Cleaning

Cleaning, Disinfection, and Sterilization of Medical Equipment

Cleaning, Disinfection, and
Sterilization of Medical
Equipment

Introduction
Medical equipments and surgical instruments are examples of devices that
are essential to the care of patients; however, because they typically are
designed for reuse, they also can transmit pathogens if any of the steps
involved in reprocessing, cleaning, disinfection, or sterilization are inadequate
or experience failures. Because the vast majority of pathogens are present in
organic matter, e.g. visible soil, the first step in reprocessing, cleaning, is the
most important. Any failure to remove soil at this point creates the potential for
transmission of infection as the efficacy of subsequent disinfection or
sterilization will be compromised. Decontamination is the process by which
microorganisms are removed or destroyed in order to render an object safe. It
includes: 31
• Cleaning,
• Disinfection, and
• Sterilization.
All hospitals and health care facilities should have a decontamination policy
and help staff to decide what decontamination process should be used for
which item of equipment. 11

Processing Instruments
Definition of Terms
Antimicrobial agent: Any agent that kills or suppresses the growth of
microorganisms.

Biocide: A chemical or physical agent that kills all living organisms,
pathogenic and nonpathogenic.

Biologic indicator (BI): A standardized preparation of bacterial spores on or
in a carrier serving to demonstrate whether sterilizing conditions have been
met. The type of spore varies by type of sterilization.

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Cleaning: Cleaning is a process, usually involving detergent or enzymatic
presoak that removes foreign material (e.g. dirt or microorganisms) from an
object. Cleaning is the most essential step in reprocessing instruments and
equipment.

Decontamination: The use of physical or chemical means to remove,
inactivate, or destroy pathogens on a surface or item to the point where they
are no longer capable of transmitting infectious particles and the surface or
item is rendered safe for handling, for use, or for disposal. Decontamination
could comprise cleaning, disinfection or sterilization as appropriate.

Disinfection: Any process, chemical or physical, that destroys pathogens
such that an item is safe to handle for its intended use.

Disinfectant: A disinfectant is a chemical agent that destroys most pathogens
but may not kill bacterial spores. Chemical disinfection should only be used if
heat treatment is impractical or if it may cause damage to the equipment.
There is a broad spectrum of chemical disinfectants that have different anti-
microbial activities. Most of them do not necessarily kill all microorganisms or
spores that are present on an inanimate object but instead reduce the number
of microorganisms to a level that is not harmful to health. Disinfectants are
used on inanimate objects only and not on living tissue. Chemicals used to kill
microorganisms on skin or living tissue are known as antiseptics.
The broad category of disinfection may be subdivided into high-level,
intermediate-level, and low-level disinfection according to the anti-microbial
activity of the disinfectant.

Low level disinfectant (LLD): LLD is an agent that destroys all vegetative
bacteria (except tubercle bacilli), lipid viruses, some nonlipid viruses, and
some fungus, but not bacterial spores.

Intermediate-level disinfectant (ILD): ILD is an agent that destroys all
vegetative bacteria, including tubercle bacilli, lipid enveloped and some
nonlipid enveloped viruses, and fungus spores, but not bacterial spores.

High-level disinfectant (HLD): A high-level disinfectant is a chemical or
physical agent or process that is capable of killing some bacterial spores
when used in sufficient concentration, temperature, and under suitable
conditions. It is therefore expected to be effective against vegetative bacteria,
fungi, viruses and other microorganisms. It does not kill high numbers of
bacterial spores.

Note:
Some of the chemicals used for disinfection can also be used as chemical
sterilants which can kill bacterial spores. Contact with the heat-sensitive items
normally requires prolonged exposure times. For more details about chemical
sterilants see the sterilization section in this chapter.

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Lipid virus: A virus whose core is surrounded by a coat of lipoprotein whose
disruption renders the virus non-infectious. Viruses included in this structural
category are generally easily inactivated by many types of disinfectants,
including low level disinfectants. Also referred to as enveloped viruses.
Examples are HIV, herpes, HCV, HBV and myxoviruses.

Nonlipid virus: A virus whose nucleic acid core is not surrounded by a lipid
envelope. These viruses are generally more resistant to inactivation by
disinfectants. These are also referred to as hydrophilic viruses as coxackie,
enteroviruses, etc.

Pasteurization: A process developed by Louis Pasteur of heating milk, wine,
or other liquids to 60 C to 100 C for approximately 30 minutes to reduce or to
significantly kill the number of pathogenic and spoilage organisms. The higher
the temperature, the shorter the time needed. Also termed as “heat
disinfection”.

Pyrogens: Fever producing agents or substances, e.g., endotoxins from the
outer membranes of gram negative bacteria.

Spaulding classification: A strategy developed by Dr. Earle H. Spaulding
for reprocessing contaminated medical devices. The system classifies devices
as critical, semicritical, or noncritical based on the risk from contamination of a
device to a patient. Three different levels of disinfection are applied based on
this risk scheme. For example a needle used for entry into tissue is critical
and needs to be sterile. A speculum (endoscopes) has contact with mucous
membranes and therefore needs to be cleaned and then undergo high-level
disinfection. A blood pressure cuff has contact with intact skin and only needs
cleaning.

Sterilant. An agent that destroys all viable forms of microbial life to achieve
sterilization.
Sterilization methods remove or destroy all forms of microbial life including
bacterial spores by either physical or chemical processes. It is recommended
that any instrument or equipment classified as critical that comes in contact
with the blood stream or with subdermal tissues be cleaned and sterilized in
between each use. 78 Sterilization is accomplished principally by steam under
pressure, by dry heat, and by chemical sterilants.
The choice of the method for sterilization depends on a number of factors
including the type of material that the object to be sterilized is made of, the
number and type of microorganisms involved, the classification of the item,
and availability of sterilization methods.

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Table 22: Decreasing order of resistance of microorganisms to disinfection
and sterilization and the level of disinfection or sterilization. 79
Types of organisms Level
Prions (e.g., Creutzfeldt-Jakob - Sodium Hydroxide
Disease) soap for one hour
Resistant - 18 min prevacuum
steam sterilization
(134-137C)
Bacterial spores (e.g. Clostridium
teteni, Clostridium difficile) Sterilization
Coccidia (Cryptosporidium)
Some spores generated by spore
forming bacteria High Disinfection

Mycobacterium tuberculosis Intermediate
Disinfection
Nonlipid or small viruses (polio,
coxsackie)
Susceptible Fungi (e.g., Aspergillus, Candida)
Vegetative bacteria (S. aureus, P. Low Disinfection
aeruginosa)
Lipid viruses (HIV, HBV, HCV,
herpes, myxoviruses)

The Instrument Processing (Decontamination Steps)
There are two steps to processing items that are used during clinical and
surgical procedures. Cleaning is the first and the most important step.
Cleaning is followed by either sterilization or disinfection and by immediate
use or proper storage of the item.

Fig. 21: Decontamination Steps

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Risks of Infection from Equipment
The risks of infection from equipment may be classified into three categories.
Placing instruments and equipment into one of the following categories can be
helpful in choosing the proper level of disinfection or sterilization needed in
order to protect the patients and the health care personnel. 11

Low risk (noncritical items)
Noncritical items are items that come into contact with normal and intact skin
as stethoscopes or with the inanimate environment (e.g. walls, floors, ceilings,
furniture, sinks, etc.). Cleaning with a detergent and drying is usually
adequate. Stethoscopes are usually cleaned and in rare cases they should be
disinfected if used on infectious patient or highly susceptible patient.

Intermediate risk (semi-critical items)
Semi-critical items are items that do not penetrate the skin or enter sterile
areas of the body but that are in close contact with mucous membranes or
with non-intact skin. Cleaning followed by HLD is usually adequate. Examples
include respiratory equipment, flexible endoscopes, laryngoscopes, specula,
endotracheal tubes, thermometers, and other similar instruments.

High risk (critical items)
High risk items are items that penetrate sterile tissues such as body cavities
and the vascular system. These items are called critical items because of the
high risk of infection if such an item is contaminated with any microorganism
before penetrating the tissue. Cleaning followed by sterilization is required.
High-level disinfection may sometimes be appropriate if sterilization is not
possible, e.g., flexible endoscopes. Examples of high-risk items include
surgical instruments, intra-uterine devices, vascular catheters, implants, etc.

Single Use Items
These items may be used in critical, semi-critical, or noncritical areas;
however, they are single use items that are prepackaged with the appropriate
level of disinfection or sterilization and are disposed of after a single use.
Examples include gloves, needles, syringes, and tongue depressors.
The figure below shows the relationship between types of items and the
sterilization or disinfection that they must undergo.

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Fig. 22: Relation between type of item & its decontamination

Cleaning
Cleaning is the removal of all foreign material (dirt and organic matter) from
the object being reprocessed. Two key components of cleaning are friction to
remove foreign matter and fluids to remove or rinse away contamination.
Thorough cleaning will remove most organisms from a surface and should
always precede disinfection and sterilization procedures. If instruments and
other items have not been cleaned, sterilization and disinfection may not be
effective because microorganisms trapped in organic material may survive
sterilization or disinfection. 80
Cleaning is normally accomplished by the use of water, detergents and
mechanical actions. Detergent is essential to dissolve proteins and oil that can
reside on instruments and equipment after use.
Cleaning may be manual or mechanical. Mechanical cleaning includes
ultrasonic cleaners or washer/disinfectors that may facilitate cleaning and
decontamination of some items and may reduce the need for handling. 31
The solution used most often to clean is an enzymatic presoak (protease
formula that dissolves protein). Alternatively a detergent can be used.
Detergents lower surface tension and lift dirt or oil away from the device.
Studies have shown that thorough cleaning alone can provide a 10 000 fold
reduction in contaminant microbes from endoscopes. 79, 81, 82 Cleaning can be
very effective in removing microbial contaminants from surgical devices.

Mechanical Cleaning
Most modern sterilization units are automated and there is minimal handling
of dirty equipment by staff. The equipment is placed in trays ready for
washing:
• Washing machine. The washing machine gives a cold rinse
followed by a hot wash at 71 °C for 2 minutes. This is followed by a
10-second hot water rinse at 80-90 °C and then by drying by a
heater or a fan at 50-75 °C.

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• Washer/disinfector. The washer/disinfector is used for anesthetic
equipment. It runs a 45-minute cycle of washing and cleaning plus a
2-minutes cycle with water at 80-100 °C and with a detergent
solution.
• Ultrasonicator. The ultrasonicator is a sophisticated and expensive
but extremely efficient piece of equipment. It uses high-power
output of 0.44 W/cm3 and dislodges all organic matter.

Manual Cleaning
All items requiring disinfection or sterilization should be dismantled before
cleaning. Cold water is preferred; it will remove most of the protein materials
(blood, sputum, etc.) that would be coagulated by heat and would
subsequently be difficult to remove. The most simple, cost-effective method is
to thoroughly brush the item while keeping the brush below the surface of the
water in order to prevent the release of aerosols. The brush should be
decontaminated after use and should be dried.
Finally, items should be rinsed in clean water and then should be dried. Items
are then ready for use (noncritical items) or for disinfection (semi-critical
items) or for sterilization (critical items).
Manual cleaning is necessary when:
• Mechanical cleaning facilities are not available;
• Delicate instruments have to be cleaned;
• Complex instruments need to be taken apart to be cleaned;
• Items with narrow lumens need to be cleaned (endoscopes).
Manual or hand-cleaning must be done with extreme caution. The staff should
follow the set procedure:

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Steps for cleaning

1. Wear heavy-duty rubber gloves, a Fig. 23: Steps for cleaning
plastic apron, eye protection, and
mask during cleaning.

2. Soak the instruments in normal tab
water containing a detergent.

3. Scrub instruments and other items
vigorously to completely remove all
foreign material using a soft brush or
old toothbrush, detergent, and water.
Hold items under the surface of the
water while scrubbing and cleaning to
avoid splashing. Disassemble
instruments and other items with
multiple parts, and be sure to brush in
the grooves, teeth, and joints to items
where organic material can collect
and stick.

4. Flush through lumens with an adapted
water jet.

5. Rinse items thoroughly with clean
water to remove all detergent. Any
detergent left on the items can reduce
the effectiveness of further
processing.

6. Inspect items to confirm that they are
clean.
7. Allow items to air dry or dry them with
a clean towel if chemical disinfection
is going to be used. This is to avoid
diluting the chemical solutions used
after cleaning. Items that will be high-
level disinfected by boiling or
steaming do not need to be dried.80

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Remember when cleaning:
• Do not use hand soap to clean instruments because fatty acids in the soap
react with hard water to leave a soap scum on the instruments.
• Always wear utility gloves, a mask, and eye protection when cleaning
instruments.
• Do not use abrasive materials that scratch or pit instruments. Scratches,
pits, or grooves can harbor microorganisms and promote corrosion.
Automatic washing machines are preferable to washing by hand.

Soaking of Instruments Prior to Cleaning
Sometimes the level of contamination of the instrument makes it necessary to
soak items prior to cleaning (e.g. instruments in operating theatres). A deep
container, e.g. a bucket, containing a wire-mesh basket can be filled with
water and detergent. The instruments are placed in the wire basket, agitated
for 3-5 minutes, and then lifted out. The basket is overturned onto a table or
tray in order to separate the instruments prior to cleaning, packing and
autoclaving.
Disinfection
Disinfection can be carried out either by thermal or chemical processes.
Thermal disinfection is preferred whenever possible. It is generally more
reliable than chemical processes, leaves no residues, is more easily
controlled, and is non-toxic. Heat sensitive items have to be reprocessed with
a chemical disinfectant.
Organic matter (serum, blood, pus or fecal material) interferes with the
antimicrobial efficiency of either method. The larger the number of microbes
present, the longer it takes to disinfect. Thus scrupulous cleaning before
disinfection is of greatest importance.

High Level Disinfection (HLD) - Semi-critical Items
There are three types of HLD:
• Disinfection by boiling
• Moist heat at 70-100°C
• Chemical disinfection
Note:
When sterilization is not available, HLD is the only acceptable alternative for
instruments and other items (=semi-critical items) that will come into contact
with the bloodstream or tissues under the skin.
Boiling is HLD, not sterilization. Flaming is not an effective method of HLD
because it doesn’t effectively kill all microorganisms.

HLD by Boiling
High-level disinfection is best achieved by moist heat such as boiling in water
(100°C for one minute holding time), which kills all organisms except for a few

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bacterial spores. It is important to note that boiling equipment items in water
will not achieve sterilization.

Steps of boiling: Fig. 24: Steps for boiling

1. Clean all items to be high-level
disinfected.

2. Open all hinged instruments and
disassemble those with sliding or multiple
parts. Place bowls and containers upright so
they fill with water. Make sure that all items
are completely submerged because water
must touch all surfaces for HLD to be
achieved.

3. Cover the pot or close the lid on the boiler
and bring the water to a gentle, rolling boil.

4. Once the water is in a rolling boil, start
timing for at least 1 minute. Use a timer or
make sure to record when the boiling
begins. From this point on do not add or
remove any water or items.

5. Lower the heat to keep the water at a
gentle, rolling boil. Too vigorous boiling may
damage items and will speed the
evaporation of the water.

6. After 1 minute holding time, remove items
using dry, high-level disinfected pickups.
Place items to air-dry on a high-level
disinfected tray or on a high-level
disinfected container that is away from dust
and insects and in a low-traffic area. Never
leave boiled instruments and other items in
water that has stopped boiling; they can
become contaminated as the water cools.

7. Store the dry items in a high-level
disinfected and covered container and use
items immediately or keep in a covered, dry,
high level disinfected container and use
within one week. 92

8. The boiler should be emptied and dried
daily.

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Note:
Addition of a 2% solution of sodium bicarbonate elevates the temperature and
helps to prevent corrosion of the instruments and utensils.

Tips for HLD by boiling:
• Instruments and other items must be completely covered with water. Open
all hinged instruments and other items and disassemble those with sliding
or multiple parts.
• Always boil for 1 minute. Start counting the one minute when the water
reaches a rolling boil. If you forget to start timing the HLD procedure, start
timing at the point at which you realize that you did not begin timing.
• Do not add anything to or remove anything from the pot/boiler once boiling
begins. 92
• A white, scaly deposit may be left on instruments and other items that
have been boiled frequently and on the pot/boiler itself. These are lime
deposits caused by lime salts in the water.
• To minimize lime deposits:
• Add some vinegar to the water to remove deposits from instruments, other
items, and the inside of the pot/boiler.
• Boil the water for 10 minutes at the beginning of each day that the
pot/boiler is used; this will precipitate the lime (make it come out of the
water and settle on the bottom or sides of the pot/boiler instead of on the
instruments or other items) before the instruments or other items are
added.
• Use the same water throughout the day, adding only enough to keep the
instruments and other items below the surface.
• Drain and clean out the pot/boiler at the end of each day that it is used. 92.
• A high-level disinfected tray or container can be prepared either by:
- Boiling it for 1 minute and drying thoroughly, or
- Filling it with a 0.5% chlorine solution and letting it soak for 20 minutes,
draining the chlorine solution, and rinsing thoroughly with boiled water.
• Stainless steel containers are preferred as containers for HLD.

HLD by mechanical - thermal disinfection
Disinfection by hot water can also be performed in specially constructed
washing machines (e.g., for linen, dishes and cutlery). In these machines the
processes of cleaning, of hot water disinfection, and of drying are combined in
a very effective procedure, providing some items ready for use (e.g.,
respiratory circuits) or safe to handle (e.g. surgical instruments). The thorough
initial rinsing and washing removes most of the microorganisms and shorter
disinfection times. If machines are used they should be regularly maintained
and checked for efficacy.

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Low to high-level disinfection is achieved depending on type of machine and
complexity of the items. 31

Chemical HLD
Before deciding to use a chemical disinfectant, consider whether a more
appropriate method is available. Chemical disinfection is used most
commonly for heat-labile equipment (e.g. endoscopes) where single use is not
cost effective.
A limited number of disinfectants can be used for this purpose. e.g.:
• Glutaraldehyde 2% for 20 min.,
• Hydrogen peroxide 6% - 7.5% for 20 – 30 min.,
• Peracetic acid 0.2-0.35% for 5 min.
• Ortho-phthalaldehyde (OPA) for 5-12 min.

The object must be thoroughly rinsed with sterile water after disinfection. If
sterile water is not available, freshly boiled water can be used. After rinsing,
items must be kept dry and stored properly.

Steps:
1. Clean and dry all items to be high-level disinfected. Water from wet
instruments and from other items dilutes the chemical solution, thereby
reducing its effectiveness.
2. When using a glutaraldehyde solution: Preparations of glutaraldehyde
are non-corrosive to metals and other materials and inactivation by
organic matter is very low. Alkaline solutions require activation; once
activated they remain active for at least 2 weeks depending on the
frequency of use. If the solution is not activated prepare it in a sterile
container by following the manufacturer’s instructions. Fresh solution
should be made each day (or sooner, if the solution becomes cloudy).
3. If using a previously prepared solution, use an indicator strip to
determine if the solution is still effective. If preparing a new solution, put
it in a clean container with a lid and mark the container with the
preparation date and expiration date.
4. Open all hinged instruments and other items and disassemble those
with sliding or multiple parts; the solution must contact all surfaces in
order for HLD to be achieved.
5. Place all items in the solution so that they are completely submerged.
Place bowls and containers upright, not upside-down, so that they fill
with the solution.
6. Cover the container and allow items to soak for 20 minutes. During this
period, do not add or remove any items from the container. Monitor the
time.

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7. Remove the items from the container using, dry, high-level disinfected
pickups (e.g., forceps).
8. Rinse thoroughly with boiled water to remove the chemical residue that
is left on items. This residue is toxic to skin and to tissues.
9. Place items to air-dry on a high-level disinfected tray or in a high-level
disinfected container before use or storage. Use instruments and other
items immediately or keep them in a covered, dry, high-level disinfected
container and use within one week. 92

Notes on Disinfectants:
• There is no all purpose disinfectant. The best housekeeping disinfectants
are not the best instrument disinfections. Example, 2% gluteraldehyde is a
good instrument and equipment disinfectant but it is inappropriate for the
floors and walls.
• Environmental sampling to verify the effectiveness of disinfectants is of no
value.
• For selection of a disinfectant, the level of disinfection required should be
determined according to the contamination likely to be present.
• Antiseptics should never be used for HLD. They are for use on the skin
and mucous membranes, not on inanimate objects.Disinfectants should
always be stored in a cool, dark place; they should never be stored in
direct light or excessive heat.

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Table 23: Comparison of the characteristics of chemical sterilants used primarily as
high–level disinfectants.
OPA HP/PA (7.35%
HP(6%-7.5%) PA (0.2%) Glut (≥2.0%)
(0.55%) 0.23%)
20-30m @ 5m@40°C 20m 12m 15m
HLD Claim
20°C
Sterilization 6h @20° 10 m@40°C 10 h None 3h@20°C
Claim
(sporicidal
effect)
Activation No No Yes (alkaline glut) No No
21 days Single use 14-30days (acid 14 d 14 d
Reuse Life1
glut-1yr)
Shelf Life 2y 6 mo 2y 2y 2y
Stability2
Disposal None None Local3 Local3 None
Restrictions
Materials Good Fair Excellent Excellent No data
Compatibility
Yes (6%) No Yes (1.5% or Yes (0.3% No
Monitor MEC4
higher) OPA)
Serious eye Serious eye Respiratory Eye Eye damage
damage & skin irritant,
Safety
(safely damage stains skin
glasses) (conc soln) 5
Manual or Automated Manual or Manual or Manual
Processing
automated automated automated
Organic material Yes Yes Yes Yes Yes
resistance

Abbreviations: HLD= high-level disinfectant; HP= hydrogen peroxide; PA= peracetic
acid; glut=glutaraldehyde; HP/PA= hydrogen peroxide and paracetic acid; OPA=
ortho-phthaladehyde; m=minutes; h=hours; NA=not applicable; TWA=time-weighted
average for a conventional 8-hours workday.
1
number of days a product can be reused as determined by re-use protocol
2
time a product can remain in storage (unused)
3
no U.S. EPA regulations but some states and local authorities have additional
restrictions
4
MEC= minimum effective concentration is the lowest concentrated of active
ingredients at which the product is still effective
5
Conc soln=concentrated solution.

Note :
Concentration of used disinfectant and contact time should be revised
because different companies provide different concentrations for a single
disinfectant, so manufacture’s instructions should be carefully read before use
of any disinfectant.

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Table 24: Disinfectant properties (High level disinfection)

Properties * Antimicrobial activity
Inactivation Viruses
Corrosive/ Irritant/Sen Myco- Other
Disinfectant Stability Organic Spores
Damaging -sitizing bacterial Bacteria E NE
matter
Moderately
Glutaraldehyde 2% No Good Good ****** Good Good Good
(14-28 No Yes ***
(20 min.) (fixative) ** 3h 20 min. 5-10 min. 5-10 min. 5-10 min.
days)
Peracetic acid 0.2- No
No Slight Slight Good Good Good Good Good
0.35% (5-10 min.) (< 1 day)
Alcohol **** 60-90%
Yes
(ethanol or Yes
(in closed Slight No None Good Good Good Moderate
isopropanol) (fixative) **
container)
(10 min.)
Peroxygen
Moderately
compounds 6-7.5% Yes Slight No Variable Variable Good Good Variable
(7 days)
(20-30 min.)
Chlorine releasing
No
agents Yes Yes Yes ***** Good Good Good Good Good
(< 1 day)
200-1000 PPM
Clear soluble Good to
Yes No Slight Yes None Good Moderate Poor
phenolics ******* moderate
Quaternary
ammonia Yes Yes No No None Variable Moderate Moderate Poor
compounds ********

* Use protective clothing when handling disinfectants
** Poor penetration
*** Should only be used in a well ventilated room
**** Flammable
***** In high concentration
****** Less active against M. avium intracellulare
******* Potentially toxic
******** Diluted solutions may allow the growth of Gram-negative bacilli
E = enveloped
NE = non enveloped

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Sterilization
Sterilization is a process which achieves the complete destruction or killing of all
microorganisms, including bacterial spores.
Sterilization is principally accomplished by: 31
• Steam under pressure (Autoclaving)
• Dry heat (Hot Air Oven)
• The use of chemicals such as ethylene oxide gas (which is mainly used in
industry) or other low temperature methods (e.g. hydrogen peroxide gas
plasma).

Note:
• Boiling and flaming are not effective sterilization techniques because they do
not effectively kill all microorganisms.
• Large health care facilities should have more than one type of sterilization
system in case of power outage, equipment failure, or shortage of supplies. 78

Pressure Steam Sterilization (Autoclaving)
Steam sterilization is the most common and most preferred method employed for
sterilization of all items that penetrate the skin and mucosa if they are heat
stable. Steam sterilization is dependable, non toxic, inexpensive, sporicidal, and
has rapid heating and good penetration of fabrics.

Method
The steam must be applied for a specified time so that the items reach a
specified temperature. For unwrapped items:
• 121 °C for 20 min. at 1.036 Bar (15.03 psi) above atmospheric pressure.
• 134 °C for 3-4 minutes at 2.026 Bar (29.41 psi) above atmospheric pressure.
• (See next table)

Types of steam sterilizers
1. Small table-top sterilizers
• Sometimes used in physicians’ and dentists’ offices and clinics.
• Are essentially horizontal pressure cookers.
• Holding temperature for unwrapped items:
• 121ºC for 20 minutes or 134 °C for 3-4 minutes. 87

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2. Portable steam sterilizer
These can be adapted for processing critical devices in low resource settings. 88
In addition, pressure cookers can provide adequate steam sterilization in
situations where conditions and resources are severely limited. 89
3. Gravity downward-displacement sterilizers
• Larger than tabletop sterilizers with addition of more automatic controls.
• The chamber fills with steam, displacing the air downward and forcing it out of
the drain valve.
• Holding temperature for unwrapped items: 121ºC for 20 minutes or 134 °C for
3-4 minutes. 87

4. Emergency (flash) sterilizers (these are a form of gravity-displacement
sterilizer):
• Normally located in operating room suite.
• Quick sterilization cycle at 134ºC for 3-4
minutes.
• Should be used only when there is
insufficient time to sterilize an item by the
preferred prepackaged method. 87
• Only for unwrapped items.

5. High-speed prevacuum vacuum sterilizers (Porous load autoclaves)
• Similar to downward-displacement sterilizers, with the addition of a vacuum
pump system.
• Vacuum pump removes the air from the chamber before the steam is
admitted, reducing the penetration time and total cycle time.
• Holding temperature 134ºC for 3-4 minutes for wrapped items. 87
• Ideally used for wrapped items and porous loads (fabrics, swabs, instruments
with lumens).

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Table 25: Sterilization times 90
Type of instruments to be Sterilization
sterilized time

Gravity sterilizer:

Unwrapped 121 ºC (1.036 Bar) 20 min.

Unwrapped: 134 ºC (2.026 Bar) 3 min.
(metal and glass only)

Unwrapped: 134 ºC 10 min.
(2.026 Bar) (e.g., rubber)

Wrapped 121 ºC (1.036 Bar) 30 min.

Wrapped 134 ºC (2.026 Bar) 15 min.

High-speed vacuum sterilizer

wrapped: 134 ºC (2.026 Bar) 4 min.

Note:
Sterilization time does not include the time it takes to reach the required
temperature or the time for exhaust and drying; therefore, it is shorter than the
total cycle time.
The temperatures required for steam sterilization are lower than those for dry-
heat sterilization because moist heat under pressure allows for more efficient
destruction of microorganisms. 90

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Steps for pressure steam sterilization:
1. Clean all items to be sterilized.
2. Open or unlock all hinged items and disassemble
items with multiple parts. Do not arrange items close
together.
3. Arrange all labeled packs, drums, or unwrapped
items in the chamber of the
autoclave in a way that allows
the steam to circulate freely. DO
NOT STACK.
4. Follow the manufacturer
X
instruction for operating the
autoclave. Adjust time, temperature and pressure
according to the table before. It is best to use a timer, which helps ensure that
the appropriate timing is achieved.
5. Do not begin timing until the autoclave reaches the desired temperature and
pressure
- If the timing process is forgotten, start the cycle again. If the autoclave is
automatic, the heat will shut off and the pressure will begin to fall off once
the sterilization cycle is complete.
- If the autoclave is not automatic, turn off the autoclave after achieving the
required time.
6. Wait until the pressure gauge reads “0” to open the autoclave. Open the lid or
door to allow remaining steam to escape. Leave all items in the autoclave
until they dry completely. It may take up to 30 minutes.
7. Remove packs, drums, or unwrapped items from the autoclave using sterile
pick-ups to handle unwrapped items. The packs of equipment should come
out of the autoclave dry. Wet packs must be considered non-sterile. Do
not store packs, drums or unwrapped items until they cool to room
temperature. This may take several hours.
8. Store items using the following guidelines:
- Wrapped items – The length of time (=shelf life) that a wrapped, sterile item
is considered sterile depends on whether or not a contaminating event
occurs not necessarily on how long an item has been stored. Store items in
a closed, dry, cabinet with moderate temperature and low humidity in an
area that is not heavily trafficked. A wrapped pack can be considered
sterile as long as it remains intact and dry. When in doubt about the sterility
of a pack, consider it contaminated and re-sterilize the items.

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- Unwrapped items – use immediately after removal from the autoclave or
keep them in a covered, dry, sterile container for up to one week. 87
9. Label accurately with contents, date of processing and expiration date and
store wrapped materials in storage cabinet.

Advantages and disadvantages of steam sterilization
Advantages:
• Highly effective;
• Rapid heating and rapid penetration of instruments;
• Nontoxic;
• Inexpensive;
• Can be used to sterilize liquids. 90
•

Disadvantages:
• Items must be heat and moisture resistant;
• Will not sterilize powders, ointments or oils. 90
• Needs good maintenance.

Wrapping instruments and other items for steam sterilization
• Wrapping instruments and other items
before steam sterilization helps to
decrease the likelihood that, after
sterilization, they will be contaminated
before use.
• To wrap instruments and other items for
steam sterilization, use two layers of
material such as paper, newsprint, or
muslin or cotton fabric. Do not use canvas
because it is difficult for steam to go
through canvas. Make points while
wrapping the instruments and other items
so that the packs can be easily opened
without contaminating their contents. 90
Fig. 25: Wrapping instruments
and other items for steam
sterilization

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Fig. 26: Steps for wrapping instruments and other items

Step 1 Step 2 Step 3 Step 4
Place the instrument or Fold the bottom section Fold the left section to Fold the right section to
other item in the center of the top wrapper to the the center, and fold the center, and fold back
of the top wrapper center, and fold back the back the point. the point.
should be positioned so point.
that the points –not the
flat edges- are at the
top, bottom, and sides.

Step 5 Step 6 Step 7 Step 8
Fold the top section to Fold the bottom Fold the left section to Fold the right
the center, and fold section of the bottom the center, and fold section to the
back the point. wrapper to the center, back the point. center, and fold
and fold back the back the point.
point.

Step 9 Step 10 Step 11
Fold the top section Tuck the point under the Fasten the folds securely,
to the center, and right left sections. using autoclave tape, if
fold back the point. available.

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Autoclave maintenance
The autoclave should be checked each time it is used in order to make sure that
it is functioning properly. An equipment log should be used to monitor
performance including temperature, timing, and cycle.
•

• The autoclave is not working correctly if:
• Steam comes out of the safety valve instead of the pressure valve. In
such a case, the pressure valve must be cleaned and inspected.
• Steam comes out from under the lid or around the door. If this
happens, the gasket must be cleaned and dried or replaced. 87

To ensure that the autoclave is properly maintained
• Routine maintenance should become standard procedure. Someone should
be assigned to be responsible for this task.
• Follow the manufacturer’s instructions whenever possible since autoclave
maintenance varies depending on the type of autoclave.

Dry-heat Sterilization
Dry heat sterilization (Hot Air Oven):
For dry heat-sterilization to be achieved, a constant supply of electricity is
necessary. Dry heat is preferred for reusable glass, metal instruments, oil,
ointments and powders. Do not use this method of sterilization for other items,
which may melt or burn. 87
Dry heat ovens should have fans to give even temperature distribution and faster
equilibrium of load to sterilization temperatures.
Steps of dry-heat sterilization:
1. Clean and dry all items to be sterilized.
2. Either (1) wrap with foil or (2) place unwrapped items on a tray or shelf, or (3)
put them in a closed metal container.
3. Place items in the oven and heat to the holding temperature.
Table 26: Dry heat sterilization temperatures & times
Holding Sterilization Time
Temperature (After reaching the holding
temperature)
180 ºC 30 minutes
170ºC 1 hour
160ºC 2 hours
149ºC 2.5 hours
141ºC 3 hours

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4. Leave items in the oven to cool to room temperature before removing. When
items are cool, remove instruments and other items (using sterile pickups for
unwrapped items) and use immediately or store.
5. Proper storage is as important as the sterilization process itself.
Store items using the following guidelines:
• Wrapped items – store in a closed, dry, cabinet with moderate temperature
and low humidity in an area that is not heavily trafficked.
• Unwrapped items – use immediately after removal from the autoclave or
hot oven, keep them in a covered, dry, and sterile container for up to one
week. 87

Note:
• The oven must have a thermometer or temperature gauge to make sure that
the designated temperature is reached.
• Do not begin timing until the oven reaches the desired temperature.
• If the timing process is forgotten, start it when the oversight is realized.

Advantages and disadvantages of dry-heat sterilization
Advantages
• Can be used for powders, anhydrous oils, and glass.
• Reaches surfaces of instruments that cannot be disassembled.
• No corrosive or rusting effect on instruments.
• Low cost.

Disadvantages
• Penetrates materials slowly and unevenly.
• Long exposure time’s necessary.
• High temperatures damage rubber goods and some fabrics.
• Limited package materials. 90

Maintenance of dry-heat ovens
Dry heat ovens should be checked to make sure that they are functioning
properly. Staff should:
• Keep the oven clean.
• Check that the temperature gauge is working correctly on a regular
basis – every few weeks is sufficient. To check the temperature gauge,

159


put a thermometer in the oven and compare the temperature reading
with the one on the gauge. 87
Low Temperature Sterilization
Low temperature sterilization is used for heat- and moisture- sensitive medical
devices. Since the 1950s ethylene oxide has been the most common method of
low temperature gas sterilization. Other methods have emerged that include
hydrogen peroxide + gas plasma and immersion in a dilute liquid peracetic acid.

Ethylene oxide gas
Uses: Ethylene oxide can be used to sterilize most articles that can withstand
temperatures of 50-60 °C. However, it should be used under carefully controlled
conditions because it is extremely toxic and explosive. Although it is very
versatile and can be used for heat-labile equipment, fluids, and rubber, etc., a
long period of aeration (to remove all traces of the gas) is required before the
equipment can be distributed. The operating cycle ranges from 2-24 hours and it
is a relatively expensive process. 87 Sterilization with ethylene oxide should be
monitored by using bacterial spore tests.

Hydrogen peroxide gas plasma
Uses: Gas plasma is generated in a chamber under deep vacuum and acted on
by radiofrequency radiation wherein free radical particles which disrupt microbial
cellular components. The plasma is combined with hydrogen peroxide. The cycle
time is approximately 75 minutes. Diffusion of the vapor and plasma into long,
narrow lumens can be enhance withuse of additional devices to assure flow of
gas through the device’s lumen. Diffusion into long lumens even with H2O2
injection is of poor quality assurance.

Chemical Sterilization
Before deciding to use a chemical sterilant, consider whether a more appropriate
method is available. Chemical sterilants are primarily used for heat- labile
equipment where single use is not cost effective. Instruments and other items
can be sterilized by soaking in a chemical solution followed by rinsing in sterile
water. 87 The immersion time to achieve sterilization or sporicidal activity is
specific for each type of chemical sterilant. The difficulty lies in the fact that
immersion for the appropriate time, rinsing with sterile water, and then
transferring the device to a sterile field for use is challenging. Also, in contrast
with steam sterilization methods, a biological indicator is not available for most
chemical sterilants. Given these limitations most liquid chemical sterilants are
instead used for high-level disinfection. If an item is sterilized chemically, it
should be used immediately after sterilization, to be sure that it is sterile.

160


Types of chemical sterilants:
Glutaraldehyde is a commonly available solution that can be used for
sterilization. Other chemical sterilants may be locally available, such as peracetic
acid, 7.5% hydrogen peroxide, or hydrogen peroxide (1%) plus peracetic acid
(0.08%).87 Formaldehyde is obsolete and toxic.
Glutaraldehyde
Uses: A 2% glutaraldehyde solution for at least 10 hours that can be used to
sterilize heat labile items. Glutaraldehyde solution is irritating to the skin, to the
eyes, and to the respiratory tract. There are two types of glutaraldehyde available
in Egypt. One alkaline solution that requires activation (e.g., Cidex®) and one
acidic solution that is stable and does not require activation but is slower in
activity than the activated alkaline buffered solution.

Precautions: Glutaraldehyde is an eye and nasal irritant and may cause
respiratory illness (asthma) and allergic dermatitis. Glutaraldehyde should not be
used in an area with little or no ventilation. Eye protection, a plastic apron, and
gloves must be worn when glutaraldehyde liquid is made up, disposed of, and
used for sterilization. Latex gloves may be worn and discarded after use if the
duration of contact with glutaraldehyde is brief, e.g. less than 5 minutes. For
longer duration, nitrile gloves must be worn. Glutaraldehyde should be stored
away from heat sources and in containers with close-fitting lids. The length of
time that glutaraldehyde solutions can be used varies but they are usually good
for up to 14 days. Solutions should be replaced any time they become cloudy. 87

Peracetic acid
Uses: A 0.2 – 0.35% peracetic solution for 10 minutes can be used to sterilize
heat-labile items (e.g. arthroscopes, dental instruments). A special advantage of
peracetic acid is that it has harmless decomposition products and leaves little
residue on sterilized items. It remains effective in the presence of organic matter
and is sporicidal even at low temperatures. Peracetic acid can corrode copper,
brass, bronze, plain steel, and galvanized iron, but additives and pH modification
can reduce these effects. It is considered unstable, particularly when diluted. It is
more effective than glutaraldehyde at penetrating organic matter, e.g. biofilms. It
is known to be highly corrosive and its use as a disinfectant in its natural state is
therefore limited unless there is a corrosion inhibitor in the formulation. Nu-
Cidex® is stabilized peracetic acid solution with a corrosion inhibitor. The solution
is activated to provide the appropriate in-use strength. Once prepared the current
manufacturer’s recommendations is that it should be used within 24 hours.
Sterilization using peracetic acid can be done through an automated reprocessor
that dilutes the 35% peracetic acid to a use concentration of 0.2%. This system
can only be used if the device being reprocessed is immersible as endoscopes.
Filtered water is used to rinse the device. Connectors to assure free flow of the
liquid chemical sterilant are important and the connectors are very specific to

161


each model of device being reprocessed. This system is used to chemically
sterilize both flexible and rigid endoscopes.

Steps for chemical sterilization:
• Wear protective clothing.
• Clean, and dry all items to be sterilized.
• Prepare the chemical sterilization solution following the manufacturer’s
instructions.
• If using a previously prepared solution, use an indicator strip to determine if
the solution is still effective.
• If preparing a new solution, put it in a sterile container with a lid and mark the
container with the preparation date and expiration date.
• Open all hinged instruments and other items. Disassemble those instruments
with sliding or multiple parts because the solution must contact all surfaces for
sterilization to be achieved.
• Place all items in the solution so that they are completely submerged. Place
bowls and containers upright so that they are filled with the solution.
• Cover the container and follow the manufacturer’s instructions regarding the
time necessary for sterilization. During this period, do not add or remove any
items from the container.
• Remove the items from the container using large sterile pickups.
• Rinse thoroughly with sterilized water to remove the residue that chemical
sterilants leave on items.
• Place items on a sterile tray or in a sterile container and allow to air dry before
use or storage.
• When items are dry, use or store immediately.
• If items are to be stored, keep them in a covered, dry, sterile container for up
to one week. 87

Monitoring the Effectiveness of Sterilization
To ensure that sterilization has been successful the process of sterilization (and
not the end product) is tested. Indicators have been developed to monitor the
effectiveness of sterilization by measuring various aspects of the process through
different indicators.

162


Mechanical indicators
These indicators, which are part of the autoclave or dry-heat oven itself, record
and allow you to observe time, temperature, and/or pressure readings during the
sterilization cycle. 87

Chemical indicators
• Tape with lines that change color when the intended temperature has
been reached.
• Pellets in glass tubes that melt, indicating that the intended
temperature and time have been reached.
• Indicator strips that show that the intended combination of
temperature, time, and pressure has been achieved.
• Indicator strips that show that the chemicals and/or gas are still
effective. 87
• Chemical indicators are available for testing ethylene oxide, dry heat,
and steam processes. These indicators are used internally, placed
where steam or temperature take longest to reach, or put on the
outside of the wrapped packs to distinguish processed from
nonprocessed packages. 11

Biological indicators
These indicators use heat-resistant bacterial endospores to demonstrate whether
or not sterilization has been achieved. If the bacterial endospores have been
killed after sterilization, you can assume that all microorganisms have been killed
as well. After the sterilization process the strips are placed in a broth that
supports aerobic growth and incubated for 7 days. The advantage of this method
is that it directly measures the effectiveness of sterilization. The disadvantage is
that this indicator is not immediate, as are mechanical and chemical indicators.
Bacterial culture results are needed before sterilization effectiveness can be
determined. 87

Recommended ideal monitoring system
Perform the following monitoring activities whenever possible.

For steam sterilization
• If the autoclave has recording chart, review it after each load. If not,
record the temperature, time and pressure information in a log book
that is reviewed after each load.

163


• Place heat-and steam-sensitive chemical indicators, if available, on the
outside of each pack.
• Perform testing with biological indicators weekly (or monthly, if testing
weekly is not possible).
• Indicators should be in the middle of the item reprocessed (the most
difficult part of the load).
• A thermometer could be put in the most difficult part of the load.
For dry-heat sterilization
• If the oven has a recording chart, review it after each load. If not,
record the temperature and time information in a log that is reviewed
after each load.
• Place heat-sensitive chemical indicators, if available, on the outside of
each pack.
• Perform testing with biological indicators weekly (or monthly, if testing
weekly is not possible). 87
• A thermometer could be put in the most difficult part of the load.

For chemical sterilization
• Record the time information in a log that is reviewed after each load.
• Use an indicator strip, if available, to determine if the solution is still
effective. 87
Correcting sterilization failure
• If monitoring indicates a failure in sterilization, attempt to determine the cause
of the failure and arrange for corrective steps, as follows:
- Immediately check that the autoclave or dry-heat oven is being used
correctly or replace the chemical solution.
- If correct use of the unit has been documented and monitoring still indicates
a failure in sterilization, discontinue using the unit and have it serviced.
- Any instruments or other items that have been processed in the faulty
autoclave or dry-heat oven must be considered nonsterile and must be
processed again with the unit is functioning properly.

Sterile Services Department (SSD)
The sterile services department (SSD) is vital for an effective Infection Control
and Prevention program. The expertise and knowledge of SSD personnel is

164


important to ensure high standards of decontamination; an effective SSD always
results in long-term savings.
Not all hospitals can afford to have an SSD and a separate surgical services unit
to deal with the operating theatres and associated departments. At the least, they
should have a single department covering all areas.

Preparing an Area for Processing Instruments and Other
Items
One goal of a comprehensive infection control program is to minimize the level of
contamination in areas in which “clean” activities take place. 86 Examples of
areas where “clean” activities take place are operating theaters, procedure
rooms, and working areas for sterilizing, high-level disinfecting, and storing
instruments and other items. Areas in which “dirty” activities take place include
rooms where soiled instruments and other items are washed. 86 It is ideal to have
separate rooms – one for receiving and cleaning instruments and other items and
another room for final processing (sterilization or high-level disinfection) and
storage. However, in many settings in Egypt this is not possible. When only one
room is available, it should be arranged so that activities and objects flow in an
organized way. It is necessary to have at least one sink (two are preferable),
sufficient counter top space for receiving dirty items and for drying and packaging
clean items, and for storage space (preferably closed cabinets). 86 It is key to
have good spatial separation between soiled handling area and the clean,
packaging area.

Establishing an SSD
Soiled, used, and recyclable equipment should be collected from the wards and
then should be transferred to the SSD where it is washed, inspected, disinfected
or packaged and sterilized, and dispatched back to the wards.

Fig. 27: Flow diagram of items processed in SSD

Delivery of
items to

Ward/Operating Receiving dirty
Theater instruments

Storage of Processing:
clean items Cleaning, Disinfection,
Sterilization, Packing

165


In the ward:
• Collect instruments that are to be re-used in a clearly labeled
container.
• Arrange for dirty instruments to be delivered to the SSD – DO NOT
ATTEMPT TO WASH THEM ON THE WARD.
• Discard cotton wool balls and dressings into regular waste disposal
containers (for more details see chapter on Waste Disposal I).

In the SSD:
• Receive instruments in the dirty area.
• Wash all instruments in water and detergent or enzymatic presoak
either mechanically or manually using appropriate protective barriers.
• Inspect all equipment for cleanliness and damage.
• Send damaged instruments for repair after appropriate
decontamination or discard them if necessary.
• Pack cleaned instruments on a tray.
• Autoclave trays at recommended temperature and/or disinfect as
required.
• Ensure that the packaged trays are dry – inspect tapes.
• Sort the packaged trays for ward collection.
• Return equipment to the ward or store in the clean treatment room.

The layout of the SSD
Ideally, physical barriers should separate dirty and clean areas in the
reprocessing room. However, if this is not possible (perhaps because of shortage
of space or of funds) the same room can be used, provided that:
• The air moves from the clean area to the dirty area.
• Both areas have separate storage facilities.
• There are adequate hand disinfection facilities.
• Activity patterns are established in which soiled objects never cross
paths with clean, sterilized, or high-level disinfected instruments and
other items.
• The doors are kept closed in the reprocessing rooms in order to
minimize dust contamination and to eliminate flies.
• There is separate equipment for each area.
• The staff work in either area– never in both.

166


Storage in the SSD
After items have been reprocessed, the sterile packs should be stored in well-
ventilated, clean stores ready for dispatch to the wards. Collection should be
regular and there should be a written record of receipt and delivery. This helps to
monitor the use and the loss of instruments.
Note!
Do not store instruments or other items such as scalpel blades and suture
needles in solutions-always store them in a dry container. Microorganisms can
live and multiply in both antiseptic and disinfectant solutions which can
contaminate instruments and other items and which can lead to infections.

SSD staff facilities
• All SSD staff should be provided with adequate protective clothing (e.g.
heavy duty gloves, plastic aprons, and eye protection if manual
cleaning is undertaken). Overshoes are not necessary.
• SSD staff should be immunized against hepatitis B. (See chapter
“Occupational Safety and Employee Health”

Fig. 28: Single room for processing instruments and other items

Receiving
Waste Waste
Sink
Cleaned
Instruments
Work area

Door

Work area Boiler

Auto-
Sterile storage cabinet clave Sterile pack work area

The flow of work in a single room for reprocessing of instruments should be
designed to minimize the likelihood of contamination. Activity patterns should be
established in which soiled objects never cross paths with clean, sterilized, or
high-level disinfected instruments and other items.

167

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