Asepsis Sterilization and Disinfection BMT335 Sterilization Asepsis It
Asepsis: Sterilization and Disinfection BMT_335 Sterilization
Asepsis • • It is keeping medical instruments free from microorganisms This is accomplished by: I. II. 2 Sterilization Disinfection BMT_335 Sterilization
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. 3 BMT_335 Sterilization
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 4 BMT_335 Sterilization
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 5 BMT_335 Sterilization
Which procedure to use? 6 Category Items in each category Procedure Critical Items that: (1) enter the tissue; (2) Enter vascular system; (3) through which blood flows Sterilization Semi-critical Items that: (1) touch mucous membranes; (2) touch non-intact skin (e. g. endoscopes, respiratory therapy equipment, and diaphragms) High level disinfection Non-critical Items such as bedpans, blood pressure cuffs, and bedside tables Low level disinfection BMT_335 Sterilization
I. Sterilization - Process 7 BMT_335 Sterilization
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: 8 – 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 BMT_335 Sterilization tightly closed
Sterilization Principles • There are 3 different sterilization principles: 1. Heat sterilization 2. Chemical sterilization 3. Radiation sterilization • Each principles is discussed in the following sections. 9 BMT_335 Sterilization
HEAT STERILIZATION. 1 BMT_335 Sterilization
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: a) Steam sterilization (Autoclaving) b) Dry heat sterilization 11 BMT_335 Sterilization
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 12 BMT_335 sterilization Sterilization
Steam Sterilization Advantages & Disadvantages • Advantages: – 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. 13 BMT_335 Sterilization
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. 14 BMT_335 Sterilization
Dry-Heat Sterilization Disadvantages • Disadvantages: – Less reliable than autoclaving – Large temp difference may arise within device. – sharp instruments get dulled – Many materials do nottolerate dry heat 15 BMT_335 Sterilization
2. CHEMICAL STERILIZATION BMT_335 Sterilization
2. Chemical Sterilization - Types • The chemical compounds used can be: a) Gas Sterilization b) Liquid Sterilization • Generally, chemical sterilization procedures have the disadvantages of presenting health hazards to users (e. g. poisonous, flammable, ) 17 BMT_335 Sterilization
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. 18 BMT_335 Sterilization
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). 19 BMT_335 Sterilization
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. 20 BMT_335 Sterilization
3. RADIATION STERILIZATION BMT_335 Sterilization
3. Radiation Sterilization • Provides effective way of sterilization when used in high doses. • Gamma radiation (from 60 Co). • Procedure: – Objects on belt conveyer – Expose objects to 25 to 30 k. Gy for about 24 hrs. 22 BMT_335 Sterilization
Radiation Sterilization Advantages and Disadvantages • Advantages: – Clean process – Dry process – Ensures full exposure of object from all directions • Disadvantages: – Posses threat to humans (radiation) – Lengthy process – Requires very qualified personnel 23 BMT_335 Sterilization
II. DISINFECTION BMT_335 Sterilization
Disinfection - Types • As mentioned before, disinfection can not kill all microorganisms but only reduce its number. • Disinfection can be accomplished with: 1. Heat disinfection 2. Chemical disinfection • Object that can be disinfected are bedpans, patient skin before operation and surgeon hands before putting gloves. 25 BMT_335 Sterilization
1. Heat Disinfection • It is accomplished by boiling water at atmospheric pressure for at least 5 min’s 26 BMT_335 Sterilization
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 27 BMT_335 Sterilization
Asepsis – Summary Asepsis Sterilization Heat Disinfection Chemical Steam Dry heat Radiation Gas Heat Gamma Boiling water Phenol Ethylene oxide 70% Alcohol Formalin Hexachlorophene Heat or chloramines solution Liquid 28 Chemical Glutaric Aldehyde BMT_335 Sterilization
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. 29 BMT_335 Sterilization
Disinfection and Sterilization - New methods BMT_335 Sterilization
Table 1. New methods in disinfection and sterilization Process Agent Regulatory agency action Disinfection Ortho-phthalaldehyde (Cidex FDA cleared, October 1999 OPA) Antimicrobial coating (Surfacine) Not FDA/EPA cleared Superoxidized water (Sterilox) Not FDA/EPA cleared Sterilization Liquid sterilization process (Endoclens) Not FDA cleared Rapid readout ethylene oxide Not FDA cleared biological indicator (Attest) New plasma sterilizer (Sterrad 50) 31 BMT_335 FDA cleared, January 1999 Sterilization
1. Ortho-Phth-alaldehyde (OPA) • Chemical Sterilizaer • Adventages: – – not eye and nasal passages irritant has excellent stability over a wide range of p. H (3 to 9) has a barely perceptible odor Like glutaric aldehyde, it has excellent material compatibility • Disadvantage: – It stains proteins gray (including unprotected skin) 32 BMT_335 Sterilization
OPA vs. Glutaric Aldehyde Table 2. Activity of glutaraldehyde and ortho-phthalaldehyde against Mycobacterium bovis Disinfectant 1. 5% glutaraldehyde 2. 5% glutaraldehyde 0. 21% ortho-phthalaldehyde Time for 6 -log 10 reductiona 28 -36 minutes 14 -18 minutes 4. 8 -6. 3 minutes a. Range of values from two different laboratories (4). 33 BMT_335 Sterilization
2. Surfacine • Surface disinfectants such as phenols • Advantages – Effective in significantly reducing microbial contamination – Cost-effective – Have long-term residual activity 34 BMT_335 Sterilization
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 35 BMT_335 Sterilization
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 – – – 36 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 BMT_335 Sterilization
5. Hydrogen Peroxide Plasma • A New Low-Temperature Sterilization Technique. • Can be used for temperature-sensitive equipment. 37 BMT_335 Sterilization
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 38 BMT_335 Sterilization
Sterilization & Disinfection End BMT_335 Sterilization
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