1. Asepsis: Sterilization and Disinfection
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2. Asepsis It is keeping medical instruments free from microorganisms
This is accomplished by:
Sterilization
Disinfection
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3. I. Sterilization It is one of the basic steps in surface asepsis.
Definition: Sterilization refers to the use of different procedures to destroy all forms of microorganisms including bacterial spores.
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4. What to sterilize? It is mandatory to sterilize :
all instruments that penetrate soft tissues and bone.
Instruments that are not intended to penetrate the tissues, but that may come into contact with oral tissues.
If the sterilization procedure may damage the instruments, then, sterilization can be replaced by Disinfection procedure
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5. II. Disinfection It a is less lethal process than sterilization.
Definition: It is a procedure intended to reduce microorganisms as far as possible (but not bacterial spores).
Thus, disinfection can never replace sterilization
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6. Which procedure to use? Procedure Category Sterilization
Items in each category
Category
Sterilization
Items that: (1) enter the tissue; (2) Enter vascular system; (3) through which blood flows
Critical
High level disinfection
Items that: (1) touch mucous membranes; (2) touch non-intact skin (e.g. endoscopes, respiratory therapy equipment, and diaphragms)
Semi-critical
Low level disinfection
Items such as bedpans, blood pressure cuffs, and bedside tables
Non-critical
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7. I. Sterilization - Process

8. Sterilization – instrument Packing
Often instruments are packed for sterilization to be stored and handled without being contaminated.
Packing depend on the intended shelf life after sterilization.
The available packing options are:
Textile has shelf life of 1 month
Paper has shelf life of 1 – 6 months
Nylon, glass, and metal have shelf life of 1 year if tightly closed
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9. Sterilization Principles
There are 3 different sterilization principles:
Heat sterilization
Chemical sterilization
Radiation sterilization
Each principles is discussed in the following sections.
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10. 1. HEAT STERILIZATION
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11. 1. Heat Sterilization
Advantages: It is the simplest, most effective and inexpensive method.
There are 2 procedures depending on the tolerance of the material used:
Steam sterilization (Autoclaving)
Dry heat sterilization
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12. 1.a. Heat – Steam Sterilization
Use saturated steam above 100º C on packed items.
Objects occupy 4/5 of autoclave volume to facilitate circulation.
Process is divided into 3 periods as follows:
Pre-vacuum period: air is withdrawn from device
Sterilizing period: steam is introduced under pressure to specific temperatures & times.
Post-vacuum: steam is withdrawn to dry autoclave
Table shows samples of time-temperature relationships for steam sterilization
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13. Steam Sterilization Advantages & Disadvantages
good penetration
maintains integrity of liquids (e.g. Lubricants) due to the 100% humidity within the chamber.
Disadvantages:
Non stainless steel metal items corrode
may damage plastic and rubber items
sharp instruments get dulled.
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14. 1.b. Dry-Heat Sterilization
Involves heating at atmospheric pressure and often use a fan to obtain uniform temperature by circulation.
Heat at 180º for half hour , 170º for 1 hr., or 160º C for 2 hrs.
Times are the periods during which object is maintained at the respective temp.
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15. Dry-Heat Sterilization Disadvantages
Less reliable than autoclaving
Large temp difference may arise within device.
sharp instruments get dulled
Many materials do nottolerate dry heat
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16. 2. CHEMICAL STERILIZATION
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17. 2. Chemical Sterilization - Types
The chemical compounds used can be:
Gas Sterilization
Liquid Sterilization
Generally, chemical sterilization procedures have the disadvantages of presenting health hazards to users (e.g. poisonous, flammable, )
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18. 2.a) Gas Sterilization
The gas used in this procedure is ethylene oxide.
Procedure:
Keep objects in constant atmospheric humidity.
Heat to temperatures between 30º and 60º C.
maintain for a period of 10 hrs.
Residual ethylene oxide must be ventilated
Formalin gas autoclaves have been developed for sterilizing endoscopes and ansthetic apparatus.
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19. Gas Sterilization – Disadvantages
Ethylene oxide (& formalin) autoclaves have the following disadvantages:
Difficult to operate
Unsuitable for hospitals but used in industry (e.g. for sterilizing disposable materials that can not tolerate high temperatures).
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20. 2.b) Liquid Sterilization
Can be performed with buffered glutaric aldehyde.
Procedure:
Immerse object in liquid for several hours.
Rinse with sterile water after end of procedure.
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21. 3. RADIATION STERILIZATION
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22. 3. Radiation Sterilization
Provides effective way of sterilization when used in high doses.
Gamma radiation (from 60Co).
Procedure:
Objects on belt conveyer
Expose objects to 25 to 30 kGy for about 24 hrs.
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23. Radiation Sterilization Advantages and Disadvantages
Clean process
Dry process
Ensures full exposure of object from all directions
Disadvantages:
Posses threat to humans (radiation)
Lengthy process
Requires very qualified personnel
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24. II. DISINFECTION
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25. Disinfection - Types
As mentioned before, disinfection can not kill all microorganisms but only reduce its number.
Disinfection can be accomplished with:
Heat disinfection
Chemical disinfection
Object that can be disinfected are bedpans, patient skin before operation and surgeon hands before putting gloves.
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26. 1. Heat Disinfection
It is accomplished by boiling water at atmospheric pressure for at least 5 min’s
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27. 2. Chemical disinfection
Number of different agents are used according to tolerance of objects and infectious agents.
Using phenol with cleaning component destroy the membrane of microorganisms.
Using 70% alcohol for skin which denatures proteins of microorganisms.
Use soap containing hexachlorophene for hands.
In case of hepatitis use 5% solution of chloramines or heat disinfection
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28. Asepsis – Summary
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29. Conclusion In summary:
Sterilization and disinfection are costly and time consuming process
However, it is an essential in all health care facilities to avoid spread of diseases.
It depends on the ehtics of the instrument users.
Users should keep in mind that contaminated instrument present risk to patient as well as the user himself.
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30. Disinfection and Sterilization - New methods
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31. Table 1. New methods in disinfection and sterilization
Regulatory agency action
Agent
Process
FDA cleared, October 1999
Ortho-phthalaldehyde (Cidex OPA)
Disinfection
Not FDA/EPA cleared
Antimicrobial coating (Surfacine)
Superoxidized water (Sterilox)
     
Not FDA cleared
Liquid sterilization process (Endoclens)
Sterilization
Rapid readout ethylene oxide biological indicator (Attest)
FDA cleared, January 1999
New plasma sterilizer (Sterrad 50)
     
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32. 1. Ortho-Phth-alaldehyde (OPA)
Chemical Sterilizaer
Adventages:
not eye and nasal passages irritant
has excellent stability over a wide range of pH (3 to 9)
has a barely perceptible odor
Like glutaric aldehyde, it has excellent material compatibility
Disadvantage:
It stains proteins gray (including unprotected skin)
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33. OPA vs. Glutaric Aldehyde
Table 2. Activity of glutaraldehyde and ortho-phthalaldehyde against Mycobacterium bovis
Time for 6-log10 reductiona
Disinfectant
28-36 minutes
1.5% glutaraldehyde
14-18 minutes
2.5% glutaraldehyde
minutes
0.21% ortho-phthalaldehyde
aRange of values from two different laboratories (4).   
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34. 2. Surfacine Surface disinfectants such as phenols Advantages
Effective in significantly reducing microbial contamination
Cost-effective
Have long-term residual activity
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35. 3. Superoxidized Water Based on the concept of electrolyzing saline.
Advantages:
Cheap
The end product (water) is not damaging to the environment
Available in the United Kingdom; Sterilox
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36. 4. Endoclens
A New rapid automated liquid Chemical Sterilization System.
The sterilant is produced, as needed, by automatic mixing of solutions of hydrogen peroxide and formic acid.
Advantages:
automatic cleaning process
capability to process two flexible scopes at same time
automated channel blockage and leak detection
filter water rinsing and scope drying after sterilization
hard-copy documentation of key process parameters
user-friendly machine interface
total cycle time less than 30 minutes
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37. 5. Hydrogen Peroxide Plasma
A New Low-Temperature Sterilization Technique.
Can be used for temperature-sensitive equipment.
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38. 6. low-temperature plasma
Technique for decontaminating thermolabile products without the severe drawbacks of gas sterilization methods.
Advantages:
Alternative to steam sterilization for sterilizing easily corroding products or electronic instruments
Takes less time.
However, Steam sterilization proved to be the cheapest method of sterilizing
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39. Sterilization & Disinfection End
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