Asepsis: Sterilization and Disinfection BMT_335 Sterilization

Asepsis It is keeping medical instruments free from microorganisms This is accomplished by: 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. 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 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 BMT_335 Sterilization

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 BMT_335 Sterilization

I. Sterilization - Process

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 BMT_335 Sterilization

Sterilization Principles There are 3 different sterilization principles: Heat sterilization Chemical sterilization Radiation sterilization Each principles is discussed in the following sections. BMT_335 Sterilization

1. HEAT STERILIZATION 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: Steam sterilization (Autoclaving) Dry heat sterilization 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 sterilization BMT_335 Sterilization

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. 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. BMT_335 Sterilization

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 BMT_335 Sterilization

2. CHEMICAL STERILIZATION BMT_335 Sterilization

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, ) 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. 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). 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. 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 60Co). Procedure: Objects on belt conveyer Expose objects to 25 to 30 kGy for about 24 hrs. BMT_335 Sterilization

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 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: Heat disinfection Chemical disinfection Object that can be disinfected are bedpans, patient skin before operation and surgeon hands before putting gloves. BMT_335 Sterilization

1. Heat Disinfection It is accomplished by boiling water at atmospheric pressure for at least 5 min’s 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 BMT_335 Sterilization

Asepsis – Summary 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. BMT_335 Sterilization

Disinfection and Sterilization - New methods BMT_335 Sterilization

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)       BMT_335 Sterilization

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) BMT_335 Sterilization

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 4.8-6.3 minutes 0.21% ortho-phthalaldehyde aRange of values from two different laboratories (4).    BMT_335 Sterilization

2. Surfacine Surface disinfectants such as phenols Advantages Effective in significantly reducing microbial contamination Cost-effective Have long-term residual activity 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 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 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. 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 BMT_335 Sterilization

Sterilization & Disinfection End BMT_335 Sterilization