Sterilization

STERILIZATION OF OPERATION THEATER & OPERATION THEATER EQUIPMENTS

Presented by :Dr. ANKITA MADAN

DEFINITIONS Antiseptic Substance that has

antimicrobial activity & that can be safely applied to living tissues.

Bacteriostatic Agent which prevents bacterial growth but doesn’t kill bacteria.

Bioburden The number & types of viable organisms with which an object is contaminated.

Biological Indicator It is sterilization process monitoring device consisting of a standardized viable population of micro-organisms of high resistance to mode of sterilization being monitored.

Chemical Indicator It is sterilization process monitoring device designed to respond with a characteristic chemical change to one or more parameters of sterilization cycle.

Chemosterilizers A chemical used for destroying all forms of microbiological life including spores.

Decontamination The process by which contaminated items are rendered safe for personnel without protective attire to handle or render item safe for reuse.

Disinfection Destruction of many but not all micro-organisms on inanimate objects.

The Center Of Disease Control & Prevention (CDC) has given 3 levels of disinfection LEVELS OF DISINFECTION

LEVELS BACTERIA LIPID & MEDIUM SIZED VIRUSES

NON LIPID OR SMALL SIZED VIRUSES

VEGETATIVE

TUBERCLE

SPORES

FUNGI

HIGH + + + + + +

INTERMEDIATE

+ + +/- + + +/-

LOW + - - +/- + -

Disinfectants chemical germicides formulated to be used on inanimate objects.

The Environmental Protection Agency (EPA) classified them as those

With Tuberculocidal activity Without Tuberculocidal activity.

Mechanical Indicators sterilizer components that gauge & record time, temperature, humidity pressure during sterilizing cycle.

Sterilization destruction of all form of micro-organisms ( high temperature).

Terminal sterilization sterilization process carried out after final packaging of the item.

Sterility Assurance Level (SAL) the probability of survival of micro-organisms after a terminal sterilization process & is predictor of efficacy of the process. A SAL of 10-6 indicates non sterile item.

ORDER OF RESISTANCE In descending order are-

Prions

Coccidia (cryptosporodium)

Bacterial spores (bacillus)

Mycobacterium

Cysts

Small non-enveloped viruses (Polio)

Trophozites

Gram Negative Bacteria (Pseudomonas)

Fungi

Large non-enveloped viruses (adenovirus)

Vegetative Bacteria (Staph Aureus)

Lipid or medium sized viruses (HIV, Hepatitis B)

STAGES IN THE PROCESS ARE

1. General Cleaning & Decontamination.

Then if required2. Sterilization3. Disinfection

CLEANING OF EQUIPMENTS

Aim To remove retained salt & organic soil which

can inactivate chemical germicides or protect organisms from destruction during disinfection.

Procedure Immersible items should be cleaned under

water, with or without detergent for atleast 3 min. to prevent aerosolization of organisms & those not immersible can be cleaned with cloth soaked in detergent & water.

Disassembly- Devices should be disassembeled &

jointed instruments must be opened. Cleaning- Before cleaning, manufacturer`s

instruction are consulted. Tapes, soils, adhesive residues are

dissolved by using appropriate solvents.

Devices must be soaked in protein dissolving solution to prevent coagulation of blood & then it should be scrubbed thoroughly inside out.

Complicated devices can be cleaned by ultrasonic cleaning after gross soil has been removed.

Rinsing- After cleaning,

rinsing should be performed; lumens & channels are well flushed during each rinse. They should be towel or air dried.

METHODS OF STERILIZATIONPASTEURIZATION It’s a high level disinfectant. The equipment is immersed in water at

an elevated temperature of usually 80°c for 10min or 70°c for 30min.

It can`t kill all spores & viruses. So it is recommended for perishable & where absolute sterility is not required.

E.g. Breathing tubes, ETT, Reservoir bags, Face masks, Laryngoscope blades, ventilator bellows & any rubber goods.

BOILING For small articles like face masks. It is suitable for metal & also for

rubber & neoprene items. Instruments are boiled in water for 5-

15min for destruction of vegetative matter.

FILTRATION Microfilters are used to prevent entry

of micro-organisms They remove particles of diameter

0.5µ or greater

STEAM STERILIZATION (AUTOCLAVING)

• Here saturated steam under pressure is used.

Principle Water boils when its

vapor pressure equals that of surrounding atmosphere.

Thus when water is boiled in closed vessel at increased pressure, the temperature at which it boils & that of steam which is formed will exceed 100°C.

When steam comes in contact with cooler surface condenses to water & gives up its latent heat to that surface.

Thus 1600ml of steam at 100°C & at atmospheric pressure condenses into 1ml of water at 100°C & releases 518calories of heat.

TEMPERATURE (°C)

PRESSURE(lb/in2)

TIME (MIN)

121 15 15

126 20 10

134 30 3.5

150 50 Few Seconds

It can also be carried out at Low Temperature & Low Pressure (LTS) i.e. at 37kPa with 74°C, but it won’t kill spores.

The addition of vapor of formaldehyde to this is

called as low pressure steam & formaldehyde (LTSF) which can kill many if not all spores.

Ordinarily rubber goods, linens & metals are autoclaved.

Post exposure/ Exhaust Phase. At the end the steam should be exhausted from

the autoclave to avoid condensation of water on the load when cool air is admitted.

Flash Sterilization

Refers to steam sterilization of items for immediate use.

DRY HEATING

Articles are packed in special craft papers and then placed in a thermostatically controlled Dry Heat Sterilizer.

Precaution temperature is raised and lowered slowly to prevent breakage by uneven expansion.

Mainly suitable for ophthalmic instruments and glass items but not plastics or rubber.

It is useful for sterilization of powders, grease, oil and glass syringes.

Holding Temperature (°C)

Time Of Sterilization (min)

180 30

170 60

160 120

150 150

CHEMICAL (COLD) STERILIZATION

Utilizes liquid chemical agents Especially useful for heat sensitive

equipment. Performed by soaking item in the

solution. Kill the organisms by coagulation /

alkylation of proteins and also by enzymatic degradation and lysis of cell membranes.

The criteria to be satisfied in the Chemical Methods are

1. Must be capable of killing spores.2. Should be non-corrosive3. Should be Non-irritant.4. Should be Economical.5. Should be stable6. Should penetrate grease & fibers.7. Should be non-toxic.

Factors Influencing Chemical Sterilization:

a) Concentration of the Chemical: Rate of kill of bacteria varies directly

with the concentration of the disinfectant.

b) Temperature: Designed to be used at room

temperature.

c) Evaporation and light deactivation:

Volatile agents evaporate easily. Exp: Chlorine Products. Exposure to light adversely affects the disinfectant.

d) PH: Alcohols work best in alkaline PH while

aldehydes work best in acidic PH.e) Bioburden: The effectiveness of the disinfectant

depends on the nature and number of contaminating microorganisms

f) Characteristics of the item to be sterilized: A disinfectant solution will be effective only if it can

contact all the surfaces on the item.

g) Time: Time required for different chemical agents to

function effectively varies from seconds to hours.

h) Use Pattern, Use Life & Storage Life: Use Pattern refers to how many times the solution

can be used. Use Life indicates limited period of time during which

activated solution can be used. Storage life is the time period after which the unused

or inactivated product is no longer deemed effective.

FORMALDEHYDE: Used principally in water based

solution called formalin. Vapor can be generated from paraformaldehyde tablets which contain 95% formaldehyde in a polymerized form.

It is a high level disinfectant. It is non corrosive and is not

inactivated by organic matter. Widely used for sterilization of

endoscopic equipment, catheters etc.

For better effect it needs relative humidity of 60-80% and temperature of 37°C.

Residual formaldehyde may affect the skin, but it can be neutralized by ammonia.

Limited by its pungent odor and fumes.

Should be handled as a potent sensitizer and probable carcinogen.

QUATERNARY AMMONIUM COMPOUNDS (QUATS)

Low level disinfectants They are bactericidal, fungicidal

& viricidal but not sporicidal. They are effective against gram

positive than gram negative and marginally effective against Pseudomonas. They inactivate HIV but not hepatitis virus.

They are inactivated by organic materials.

Side effects are allergic reactions and contact dermatitis.

PHENOLIC COMPOUNDS They are intermediate to low level disinfectants.

Derived from carbolic acid (phenol), one of the oldest germicides.

They are bactericidal, fungicidal and viricidal but not sporicidal.

They are active in the presence of organic matter.

They are irritant to skin & mucous membranes, have bad odour.

They are absorbed by rubber and residual disinfectant may cause tissue irritation.

ALCOHOL Intermediate level disinfectants. Ethyl alcohol is bactericidal in 60-

90% concentration and isopropyl alcohol in 60% concentration.

They kill bacteria but not spores, action against viruses is variable.

CDC recommends exposure to 70% ethanol for 15mins to inactivate the hepatitis virus but 1 min for HIV.

Their effectiveness is limited because

of rapid evaporation, lack of ability to penetrate organic matter.

They are used mainly to disinfect external surfaces of equipment like stethoscopes, ventilators, fiberoptic cables.

They can damage mounting of lensed instruments and tend to swell and harden rubber.

Chlorhexidine (Savlon) : It is a non detergent

chemical disinfectant usually used in the concentration of 0.5% in 70% alcohol for skin.

Tubes, masks etc. are sterilized by keeping for 20 min in 0.1% aqueous solution.

Chloroxylenol (Dettol): It is used as mild antiseptic

agent

IODOPHORS It is a combination of iodine and

carrier with a resulting complex providing sustained release reservoir of iodine.

They are bactericidal, viricidal and tuberculocidal but not sporicidal.

These are intermediate to low level disinfectants.

They corrode the metallic items and non-metallic items may be stained or discolored.

PERACETIC (PEROXYACETIC) ACID It is acetic acid with an extra oxygen atom. It is bacteriocidal, sporicidal, fungicidal

and viricidal. They are effective in the presence of

organic matter. But it is corrosive and irritating to skin in concentrated solution.

It is active ingredient in the steris sterilant. This is a single use concentrate of 35% peracetic acid + corrosion and degradation inhibitors.

Used in wide variety of heat sensitive and delicate instruments.

Used on wet or dry items and there is no personnel exposure. It can be situated in the Operating room suite.

It is useful only for totally immercible objects and only small number instruments can be processed in a cycle.

CHLORINE AND CHLORINE PRODUCTS They are intermediate level

disinfectants. They are active against bacteria and

viruses but not spores. They are available both in liquid

(sodium hypochlorite) and solid (Calcium hypochlorite) forms.

They are most widely used, inexpensive and fast acting.

Highly effective against HIV.

Household bleach is an inexpensive and excellent source of sodium hypochlorite.

A 1:100 to 1:1000 dilution is effective against HIV.

1:5 to 1:10 dilution is effective against hepatitis.

It also inactivates Cruetz Feldt Jakob disease with an exposure time of 1 hr.

Their use is limited by their corrosiveness, inactivation by organic matter and may leave residue which causes irritation to skin, eye and respiratory tract

Potential hazard is the production of carcinogen bis-chloromethyl ether, when hypochlorite solutions come into contact with formaldehyde.

A mixture of hypochlorite with acid will cause rapid evolution of toxic chlorine gas.

HYDROGEN PEROXIDE It is an effective bactericidal, fungicidal,

viricidal and sporicidal. It is commercially available as 3%

solution but can be used upto 25% concentration.

It is non corrosive and not inactivated by organic matter but irritant to skin and eyes.

GLUTARALDEHYDE (CIDEX) It is a saturated dialdehyde. It is used in

1.0% concentration (but highly effective in 2% concentration).

It is high level disinfectant. It kills spores within 12 hrs and viruses within 10 min.

Widely used because of their excellent biocidal properties, activity in the presence of organic matter, non corrosiveness and noncoagulation of proteinaceous material.

Disadvantages : It is noxious and

irritating to tissues and hence thorough rinsing of all exposed materials is mandatory.

Prepackaging is not possible and equipment will be wet.

Pseudo-membranous laryngitis has been linked to disinfection of tracheal tubes with glutaraldehyde.

OZONE: Sterilizers use O2, water & electricity to

produce Ozone.Advantages: Useful for most goods that need low

temperature sterilization. Process is environmentally friendly. Treated objects are dry.Disadvantages: Not approved for flexible scopes & reactive

materials such as copper & brass. Unsuitable for natural gum rubber products

Advantages of Chemical Sterilization

Technically easier. Suitable for equipments damaged by heat

sterilization. Sophisticated chemical methods like Ethylene Oxide

achieve perfect sterilization.

Disadvantages:

Act only on exposed surfaces Some chemicals react with metals. Some impregnate with the materials such as rubber

& plastics & some agents destroy it. Residual chemicals may form the source of infection.

Disinfectant Gm +ve Bacteria

Gm –ve Bacteria

Tubercle bacillus

Spores

Viruses

Fungi

Formaldehyde + + + - +

QUATS + + - - + +

Phenolic compounds

+ + +/- - + +

Alcohol + + + - + +

Chlorine + + + - + +

Hydrogen Peroxide

+ + + +/- + +

Glutaraldehyde + + + +/- + +

GAS STERILIZATION EO is used for this purpose.

It is a liquid below 11°C. It is available in high

pressure tanks, unit dose ampoules and cartridges.

1. Preparation for ethylene oxide (EO) sterilization (propylene oxide):

Before packaging, items must be disassembled, cleaned and dried to allow the gas to penetrate throughout the whole product.

Caps, plugs, valves, stylets must be removed. Hollow bore products and needles should be open at both ends.

They should be towel or air dried.

A relative humidity of 35% to 70% and a temperature of 18 to 22°C are recommended.

Items to be sterilized are placed in carries that do not absorb E.O. They should be loaded loosely to allow for uniform penetration of gas throughout the load.

Factors affecting EO Sterilization : Gas concentration: The solubility of

EO in the product and the gas diffusion rate through the product will influence the sterilant concentration.

Temperature: Exposure time can be decreased by increasing the temperature.

Humidity: Moisture hydrates microbes, making then susceptible to destruction by EO.

Protective barriers: Blood and other proteinaceous materials can act as barriers to EO.

Packaging: The wrapping must be permeable to EO gas and water vapor and allow for proper aeration.

Exposure time: Depends on factors mentioned above, generally range from 1.5 to 6 hrs. or many require upto 12 hrs

3. Sterilizers:

EO sterilizers are of two types,

⁻ general purpose and

⁻ special purpose.

7. Advantages: It is effective against all organisms: Damage to most equipment is minimal. Items can be prepackaged. Used for sterilization of delicate

instruments like pump oxygenators, valves, ventilators etc.

8. Disadvantages: More expensive Fire and explosions have been reported. Long duration. Personnel need to be highly trained and

supervised.

RADIATION STERILIZATION Mainly used for disposable products.

Gamma radiation is an electromagnetic wave produced during the disintegration of certain radioactive elements like cobalt-60.

All organisms including spores, viruses will be killed. Lethal dose is 2.5 megarads(kills bacteria by ionizing there DNA).

The products can be prepackaged.

As there is no temperature rise, thermolabile materials can be sterilized.

Equipments may be used immediately after treatment, with no risk from retained radioactivity.

Disadvantage is that it is not practical for every day use and it is expensive.

INFRARED RADIATION This is method of sterilization by dry

heat usually used to sterilize the syringes and small instruments

STERILIZATION OF INDIVIDUAL EQUIPMENT

ANAESTHESIA CARTS & MACHINES

Top surface should be cleaned of visible material between cases.

Disinfected with germicide at end of day

GAS CYLINDERS

Washed with water & detergent.

Then wiped or sprayed with germicide

UNIDIRECTIONAL VALVES, APL VALVES & WATER TRAPS Cleaned & disinfected

periodically. They are

disassembled & cleaned by wiping disc. The inside of the plastic dome & the valve seat with alcohol or detergent.

Some APL valves may be autoclaved & some may be Pasteurized.

TRACHEAL TUBES, SUCTION CATHETERS, AIRWAYS

Washed with soap & water & rinsed.

A malleable brush may be used to clean the inner aspect of tubes & airways.

Boiling will sterilize it but tubes will be softened.

Chlorhexidine 0.1% solution can be used. Here equipments should be soaked for 30-60min for complete sterilization.

Autoclaving will be effective. But ETT should be replaced after 6 uses.

Gamma radiation is satisfactory.

FACE MASKS Rinsed, soaked &

scrubbed after use. Wash with soap & water

& thoroughly dried. Keep in water at 60-

70°C for 20min. this reduces number of pathogens to very small no.

Gas sterilization is v.effective method.

It should not be boiled as boiling deteriorates masks

LARYNGOSCOPE BLADES Boiled or Autoclaved

after cleaning, but they may spoil electric connections.

Carbolic acid 1-20% for 30min. can be used.

Formalin oven can be used.

Wiping with 70% alcohol or 0.1% Chlorhexidine in 70%alcohol is useful.

BREATHING TUBES & RESERVOIR BAGS Wash thoroughly, rinse &

allow it to dry in air. Repeated boiling spoils the

antistatic properties, so it can be boiled once a week for 10min.

Can be Pasteurized at 75°C for 10min.

Chemical disinfection with glutaraldehyde for 1hr can be carried out by using automatic washing machine or by immersion. Tube should be inserted vertically during procedure

Y-PIECE Chemical

disinfection. Ethylene oxide or

Plasma sterilization can be used.

It can be soaked in solution of water & detergent, then scrubbed manually or placed in washing machine.

MAPLESON SYSTEM

Should be disassembled & component cleaned

Metal components can undergo Autoclaving.

Rubber & Plastic parts can undergo Gas or Plasma Sterilization.

ADAPTORS Rinsed & soaked in

solution of detergent & water.

May be washed manually or in washing machine.

Rubber & plastic adaptors- sterilized with EO, plasma sterilization or in Glutaraldehyde.

Metal adaptors may be autoclaved or Pasteurized.

WATER`S CANISTER

Can be washed & boiled.

Can be Steam Autoclaved.

Can be sterilized using Ethylene Oxide.

CIRCLE ABSORBER Gamma radiation Ethylene oxide. Formalin chamber. Can be dismantled

& disinfected with spirit.

Entry of organisms, while in use, can be prevented by using filters.

VENTILATORS Bacterial filters Ethylene oxide Internal irrigation with

antiseptics, provided the circuit is water tight.

Ultrasonic nebulization with alcohol, hydrogen peroxide.

Some have breathing units which can be autoclaved.

Formalin Chambers can be used.

HUMIDIFIERS Pasteurized at

60°C. copper sponges may be used during this process as it has antibacterial effect.

Frequent & thorough washing may be effective

SYRINGES & NEEDLES Disposable syringes

& needles are ideally gamma irradiated.

Glass syringes are ideally autoclaved.

In case of emergency, boiled in distilled water for 5min.

INSTRUMENTS FOR LOCAL BLOCKS

Lignocaine & Bupivacaine syringes, ampoules can stand Autoclaving at 160°C for 20min at 20psi.

Repeated Autoclaving is avoided.

Adrenaline ampoules should be autoclaved only once.

Disposable sets are gamma irradiated.

BLOOD PRESSURE CUFFS, TUBING'S & STETHOSCOPES

Washed & dried thoroughly.

Then subjected to chemical disinfection or Gas Sterilization.

Nonfabric cuffs – plasma Sterilization is used.

Stethoscopes can be washed with water & wiped with alcohol.

SPECIAL CONCERNS

SPECIAL CONCERN IN OPEN CASE OF PULMONARY TUBERCULOSIS.

Endotracheal tubes & suction catheters are disposed off.

If it is to be reused then keep in 0.1%Chlorhexidine solution for 1hr, then it is cleaned & scraped with soap & water & then sterilized by boiling or autoclaving.

Boiling for 3min will kill tubercle bacilli. It can also be immersed in

2%Glutaraldehyde solution for 1hr.

SPECIAL CONCERN IN HEPATITIS B POSITIVE CASES

The virus is killed by Autoclaving & Gamma Radiation.

Chemical sterilization- Sodium Hypochlorite 50ppm,

Glutaraldehyde 2% for 10 min. Iodophor 80ppm Isopropyl alcohol 70% for 15 min.

SPECIAL CONCERN IN HIV CASESThe virus is relatively unstable in environment &

can easily be inactivated by wide range of Chemical Disinfectants like-

Glutaraldehyde 2% for 10 min. Sodium Hypochlorite 50ppm. Hydrogen peroxide 0.3%. Ethyl alcohol 50%, Isopropyl alcohol 70% for 1

min. Phenol.

SPECIAL CONCERN IN PRION DISEASES It is extremely resistant to normal

Sterilization methods. For Critical Devices – Steam

Sterilization for 30min at 132°C is recommended.

For Non-Critical Devices- Sodium Hypochlorite, undiluted or 1:10 dilution is used. 1N sodium hydroxide at room temperature for 15min can also be used.

OPERATION THEATRE CLEANING AND FUMIGATION

Cleaning programme should be simple and clearly laid out policy which can be adhered to.

Daily cleaning should be carried out after the

operating sessions are over. All the surfaces should be cleaned with

detergent and water and may be wiped over with a phenol if any spills with blood / body fluid are present.

All the walls must be wiped down to hand

height everyday.

The floors should be scrubbed with warm water and detergent and dried. No disinfectant is necessary.

The O.T. table and other non clinical equipments must be wiped to remove all visible dirt and left to dry.

Weakly cleaning of all the areas inside the

operating theatre complex should be done thoroughly with warm water and detergent and dried.

The storage shelves must be emptied and wiped over, allowed to dry and restacked.

Procedure for fumigation:

The windows should be sealed and formaldehyde should be generated either by boiling a solution of formalin 40% or by adding it to potassium permanganate, in a metal vessel on the floor, since heat is also generated. The door is than closed and scaled.

For a 10 x 10 x 10 ft room - 150 gm potassium permanganate and 280 ml of formalin are used

Duration: In case of any construction in O.T. 48

hrs In case of inflected cases 24hr For routine clean cases 12 hrs. Alternatively 250 ml of formalin and 3000 ml

of tap water are put into a machine (auto mist) and time is set for 2 hrs. The mist is circulated for 2hrs inside the closed room.

Room is kept sealed for another 2 hrs for action of vapor. Ventilate for suitable time for vapor to dissipate. Room then can be used.

Three swabs are taken from walls, all equipments, floor or O.T. table at intervals.

1st swab - 48 hrs after fumigation 2nd swab- 24 hrs after Is' swab 3rd swab - 12 hrs after 2"d swab

All three consecutive swabs should come negative.

In some centres, Bacillocid is being used for fumigation. It is combination of chemically bound formaldehyde and glutaraldehyde.

Ideally all O.T. rooms should be fumigated once a week

REFERENCES Understanding Anesthesia Equipments-

Dorsch & Dorsch. Anaesthesia Equipments- Wards. Textbook of Microbiology –CP Baweja Google

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