Transcript Calculating Parenteral Dosages (con`t) - McGraw

PowerPoint® to accompany
Math and Dosage Calculations for
Medical Careers
Second Edition
Booth • Whaley
Chapter 9
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Chapter 9
Parenteral Dosages
Learning Objectives
When you have completed Chapter 9,
you will be able to:




Calculate the amount of a parenteral
medication to administer.
Select the appropriate syringe.
Correctly reconstitute powdered
medications.
Measure insulin doses correctly.
Chapter 9
3
Learning Objectives (con’t)


Accurately calculate doses of
inhalant, rectal, and transdermal
medications.
Identify errors that occur when
calculating and preparing
parenteral doses.
Chapter 9
4
Introduction
Parenteral medications are not taken by mouth.
They need to bypass the digestive tract.
 Injections
 Inhalants
 Rectal
 Transdermal
Chapter 9
5
Parenteral Medications
Types




Intramuscular (IM)
Subcutaneous (SC)
Intradermal (ID)
Intravenous (IV)
Chapter 9
6
Calculating Parenteral Dosages
 Injections are mixtures that contain

the drug dissolved in an appropriate
liquid.
Dosage or medication strength on
the label indicate the amount of drug
contained within a volume of
solution.

For example lidocaine 1% has 1 g
lidocaine in 100 mL
Chapter 9
7
Calculating Parenteral Dosages
(con’t)



Dosage strength may be in
milligrams per milliliter as a
percent or as a ratio.
Physician will order specific
amount of the medication to be
given.
You must calculate how many
milliliters of solution contain the
desired dose.
Chapter 9
8
Calculating Parenteral Dosages
(con’t)


You will calculate the amount to
administer starting with the
dosage ordered, dose on hand,
and dosage unit.
You may have to convert the
units of the dosage ordered to the
units of the desired dose.
Chapter 9
9
Calculating Parenteral Dosages
(con’t)
 After you determine the
amount to give, you must
select the appropriate
syringe and needle.
Chapter 9
10
Calculating Parenteral Dosages
(con’t)
 You must also select the correct needle
length and gauge.
Chapter 9
11
Calculating Parenteral
Dosages (con’t)
Rule 9 - 1 Selecting a syringe:
1. If the amount of injection to administer is 1 mL
or more, use a standard 3 mL syringe.
2. If the amount of injection to administer is less
than 1 mL, use a 1-mL tuberculin syringe.
3. If the amount of injection to administer is less
than 0.5 mL, use a 0.5-mL tuberculin syringe.
Chapter 9
12
Calculating Parenteral Dosages
(con’t)
Example
Amount to be administered is calculated at
0.6 mL.
Since this is less than 1 mL and greater than
0.5 mL, a tuberculin syringe should be
used.
Chapter 9
13
Calculating Parenteral
Dosages (con’t)
Rule 9 - 2 Rounding the Amount to
Administer:
1. Round volumes greater than 1 mL to the
nearest tenth (one decimal).
2. Round volumes less than 1 mL to the
nearest hundredths (two decimals).
Chapter 9
14
Calculating Parenteral Dosages
(con’t)
Example
Amount to be administered is calculated at 1.66 mL. - Since the volume is greater than 1 mL you
would round to the nearest tenth, which is 1.7 mL.
Amount to be administered is calculated at 0.532 mL.
-- Since the volume is less than 1 mL you would
round to the nearest hundredth, which is 0.53 mL.
Chapter 9
15
Calculating Parenteral Dosages
(con’t)



You must decide whether the amount to be
administered can be safely injected in a
single site.
If amount to administer exceeds the
amount that can be safely given in one site,
divide the amount into equal (or nearly
equal) parts.
Administer them in separate sites.
Chapter 9
16
Calculating Parenteral
Dosages (con’t)
Rule 9 - 3 Maximum volumes for infections:
Intramuscular Injections
 Adult
3 mL
 Adult Deltoid (arm)
2 mL
 Child (6-12 years old)
2 mL
 Child (0-5 years old)
1 mL
 Infant (premature)
0.5 mL
Chapter 9
17
Calculating Parenteral Dosages
(con’t)
Rule 9 - 3 Maximum volumes for infections:

Subcutaneous injections
1 mL
Dosages larger than these maximum
volumes should be checked and
verified.
Chapter 9
18
Calculating Parenteral Dosages
(con’t)
Example: (Use favorite calculate method)
Find the amount to administer and select the
proper syringe.
Ordered: Compazine 7.5 mg IM
On hand: Compazine 5 mg/mL
Answer: 1.5 mL
Standard syringe in a single injection
Chapter 9
19
Medications Expressed in
Percent or Ratio Format
Rule 9 - 4 When a solution strength is
expressed as a percent or ratio:
1. Convert the percent or ratio to a dosage
strength of g/mL, mg/mL, or units/mL.
2. Calculate the amount to administer
then apply Rules 9-1 to 9-3.
Chapter 9
20
Medications Expressed in
Percent or Ratio Format (con’t)
Example: (Use favorite calculate method)
Find the amount to administer and select the
proper syringe.
Ordered: magnesium sulfate 300 mg IM
On hand: magnesium sulfate 10% solution
Patient: 75 pound 8 year-old female
Answer: 3 mL - Divide into two syringes
of 1.5 mL each in two different sites
Chapter 9
21
Review and Practice
Find the amount to administer.
Ordered: Dilaudid 6 mg IM now
On Hand:
Answer: 0.6 mL in a 1 mL tuberculin syringe
Excellent!
Chapter 9
22
Review and Practice
Find the amount to administer.
Ordered: Zinacef 500 mg IM
On Hand: Zinacef (cefuroxime for
injection) 750 mg
Dosage strength after
reconstitution is 220 mg/mL
Answer: 2.3 mL in a standard syringe
Excellent!
Chapter 9
23
Reconstituting Powdered
Medications



Medication which loses potency quickly in
solution may be supplied in powdered form
They are reconstituted by dissolving them
in an appropriate solvent (or diluent)
Instructions are provided in:



Drug label
Package insert
PDR
Chapter 9
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Reconstituting Powdered
Medications (con’t)

Determine the solvent to be used to dilute
medication




Sterile water
Saline
Bacteriostatic solution
Some meds are packaged with separate
container of the appropriate solvent
Chapter 9
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Reconstituting Powdered
Medications (con’t)



Many meds are mixed with lidocaine (a
local anesthetic) to reduce the pain.
Label or package insert indicates when
lidocaine can be used.
Since lidocaine is a medication, you must
have a physician’s order to use it.
Chapter 9
26
Reconstituting Powdered
Medications (con’t)



Do not confuse it with a
combination of lidocaine
and epinephrine.
Epinephrine causes vasoconstriction
(tightening of the blood vessels which
delays medication absorption).
The package lists how much solvent to
combine with the medication.
Chapter 9
27
Reconstituting Powdered
Medications (con’t)
Rule 9 - 5
To reconstitute a powdered medication:
1. Find the directions on the medication label
or package insert.
2. Use a sterile syringe and aseptic (germfree) technique to draw up the correct
amount of the appropriate diluent.
Chapter 9
28
Reconstituting Powdered
Medications (con’t)
Rule 9 - 5 (con’t)
3. Inject the diluent into the medication vial.
4. Agitate the mixture by rolling, inverting, or
shaking the vial. Check the directions on
the label or package insert for which of
these methods to use.
Chapter 9
29
Reconstituting Powdered
Medications (con’t)
Rule 9 - 5 (con’t)
5. Make sure the powdered medication is
completely dissolved and that the solution
is free of visible particles before using it.
Chapter 9
30
Error Alert!

Select the correct instructions for
the strength and route ordered.
Chapter 9
31
Review and Practice
How much diluent should you
add to this vial?
Answer: 1 mL
Wow, Great!
Chapter 9
32
Review and Practice
Ordered: Synagis 75 mg IM Q8H
On hand:
What is the amount to administer?
Answer: 0.75 mL
Excellent!
Chapter 9
33
Other Medication Routes
 Intradermal injections
 Metered dose inhalers (MDI)
 Rectal
 Transdermal
Chapter 9
34
Other Medication Routes (con’t)
 Metered dose inhalers (MDI)

These provide a measured dose of
medication in each puff.
 Nebulizers
 These are supplied as liquids which are
mixed with sterile saline solution.
 Single doses premixed with saline are
available.
 Multiple-dose containers usually come
with special droppers for calibration.
Chapter 9
35
Intradermal Injections
 Injected under the first layer of the skin
 Often used for diagnostic testing such as


tuberculosis or allergies
Usually 0.1 mL or less
Always use a tuberculin syringe
Chapter 9
36
Rectal Medications
 Usually given in suppository form
 Suppositories cannot be accurately divided
Chapter 9
37
Transdermal Systems
 Patches




A patch is a special membrane which releases liquid
medication at a constant rate
Adhesive edges
A patch’s dosage strength is usually expressed in mg
or mcg per hour
A patch cannot be divided
 Ointments
 Creams
Chapter 9
38
Apply Your Knowledge
How would you interpret a
label that reads as follows?
 Heparin 5000 units/mL
Answer:
Each 1 mL contains 5000 units of heparin.
Chapter 9
39
Apply Your Knowledge
What kind of syringe would you use to
administer 0.8 mL IM?
Answer: Tuberculin syringe
What kind of syringe would you use to
administer 2.3 mL IM?
Answer: Standard syringe
Chapter 9
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Apply Your Knowledge
 What is the
maximum amount of
medication that can be
administered IM in
one site to an adult?
Answer: 3 mL
Chapter 9
41
Apply Your Knowledge

A 20% solution means that there is
20 g in how many mL?
Answer: 100 mL
Chapter 9
42
Parenteral Medications
The best
way to
escape from
a problem is
to solve it.
-- Alan
Saporta
Chapter 9
THE END
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