Transcript Preparing Sterile Intravenous Products

Chapter 11
Preparing Sterile
Intravenous
Products
Chapter 11 Topics
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Intravenous Preparations
Equipment Used in IV Preparation
Preparing IVs
Calculations for the Hospital Pharmacy
Technician
Learning Objectives
• Describe the characteristics of intravenous solutions
including solubility, osmolality, and pH
• Identify common vehicles for intravenous solutions
• Describe the equipment and procedures used in
preparing parenterals
• Identify the components of an intravenous
administration set
• Convert from Fahrenheit to Centigrade and vice versa
• Calculate the molecular weight and milliequivalents of
certain substances used in the pharmacy
• Compute the specific gravity of liquids
• Calculate intravenous rates and administration
Intravenous Preparations
• The IV route of administration is used
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to reach appropriate drug serum levels
to guarantee compliance
for drugs with unreliable gastrointestinal (GI) absorption
for the patient who can have nothing by mouth
for the patient who is unconscious or uncooperative, and for
rapid correction of fluid or electrolytes
• Most parenterals are introduced directly into the
bloodstream
– must be free of air bubbles or particulate matter
– have many characteristics including solubility, osmolality,
and pH
Characteristics of IV Preparations
• Intravenous (IV) preparations are either:
– solutions (in which ingredients are dissolved)
– suspensions (in which ingredients are suspended)
• Most parenteral preparations are made of
ingredients in a sterile water medium
• Some parenteral preparations may be oleaginous
(oily)
Characteristics of IV Preparations
• Parenteral IV preparations must have chemical
properties that will not
– damage vessels or blood cells
– alter the chemical properties of the blood serum
• With blood, IVs must be
– iso-osmotic (having the same number of particles in
solution per unit volume)
– isotonic (have the same osmotic pressure, meaning the
pressure produced by or associated with osmosis)
Characteristics of IV Preparations
• The osmolality is the amount of particulate per unit
volume of a liquid preparation
– measured in milliosmoles (mOsm)
– osmolality of blood serum = 285 mOsm/L
• An isotonic solution is a solution in which body cells
can be bathed without a net flow of water across a
semipermeable membrane
– 0.9% normal saline (NS)
Characteristics of IV Preparations
• Pharmacists sometimes must adjust tonicity of
parenteral preparations to ensure they are near isotonic
• A hypertonic solution has a greater number of
particles than the blood cells themselves
– 50% dextrose or 3% sodium chloride
• A solution of less than normal tonicity is hypotonic,
which has fewer numbers of particles than blood cells
– 0.45% NS
Characteristics of IV Preparations
• The pH value is the degree of acidity or alkalinity
of a solution
– acidic solution: pH of less than 7
– alkaline solution: pH value more than 7
• Human blood plasma has a pH of 7.4
– slightly alkaline
– parenteral IV solutions should have a pH that is neutral
(near 7)
Methods of Injection
• The bolus, or injection, is one of the most
common routes of IV administration
• The injection is performed using a syringe
– prepackaged in the form of filled, disposable plastic
syringes
– injectable drug must be taken up into the syringe from a
single- or multi-dose glass or plastic vial, or from a
glass ampule
• Sometimes the solid drug in the vial has to be
reconstituted by addition of a liquid before use
Methods of Injection
• IV infusions deliver:
– large amounts of liquid into the bloodstream over
prolonged periods of time
• IV infusion is used to deliver:
– blood
– electrolytes
– water
– drugs
– other fluids
– nutrients
Discussion
What are some characteristics of parenteral
preparations, and why are they important?
Discussion
What are some characteristics of parenteral
preparations, and why are they important?
Answer: Tonicity, osmolality, and pH are
characteristics of parenteral preparations. It is
important that they be adjusted to be as close as
possible to the values for human blood, to
prevent damage to blood cells and organs.
Terms to Remember
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osmotic pressure
osmolality
isotonic solution
hypertonic solution
pH value
Equipment Used in IV Preparation
• Pharmacies use plastic disposable products to
– save time and money
– provide the patient with an inexpensive sterile product
• Often the entire system sent out to the patient
floors is composed of plastic
– thin, flexible plastic catheters are replacing metal shafts
that deliver the medication into the vein
– in many cases the only durable, nondisposable product
used to deliver IV medication is the IV pump or
controller
Commonly Used IV Abbreviations:
Fluids
IV Component
Abbreviation
2.5% dextrose in water
D2.5W
5% dextrose in water
D5W
5% dextrose and lactated Ringer’s solution
D5RL or D5LR
10% dextrose in water
D10W
5% dextrose and normal saline
D5NS
2.5% dextrose and 0.45% normal saline
D2.5½ NS
5% dextrose and 0.45% normal saline
D5 ½ NS
Commonly Used IV Abbreviations:
Fluids
IV Component
Abbreviation
normal saline
NS
0.45% normal saline
0.45%NS or ½ NS
lactated Ringer’s solution
RL or LR
sterile water for injection
SWFI
bacteriostatic water for injection
BWFI
sterile water for irrigation
SW for irrigation
normal saline for irrigation
NS for irrigation
Commonly Used IV Abbreviations:
Electrolytes
IV Component
Abbreviation
potassium chloride
KCl
potassium phosphate
K phos or KPO4
potassium acetate
K acet
sodium phosphate
Na phos or NaPO4
sodium chloride
NaCl
Commonly Used IV Abbreviations:
Additives
IV Component
Abbreviation
multivitamin for injection
MVI
trace elements
TE
zinc (a trace element)
Zn
selenium (a trace element)
Se
Syringes and Needles
• Syringes are used for IV push and in the preparation
of infusions, are made of glass or plastic
• Glass syringes are more expensive
– use limited to medications that are absorbed by plastic
• Plastic syringes
– are less expensive
– are disposable
– come from the
manufacturer sterile
Syringes and Needles
• Needles are made of stainless steel or aluminum
– needle lengths range from 3/8 of an inch to 6 inches
– needles come in gauges ranging from 30 to 13 (higher the
gauge, smaller the lumen)
• After use, needles must be discarded in a designated
sharps container
IV Sets
• An IV administration set is a sterile, pyrogen-free
disposable device used to deliver IV fluids to patients
• The set may
– be sterilized before use by means of radiation or ethylene
oxide
– come in sterile packaging and a sealed plastic wrap
• Sets do not carry expiration dates
• Sets carry the following legend:
– “Federal law restricts this device to sale by or on the order
of a physician.”
IV Sets
• Nurses generally have the responsibility for
– attaching IV tubing to the fluid container
– establishing and maintaining flow rate
– overall regulation of the system
• Pharmacy personnel must assess aspects of IV
systems, including infusion sets
• A complete understanding of IV sets and their
operation is important to pharmacists and
pharmacy personnel
IV Sets
• IV sets are sterile and nonpyrogenic
• Each unit is supplied in packaging that ensures the
maintenance of sterility
• Flanges and other rigid parts of an IV set are molded
from tough plastic
• Most of the length of the tubing is molded from a
pliable polyvinyl chloride (PVC)
• PVC sets should not be used for
– nitroglycerin, which is absorbed by the tubing
– IV fat emulsions, which may leach out of the tubing
IV Sets
A damaged package cannot ensure sterility, even
if all protectors are in place. It is best to discard
sets that are found in unoriginal, opened, or
damaged packages.
IV Sets
Do not use PVC IV sets for nitroglycerin or fat
emulsions. Special types of plastic sets are required
for such infusions.
IV Sets
• The length of sets varies from 6-inch extensions up to
110- to 120-inch sets used in surgery
– the priming of tubing depends on the length of the set
• Standard sets have a lumen diameter of 0.28 cm
– varying the size of the lumen diameter achieves different
flow rates
– regulation of flow rates is critical in neonates and infants
IV Sets
• The tubing’s interior lumen may contain particles
that flush out when fluid is run through the set
• Use of final filtration has reduced the need for
flushing the line with the IV fluid before attaching
the set to the patient
IV Sets
• A spike to pierce the rubber
stopper or port on the IV container
• A drip chamber for trapping air
and adjusting flow rate
• A control clamp for adjusting flow
rate or shutting down the flow
• Flexible tubing to convey the fluid
IV Sets
• A needle adapter for
attaching a needle or a
catheter
• A catheter, or tube, may
be implanted into the
patient and fixed with
tape to avoid having to
repuncture the patient
each time an infusion is
given
IV Sets
• Most IV sets contain a Y-site, or injection port
– a rigid piece of plastic with one arm terminating in a
resealable port
– used for adding medication to the IV
• Some IV sets also contain resealable in-line filters
– protection for the patient against particulates, including
bacteria and emboli
Go to www.baxter.com to see IV tubing products from a major
manufacturer
IV Sets
• The spike is a rigid, sharpened plastic piece used
proximal to the IV fluid container
– covered with a protective unit to maintain sterility
– generally has a rigid area to grip while it is inserted into
the IV container
• If an air vent is present on a set, it is located below
the spike
– the air vent points downward and has a bacterial filter
covering
– the vent allows air to enter the bottle as fluid flows out
of it
– necessary for glass bottles without an air tube
IV Sets
• The drip chamber is a transparent, hollow chamber
located below the set’s spike
– drops of fluid fall into the chamber from an opening at the
uppermost end, closest to the spike
– number of drops it takes to make 1 mL identifies an IV set
IV Sets
• The most common IV
drop sets are
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10 (10 gtt/mL)
15 (15 gtt/mL)
20 (20 gtt/mL)
60 (60 gtt/mL)
• An opening that provides 10,
15, or 20 gtt/mL is commonly used
for adults
• An opening that provides 60 gtt/mL
is used for pediatric patients and is
called a mini-drip set
IV Sets
• The person administering the fluid starts the flow
by filling the chamber with fluid from an attached
inverted IV container
– the chamber sides are squeezed and released
– fluid flows into the chamber
– procedure is repeated until an indicated level is reached
or approximately half the chamber is filled
– entering drops are counted for 15 seconds
– adjustments made until approximate number of drops
desired is obtained
– rate should be checked five times, at 30-second
intervals, and again for a last count of 1 minute
IV Sets
• Clamps allow for adjusting the rate of the flow and
for shutting down the flow
• Clamps may be located at any position along the
flexible tubing
• Usually a clamp moves freely, allowing its location
to be changed to one that is convenient for the health
professional administering the medication
IV Sets
• Types of clamps used for IV solutions include:
– slide clamp: has an increasingly narrow channel that
constricts IV tubing as it is pressed further into the
narrowed area
– screw clamp: consists of a thumbscrew that is tightened or
loosened to speed or slow the flow
– roller clamp: a small roller that is pushed along an incline
• moving down the incline, constricts tubing and reduces fluid
flow
• moving up the incline, increases the flow
IV Sets
• Clamp accuracy can be affected by:
– creep: tendency of some clamps to return to a more open
position with increased fluid flow
– cold flow: tendency of PVC tubing to return to its previous
position
• The needle adapter
– usually located at the distal end of the IV set, close to the
patient
– has a standard taper to fit all needles or catheters
– is covered by a sterile cover before removal for connection
IV Sets
• A set may have a built-in or in-line filter
• Final filtration should protect the patient against
particulate matter, bacteria, air emboli, and phlebitis
– a 0.22-micron filter is optimal
– a 5-micron filter removes particles that block pulmonary
microcirculation but will not ensure sterility
• A Y-site is an injection port found on most sets
– the Y is a rigid plastic piece with one arm terminating in a
resealable port
– the port, once disinfected with alcohol, is ready for the
insertion of a needle and the injection of medication
Filters
• Filters are devices used to remove contaminants such
as glass, paint, fibers, and rubber cores
– will not remove virus particles or toxins
– will occasionally become clogged, thus slowing expected
flow rates
• Filter sizes include:
– 5.0 microns – random path membrane (RPM) filter, removes
large particulate matter
– 0.45 microns – in-line filter for IV suspension drug
– 0.22 microns – removes bacteria and produces a sterile
solution
Catheters
• IV administration for fluids and drug therapy can be
accomplished through needle-like devices called
catheters
• Catheters are devices inserted into veins for direct
access to the blood vascular system and are used in
two primary ways:
– peripheral venous catheters, which are inserted into a vein
close to the surface of the skin
– central venous catheters, which are inserted deeper in the
body
Catheters
• A peripheral venous catheter is inserted into veins
close to the surface of the skin and used for up to 72
hours
– unit is inserted into a vein
– needle portion is withdrawn
– flexible, Teflon catheter is left in place
• Peripheral catheters are easy to insert, and most nurses
can do this at a patient’s bedside
– usually inserted in sites on the arms or hands
– can be inserted in the feet and scalp if the nurse or physician
cannot locate “good” veins in the arms or hands
Catheters
• Peripheral venous catheters will likely cause
problems 20 to 50% of patients
– pain
– irritation
– infiltration
• Infiltration is a breakdown or collapse of a vein that
allows the drug to leak into tissues surrounding the
catheter site, causing edema and/or tissue damage
Catheters
• A central venous catheter is one placed deep into the
body
– more complicated to place
– inserted by a physician to minimize the risk of infection
• Central catheters are commonly used for therapy of
1 to 2 weeks or even longer
• A central venous catheter is used to administer:
– hypertonic solutions such as total parenteral nutrition (TPN)
solutions
– potentially toxic drugs such as cancer chemotherapeutic
drugs
Catheters
• The most common sites of insertion are
– subclavian vein, lying below the clavicle and joining the
jugular vein
– jugular vein, in the neck
– femoral vein, in the groin area
• Placed deep in the vein so that the end enters the
superior vena cava close to the heart where the
blood flow is the greatest
Visit the Web site of the American Society of Enteral and Parenteral
Nutrition, a good source for information and networking
Catheters
• Problems with subclavian catheters are:
– possibility of subclavian vein laceration (i.e., missing the
vein and puncturing a lung)
– greater risk of infection because the procedure is more
invasive
• A larger blood flow in the subclavian vein will dilute a
more concentrated solution such as TPN
– TPN solutions provide
• needed calories in the form of amino acids and dextrose
• vitamins, minerals, trace elements, and electrolytes
Catheters
• A multiple-lumen catheter is used to separately
administer potentially physically incompatible
drugs
– comes with one, two, three, or four lumens
• Each lumen exits the catheter at a different location
– no opportunity exists for the drugs to mix before being
diluted in the bloodstream
Catheters
• Midline catheters are longer peripheral catheters that
go from insertion site into a deep vein
– designed to stay in place 1 week or longer
• The peripherally inserted central (PIC) line is a very
fine line that is threaded through the peripheral vein
into the subclavian vein
– has the same characteristics as a central line
– can be inserted by a skilled nurse at the bedside
Catheters
• Some patients may be on TPN therapy for months or
even years in the hospital or at home
• Infusion devices are surgically implanted to:
– provide long-term therapy
– reduce the risk of infection
Catheters
• Implantable infusion devices include the Hickman and
Broviac external catheters
• Surgeon inserts the catheter below the breast and
tunnels it under the skin into the subclavian vein
– catheter has a cuff to which the body’s connective tissue
heals, sealing off bacterial entry
– lower point of body insertion makes the catheter easier for
the patient to see and clean
Catheters
• Another form of implantable device is the internal
port, such as the Port-A-Cath, Life Port
– when implanted the only evidence is a bump in the skin
– drugs, especially cancer chemotherapeutic drugs, are
administered by a small needle through the skin in an
injection port in the device
Pumps and Controllers
• Fluids and drugs are often delivered to catheters
by some form of device, including electronic
devices, to control the infusion rate
• The first system to deliver a drug IV was the
syringe system
• Care must be taken when administering drugs that
have to be diluted or given very slowly
• The syringe system is very nurse labor-intensive
and pharmacy labor-intensive
Pumps and Controllers
• The Buretrol or Soluset were in use before infusion
pumps and replaced the syringe system and has a builtin graduated cylinder
– fluid is run into the cylinder
– nurse can add a drug in the top of the cylinder injection port
for dilution and mixing before it is infused
• Safer than the syringe system because the drug is
being diluted in the cylinder and it can be infused over
a long period of time
Pumps and Controllers
The Buretrol or the Soluset have the following
problems:
• labor intensive
• potential drug incompatibility
• controllers are low-pressure devices (2 to 3 psi)
– pressure of controller is generated by gravity
– flow rate is controlled by rate of fluid drops falling
through a counting chamber
• alarms sound with a kink in a line or even
interruption of blood flow when patient bends an
elbow
Pumps and Controllers
• Infusion pumps are preferred by both nurses and
physicians
– produce a positive pressure of 10 to 25 psi
– are more accurate than controllers
– have fewer flow interruptions
• Infusion pumps control the flow of IV
medications
• Maximum flow is 999 mL/hr
– provides a higher rate of infusion
– higher pressure increases possibility
of infiltration
Pumps and Controllers
• A patient-controlled analgesia (PCA) device is a type
of medication delivery that uses a parenteral route
and allows the patient to administer analgesics by
pressing a button
– controls the medication so the patient cannot overdose or
give the medication too soon after the previous dose
• Often, after surgery or severe injuries, a physician
will order a PCA for the patient for 24 to 72 hours
Pumps and Controllers
PCA pumps should carry the following label: “This
PCA pump button should be pushed only by the
patient.”
Discussion
What is the most important characteristic that
all equipment used in IV preparation and
administration have in common?
Discussion
What is the most important characteristic that
all equipment used in IV preparation and
administration have in common?
Answer: Sterility is a requirement for all
equipment used in IV preparation and
administration.
Terms to Remember
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•
•
•
IV administration set
filter
catheter
peripheral venous
catheter
• infiltration
• central venous catheter
• subclavian vein
• multiple-lumen
catheter
• peripherally inserted
central (PIC) line
Preparing IVs
• Pharmacists and technicians prepare drugs and IV
solutions in a form ready to be administered to a
patient
• IV push (i.e., bolus) and IV infusion dose forms
should be prepared in laminar airflow hoods using
aseptic techniques
– products used during the preparation must always be
sterile and handled in such a manner as to prevent
contamination
Preparing IVs
• Preparation should always
be done under the
supervision of a licensed
pharmacist
• Medication that is prepared by the technician must
be reviewed and approved by the pharmacist
Visit the ASHP Web site for a standard for quality assurance of
sterile products
IV Preparation Guidelines
• Begin any IV preparation by washing your hands
thoroughly using a germicidal agent such as
chlorhexidine gluconate or povidone-iodine
• All jewelry should be removed from the hands and
wrists before scrubbing and while making a sterile
product
• Wear gloves during procedures
• Laminar airflow hoods are normally kept running
• Eating, drinking, talking, or coughing is prohibited in
the laminar airflow hood
• Working in the laminar flow hood should be free
from interruptions
IV Preparation Guidelines
• Before making the product, thoroughly clean all
interior working surfaces
• Gather all the necessary materials for the operation
and make sure they are:
– not expired
– free from particulate matter such as dust
– check for leaks by squeezing plastic solution containers
• Only essential objects and materials necessary for
product preparation should be placed in the airflow
hood
IV Preparation Guidelines
• Work in the center of the work area within the laminar
airflow hood
– at least six inches inside the edge of the hood
– make sure nothing obstructs the flow of air from the highefficiency particulate air (HEPA) filter over the preparation
area
– nothing should pass behind a sterile object and the HEPA
filter in a horizontal airflow hood or above a sterile object in a
vertical airflow hood
IV Preparation Guidelines
• Follow proper procedure for handling sterile
devices and medication containers
• Remember that the plunger and tip of the syringe
are sterile and must not be touched
• For greatest accuracy, use the smallest syringe that
can hold the desired amount of solution
– syringe should not be larger than twice the volume to be
measured
– syringe is considered accurate to half the smallest
measurement mark on its barrel
IV Preparation Guidelines
• The volume of solution drawn into a syringe is
measured at the point of contact between the rubber
piston and the side of the syringe barrel
• Additives are commonly added to IV solutions
– medications, electrolytes, vitamins and/or minerals
• Additives may be packaged in vials or ampules
• Proper technique in using vials and ampules is an
important skill for the pharmacy technician to learn
Vials
• Powders are reconstituted by introducing a diluent
(e.g., sterile water for injection)
• Vials are closed systems
– the amount of air introduced should be equal to the
volume of fluid removed
– an exception to this guideline is the withdrawal of
cytotoxic drugs from vials
Vials
With the exception of cytotoxic drugs, inject an
equal amount of air into the vial with the syringe
and needle before withdrawing the medication.
Vials
Use a Syringe to Draw Liquid from a Vial
1. Choose the smallest gauge needle appropriate for
the task, and avoid coring the rubber top of the vial
and thus introducing particulate into the liquid
within it
2. Attach the needle to the syringe.
3. Draw into the syringe an amount of air equal to the
amount of drug to be drawn from the vial.
Vials
4. Swab or spray the top of the vial
with alcohol before entering the
laminar flow hood; allow the
alcohol to dry. Puncture the
rubber top of the vial with the
needle bevel up. Then bring the
syringe and needle straight up,
penetrate the stopper, and depress
the plunger of the syringe,
emptying the air into the vial.
Vials
5. Invert the vial with the attached syringe.
6. Draw up from the vial the amount of
liquid required.
7. Withdraw the needle from the vial. In the
case of a multidose vial, the rubber cap
will close, sealing the contents of the vial.
8. Remove and properly dispose of the
needle, and cap the syringe. A new needle
will be attached at the time of injection
into a patient.
Ampules
• An ampule is a single-dose-only drug container
• The glass ampule offers another challenge because
one must first break the top off the ampule before
withdrawing the medication
Ampules
Opening an Ampule
1. Gently tap the top of the ampule to bring the
medication to the lower portion of the
ampule.
Ampules
Opening an Ampule
2. Clean the neck with an alcohol swab; then grasp
the ampule between the thumb and index finger at
the neck with the swab still in place.
Ampules
Opening an Ampule
3. Forcefully snap the neck away from you.
Ampules
• To withdraw from an ampule, tilt the ampule, place
the needle bevel of a filter needle or tip of a filter
straw in the corner near the opening, and withdraw the
medication
• Use a needle equipped with a filter for filtering out
any tiny glass particles, fibers, or paint chips that may
have fallen into the ampule
Ampules
• Before injecting the contents of a syringe into an IV,
the needle must be changed to avoid introducing glass
or particles into the admixture
• A standard needle could be used to withdraw the drug
from the ampule; it is then replaced with a filter
device before the drug is pushed out of the syringe
• Filter needles are for one directional use only
IV Solutions
• Most IV, intrathecal, intra-arterial, and intracardiac
injections will be solutions
• A diluent is a sterile fluid to be added to a powder to
reconstitute or dissolve the medication
– check the medication package insert to verify which diluent
and what volume should be added to the medication vial to
make a sterile solution
• Alternative routes of administration may also require
special preparation, storage, and needles
– it is best to check with the pharmacist if such a medication
order is received
IV Solutions
• The vehicles most commonly used for IV infusions
are:
– dextrose in water
– NS solution
– dextrose in saline solution
• The two main types of IV solutions are:
– small-volume parenterals (SVPs) of 50 or 100 mL
– large-volume parenterals (LVPs) of more than 100 mL
IV Solutions
• SVPs are typically used for delivering medications at
a controlled infusion rate
• Large-volume parenterals (LVPs) are used
– to replenish fluids
– to provide electrolytes (i.e., essential minerals)
– to provide nutrients such as vitamins and glucose
– LVPs are commonly available in 250 mL, 500 mL, and
1000 mL sizes
Different Types of IV Containers
IV Solutions
• A piggyback is a small-volume parenteral admixture
that is attached to an existing IV line
• The piggybacked solution is infused into the tubing of
the running IV
– usually over a short time, from 30 minutes to 1 hour
• Some IV piggybacks are prepared in 250 mL solution
because they contain a medication that is irritating to
the veins
• In some cases, syringes are used instead of piggyback
containers to deliver medication into a running IV
IV Solutions
• A LVP usually contains one or more electrolytes
– potassium chloride is the most common additive
– other salts of potassium, magnesium, or sodium can be
added
• Additives to IV solutions can also be multivitamins
or trace elements
Preparing a Label for an IV Admixture
Labels for IV admixtures should bear the following
information:
– patient’s name and identification number
–
–
–
–
–
–
–
room number
fluid and amount
drug name and strength (if appropriate)
infusion period
flow rate (e.g., 100 mL/hr or infuse over 30 min)
expiration date and time
additional information as required by the institution or by state
or federal guidelines
Examples of Pharmacy-prepared
Labels
• for a minibag
• for a large-volume parenteral (LVP)
Discussion
What principle guides the techniques and
procedures applied to IV solution
preparation?
Discussion
What principle guides the techniques and
procedures applied to IV solution
preparation?
Answer: IV preparation is based on aseptic
technique and all dosage forms and equipment
must be handled in a way that prevents
contamination.
Terms to Remember
•
•
•
•
•
ampule
diluent
small-volume parenterals (SVPs)
large-volume parenterals (LVPs)
piggyback
Calculations for
the Hospital Pharmacy Technician
• In preparing sterile IV preparations in the hospital or
home healthcare setting, it is important to:
– understand math skills somewhat unique to these
environments
– double- and triple-check calculations and flow rates for IV
admixtures or TPN solutions
Calculations for
the Hospital Pharmacy Technician
• Important math skills are needed in the areas of
– reading time
– temperature and temperature conversions
– electrolyte replacement therapy
– specific gravity
– IV infusion flow rates
Calculations for
the Hospital Pharmacy Technician
Always carefully check and double check all
calculations.
Time Conversions
• Hospital medication orders are often stamped with
international or military time
– dose administration schedules for unit dose and IV
admixtures also use this method
• This time is based on a 24-hour clock, with midnight
being considered time 0000
– time in hours are the first two digits
– time in minutes are the last two digits
– no A.M. or P.M. are used
Time Conversions
Examples:
0000 = Midnight
0600 = 6 AM
1200 = Noon
1800 = 6 PM
Temperature Conversions
• The United States is one of the few countries in the
world where the Fahrenheit temperature scale is
commonly used
– The Fahrenheit temperature scale uses 32° F as the
temperature when ice freezes and 212° F as the temperature
that water boils
– the difference between these two extremes is 180° F
Temperature Conversions
• The Celsius temperature scale is commonly used in
Europe and globally in science, and it is often the
scale used in the pharmacy
– the Celsius temperature scale uses 0° C as the temperature
when ice freezes and 100° C as the temperature that water
boils
– the difference between these two extremes is 100° C
Temperature Conversions
• Storing drugs under the proper refrigeration and
maintaining refrigerating equipment at the
appropriate temperature are responsibilities of the
pharmacy technician
– most refrigerators in the pharmacy need to maintain a
temperature of 5º C to 10º C
• Temperatures in the drug package inserts or in the
policy and procedure manual are often in centigrade
– pharmacy technicians will need to know how to convert
between the Celsius scale and the Fahrenheit scales
Temperature Conversions
Temperature Equivalencies
• Every 5° C change in temperature is equivalent
to a 9° F change
Celsius
0º C
5º C
10º C
15º C
20º C
Fahrenheit
32º F
41º F
50º F
59º F
68º F
Temperature Conversions
• These equations allow conversions between the two
temperature scales:
º F = (1.8 × º C) + 32
º C = (º F – 32) ÷ 1.8
• An alternative method uses this equation:
5F = 9C + 160
• The final temperature is usually rounded up to the
closest whole number
Electrolytes
• Many IV fluids used in pharmacy practice contain
electrolytes:
– dissolved mineral salts
– so-named because they conduct an electrical charge
through the solution when connected to electrodes
• Electrolytes are measured in millimoles (mM) and
milliequivalents (mEq)
Understanding
Millimoles and Milliequivalents
• Milliequivalents (mEq) are related to molecular weight
• Molecular weights are based on the atomic weights of
elements
– the atomic weight of an element is the weight of a single atom
of that element compared with the weight of one atom of
hydrogen
– the molecular weight of a compound is the sum of the atomic
weights of all the atoms in one molecule of the compound
Understanding
Millimoles and Milliequivalents
• A millimole (mM) is an amount of a substance
weighing its molecular weight in milligrams
• The valence of an element is a number that represents
its capacity to combine to form a molecule of a stable
compound
– an element can exist in various forms
– valence may vary depending on an elemental form
Valences and Atomic Weights of
Common Elements
Element
Valence
Atomic Weight
Rounded
Value
hydrogen (H)
1
1.008 g
1g
carbon (C)
2, 4
12.011 g
12 g
nitrogen (N)
3, 5
14.007 g
14 g
oxygen (O)
2
15.999 g
16 g
sodium (Na)
1
22.9898 g
23 g
sulphur (S)
2, 4, 6
32.064 g
32.1 g
chlorine (Cl)
1, 3, 5, 7
35.453 g
35.5 g
potassium (K)
1
39.102 g
39.1 g
calcium (Ca)
2
40.08 g
40.1 g
For pharmaceutical calculations, atomic weights are usually rounded to the
nearest tenth (i.e., one unit to the right of the decimal point).
Understanding
Millimoles and Milliequivalents
• One mole (M) of an element weighs its atomic
weight in grams
– one mole of sodium (Na) is 22.9898 (rounded to 23 g)
• Compounds are also measured in moles
– one mole of salt or sodium chloride (NaCl) would weigh
its molecular weight in grams
• atomic weight of sodium (23 g) + atomic weight of
chlorine (35.5 g) = 58.5 g
• 1 mM is an amount equal to the molecular weight in
milligrams
– because 1 g equals 1000 mg, 1 mole equals 1000 mM
• 1 mM of sodium chloride equals 58.5 mg
Understanding
Millimoles and Milliequivalents
• One equivalent (Eq) is equal to one mole divided
by its valence
Equivalent weight = molecular weight (expressed in milligrams)
valence
• One milliequivalent (mEq) is equal to 1 millimole
divided by its valence
– thus one equivalent equals 1000 mEq, or one thousandth
of a gram equivalent
Determining Milliequivalents of
Compounds
To determine the number of milliequivalents of a
compound:
(1) identify the formula of the compound
(2) separate the formula into atoms
(3) determine the moleclular weight of the compound
– multiply the weight of each atom by the number of those atoms
– add the products together, the sum is the molecular weight
mEq
=
molecular weight (expressed in milligrams)
valence
Measuring Electrolytes
• Milliequivalents (and sometimes millimoles) are used
to measure electrolytes in the bloodstream and/or in
an IV preparation
• Example:
– You must add 44 mEq of sodium chloride (NaCl) to an IV
bag. Sodium chloride is available as a 4 mEq/mL solution.
How many milliliters will you add to the bag?
Measuring Electrolytes
• You must add 44 mEq of sodium chloride (NaCl) to an
IV bag. Sodium chloride is available as a 4 mEq/mL
solution. How many milliliters will you add to the
bag?
– set up a proportion, comparing the solution you will need to
create to the available solution, and solve for the unknown
Measuring Electrolytes
• Set up a proportion, comparing the solution you will
need to create to the available solution, and solve for
the unknown
x mL
44 mEq
(44 mEq) x mL
44 mEq
=
=
x mL
=
x mL
=
1 mL
4 mEq
(44 mEq) 1 mL
4 mEq
44 mL
4
11 mL
Specific Gravity
• Specific gravity can be defined as the ratio of the
weight of a substance to the weight of an equal
volume of water when both have the same
temperature
• Final weight can be measured in grams because 1 mL
of water weighs 1 g
– 1 mL, volume of water = 1 g, weight of water
– specific gravity of water = 1
specific gravity
=
weight of a substance
weight of an equal volume of water
Specific Gravity
• When the specific gravity is known, certain
assumptions can be made regarding the physical
properties of a liquid
– liquids that are viscous or have particles floating in them
often have a specific gravity higher than 1
– solutions that contain volatile chemicals (or something
that is prone to quick evaporation), such as alcohol, often
have a specific gravity lower than 1
Specific Gravity
Usually numbers are not written without units;
however, no units exist for specific gravity.
Therefore, you must label specific gravity carefully.
Calculation of
IV Rate and Administration
• IV flow rates are usually described as milliliters per
hour or as drops per minute (expressed as gtt/min)
– pharmacy usually uses milliliters per hour
– nurses sometimes prefer drops per minute
• The formula used to determine the rate in drops per
minute is as follows:
x gtt/min =
(volume of fluid ÷ delivery time in hrs) × (drop rate of administration set)
60 min/hr
Calculation of
IV Rate and Administration
Example:
• A physician orders 4000 mL of a 5% dextrose and
normal saline (D5NS) IV over a 36-hour period. If
the IV set will deliver 15 gtt/mL, then how many
drops must be administered per minute?
Begin by identifying the amounts to insert into the
equation.
volume of fluid
delivery time
drop rate of the administration set
=
=
=
4000 mL
36 hr
15 gtt/mL
Calculation of
IV Rate and Administration
x gtt/min
x gtt/min
=
=
x gtt/min
=
x gtt/min
=
(volume of fluid ÷ delivery time in hrs) × (drop rate of administration set)
60 min/hr
(4000 mL ÷ 36 hr) × (15 gtt/mL)
60 min/hr
111 mL/hr) × (15 gtt/mL)
60 min/hr
27.75 gtt/min, rounded to 28 gtt/min
Calculation of
IV Rate and Administration
• The number of hours that the IV will last can be
determined by dividing
– the volume of the IV bag (expressed in milliliters)
by
– the flow rate (expressed in milliliters per hour)
Calculation of
IV Rate and Administration
Example:
• A 1 L IV is running at 125 mL/hr. How often will a
new bag have to be administered?
Begin by converting 1 L to 1000 mL, and then divide the
volume by the volume per hour rate.
hours the IV will last
=
1000 mL
125ml/hr
= 8 hr
Discussion
What are some of the special areas of
calculations skills that are important for
technicians preparing IV solutions?
Discussion
What are some of the special areas of
calculations skills that are important for
technicians preparing IV solutions?
Answer: Skills for accurate conversion between
time and temperature systems, electrolyte
measurement, specific gravity determinations,
and infusion flow rate calculations are vital in IV
preparation and labeling.
Terms to Remember
• Fahrenheit
temperature scale
• Celsius temperature
scale
• electrolytes
• atomic weight
• molecular weight
•
•
•
•
•
millimole (mM)
valence
mole (M)
equivalent (Eq)
milliequivalent (mEq)