Sterilization PPdesign Final

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Asepsis: Sterilization and Disinfection


Asepsis

• It is keeping medical instruments free from microorganisms

• This is accomplished by:I. Sterilization

II. Disinfection


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.


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


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


Which procedure to use?

CategoryItems in each category Procedure

CriticalItems 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-criticalItems such as bedpans, blood pressure cuffs, and bedside tables

Low level disinfection

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


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.


1 .HEAT 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


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


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.


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.


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


2. CHEMICAL STERILIZATION


2. Chemical Sterilization - Types

• The chemical compounds used can be:a) Gas Sterilizationb) Liquid Sterilization

• Generally, chemical sterilization procedures have the disadvantages of presenting health hazards to users (e.g. poisonous, flammable, )


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.


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).


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.


3. RADIATION 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.


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


II. DISINFECTION


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.


1. Heat Disinfection

• It is accomplished by boiling water at atmospheric pressure for at least 5 min’s


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


Asepsis

Sterilization Disinfection

Heat RadiationChemical Heat Chemical

Steam

Dry heat

Gas

Liquid

Gamma Boiling water Phenol

Heat or chloramines solution

Hexachlorophene

70% AlcoholEthylene oxide

Formalin

Glutaric Aldehyde

Asepsis – Summary


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.


Disinfection and Sterilization - New methods


Table 1. New methods in disinfection and sterilization

ProcessAgentRegulatory agency action

DisinfectionOrtho-phthalaldehyde (Cidex OPA)

FDA cleared, October 1999

Antimicrobial coating (Surfacine)

Not FDA/EPA cleared

Superoxidized water (Sterilox)

Not FDA/EPA cleared

SterilizationLiquid sterilization process (Endoclens)

Not FDA cleared

Rapid readout ethylene oxide biological indicator (Attest)

Not FDA cleared

New plasma sterilizer (Sterrad 50)

FDA cleared, January 1999


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)


OPA vs. Glutaric Aldehyde

Table 2. Activity of glutaraldehyde and ortho-phthalaldehyde against Mycobacterium bovis

Disinfectant Time for 6-log10 reductiona

1.5% glutaraldehyde28-36 minutes

2.5% glutaraldehyde14-18 minutes

0.21% ortho-phthalaldehyde4.8-6.3 minutes

aRange of values from two different laboratories (4).

http://www.cdc.gov/ncidod/eid/vol7no2/rutala.htm#Asepsis:%20%20Sterilization%20and%20Disinfection


2. Surfacine

• Surface disinfectants such as phenols

• Advantages– Effective in significantly reducing microbial

contamination– Cost-effective– Have long-term residual activity


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


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


5. Hydrogen Peroxide Plasma

• A New Low-Temperature Sterilization Technique.

• Can be used for temperature-sensitive equipment.


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


Sterilization & DisinfectionEnd

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