Decontamination Procedures t.ppt

8/10/2019 Decontamination Procedures t.ppt

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Decontamination Procedures

for Medical Equipment
http://www.infectioncontroltoday.com/articles/articles/241microbe.htmlhttp://www.infectioncontroltoday.com/articles/articles/241microbe.htmlhttp://www.infectioncontroltoday.com/articles/articles/241microbe.html


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Introduction

Decontamination of medical

equipment involves thedestruction or removal of any

organisms present in order toprevent them infecting otherpatients or hospital staff.


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M icrobes (bacter ia & viruses)

Microbes can be carried from one person toanother on the surface of any equipment thatis shared between them unless it is decontaminatedbetween use.

They can also be carried on the skin surfacewhich is why hand washing between examiningpatients is important.

Microbes gain access to the body, through openwounds, inhalation of infected secretions orby close contact with mucous membranes.


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decontamination processThe process by which microbes arepassed from one infected person, tocause infection in another, is known as

'cross-infection'.Cleaning, disinfection and sterilizationare all procedures that are used in thedecontamination process.Decontamination reduces the risks ofcross infection and helps to maintainthe useful life of equipment.


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Cleaning is the process that removes contaminantsincluding dust, soil, large numbers ofmicro -organisms and organic matter

(e.g. blood, vomit).It is an essential prerequisite to

disinfection and sterilization.It also removes the organic matter on

which micro-organisms mightsubsequently thrive.


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DisinfectionIs a process used to reduce thenumber of micro-organisms but

not usually bacterial spores.The process does not necessarilykill or remove all micro-organisms, but reduces theirnumber to a level which is notharmful to health.


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Sterilizationremoves or destroysall forms of microbiallife including bacterialspores.


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Groups of r iskEach instrument or piece ofmedical equipment which comes

into contact with a patient is apotential source of infection.These are divided into 3 groups

of risk:High riskIntermediate risk

Low risk .


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H igh r isk i temscome into close contact with a break in theskin or mucous membranes or areintroduced into a normally sterile body area.e.g. surgical instruments, needles, urinary

and other catheters.Sterilization is required for this group.


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I ntermediate r isk i temscome into close contact with mucousmembrane or are items contaminated withparticularly virulent or readily transmissibleorganisms.e.g. Items of respiratory equipment including

laryngoscope blades, endotracheal andtracheostomy tubes, oropharyngeal and nasalairways.Disinfection is required for this group.


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L ow r isk i temsonly come into contact with normalintact skin.e.g. stethoscopes or washing bowls.Cleaning and drying is usually adequatefor this group


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Techniques of disinfection and ster i l ization

Before equipment is to be disinfected orsterilized, it should be thoroughly cleanedto remove any visible dirt or secretions.This involves washing with water anddetergent (soap).Protective clothing (an apron, gloves and afacemask) should be worn.


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DisinfectionDisinfection is best achieved by moist heat such asboiling in water (100 C for 10 minutes at sea level)which kills all organisms except for a few bacterialspores.

temperature at which water boils decreases withaltitude and a longer boiling time will be required. e.g.at 4000m above sea level where boiling occurs at86 C a minimum of 20 minutes is required for

disinfections.It is important to note that boiling equipment items in

water will not achieve sterilization.


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DisinfectionDisinfection can also be achieved by usingchemicals which however may themselvesbe toxic when allowed contact with skinor are inhaled.They can also be corrosive and flammableso that protective clothing (gloves, apronand a facemask) should be worn.


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Chemical disinfectantsChemical disinfectants may be suppliedready to use or may need accuratedilution to provide an appropriatesolution.disinfectants can decay and lose activityDecay is more rapid at high

temperatures and can be accelerated bythe presence of impurities. All disinfectants take time to work.


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Range of Activity of

Disinfectants Gram positive bacteria. E.G. Staphylococci, are more sensitive thangram negative bacteria e.G. Pseudomonas.Mycobacteria and spores are relativelyresistant.

Enveloped viruses e.G. HIV are killed by mostdisinfectants but non-enveloped viruses e.G.Coxsackie tend to be more resistant.


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Spores Fungal spores are easily killed bydisinfectants.Other bacterial spores e.g. Clostridia are

resistant to most disinfectants in commonuse.Tubercle bacteria are more resistant tochemical disinfectants than other bacteria.They can be killed by exposure to 2% alkalineGlutaraldehyde solution (Cidex) for 60minutes.


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Viruses .Hepatitis B virus (HBV) and HumanImmunodeficiency Virus (HIV) are inactivatedby Cidex in 1 - 2 minutes.to ensure adequate penetration, soiled itemsshould be placed in a 2% glutaraldehydesolution for 30 minutes.Exposure to 70% alcohol solution for 10minutes is also effective. Viruses causing Rabies, Lassa fever andother haemorrhagic fevers are also killed byCidex.


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Heat In order to kill microbial agents, heat can beapplied in dry or wet form.The advantage of wet heat is a better heattransfer to and into the cell resulting inoverall shorter exposure time and lowertemperature.


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Steam ster il izationSteam sterilization uses pressurized steam at121-132 C (250-270 F) for 30 or 40 minutes.

This type of heat kills all microbial cellsincluding spores, which are normally heatresistant.In order to accomplish the same effect withdry heat in an oven, the temperature needs to

be increased to 160-170 C (320-338 F) for periods of 2 to 4 hours.


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Liquid Chemicals Used as

Disinfectants Liquid disinfectants are preferably used forsolid surfaces and equipment.They vary greatly in their efficiency,depending on the chemical constituents andthe agents involved.


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Variables to remember when disinfecting:

Nature of surface being disinfected - Porous or smooth

the more porous and rough the surface, thelonger a disinfectant will need to beeffective.


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Number of microorganism presentHigher concentrations require a longerapplication time and/or higher concentrationof disinfectant.


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Resistance of microorganisms- Microbial agents can be classifiedaccording to increasing resistance todisinfectants and heat


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Duration of exposure and temperatureIncreased exposure time increases theeffectiveness of disinfectants.Low temperatures may slow down theactivity requiring more exposure time.


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Surface Disinfectants andM icrobial Activity

Disinfectants work by absorbing onto anymicrobial cell.such absorption increases the permeability of

the cell membrane, ultimately leading torupture and leakage of the contents of the

cell.The cell dies.There is no chance for mutation.


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Chemicaldisinfectant

solutions


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concentrations 5% to 10 %.Unpleasant odor

Toxic. protective equipmentused for disinfection of walls, floors, bench tops.They effectively kill bacteria including

Mycobacterium tuberculosis , fungi and lipid-containing viruses.They are not active against spores

Phenol and Phenol Derivatives:


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Halogens (Chlorine and Iodine):Sodium hypochlorite is the most commonCommon household bleach (5% available

chlorine) can be diluted 1/10 to 1/100 with waterAlways use personal protective equipmentAt high concentrations and extended contact time,considered cold sterilantsIodine has similar properties to chlorine.They are most often used as antiseptics and insurgical soaps and are relatively nontoxic tohumans.


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AlcoholsEthyl or isopropyl alcohol in concentration of 70% to 90%are good general-use disinfectants.they evaporate fast and therefore have limited exposure

time.They are less active against non-lipid viruses and

ineffective against bacterial spores.Concentrations above 90% are less effective.

(eg methanol, ethanol & isopropanolol) have good activityagainst bacteria & viruses.They should only be used after all the visible surface dirt

has been removed from the area to be disinfected.


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AldehydesFormalin: Formalin is 37% solution of formaldehydein water.Dilution of formalin to 5% results in aneffective disinfectant.

Formaldehyde is a human carcinogen andcreates respiratory problems at low levels ofconcentration.


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Glutaraldehyde:

chemically related to formaldehyde, is moreeffective against all types of bacteria, fungi,and viruses.Vapors of glutaraldehydes are irritating tothe eyes, nasal passages and upperrespiratory tract.


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Quaternary Ammonium Compounds (Quats):

detergents with strong surface activity.They are active against Gram-positive bacteria

They are less active against Gram-negative bacteria .Quats are relatively nontoxic and can be used for

decontamination of food equipment and forgeneral cleaning.


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FormaldehydeFormaldehyde is irritant to the eyes, respiratory tractand skin.It can also be absorbed by some materials andsubsequently slowly released with potentiallyhazardous results.

Hot air sterilization takes a long time and itemsmust be able to withstand temperatures of at least160 C for periods of 2 hours or more.


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Formaldehyde gasFormaldehyde gas is primarily used in thedecontamination of spaces or biologicalcontainment equipment like biologicalsafety cabinets.Formaldehyde is a toxic substance and a

suspected human carcinogen.Considerable caution must be exercised inhandling, storing, and using formaldehyde


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Ethylene oxideEthylene oxide is a colorless gas which is toxic to inhale.It is effective against all organisms and does not damage

equipment.The operating cycle ranges from 2 - 24 hours so theturnaround time is prolonged and it is a relativelyexpensive process.

A variety of vapors and gases possess germicidal properties.The most commonly used are formaldehyde and ethyleneoxide.


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Applied in closed systems under controlledconditions (e.g., humidity) these gasesachieve sterility.Ethylene oxide is used in gas sterilizersunder controlled conditions.

Ethylene oxide is also a human carcinogenand monitoring is necessary during its use.


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Sterilisation by irradiationSterilisation by irradiation is an industrial

process and particularly suited to thesterilization of large batches of products.Irradiation can cause serious deteriorationof materials and is therefore not a suitablemethod for the resterilisation of equipmentitems


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Radiation Gamma and X-ray are two principal types ofionizing radiation used in sterilization.Their application is mainly centered on thesterilization of prepackaged medical devices. Ultraviolet (UV) radiation is a practical methodfor inactivating viruses, mycoplasma, bacteria andfungi.UV radiation is successfully used in the

destruction of airborne microorganisms.UV light sterilizing capabilities are limited onsurfaces because of its lack of penetrating power .

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