Sterilization In General

1
Sterilization In General

• Whats the process?
• Decontamination removes gt 80 of microbes
• Sterilization Kills/inactivates the remaining
  microbes
• What are the Sterilants?
• Saturated Steam
• Ethylene Oxide
• Ozone
• Hydrogen Peroxide
• High Level Disinfectants (Glutaraldehyde, OPA,
  PAA)

2
Sterilization In General

• Whats the process?
• Decontamination removes gt 80 of microbes
• Sterilization Kills/inactivates the remaining
  microbes
• What are the Sterilants?
• Saturated Steam
• Ethylene Oxide
• Ozone
• Hydrogen Peroxide
• High Level Disinfectants (Glutaraldehyde, OPA,
  PAA)

3
Steam Sterilization

• Critical Variables
• Time.
• Temperature.
• Saturated Steam. (Depends on Temperature and
  Pressure)
• Other Variables (Incomplete List)
• Loading
• Sterilant contact with items to be sterilized
• Outside weather changes
• Boiler Chemicals
• Wrapping Materials
• Etc, etc, etc.

4
Saturated Steam
Superheated Steam
Wet Steam/ Liquid Water
5
Saturated Steam What is it?

• It is a colourless gas, containing lt 3 liquid
  water
• Depends on temperature and pressure
• It will condense if it cools down a fraction of a
  degree
• It releases latent or potential heat energy as it
  condenses
• It is the latent or potential heat transferred to
  microbes that kills/inactivates them

6
Latent Heat Potential Energy
Researcher knows the 16 ton weight has
zero Potential energy. She is not afraid.
16 Ton weight is sitting on the floor It has zero
Potential energy
16 Tons
7
Latent Heat Potential Energy
16 ton weight is now 2 meters off the ground. It
has quite a lot of potential energy with respect
to the researcher
16 Tons
The researcher is now very afraid of the 16
ton weights potential energy
2 meters
8
Latent Heat Potential Energy
Latent or Potential energy from the 16 ton weight
is now realized. Especially by the
late Researcher.
2 meters
16 Tons
9
Latent Heat Potential Energy
16 Tons
Steam (Gas)
Water (Liquid)
16 Tons
10
The ExperimentGenerating Saturated Steam at 1
Atmosphere
100ºC
Temp
All the energy is now going in To creating
latent heat in the steam With no increase in
temperature
It takes 150 KJoules to heat 1 lb of water from
20ºC to 100ºC and 1023 Kjoules to convert 1 lb of
water from liquid to gas at 100ºC
Time
11
Typical Steam Sterilizer
12
Sterilization Monitoring

• We monitor the Process not sterility of items
• Because the process is validated (by the
  manufacturer of the sterilizer) we assume that,
  if the process functions correctly, the goods in
  the process will be sterile.

13
Process Monitors for Steam Sterilization

• 3 Major types used
• Biological Indicators
• Monitor all variables in the process
• Chemical Indicators
• Monitor one or more of the critical variables
• Mechanical Indicators
• Monitor one of the critical variables

14
Process Monitors for Steam Sterilization

• Individually they provide information, but only
  together do they tell the whole story!
• A failure in any one of the monitors implies the
  process is incomplete in one or more necessary
  variables

15
Biological Indicators

• Large (gt 105 or 106) of resistant spores
• Usually Self-contained type
• Placed in a normally loaded sterilizer
• At least one per day per cycle (CSA)
• Final Readout made at 1, 3, 24 or 48 hours
• Test the process to ensure it is capable of
  killing microorganisms

16
Self-contained Biological Indicator
Vial
Ampoule Growth media Indicators
Cap
Spore Strip
Filter
17
How do they Work?

• Colour change indication
• If spore survives, it is incubated
• Spore consumes nutrients, excretes acid
• Spore creates subsequent generations that also
  consume nutrients and excrete acids
• Purple (or other) dye is acid sensitive
• If enough acid is produced, dye will change from
  purple to yellow (or other colour change)
• Process can take up to 48 hours to get reliable
  prediction of kill

18
How do they Work?

• Rapid Read BIs
• Spore survives the sterilization cycle and is
  incubated
• Nutrients are tagged with a U.V. fluorescent
  dye
• As spore consumes nutrients the dye is released
  and begins to fluoresce
• Fluorescence is detected electronically
• Process takes up 3 hours to get reliable
  prediction of kill

19
What bout these Extended Cycles?

• G.stearothermophilus will still be the test
  spore.
• Requires a new Process Challenge Device (test
  pack) not a new BI
• Extended cycle required because bigger. Heavier
  more complex sets protect microbes better
• PCD must provide the same protection to the BI

20
BIs and CIs

• All current sterilization standards (AAMI, CSA
  and ISO) require the use of Biological
  indicators.
• Chemical Indicators cannot replace Biological
  indicators because
• Biologics are far more complex
• Biologics have the potential to recover after
  serious damage
• Chemistries only approximate the response of
  Biologics
• Chemical kinetics are far simpler than biologic
  kinetics
• Chemical indicators only measure the critical
  variables of the process. Biologics integrate
  all the variables of microbial death

21
Understanding Chemical Indicators

• To fully understand Chemical indicators one must
  understand
• BIER/CIER Vessels/Test methods used by
  manufacturers
• Stated Values (SVs)
• ISO/AAMI Classifications of Chemical Indicators
• How it all relates to YOUR sterilization process
• What a pass/fail result really means

22
Test Methods for Testing Chemical Indicators

• Must be reproducible, controlled and consistent
• Based on standard test Sterilizers called BIER
  or CIER vessels
• BIER Biological Indicator Experimental
  Resistometer
• CIER Chemical Indicator Experimental
  Resistometer
• BIER/CIER vessels performance specified by ISO
  18472
• BIER/CIER Vessels behave very differently from a
  typical health care sterilizer

23
BIER/CIER Vessels

• Very Small Chamber
• Very tight controls
• Highly reproducible results
• Basis for all Biological and Chemical indicator
  testing
• All CI Stated Values are based on this vessel

24
Some Requirements of CIER Vessels

• Come-up time lt 10 seconds
• Come-down time lt 10 seconds
• Vacuum air removal lt 2 minutes
• No steam allowed during air removal
• Set Temperature within 0.5ºC
• Set Time within 1 second
• Pressure within 3.5 Torr
• One data point recorded per second

25
Contrast CIER Vessel to Health Care Sterilizer

• Come-up time 5 to 15 minutes
• Come-down time 5 to 15 minutes
• Vacuum air removal 5 to 15 minutes
• Steam used during air removal
• Set Temperature within 2ºC (?)
• Set Time within ??
• Pressure within ??
• One data point recorded per 30 seconds

26
Test Methods for Chemical Indicators

• All testing done in a CIER Vessel
• Must meet requirements of ISO 11140-1
• ISO 11140 is written for Manufacturers not end
  users
• Specifications are broken in to 6 categories
• Only need to show the ability to reach the stated
  values.

27
Stated Values What are they?

• For any given chemical indicator to be compliant
  with ISO 11140-1, it must have Stated Values
  for the parameters it measures.
• Example For a Class 3 Chemical Indicator, it
  must have a stated value for temperature. This
  is the temperature at which we can expect to see
  the change in the CIER vessel.

28
Stated Values and ISO 11140-1

• The standard uses the Stated Values to define
  how the indicator will perform.
• Example A Class 4 Indicator
• Stated Values
• 134ºC
• 4 Minutes
• ISO allows a range
• Colour change (Pass result) must be seen at
  134ºC, after 4 minutes exposure in the CIER
  vessel. A fail (no colour change) result must be
  seen at 132ºC after only 3 minutes exposure. No
  additional testing is required at points in
  between.

29
Stated Values and ISO 11140-1

• A Class 6 example
• Stated Values
• 134ºC, 4 Minutes (Saturated steam)
• A pass result must be seen ( in the CIER vessel)
  after 4 minutes exposure at 134ºC
• A Fail result must be seen at 133ºC after 3 min
  45 second exposure in a CIER vessel.
• No additional testing of points in between is
  required.

30
Stated Values and ISO 11140-1

• The BIG QUESTION
• So, if a chemical indicator shows a pass result
  in your sterilizer does it mean that the Stated
  Values given for that particular chemical
  indicator have been achieved?

31
Chemical Indicators

• Changes (reactions that cause colour change)
  start at temperatures well below the stated
  values for the CI
• Temperature at which the reaction starts is the
  initiation temperature
• Changes (reactions) will continue once initiated
  and the temperature is above the initiation
  temperature

32
Rates of Reaction and Initiation Energies
In our house my wife allows me the honour of
pressing my own shirts. As part of that process
I have learned a lot about the chemistry of
burning fabrics.
33
Rates of Reaction and Initiation Energies
For example, I discovered that if I place an
unplugged (cool) iron on a shirt, I can leave it
there indefinitely and it will not scorch the
shirt. Thats because the energy imparted to the
shirt from the cool iron is well below the
initiation energy required to start the burning
reaction of the fabric. It also doesnt remove
wrinkles
34
Rates of Reaction and Initiation Energies

• Ive also learned that I can leave an iron on its
  lowest setting on the shirt indefinitely and it
  will not scorch the shirt either. I guess the
  low setting still doesnt deliver enough energy
  to start the burning reaction

35
Rates of Reaction and Initiation Energies

• Of course, an iron on medium setting will scorch
  the shirt, but it takes quite a few minutes to do
  so,
• On high setting, the wrinkles go, but if I leave
  the iron on the shirt for even a short time, it
  will scorch.

36
The Scorched Shirt Example
37
Chemical Indicators

• Example (Theoretical) CI has stated values of
  134ºC, 4 minutes Initiation temperature may be
  100ºC and reaction (change) will start to occur
  at that temperature and continue while the
  temperature remains over 100ºC.
• The rate of change will vary with temperature
  once initiated. Usually faster as temperature
  increases

38
BIER/CIER Vessel Testing
39
Same CI in a Health Care Sterilizer
40
Next Big Question(s)

• If chemical indicators start to react below the
  stated values
• How fast do they react at lower temperatures?
• Will they change if they spend sufficient time at
  lower temperatures?
• What does that mean for monitoring my sterilizer?

41
Extended Cycle Time Temperature Plot Set Points
132ºC, 18 min)
42
Conclusions so far..

• Stated Values cannot be duplicated in Health Care
  Sterilizers
• Stated values can be used only for comparative
  purposes between Chemical Indicators of the same
  class
• Stated Values are used by Manufacturers of
  Chemical Indicators to make CSA/ISO or AAMI
  Classification claims.

43
CSA/ISO/AAMI Classification of Chemical Indicators

• All follow the ISO 11140, 6 tier classification
  structure
• All state the class has no hierarchical
  significance. (i.e. a Class 2 is not better
  than a Class 3 or a Class 6 is not better than
  a Class 5.)
• Classification structure is to provide
  specifications and targets for manufacturers of
  chemical indicators
• It may be used by users for comparing CIs within
  the same class

44
Definitions

• Critical Variable
• For steam sterilization Time, Temperature and
  Saturated Steam
• For Ethylene Oxide EtO concentration, humidity,
  time, temperature
• Critical Parameter
• A set value of a critical variable that must be
  attained
• Stated Values
• The critical parameters measured by a Chemical
  Indicator in a CIER vessel

45
CSA/ISO/AAMI Classification

• Class 1 Process Indicators
• Autoclave tapes, built-in CIs on peel pouches
• Simply identify processed from unprocessed
  packages
• Class 2 Special Indicators
• Bowie-Dick Type Tests
• Class 3, 4, 5, and 6 are all Internal Indicators

46
Classes 3 - 6

• Class 3 Indicator
• Measures only one of the critical variables of
  the process
• Class 4 Indicator
• Measures 2 or more of the critical variables of
  the process
• E.g. Time and temperature, or time saturated
  steam.

47
Classes 3 - 6

• Class 5 Integrating Indicator
• Measures all critical variables of the process,
  and correlates with the test spore for that
  process across a range of sterilization
  conditions
• For steam sterilization, the Class 5 must
  correlate with G.stearothermophilus at 121ºC,
  128ºC and 135ºC
• Has a known response over a range of
  sterilization temperatures

May be other temperatures within the range of
121 - 135ºC
48
Class 5 Integrating Indicator Response
49
Class 3 - 6

• Class 6 Emulating Indicator
• Measures all critical variables of the process
• Tightest specifications of all indicators
• Stated Values are for a specific time and
  temperature for steam sterilization

50
Class 6 Emulating Indicator Response
51
Class 6 Emulating Indicator Response
52
Conclusions

• Saturated Steam is critical to the sterilization
  process
• Non-condensable gases (air, CO2, N2) are poor
  heat transfer media and poor sterilants
• It is the latent heat of saturated steam, not the
  temperature that kills the microbes

53
Conclusions

• All process monitors must agree that the cycle
  was successful
• A failure in any one of the 3 types of monitor
  (Biological, chemical or mechanical) means the
  process was insufficient and processed goods are
  suspect

54
Conclusions

• Biological Indicators are the only indicator to
  integrate all the variables of he sterilization
  process
• They are the only direct measure of the lethality
  of the process
• The BI response can be approximated by chemical
  indicators, but CIs cannot replace BIs

55
Conclusions

• The basis for classification of Chemical
  Indicators in Canada is CANISO 11140
• This standard is written for manufacturers of
  chemical indicators.
• The standard has no hierarchical significance
• Stated values are only realizable in the test
  vessel (CIER vessel)

56
Conclusions

• Selection of biological indicators and chemical
  indicators must be made considering patient
  safety, the information needed from the
  indicators, the standard requirements, best
  practices and economic considerations. No single
  indicator will likely accommodate every
  circumstance