3. DEFINITION
• STERILIZATION
– Process by which an article, surface or medium is
freed of all living micro organisms either in the
vegetative or spore state.
• DISINFECTION
– Destruction or removal of all pathogenic
organisms, or organisms capable of giving rise to
infections.
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5. HISTORICAL PERSPECTIVE
• ANCIENT CIVILIZATION
-Used flame
• ARISTOTLE
– Advantage of Boiling of drinking water
• HIPPOCRATES
– Lightning fires to control plague
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6. HISTORICAL PERSPECTIVE
• ROBORT KOCH
– usefulness of steam for sterilizing surgical
instruments and dressings (1878)
• CHARLES CHAMBERLAND (1851-1908)
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7. HISTORICAL PERSPECTIVE
• GASTON POUPINEL 1885
– Dry heat sterilization
• Joseph Lister (1827-1912)
– A machine that pumped out a fine mist of carbolic
acid into the air around an operation
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8. SPAULDING CLASSIFICATION
• Strategy for reprocessing contaminated
medical devices
• The system classifies a medical device as
– critical
– semi critical
– noncritical
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9. SPAULDING CLASSIFICATION
CATEGORY DESCRIPTION REQUIREMENT EXAMPLE
CRITICAL Enters sterile body
cavity or vascular
system
Sterile Surg instrument,
cardiac catheters ,
implants
SEMI-CRITICAL Contacts mucous
membrane and non
intact skin
High level
disinfection
Endoscope,
bronchoscope,
Laryngeal mirror,
speculum
NON- CRITICAL Contacts intact skin Low level
disinfection
Bed pans, BP cuff,
bed rails
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13. STEAM STERILIZATION (AUTOCLAVING)
Principle –
• Water boils when its vapour pressure equals that of
surrounding atmosphere.
• Thus when water is boiled in closed vessel at
increased pressure, the temperature at which it boils
& that of steam which is formed will exceed 100°C.
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14. STEAM STERILIZATION (AUTOCLAVING)
• When steam comes in contact with cooler
surface, it condenses to water & gives up its
latent heat to that surface.
• Thus 1600ml of steam at 100°C & at
atmospheric pressure condenses into 1ml of
water at 100°C & releases 518calories of heat
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15. • Air in Autoclave Chamber
– Air in the chamber will impair sterilization as it is
poor conductor of heat & retards the penetration
of steam.
– Efficacy of air removal process can be tested by
Bowie-Dick test.
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17. STEAM STERILIZATION (AUTOCLAVING) ct..
• TYPES OF AUTOCLAVE STERILIZERS
– Downward Displacement
– Positive Pressure Displacement
– Negative pressure
– Super atmospheric cycles
– Sub atmospheric cycles
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18. STEAM STERILIZATION (AUTOCLAVING)
ct..
Downward Displacement
• Also known as a gravity displacement unit.
• It uses a heating element to heat up the water and
produce steam.
• The steam, which is lighter than air, forces the air inside
the sterilization chamber to move downward.
• Eventually the air moves out through the drain hole of
the sterilization chamber.
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20. STEAM STERILIZATION (AUTOCLAVING)
ct..
Positive Pressure Displacement
• It uses a separate chamber to create and hold steam.
• Once sufficient amount of steam is accumulated, it is
released into the sterilization unit in a pressurized blast
• This forces the air to move out through the drain hole
and starts the sterilization process.
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22. STEAM STERILIZATION (AUTOCLAVING)
ct..
Super atmospheric cycles
– achieved with a vacuum pump
– It starts with a vacuum followed by a steam pulse
– The number of pulses depends on the particular
autoclave and cycle chosen.
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23. STEAM STERILIZATION (AUTOCLAVING)
ct..
Sub atmospheric cycles
– similar to the super atmospheric cycles
– chamber pressure never exceeds atmospheric
pressure until they pressurize up to the sterilizing
temperature
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25. STEAM STERILIZATION (AUTOCLAVING)
ct..
• PHASES OF AUTOLAVING
– Heat up Phase
• Air, if present, should be evacuated before sterilization
• Vacuum may be applied
– Sterilization phase
• Gives latent heat to materials rapidly on contact
• Microbial destruction will be most effective at these
locations
• Once intended temperature is reached, sterilization time is
set
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26. STEAM STERILIZATION (AUTOCLAVING)
ct..
• PHASES OF AUTOLAVING
– Exhaust Phase-
• At the end the steam should be exhausted from the
autoclave to avoid condensation of water on the load
when cool air is admitted
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27. STEAM STERILIZATION (AUTOCLAVING)
ct..
• Steam criteria
– Dry:
• no suspended droplets of water
– Close to its point of condensation:
• not superheated
– Free from air
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29. STEAM STERILIZATION (AUTOCLAVING)
ct
• ADVANTAGES
– Can kill all bacteria, spores & viruses.
– Rapid sterilization.
– Ease of use.
– Good penetration
• Economical.
– Absence of toxic products/ residues.
– Materials can be pre-packaged & kept sterile until use.
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30. STEAM STERILIZATION (AUTOCLAVING)
ct..
• DISADVANTAGES
– Heat sensitive materials are damaged like plastic
& rubber goods.
– Cause blunting of cutting edges, crossing of metal
surfaces.
– Oil, grease, powders are not sterilized because of
lack of penetration.
– Shortened life of electronic components.
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31. • Articles are packed in special craft papers and then
placed in a thermostatically controlled Dry Heat
Sterilizer.
• Mainly suitable for ophthalmic instruments and glass
items but not plastics or rubber.
• It is useful for sterilization of powders, grease, oil and
glass syringes.
• Precaution- temperature is raised and lowered slowly
to prevent breakage by uneven expansion.
DRY HEAT
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36. • Manual cleaning
• For instruments which cannot be immersed in
water or machine washed
• orthopedic power drills & saws
• For instruments that are heat-sensitive
• laparoscopic & arthroscopic cameras
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37. Mechanical Cleaning
• Instruments that are heat, moisture, and
pressure-sensitive should not be washed in
mechanical washers
• Examples: powered instruments, microsurgical
instruments, cameras
• Ultrasonic baths.
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38. Packaging
• Once items are cleaned, dried, and inspected,
items are wrapped or placed in a rigid container
• Arranged in tray/basket according to guidelines
– Hinged instruments opened
– Items with removable parts should be disassembled
– Heavy items positioned not to damage delicate items
• Several choices to maintain sterility of
instruments: rigid containers, peel pouched;
sterilization wraps
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39. Packaging
• An effective sterilization wrap would:
– Allow penetration of the sterilant
– Provide an effective barrier to microbial
penetration
– Maintain the sterility of the processed item after
sterilization
– Puncture resistant and flexible
• Multiple layers are still common practice due
to the rigors of handling
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41. Loading
– Arranged so all surfaces will be directly exposed to
the sterilizing agent
– Allow for proper sterilant circulation;
– Perforated trays should be placed so the tray is
parallel to the shelf
– Small items should be loosely placed in wire
baskets
– Peel packs should be placed on edge in perforated
or mesh bottom racks or baskets
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42. Sterilization Monitoring
• Sterilization monitored routinely by combination of
physical, chemical, and biological parameters
• Physical - cycle time, temperature, pressure
• Chemical - heat or chemical sensitive inks that
change color when germicidal-related parameters
present (Class 1-6)
• Biological - Bacillus spores that directly measure
sterilization
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43. MONITORING
• Mechanical Monitors: Devices that record time,
temperature & pressure.
• Biological Indicators: they are standardized
preparation of spores. A positive biological indicator
is indicative of possible sterilization process failure.
They should be used atleast once a week but time
needed for incubation is long. Eg: spores of Bacillus
Stearothermophilus
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44. Biological Monitors
• Steam - Bacillus stearothermophilus
• Dry heat - B. subtilis
• ETO - B. atrophaeus
• New low temperature sterilization
technologies
HP gas plasma - B. stearothermophilus
Ozone-B. stearothermophilus
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46. • Class 1- These are Internal & External Process
Indicator E.g. External Process Indicator –
Autoclave Tape.
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47. • Class 2- E.g. Bowie-Dick test for vacuum
steam sterilizer. They only assess Vacuum
Pump efficiency & detect the presence of air
leaks &/or gases in steam.
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48. • Class 3 -
E.g. Temperature Tube. Contains chemicals that
melts & sometimes changes color when the
appropriate temp is attained.
• Class 4 -
Respond to one or more sterilization parameters.
Contains Ink that changes color when exposed to
correct combination of sterilization parameters.
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49. • Class 5-
Known as Integrating Indicators. Respond to all
parameters of sterilization over a specified range of
temperatures.
• Class 6-
These are emulating indicators. These are designed
to react to all critical parameters over a specified
range of sterilization cycles for which the stated
values are based on the settings of the selected
sterilization cycles
54. Non- Ionising radiation
• Eg: UV rays, IR rays
• Electromagnetic rays with wavelength longer than light
• Low energy type
• Absorbed as heat
• Used in rapid mass sterilisation of prepacked syringes
and catheters
• Used for disinfecting enclosed areas like entryways,
operation theatres and laboratories.
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55. Ionising radiation:
• Eg; X- rays, gamma rays & cosmic rays
• Highly lethal to DNA
• High penetrative power
• High energy type
• No appreciable increase in the temperature – COLD
STERILISATION
• To sterilize plastics, syringes,catheters, swabs.
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56. GASEOUS STERILISATION
Ethylene oxide
• Colorless gas, available as cartridges
• Toxic and flammable, Odor similar to ether
• Has an extremely well penetration, even through
plastics
• Effective sterilization is dependent on concentration of
gas, exposure time, temperature, and relative humidity
• Powerful sterilizer: Kills all known viruses, bacteria
(including spores), and fungi
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57. EO Gas Sterilizer
• Is used in large hospitals, as it is expensive,
dangerous, needs more expertise.
• Used for heat sensitive instruments: fabrics, plastics,
suture material, Mesh,lenses, endoscopes, electrical
equipment, anaesthesia equipments and finely
sharpened instruments.
• At 20°C-25°C: sterilization takes 18hours
• At 50°C-60°C: sterilization takes 4 hours
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58. Ethylene Oxide
• Advantages
– Very effective at killing microorganisms
– Penetrates medical packaging and many plastics
– Compatible with most medical materials
– Cycle easy to control and monitor
• Disadvantages
– CFC (inert gas that eliminates explosion hazard)
banned after 1995
– Potential hazard to patients and staff
– Lengthy cycle/aeration time
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59. HYDROGEN PEROXIDE GAS PLASMA
STERILIZATION
• Plasma is ionised gas made up of ions and electrons
referred to as fourth state of matter
•Plasma sterilization operates synergistically via three
mechanisms:
– Free radicals interactions
– UV radioactive effects
– Volatilization
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60. • Stage I- vaccum or pre plasma state
• Low air pressure is achieved and low temperature air
plasma is generated
• Helps remove residual moisture of chamber
• Stage II- sterilization stage
• Aqueous solution of H2O2 injected and vaporised
• Diffuses throughout the chamber, surrounds the items
to be sterilized
• Inactivation of microorganisms by free radicals
generated in plasma by breaking apart H2O2 vapours
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61. Advantages
• Safe for the environment and staff; it leaves no toxic
residuals(water and oxygen).
• Fast - cycle time is 35-40 min and no aeration
necessary
• Used for heat (process temperature 50oC) and
moisture sensitive items.
• Simple to operate, install, and monitor.
• Rubber, plastics,laparoscopic
instruments,ureteroscope, cystoscope,
bronchoscope,electronic power devices
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62. Disadvantages
• Paper, linens and liquids cannot be processed
• Sterilization chamber is small (volume- 80L)
• Requires synthetic packaging (polypropylene) and
special container tray
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64. Other sterilisation methods
• Ozone –
- Sterilises by oxidation
- highly reactive
- high concentration required to produce sporicidal
effects
-Conc: 6-12%. Contact time-60min.
Disadvantage-
- Corrosive when used at high concentrations
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