SERILIZATION
ZONE
158
Table
of Contents
Introduction 160
Device Compatibility 161
Steam Sterilization 161
Sterilization Validation 167
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10 SERILIZATION ZONE
Sterilization is the complete destruction of microorganisms including bacterial spores. This
level of decontamination is required for all reusable invasive medical devices (RMD).
Ideally, sterilization methods:
• Have rapid throughput
• Are easily validated
• Are capable of processing wrapped items to enable storage after processing without the
risk of environmental contamination of processed items.
Sterilization is most commonly achieved by using either thermal energy (heat) or low
temperature chemical processes with the following methods:
• Steam (moist heat) at high pressure—cycle time approximately 40–60 minutes
• Dry Heat, similar to an oven, using normal pressure—cycle time up to 2 hours
• Gas plasma at ambient temperature—cycle time 45–75 minutes
• Ethylene Oxide (EO) at sub- atmospheric or high pressure1
• Low temperature steam and formaldehyde vapor—cycle time <3 hours
Always use moist heat sterilization using steam under pressure in preference to other meth-
ods since it is more reliable and can be more effectively monitored and validated. However,
this method is not suitable for items that are damaged by heat or moisture, including flexible
endoscopes. Remember to establish the sterilization requirements before the reusable medi-
cal device is purchased so that the correct sterilization method is available.
Always use moist heat sterilization using steam under pressure in preference to other meth-
ods since it is more reliable and can be more effectively monitored and validated. However,
this method is not suitable for items that are damaged by heat or moisture, including flexible
endoscopes. Remember to establish the sterilization requirements before the reusable medi-
cal device is purchased so that the correct sterilization method is available.
When is Sterilization Required?
This is based on the Spaulding classification of risk assessment. Sterilization is required for
RMD, medical devices that come into contact with a break in the skin or mucous membrane
or enter a sterile body cavity.
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Risk Category Recommended Medical Device Examples
Decontamination level
High (critical) Items that Sterilization Surgical instruments, implants/
are in contact with a break prostheses, rigid endoscopes and
needles
in the skin or mucous
membrane or entering a
sterile body cavity
Intermediate (semi-crit- Disinfection (high level) Respiratory equipment, non-inva-
sive flexible endoscopes, bedpans,
ical) Items in contact urine bottles
with mucous mem-
branes
Low (non-critical) Cleaning (Visibly Cleaned) Blood pressure cuffs, stethoscopes
Items in contact with
intact skin
Choosing the correct sterilization process is important to avoid damage to the item or
compromising sterility. Sterilization and providing sterile devices for patient procedures is
dependent on the whole cycle of decontamination, including cleaning, packaging, steriliza-
tion, and storage/transport. Handling the device in theatre may also have an impact on main-
taining sterility until actual patient use.
Device Compatibility
The ability of the sterilization system to effectively sterilize the medical device depends on
the device’s component materials and design, as well as the level of bioburden (microbes)
prior to sterilization.
If items are not cleaned and disinfected correctly, effective sterilization may not be achieved.
Functionality is the ability of a medical device to withstand the sterilization process and to
remain within operating specifications. The device manufacturer will test its functionality
after processing through repeated sterilization cycles and provides fully validated IFU on
how to process the medical devices they supply (ISO EN 17664).
CSSD Specialist must be aware of the appropriate sterilization method recommended by the
manufacturer of the surgical instruments or medical devices being processed in CSSD to
avoid any damage.
Steam Sterilization
The process of steam sterilization requires direct contact between the material being steril-
ized and pure dry2 saturated steam at the required temperature for the required
2Dry steam is steam that is at the temperature of saturation, but does not contain water parti-
cles in suspension. It has a very high dryness fraction, with almost no moisture.
time in the absence of air. The recommended combinations of time and temperature are
shown below.
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Communicates 115 121 126 134 132
Conveyed Through 118 124 129 137 135
Transparency Status
30 15 10 3 4
Advantage of Steam sterilization process:
Low cost
Relatively Rapid sterilization process
Simple technology
Non-toxic process as there is no chemical required
The higher temperature of 134°C for 3 minutes is the preferred time/temperature for devic-
es that will withstand this temperature and associated pressure.
A steam sterilization cycle involves air being displaced and removed by steam entering the
chamber. This can be done with gravity using a gravity displacement sterilizer, or with a
vacuum using a porous load or vacuum assisted sterilizer. Air removal is essential for effec-
tive sterilization, as it will affect steam access to all areas of the device or pack.
Types of Steam Sterilizations Used in CSSD:
1/ Tabletop Sterilizers
Often used in clinics and dental offices. (a figure of tabletop sterilizer should be added)
2/ Gravity Air Displacement Sterilizers
This type of sterilizer has no assisted air removal and is dependent on gravity, so steam pene-
tration is slow and cannot be assured. Cycle times are much longer for this type of sterilizer
and load selection is critical. They are not suitable for wrapped items or items with channels
(lumens) as they trap air and prevent correct temperatures from being attained. Gravity
displacement steam sterilizers may be used for solid metal items such as non-complex
surgical instruments.
3/ Porous Load Steam Sterilizer (Prevacuum Steam Sterilizer)
Porous load sterilizers incorporate a vacuum-assisted air removal stage prior to steam
admission and they require a consistent supply of suitable quality steam.
A typical cycle consists of:
Conditioning: steam enters the sterilizer chamber and air exits the chamber through the
drain.
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Exposure: sterilization of the load occurs at predetermined sterilization parameters (time
and temperature).
Exhaust: the steam is removed and filtered air is introduced gradually to the chamber.
Drying: it starts at the end of the exhausting phase. The drying time depends on the device,
packaging and the sterilizer’s IFU.
4/ immediate use steam sterilizer
Immediate use steam sterilization (IUSS) or flash sterilization is a common term that
describes the practice of fast sterilization of surgical instruments at the point of use, often
associated with dropped instruments.
Flash sterilization is for non-porous and/or non-hollow surgical instruments in an
unwrapped condition. These gravity-type steam instrument sterilizers are usually located in
the operating room, in order to process instruments for extremely urgent use, for example a
dropped instrument when no alternative is available. These sterilizers operate at 134oC for
3–10 minutes, resulting in wet and very hot medical devices in the operating room environ-
ment.
Indications for Use of IUSS
An IUSS sterilizer must be used only after all of the following conditions have been met:
• Proper cleaning, inspection, and arrangement of surgical instruments before sterilization
• Physical layout of the area which ensures direct delivery of sterilized items to the point of
use
• Procedures are developed, followed and audited to ensure aseptic handling and staff safety
during transfer of the sterilized items from the sterilizer to the point of use
• Items are needed for use immediately following IUSS, as soon as the device cools so as not
to burn the patient
• Sterilizers are routinely tested prior to use and appropriate records maintained There is
now a strong movement towards the routine preparation of sterile instruments in a dedicat-
ed area like the CSSD for the following reasons:
• Immediate advantages of case-by-case organization of sterile instruments by operating
theatre staff
• The typical operating theatre is not designed or equipped to wash and clean instruments as
reliably and consistently as a properly located and designed CSSD, and there are concerns
regarding the adequacy of cleaning and drying of surgical instruments in the operating
theatre prior to using IUSS processing.
• Sterility of sets of instruments can be uncertain following the use of sterilizers designed
and intended only for single dropped instruments; they should not be used for routine steril-
ization of instrument sets
• The sterilizer may not be located in an area immediately adjacent to the operating theatre;
so the delivery of IUSS-sterilized devices to their point of use compromises
their sterility
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IUSS Recommendations
• Restrict use to emergencies, such as unexpected surgery, or dropped devices.
• In most emergency situations, the risk/benefit ratio is low enough to justify the use of
IUSS-sterilized devices.
• IUSS sterilizers must never be used for implants, suction tubing or cannulae or any other
product not specifically validated for the IUSS process. In non-emergency situations, the
risk/benefit
Loading
It is essential to load the items inside the sterilizer chamber properly to allow for adequate
penetration, removal and contact between the sterilant and items being processed.
Load steam sterilizers in the following manner to ensure steam contact and penetration:
• Avoid overloading
• Place non-perforated trays and containers on their edge
• Keep packages away from chamber walls
• Place concave items such as basins on an angle to avoid condensate pooling
• Load textile packs perpendicular to the sterilizer cart shelf
• Place pouches on their edge
• Place multiple packages paper to plastic
• Do not stack rigid containers unless validated by the manufacturer
Unloading
When the cycle is complete, unload the sterilizer in the following manner:
• Place heavier items, trays and containers on lower shelves and lighter items e.g. peel packs
on higher shelves
• Review the sterilizer printout for the following:
• Correct sterilization parameters
• Cycle time and date
• Verify that the cycle number matches the lot control label for the load
• Verify and initial that the correct cycle parameters have been met
• Examine the load items for:
Any visible signs of moisture, consider wet items contaminated even if you have not touch
them.
Any signs of compromised packaging integrity
• Retain printed records of each cycle parameter (i.e., temperature, time) in accordance with
the local policy
Load Cool-Down
After removing the sterilized load:
• Visually verify the results of the external chemical indicators
• Allow the load to cool to room temperature before touching or moving sterile packs. The
amount of time for cooling depends on the Type of packaging used, type of sterilizer and
devices that have been sterilized for example, a heavy item such as an orthopedic mallet
may require a longer cooling time.
• Ensure that cool-down occurs in a traffic-free area without strong warm or cool air
currents.
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Troubleshooting—Wet Pack Problems
Packages are considered wet when moisture in the form of dampness, droplets or puddles
are found on or within a package. There are two types of wet packs; those with
external wetness and those with internal wetness. When wet packs are found, either on
removal from the sterilizer or upon opening in the operating theatre, sterility is considered
to be compromised and the package contents may be contaminated. Wet packs should be
rejected and re-processed according to the local policy.
If moisture is noticed on or in one pack, so the problem is isolated to this pack. However,
other packs of the same load should be opened and checked for wetness. If there are several
wet packs in one load, the entire load should be rejected and reprocessed.
The incident of wet packs must be investigated to identify the root cause and documented to
prevent any future re-occurrence.
Steam Quality
Proper steam quality will prolong the life of RMDs by reducing water impurities that have
adverse effects on device materials. Lime, rust, chlorine and salt can all be left as deposits
on devices if treated (reverse osmosis) water is not used. These compounds can lead to
stress corrosion, pitting and discoloration of the devices and the sterilizer. Pitting, corrosion
and precipitates provide areas where organisms can accumulate and be protected from the
killing effects of the steam process; increasing the infection transmission risk due to inade-
quate sterilization.
Steam Sterilization: Advantages and Disadvantages
Advantages Disadvantages
Highly effective Moist Process
Inexpensive Unsuitable for heat sensitive
items
Rapid Process
Items may be packaged
No toxic residues
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Dry Heat Sterilization
The dry heat method may be used for glassware and metal items, heat stable powders and
non-aqueous liquids like paraffin. A typical cycle consists of heating the chamber to the
required sterilization temperature, holding the load at this temperature for a defined time
period and then cooling the load.
This process does not use steam so the typical times required for sterilization are much
longer. The typical time and temperatures used are:
Temperature (ْC) Advantages Disadvantages
Suitable for non-aqueous fluids High temperatures
160 120 and glassware
Unsuitable for heat sensitive
items
170 60
Long sterilization and cooling
times
180 30 Items cannot be wrapped
Low Temperature Sterilization Considerations
• Temperature involved—is the method compatible with the devices being processed?
• Cycle time—will this fit with the workload/turnaround time of the CSSD? Will more devices
be required?
• Availability of equipment
• Validation requirements
• Compatibility with devices being processed
Low temperature sterilization methods have been increasingly used in CSSD due to the
increase use of delicate sensitive to heat surgical instruments and devices. Ethylene Oxide
(EO), Hydrogen Peroxide (H2O2) and Ozon are the most commonly low temperature Steriliz-
ers used in CSSD worldwide.
Low temperature sterilization involves using chemicals with potential toxic properties. CSSD
Specialists most be fully trained on how to use these types of sterilizers in optimum safe and
effective manner.
Types of low temperature sterilization:
1/ Ethylene Oxide (EO)
These sterilizers operate at 37 ºC or 55 ºC and duration time of 8-12 hours so are suitable for
heat sensitive items. They are used commercially and in some hospitals, but are banned in
hospital settings in many countries due to the costly health and safety
requirements for operating and housing these machines. The EO process works well for heat
sensitive equipment such as invasive flexible endoscopes, and cardiac and ophthalmic devic-
es, but requires very long cycle durations to allow of adequate aeration.
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A typical cycle consists of:
• Load pre-conditioning—vacuum and humidification
• Sterilizing gas exposure
• Gas exhaust and air purge
Advantages Disadvantages
Suitable for heat sensitive Equipment is expensive
reusable medical devices
Extremely penetrative—suitable Lengthy cycle with aeration
for lumened devices and validation
Items may be wrapped Ethylene oxide gas is toxic,
explosive and flammable
Dry process Separate accommodation is
recommended
Non-damaging Lengthy aeration required to
remove toxic residues
2/ Gas plasma
This method is also suitable for heat sensitive items such as flexible endoscopes or complex
laparoscopic instruments as the operating temperature is 45 less than 55 ºC. The cycle time
can vary from 45–75 24-75 minutes but no aeration is
required as the byproducts are non toxic(water vapor and oxygen).
A typical cycle consists of:
A vacuum to remove air,
Injection and diffusion of the Hydrogen Peroxide
Gas plasma generation via radio (RF) ENERGY for a defined sterilization time
Venting of filtered air into the chamber through High Efficiency Particulate Air (HEPA) filter
Advantages Disadvantages
Suitable for heat sensitive Non-cellulose wrapping materials
devices required
Short cycle May not be suitable for long
narrow lumens
3/ Vaporized hydrogen Peroxide
It is a sterilization method utilizes hydrogen peroxide to kill wide spectrum of microorganism
through oxidization. The cycle takes 28-55 minutes at less than 50 ºc. lumened and non-lu-
mened instruments can be sterilized in these machines based on the program you select.
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Typical cycle consist of:
Conditioning to remove air and moisture
Leak test
Injection of Hydrogen Peroxide to the chamber for sterilization
Aeration
Cellulose – containing packaging material can not be used in Hydrogen peroxide sterilizers
as the absorb the peroxide and interrupt effective sterilization.
4/ Ozon Sterilization
This low temperature sterilization system eliminates the need for purchasing a sterilant by
generating O3. The processing cycle takes 4 hours and 30 minutes at 30.8-36 cº. The method
must be approved by the medical device manufacturer for sterilization.
Typical cycle consist of:
Vacuum and humidification
Injection of the O3
Sterilization
Ventilation
Sterilization Validation
Validation establishes documented evidence providing a high degree of assurance that a
specific process will consistently produce an end result meeting specifications and quality
attributes by:
• Measuring the critical parameters of the process such as temperatures, time and pressure,
load configuration (contents) and documentation of the results
• Assuring all components of the process such as proper cleaning, functionality, packing,
wrapping are met
• Proper protocol management
Steam Sterilizer Testing
Routine testing of sterilizers should be performed daily, weekly, quarterly and yearly as per
ISO 17665.
Daily
Bowie-Dick test for steam penetration (also known as air removal test).
Weekly
• Safety checks
• Vacuum leak test
• Air detector function test (if equipped)
• Automatic control test
• Bowie-Dick test
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Quarterly
• All the above plus
• Thermometric test,
• Surgical instrument calibration verification
Yearly
• All the above plus
• Steam quality tests
- Non-condensable gas
- Steam superheat
- Steam dryness
- Endotoxins
• Testing of dry heat sterilizers
• Thermocouple test
• Biological indicators
• Chemical indicators
Ethylene Oxide Sterilizer Testing
• Physical parameters i.e. temperature, pressure and humidity
• Biological indicators
• Chemical indicators
Gas Plasma Sterilizer Testing
• Physical parameters i.e. temperature, pressure and humidity
• Biological indicators
• Chemical indicators
Chemical Indicators for Sterilization
ISO 11140 classifies chemical indicators into six types, according to their intended use. They
are further subdivided by their indicated sterilization process. The classifications describe
the characteristics and intended use of each type of indicator and has no hierarchical signifi-
cance.
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Chemical Indicator Types
Type Purpose
Type 1 These indicators are intended for use with packs or containers
to indicate that they have been directly exposed to the steriliza-
Process indicators tion process and to distin¬guish between processed and
unprocessed units.
They do not indicate that the reusable medical devices are
sterile.
These indicators are intended for use in specific test proce-
dures, such as the Bowie-Dick test for air removal.
Type 2
Indicators for use in specific tests
These indicators are designed to react to one of the critical
Type 3 sterilization variables, e.g., time and temperature, and are
intended to indicate exposure to a predetermined sterilization
Single variable indicators process variable, e.g.134°C
These indicators are designed to react to two or more of the
Type 4 critical sterilization variables, e.g., time and temperature, and
are intended to indicate exposure to predetermined steriliza-
Multivariable indicators tion process
variables, e.g., 134°C, 3 minutes
These indicators are designed to react to all critical variables
Type 5 of the sterilization process, e.g., time, temperature and
presence of moisture, and are intended to be equivalent to or
Integrating indicators exceed the perfor-mance requirements given in the ISO
11138 series for biological indicators
Type 6 These indicators are designed to react to all critical variables
Emulating indicators of the sterilization process, e.g., time, temperature and
presence of moisture, and are intended to match the critical
variables of specified sterilization cycles
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