours
Total number of milliters/hour
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Question
The physician has ordered regular insulin 21 units/hour
IV. The medication is available 250 units in 250 mL
normal saline. The insulin IV is being run on an infusion
pump. What is the rate per hour?
A. 19
B. 20
C. 21
D. 22
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Answer
C. 21
Total number of 21 units/hour x 250 mL= 21 mL/hour
Number of 250 units to run
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Infusion Formula for Drugs
Ordered in mcg/min
• Reduce the numbers in the standard solution to mg/mL.
• Change mg to mcg.
• Divide by 60 to get mcg/min.
• Use either the formula, ratio, or proportion method to
solve for mL/hr.
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Infusion Formula for Drugs
Ordered in mcg/kg/min
• Reduce the numbers in the standard solution to mg/mL.
• Change mg to mcg.
• Divide by 60 to get mcg/kg/min.
• Use either the formula, ratio, or proportion method to
solve for mL/hr.
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Question
The physician has ordered Intropin (dopamine) 200
mcg/min IV. The medication is available 400 mg in 250
mL D5W. What is the rate in mL/hr?
A. 7 mL/hr
B. 7.5 mL/hr
C. 8 mL/hr
D. 8.5 mL/hr
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
B. 7.5 mL/hr
• Reduce the numbers in the standard solution to mg/mL:
400 mg/250 mL = 1.6 mg/mL.
• Change mg to mcg: 1.6 mg x 1000 = 1600 mcg/mL.
• Divide by 60 to get mcg/min: 1600 mcg/60 min = 26.67
mcg/min.
• Use either the formula, ration, or proportion method to
solve for mL/hr:
200 mcg/min x 1 mL/hr= 7.5 mL/hr
26.67 mcg/min
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Body Surface Area
• Antineoplastic drugs based on body surface area in
square meters
• Mathematical formulas
– Square root of weight (kg) X height (cm) = BSA
3600
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Body Surface Nomogram
• Mark the client’s height in first column.
• Mark the client’s weight in the third column.
• Draw a line between these two marks.
• Point at which the line intersects in the middle column
indicates estimated body surface in meters squared.
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Body Surface Nomogram
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Patient Controlled Analgesia
• Basal rate: amount of medication infused continuously
every hour
• PCA dose: amount of medication infused when the client
activates the button control
• Lockout time or delay: interval during which patient
cannot initiate another dose after giving a self dose;
prevents overdosage
• Total hourly dose: maximum amount of medication the
client can receive an hour
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Heparin and Insulin Protocols
• Protocols are based on a parameter, usually a lab test
ordered by healthcare provider
• After receiving the lab test results, the nurse uses the
protocol to determine the change in the dosage amount.
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