Asepsis: Sterilization and Disinfection

1. Asepsis: Sterilization and Disinfection BMT_335

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

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. BMT_335

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 BMT_335

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 BMT_335

6. Which procedure to use? BMT_335

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 BMT_335

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

10. 1. HEAT STERILIZATION BMT_335

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 BMT_335

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 • Process is divided into 3 periods as follows: • Pre-vacuum period: air is withdrawn from device • Sterilizing period: steam is introduced under pressure to specific temperatures & times. • Post-vacuum: steam is withdrawn to dry autoclave Table shows samples of time-temperature relationships for steam sterilization BMT_335

13. Steam SterilizationAdvantages & 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. BMT_335

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. BMT_335

15. 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 BMT_335

16. 2. CHEMICAL STERILIZATION BMT_335

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, ) BMT_335

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. BMT_335

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). BMT_335

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. BMT_335

21. 3. RADIATION STERILIZATION BMT_335

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. BMT_335

23. Radiation SterilizationAdvantages 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 BMT_335

24. II. DISINFECTION BMT_335

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. BMT_335

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

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 BMT_335

28. Asepsis – Summary BMT_335

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. BMT_335

30. Disinfection and Sterilization - New methods BMT_335

31. BMT_335

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) BMT_335

33. OPA vs. Glutaric Aldehyde BMT_335

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

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 BMT_335

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 BMT_335

37. 5. Hydrogen Peroxide Plasma • A New Low-Temperature Sterilization Technique. • Can be used for temperature-sensitive equipment. BMT_335

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 BMT_335

39. Sterilization & DisinfectionEnd BMT_335