Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Sterilization and Disinfection
Chris Gross, Sanaz Dovell
INTRODUCTION:
This chapter will cover the topics of
decontamination, disinfection, and sterilization of
medical items, instruments and equipment
...
Our hope is that this
overview will set a foundation for understanding the
basics of decontamination, disinfection and
sterilization
...

Scope of problem:
1
...
Sterile
procedures require sterile instruments
...
Global access to safe surgery is limited by a
lack of access to sterilization
...
Resource-constrained settings may not have
reliable access to reliable electricity, making
the use of the autoclave, the WHO standard
for sterilization, difficult or impossible
...
Staff responsible for cleaning and sterilizing
the surgical equipment may have limited
training in sterile processing techniques
...
Approximately five billion people around the
world do not have access to much-needed
surgical care, and as much as 33% of
worldwide deaths are from surgically
treatable conditions
...
Lack of proper instrument sterilization has
led to post-surgical infection rates as high as
46%
...
Disposable kits, often thought of as a fix to
the problem, are not a viable solution because
they generate large amounts of biowaste that
is difficult to properly dispose of in lowresource areas
...
Cleaning is defined as removing any visible
soil
...

It is important to note that clean does not mean
sterile or disinfected
...
Decontamination is defined as removing
pathogenic organisms in order to make objects
safe enough to handle, use, or dispose of
...
Disinfection is the process of eliminating most
pathogenic organisms with the exception of
spores
...

4
...

5
...

6
...

7
...

8
...
Agents with ‘cide/cidal’
suffixes have some type of killing action that is
referenced in the name (i
...
Note that
germicides include both antiseptics and
disinfectants (remember disinfectant differs
from disinfection)
...
Antiseptic germicides are agents that can
be applied to living tissue (i
...

b
...
e
...
It is only used to disinfect
surfaces of inanimate objects because of
the risk of injury to tissue
...
Critical items are any items with a high chance
of transmitting an infection if that
instrument/item becomes contaminated (surgical
instruments, urinary catheters, implants)
...

10
...
These items should undergo
cleaning, followed by high-level disinfection
...
vumc
...
0 Unported License

Sterilization and Disinfection
Chris Gross, Sanaz Dovell
11
...
It is not
critical for these items to be sterile as long as they
do not come in contact with non-intact skin or
mucous membranes
...
We
will divide these factors into those that are internal to
the offending organism and factors that are external
to the offending organism
...
The
major types of organisms to consider for
disinfection, listed in order of most-to-least difficult
to eradicate, are prions, bacterial spores,
mycobacteria, non-lipid viruses, fungi, bacteria, and
lipid viruses
...
e lipid envelope or protein
capsid)
...

Organism quantity: Just as microbes grow at
an exponential rate, microbes also die at an
exponential rate
...
Proper cleaning with
water and detergent or enzymatic cleansers prior to
disinfection or sterilization can help to reduce the
microbial load and increase the effectiveness of the
disinfectant or sterilant
...
The biofilms
contain an extracellular matrix of proteins and
polysaccharides that encourage binding of more

bacteria both to the matrix and to each other,
providing stability, nutrition, and protection
...

Factors external to the organism
Surface factors: Smooth surfaces are easier
to disinfect while objects with rough surfaces are
more difficult because of the microscopic crevices
that can house microorganisms
...

A high organic load can block neutralizing agents
from reaching the surface, and biomaterial itself can
even inactivate agents such as bleach
...

Similarly, biofilms created by certain organisms
prevent agent contact with the organism itself,
thereby requiring both a longer contact time overall,
as well as higher agent concentration
...
For
example, a 70% isopropyl alcohol solution can kill
microorganisms in seconds because water both
allows the isopropyl alcohol to enter and penetrate
the entire cell and increases the contact time of the
disinfectant on the surface by slowing the rate of
evaporation of the isopropyl alcohol
...
Lastly, no
concentration of isopropyl alcohol effectively kills

OPEN MANUAL OF SURGERY IN RESOURCE-LIMITED SETTINGS
www
...
org/global-surgical-atlas
This work is licensed under a Creative Commons Attribution-ShareAlike 3
...

Duration of exposure: Time is also
important
...
For example, 70% isopropyl
alcohol can kill Mycobacterium tuberculosis in 5
minutes, whereas a 3% solution of phenol requires 23 hours to achieve the same effect
...
For example, an antimicrobial agent with
a D-value of one minute will kill 90 million cells in
a population of 100 million bacterial cells, leaving
10 million cells alive after one minute
...
Therefore,
sterilization, which requires eradication of all living
cells, viruses, and spores, can be achieved by certain
agents by increasing the duration of sterilization to
several D-values longer than the time needed to
theoretically reduce the microbial population down
to one cell
...

Proper protocols, including concentration and
exposure time, should be carefully considered and
adhered to when selecting the appropriate agent for
disinfection or sterilization
...

Certain disinfectants require a specific pH to be
active, while others cannot be used together because
they can neutralize one another
...
For an antimicrobial agent to effectively kill
microbes at the concentration and amount of time
determined by studies, the agent must remain in

contact with the item being disinfected for the entire
duration of time
...
tuberculosis in 5 minutes, if the
70% isopropyl alcohol being used evaporates within
30-60 seconds, then disinfection will not be
achieved
...

Broadly, the techniques can be divided into physical
methods (heat) and chemical methods
...

Failure to do so can significantly limit the
effectiveness of the sterilization process
...

Dry heat: Dry heat is used for sterilizing
metal objects, powders and glassware (all other
materials will melt)
...
Ovens are very
common in dental offices, and due to their simplicity,
they can be used in resource-constrained settings
...
vumc
...
0 Unported License

Sterilization and Disinfection
Chris Gross, Sanaz Dovell
Moist heat: Moist heat at high pressure, also
known as steam sterilization, is the simplest and most
frequently used method of heat sterilization
...
The
use of moist heat at high pressure raises the boiling
point of water to produce steam at a temperature that
can effectively kill spores and achieve sterilization
...
Unlike
dry heat, some hard plastics can be safely sterilized
in this manner, such as orthopedic implants or some
laparoscopic equipment
...
Standard
sterilization procedures use steam at 121 °C (250 °F)
at 15 psi (pounds per square inch) for 20-30 minutes,
which effectively kills all spores to achieve sterility
in a gravity displacement autoclave
...
Note that instruments packaged in kits with
multiple layers, as well as liquids, require longer
times in the autoclave
...
)

likely melt any plastics in the device (in this case sizers for a
knee arthroplasty set
...
It is
designed for use only in emergency situations, when
there is not enough time for a standard sterilization
cycle
...
Since items are unwrapped, contamination
can occur as soon as the item is removed from the
sterilizer, increasing the risk of infection
...

Filtration: Filtration can be useful if an IV
medication used during a procedure must be
sterilized, since heat or chemical sterilization will
denature drug compounds
...
2 μm will remove bacterial cells, but
not viruses
...

Irradiation: Ultraviolet radiation has poor
penetration, therefore, it can only be used to sterilize
surfaces
...
Therefore, sterilization via
irradiation is not recommended
...
Not all
chemicals can be used for sterilization, even with
increased exposure time, and careful consideration of
proper storage and disposal of these chemicals must
be taken when selecting the appropriate agent to use
...
vumc
...
0 Unported License

Sterilization and Disinfection
Chris Gross, Sanaz Dovell
spores
...
25% concentration (0
...
As mentioned
previously, organic matter can inactivate bleach, so
proper cleaning to remove biomaterial prior to the
use of bleach is essential for proper disinfection
...


Iodine: Iodine often comes in the form of a
tincture mixed with an alcohol or as an iodophor
(iodine mixed with a solubilizing agent)
...
For iodine to become
effective, it must be properly diluted (~ 10%
solution), and have at least 30 seconds of contact
time with the object
...

Alcohols: Isopropyl and ethyl alcohols are
the most common type of alcohol used for low-level
disinfection, but not sterility
...
These agents work well against most gram
negative and gram positive bacteria, and are a
common option in severely resource-limited settings
...

Chlorine: Chlorine and its derivative
compounds are halogens that are commonly used for
disinfection, as it can kill all microbes but cannot kill

Left: sodium percarbonate, tetraacetyl- ethylenediamine and
N-alkyl(C12-14)-N-benzyl-N, N-dimethylammonium chloride
tablets
...


Enzymatic solutions: Enzymatic solutions
use various proteases to break down biomaterial at
neutral pH
...
For this reason, enzymatic
solutions are ideal for endoscopic equipment
...
The enzymes used in these cleaners break
down proteins on any surface it comes in contact
with; therefore, care must be taken while using these
cleaners to avoid skin contact, accidental ingestion,
contact with mucous membranes, or inhalation if
aerosols are used
...
vumc
...
0 Unported License

Sterilization and Disinfection
Chris Gross, Sanaz Dovell
Enzymatic cleaner, a mixture of protease, amylase, lipase,
carbohydrase, and “proprietary enzymes
...


Glutaraldehyde: This solution, also known as
“Cidex” is a chemical solution that can be used for
cold disinfection
...
Items are submerged in a ≥2%
solution for 20-90 minutes at 20 oC to achieve highlevel disinfection or 10 hours to achieve sterility
...
Note that
this solution can be quite toxic, therefore proper PPE
and procedural care must be taken to avoid inhalation
or skin contact
...


2% Glutaraldehyde solution: this is not to be diluted
...
5% solution for 30
minutes at 20 oC
...
This solution can
be reused for 21 days
...
2% at
o
50-56 C can be used to achieve sterility when items
are submerged for 12 minutes
...
35%
hydrogen peroxide with 0
...
Increasing exposure time to 3 hours is
effective for sterilization
...

Ethylene oxide: This is a poison gas that very
effectively sterilizes laparoscopic equipment as well

as plastic materials since it does not use heat or
moisture
...
4 oF) in eight hours and at 54 oC (129
oF) in four hours
...
In addition, this gas is explosive
...

PRACTICE
Given that this topic is vast and
sprawling, focus will be placed on a few topics
related to common practices: general operating room
layout for optimal sterilization, a case-based walk
through of general steps to be taken after an
operation, and finally a few tips for operating
common sterilization tools
...

Operating room and sterilization area design
...
Each of these distinct
zones are necessary within your operating facility to
keep operations going
...
It has a sink
used for mechanical removal of any bioburden, via
high pressure water, air, or manual scrubbing
...
e
enzymatic cleaner or glutaraldehyde
...


OPEN MANUAL OF SURGERY IN RESOURCE-LIMITED SETTINGS
www
...
org/global-surgical-atlas
This work is licensed under a Creative Commons Attribution-ShareAlike 3
...


Packing area: This area, which is separate
from the decontamination area, has large surfaces
such as tables where disinfected instruments can be
sorted, packed and wrapped
...


In the packing area, clean and dry instruments are wrapped for
sterilization
...
) Once
they are dry they are transferred to this area for wrapping
...
Ideally, multiple
autoclaves would be operating to allow for a more
efficient sterilization process, as autoclave cycles are
time-consuming and require an adequate drying time
before sterile packs can be handled and transported
...


Sterile supply room: After sterilization has
been achieved, the items must be properly stored
...
Moisture encourages microbial growth,
and microbes can even travel to the inside of the
sterile packs causing contamination
...


Case-based example:
Sterilization to Storage

Decontamination

to

1
...
vumc
...
0 Unported License

Sterilization and Disinfection
Chris Gross, Sanaz Dovell
At the conclusion of an operation, all
instruments (including unused instruments) must be
handled as if they are contaminated and moved to the
decontamination area
...
Any fluids from
this cart can be offloaded into a fluid hopper once in
the decontamination area
...

If possible, forceps should be used to empty the
instruments from the cart or, more simply,
instruments can be dumped out onto a towel
...
Any
biohazard or soiled linens should be placed in the
appropriate receptacle
...


A note about instruments: Stainless steel
is not actually stainless and can experience corrosion
from biological and chemical liquids
...
If
immediate cleaning is not possible, organic matter
such as blood or tissue can be prevented from drying
on the surface of the instrument by submerging dirty
instruments in water containing enzymatic detergent
...

The leading cause of pitting/stained surgical
equipment is moisture (pus, blood, cleaning
solutions)
...
Make note of any instrument in disrepair
and set it to the side
...
They are
placed in an enzymatic solution to soak in case any unknown
contamination occurred during the surgery
...
Cleaning while in decontamination area
All reusable instruments, tubes, suction
devices, and packing trays used during an operation
must be cleaned thoroughly prior to disinfection or
sterilization
...
The general workflow is
to disassemble and sort, spray/soak, scrub, rinse, dry,
lubricate, and then disinfect or sterilize
...
vumc
...
0 Unported License

Sterilization and Disinfection
Chris Gross, Sanaz Dovell
Disassembly: All equipment or devices with
removable parts should be disassembled according to
the manufacturer’s guidelines to facilitate removal of
all organic debris and allow better access to all parts
of the instrument by the disinfectant or sterilant
...
Sorting equipment into groups
that will be processed in the same way helps to
streamline the overall process
...
Items can then be
soaked in an enzymatic cleaning solution with a
neutral pH for 10-20 minutes to help remove debris
from hard-to-reach places and make the cleaning
process easier and more effective
...


gently used, with care being taken to prevent scoring
or scratching of metal (which creates crevices for
organisms to hide, grow, and form biofilms)
...
) The
needle holder in her left hand has been opened and she is
scrubbing the rough surface inside its jaws with a heavy brush
...


Scrub: If available, an ultrasonic cleaner
should be used to mechanically scrub items after
spraying down and soaking them
...
It is important to
note that low-mineral water (distilled or reverse
osmosis water) is essential for cleaning instruments
because damage can be caused by high mineral
content water
...
A nylon brush can be used to
manually scrub organic debris from instruments
...
Examples include
penetrating towel clips (shown here) osteotomes, and other
sharp instruments
...
Residual detergent can react with
sterilizing solutions and disinfectants and hinder the
disinfectant or sterilization process
...
vumc
...
0 Unported License

Sterilization and Disinfection
Chris Gross, Sanaz Dovell
Dry: After thoroughly rinsing, equipment
must then be allowed to completely dry, either by
hand or air-dried, for maximal efficacy of chemical
disinfectants
...

Here, cleaned but still wet instruments are passed through a
window from the decontamination area to the sterilization area
to dry before being wrapped for sterilization
...


Lubricate: After the instrument has been
cleaned of visible debris, a process called gross
decontamination, surgical instrument lubricant
should be applied to any mobile joints or hinges
before sterilization
...
Instead, water soluble
lubricants that are steam-permeable should be
used
...

Critical medical and surgical items should be
packaged for sterilization
...
A technician then loads them into a sterile container
...
High-level disinfection
...

Lengthy submersion may cause damage, especially
to finer instruments
...
vumc
...
0 Unported License

Sterilization and Disinfection
Chris Gross, Sanaz Dovell

Laparoscopic instruments that have been treated as above and
placed in a sterile container
...


When packing surgical instruments into
sterilization pouches, ensure that the instruments are
open and in their UNLOCKED position, which
allows steam to reach all active surfaces, and
prevents cracks from heat expansion
...
Ensure that any sharp
tips are covered, yet are covered in a way that still
allows steam to penetrate the covering
...
Pouches should
not be overpacked with instruments, and there should
be adequate room in the pouch for steam to reach the
surfaces of the instruments
...


Avoid using any benzyl ammonium chloride
solutions with instruments that have tungstencarbide inserts
...


The technician here is using a combination of paper and cloth
...


3b
...
First, a pack must be created
...

By creating smaller packs that can be added together
Here, he has secured the wrapping with both tape and string
...

can be avoided, which in turn minimizes repairs
...
vumc
...
0 Unported License

Sterilization and Disinfection
Chris Gross, Sanaz Dovell

The smaller strip of tape with the date on it is autoclave tape:
the fine white stripes on it will turn black when exposed to
sufficient temperature and pressure to sterilize the instruments
...
The name of the instrument tray is noted on the
lower part
...
Source: Viv Rolfe,
CC BY-SA 4
...
org/licenses/by-sa/4
...
Most commercial pressure
decontaminated, but non-sterilized packs have been
cookers can sterilize effectively since they can
created, the pouches may be placed into the
achieve the pressure, temperature, and time
autoclave to be sterilized
...
Store-bought, or home
from circulating throughout the chamber
...

most are unable to reach the temperature and
Depending on the model of the autoclave, once the
pressure requirements needed to kill spores
...
The
Pot,” home pressure cooker, but it required a duration
door should not be opened fully as condensation can
of 150 minutes to kill the spores in the test sample
...
After running the dry
account when operating in low-resource settings
cycle, sterile tongs should be used to remove the dry
where electricity may not be reliable
...

has created a pressure cooker, the EcoClave, that can
Storage after sterilization: The sterilized
sterilize instruments in 30 minutes using burning
packs should be completely dry on the wire racks
wood as the fuel source, making it a potentially ideal
before moving to sterile storage
...
)
dry and closed space such as a cabinet (provided the
When operating any pressure cooker, all
pack remains intact and dry)
...
First, all instruments must
Sterilization Tips and Procedures for Various
be cleaned and decontaminated as discussed
Appliances
previously
...
Commercial or Domestic Pressure Cookers
cooker and the items being processed
...
vumc
...
0 Unported License

Sterilization and Disinfection
Chris Gross, Sanaz Dovell
or bags, just like when using an autoclave
...
When placing items inside the cooker,
adequate spacing should be maintained to allow
proper circulation (just like an autoclave)
...
5 cm from the bottom of the pot for steam
production
...
At this point, the external heat
source should be applied to the pressure cooker,
either wood fire, gas stove, or electric burner
...
After heating has
started, steam should be allowed to exhaust for about
four minutes before closing the outlet
...
When the pressure has reached the green
area, or 15 psi, sterilization has begun
...
After sufficient processing, the
pressure cooker should be removed from its heating
source and depressurized by opening the steam
outlet
...
Once the gauge has reduced to zero, the
pressure cooker can be opened by lifting the lid in a
direction that is away from any person’s face or
body
...

Once items are removed, they must be dried
properly before storing
...
Once dry, these
items can be placed in a dated and labeled ziplock
bag
...
In fact, they may fail and rupture
...

2
...


When using autoclaves, one of the most
important components of maintenance is regular use
and testing
...
Autoclave pouches
that can be penetrated by steam should be used, and
the packs should not be stacked on top of one
another
...
If
liquids are to be sterilized, a secondary container
should be used to house the primary container to
catch any spills
...

Considerations for special equipment
This chapter has focused on general
instructions for routine sterilization of common
surgical instruments
...

Endoscope
sterilization:
Endoscope
sterilization is a unique process, requiring different
steps than a metal instrument like a clamp
...
vumc
...
0 Unported License

Difference:
S
...

1
...


2
...


Kills most microorganisms, but may not Destroys

all

microorganisms,

eliminate all viruses, fungi, or bacterial including bacteria, viruses, fungi and
spores
3
...


Disinfection results in reduction of The medium is made completely free
microbial load to a safe level but it does from all microbes
...


4
...


5
...


Chemical agents such as phenol, alcohol, Combination of heat, irradiation, high
chlorine and iodine are commonly used as pressure,
disinfecting agents
...

Methods of sterilization include use of
pressurized

steam

(autoclaving),

hydrogen peroxide gas, ethylene oxide
(EtO) gas, ionizing radiation (typically
used for medical equipment), dry heat
cabinets (for medical instruments),
infrared

radiation

and

advanced

filtration
...


Wounds are disinfected
...


7
...


use
...


1

8

---