Download Chapter 08

Math for the Pharmacy Technician:
Concepts and Calculations
Egler • Booth
Chapter 8: Intravenous
Calculations
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Intravenous Calculations
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Learning Objectives
When you have successfully completed Chapter 8, you will
have mastered skills to be able to:
Identify the components and
concentrations of IV solutions.
Calculate IV flow rates.
Calculate infusion time based on
volume and flow rate.
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Learning Objectives
(con’t)
Calculate infusion completion time
based on flow rate.
Calculate volume based on infusion
time and flow rate.
 Calculate medications for
intermittent IV infusions.
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Introduction
 Intravenous (IV) fluids are solutions
including medication that are
delivered directly into the
bloodstream via a vein
 Blood is also delivered by IV
 IV fluids have a rapid effect
 Are necessary during emergencies or
other critical care situations
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IV Solutions-Functions
 Replacement fluids
 Maintenance fluids
 KVO (Keep Vein Open) fluids
 Therapeutic fluids
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IV Replacement Fluids

Replace electrolytes and fluids
lost due to hemorrhage,
vomiting, or diarrhea
Examples:

Whole blood

Nutrient solutions

Fluids to treat dehydration
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IV Maintenance Fluids

Maintain normal
electrolyte and fluid
balance
Example:
– Normal
saline given
during and after
surgery
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IV KVO Fluids
 To keep the vein open (KVO or
TKO)
Example:
 5% dextrose in water
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Therapeutic Fluids
•
Deliver medication
to the patient
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IV Labels
Solutions are labeled
with
 The name of the
components
 The exact amount of the
components
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IV Labels
(con’t)
 In abbreviations for IV
solutions:
 Letters identify the
component
 Numbers identify the
concentration
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IV Labels
(con’t)
Example:
An order for 5% dextrose in
Lactated Ringer’s solution might
be abbreviated in any of the
following ways:
 D5LR
 D5LR
 5% D/LR
 D5%LR
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Common Abbreviations
D
W, H20
S
NS, NSS
Dextrose
RL
LR
Ringer’s Lactate
Water
Saline
Normal Saline
(0.9% NaCl)
Lactated Ringer’s
1
2 NS
Half Normal Saline Solution
(0.45% NaCl)
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IV Concentrations

5% Dextrose
It contains 5 g of dextrose per 100 mL.
 Normal saline is 0.9% saline
It contains 900 mg, or 0.9 g, of sodium chloride per
100 mL.

½ Normal saline is 0.45% saline
It contains 450 mg, or 0.45 g, of sodium chloride per
100 mL.
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IV Concentrations
(con’t)
Isotonic
They have no effect on the fluid balance of the
surrounding cells or tissues.
Examples: D5W, NS, LR
Hypotonic
 Fluid moves across the cell membrane into
surrounding cells and tissues.
 This movement restores the proper fluid level in cells
and tissues of patients who are dehydrated.
Examples: 0.45% NS, 0.33% NaCI
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IV Concentrations
(con’t)
Hypertonic
 These solutions draw fluids from cells and
tissues across the cell membrane into the
bloodstream.
 They are helpful for patients with severe fluid
shifts such as those caused by burns.
Example: 3% saline
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IV Concentrations
(con’t)
Patients with normal electrolyte levels
are likely to receive isotonic
solutions.
 Patients with high electrolyte levels
will receive hypotonic solutions.
 Patients with low electrolyte levels
will receive hypertonic solutions.
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Compatibility

Additives
 Medications, electrolytes, and


nutrients combined with IV
solutions
Common additives: potassium
chloride, vitamins B and C, and
antibiotics
Come prepackaged in the solution
or may need to be mixed
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Compatibility
(con’t)
Before combining any medications,
electrolytes, or nutrients with an
IV solution, be sure the
components are compatible.
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Incompatible Combinations
Examples
 Ampicillin + 5% dextrose in water
 Cefotaxime sodium +
Sodium






bicarbonate
Diazepam + Potassium chloride
Dopamine HCl + Sodium bicarbonate
Penicillin
+ Heparin
Penicillin
+ Vitamin B complex
Sodium bicarbonate + Lactated
Ringer’s
Tetracycline HCl + Calcium chloride
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Calculating Flow Rates
To calculate flow rates in milliliter per
hour, identify the following:
V (volume) is expressed in milliliters
T (time) must be expressed in hours (convert the units
when necessary using calculation methods)
F (flow rate) will be rounded to the nearest tenth
V Use the formula method or dimensional analysis to
F
determine the flow rate in milliliters per hour.
T
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Review and Practice
Find the flow rate.
• Ordered: 500 mg ampicillin in 100 mL NS to
infuse over 30 minutes
Flow rate = 200 mL/h
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Calculating Flow Rates
for Manual Regulation
To determine the flow rate (f) in drops
per minute:
1. Change the flow rate mL/h (F) to
gtt(drops)/min (f) using the formula
FxC
f 
60
where
F = the flow rate in milliliters/hour
C = the calibration factor of the tubing in drops per mL
60 = number of minutes in an hour
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Review and Practice
• Find the flow rate in drops per minute that is
equal to 35 mL/hour using 60 gtt (Drops) /mL
microdrop tubing.
Flow rate = 35 gtt/min
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Infusion Time and Volume
 An order may call for a certain
amount of fluid to infuse at a specific
rate without specifying the duration.
 You will need to calculate the duration
or amount of time the IV will take to
infuse.
 You may know the duration and flow
rate and will have to calculate the
fluid volume.
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Calculating Infusion
Time
To calculate infusion time in hours (T),
identify the:
V (volume) expressed in milliliters
F (flow rate) expressed in milliliters per
hour
Fractional hours by multiplying by 60
V
T
F
Use this formula or dimensional
analysis to find T, the infusion
time in hours.
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Review and Practice
Find the total time to infuse.
Ordered: 1000 mL NS to infuse at a rate of
75 mL/h
Total time to infuse the solution is
13 hours and 20 minutes
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Review and Practice
Find the total time to infuse.
Ordered: 750 mL LR to infuse at a rate of
125 mL/hr started at 11 p.m.
T = 6 hours = total time to infuse the 750 mL
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Calculating Infusion Completion
Time
To calculate the time when an
infusion will be completed, you
must first know the time the
infusion started in military
time and the total time in
hours and minutes to infuse
the solution ordered.
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Calculating Infusion
Completion Time (con’t)
Since each day is only 24 hours
long, when the sum is greater
than 2400 (midnight), you must
start a new day by subtracting
2400.
This will determine the time of
completion, which will be the
next calendar day.
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Review and Practice
Determine when the infusion will be
completed.
Ordered: 750 mL LR to infuse at a rate of 125
mL/hr, started at 11 p.m. on 08/04/05
The infusion will be complete at
0500 or 5:00 a.m. on 08/05/05
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Calculating Infusion
Volume
Use the formula V = T X F or
dimensional analysis to find V the
infusion volume in mL, where the
 T (time) must be expressed in hours
 F (flow rate) must be expressed in
milliliters per hour
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Review and Practice
Find the total volume infused in 5
hours if the infusion rate is 35 mL/h.
V=175 mL or the volume that
will infuse over 5 hours
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Review and Practice
Find the total volume infused in 12
hours if the infusion rate is 200 mL/h.
V = 2400 mL = the volume
that will infuse over 12 hours
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Intermittent IV Infusion
 IV medications are sometimes
delivered on an intermittent basis
 Delivered through
 IV secondary line
 Saline
 Heparin lock
 Can be delivered with continuous IV
therapy or when no continuous IV
solutions are infusing
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Secondary Lines
(Piggybacks or IVPB)
 IV setup that attaches to a primary
line
 Used to infuse medications or other
compatible fluids on an intermittent
basis (such as q6h)
 Uses shorter tubing
 IVPB bags are smaller: 50,100, or 150
mL
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Intermittent Peripheral
Infusion Devices
 Saline or heparin locks
 An infusion port attached to an
already inserted IV needle or
catheter
 Allow direct injection of medication
or infusion of IV medications
 Medications ordered as IV push or
bolus
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Intermittent Peripheral
Infusion Devices (con’t)
 Since there is no continuous flow of fluids
through the IV line you must flush the
device 2 to 3 times per day to prevent
blockage.
 Saline lock -- is an infusion port attached
to an already inserted catheter for IV
access, flushed with saline.
 Heparin lock -- is an infusion port attached
to an already inserted catheter for IV
access, flushed with heparin.
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Preparing and Calculating
Intermittent Infusions
 Flow rate is calculated for prepared
medications the same as regular IV
infusions.
 Amount of fluid may be less and time
to infuse may be less than an hour.
 Calculate the flow rate you will need
to change the number of minutes
into hours.
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Preparing and Calculating
Intermittent Infusions (con’t)
When preparing medications for an
intermittent IV infusion:
Reconstitute the medication using the
label and package insert.
Calculate amount to administer and
the flow rate.
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Review and Practice
 Identify four functions of IV fluids.
Answers:
1. Replacement
2. Maintenance
3. KVO
4. Therapeutic
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Review and Practice
 How many mg of sodium chloride
is in 100 mL of normal saline?
Answer: 900 mg NaCl
 How many mg of sodium chloride
is in 100 mL of 0.45% NS?
Answer: 450 mg NaCl
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Intravenous Calculations
As a pharmacy technician you will need to
know how to perform accurate IV
calculations.
Results can be fatal if the wrong
medication or dosage is given
THE END
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