Surgical Preparation and Instrument Care
Sanitation, Disinfection and Sterilization
Learning Outcomes
After this section is completed you should be able to:
List the classes of pathogenic organisms in order of their resistance to destruction
Differentiate between sanitation, disinfection and sterilization
List the different ways that microbial control methods destroy or inhibit pathogenic organisms
After this section is completed you should be able to:
List the five categories of physical methods of microbial control
Name and describe the physical methods of microbial control
Identify the level of microbial control achieved with each of the physical methods
State an example of the application of each of the physical methods of microbial control
List the properties of the “ideal chemical agent” for microbial control
Name and describe the classes of microbial control chemicals
Identify the level of microbial control achieved by the chemical classes
List the advantages and disadvantages of the autoclave in animal care facilities
Explain the function of the autoclave
Compare and contrast the different autoclaves
Describe the preparation of each of the following for processing in the autoclave: linen packs, pouch packs, hard goods, liquids and contaminated objects
List the guidelines for loading the autoclave chamber
Compare the three different autoclave cycles
List and define the five methods of quality control for sterilization
List and define the two methods of quality control for disinfection
Section Outline
Levels of microbial resistance
Degrees of microbial control
How microbial control methods work
Methods of microbial control
Autoclave
Quality control for sterilization and disinfection
Overarching Principle
The objective in sanitation, sterilization and disinfection is to control microorganisms, or pathogens, in the environment, thus protecting patients and staff from contamination and disease, and thereby promoting optimal healing and wellness.
The Ever Present Danger
Improper application of the methods of sanitation, sterilization and disinfection can lead to microbial resistance and increase the risk of nosocomial infection
Levels of Microbial Resistance
Pathogens
Microorganisms that cause disease
Viruses
Bacteria
Fungi
Protozoan
Prions
Different classes of pathogens vary in their resistance to destruction by chemical methods
Protozoan Cysts
Bacterial Spores
Non-enveloped virus
TB organisms
Enveloped viruses
Fungi
Vegetative bacteria
Most Resistant
Least Resistant
Levels of Microbial Resistance
Microbial control
Is achieved by using methods of sanitation, disinfection and sterilization
Microbial control
Done to a degree that is practical, efficient and cost effective
Levels of Microbial Resistance
Sterility is used only when necessary
In many situations sanitation and disinfection create acceptable levels of microbial control
Degrees of Microbial Control
Sterilization is the elimination of all life from an object
Complete microbial control
Asepsis is a condition in which no living organisms are present
Free of infection or infectious material
Degrees of Microbial Control
Sanitation: The state of being clean and conducive to health.
Disinfection: To cleanse so as to destroy or prevent the growth of disease-carrying microorganisms
Degrees of Microbial Control
Disinfection, sanitation and cleaning remove most microorganisms
Most disinfectants are microbiocidal
Microbes are killed
Some disinfectants are bacteriostatic
Microbial growth is inhibited
Degrees of Microbial Control
Disinfectants can be classified according to their spectrum of activity
Bacteriocidal
Bacteriostatic
Sporocidal
Virucidal
Fungicidal
How Microbial Control Methods Work
Mode of Action
Different physical and chemical methods destroy or inhibit microbes in several ways
Damage cell walls or membranes
Interfere with cell enzyme activity or metabolism
Destroy microbial cell contents through oxidation, hydrolysis, reduction, coagulation, protein denaturation or the formation of salts
Efficacy of Microbial Control
The effectiveness of all microbial control methods depends on the following factors:
Time
Most methods have minimum effective exposure times
Temperature
Most methods are more effective as temperature increases
Efficacy of Microbial Control
The effectiveness of all microbial control methods depends on the following factors:
Concentration and Preparation
Chemical methods require appropriate concentrations of agent
Disinfectants may be adversely affected by mixing with other chemicals
Organisms
Type, number and stage of growth of target organisms
Efficacy of Microbial Control
The effectiveness of all microbial control methods depends on the following factors:
Surface
Physical and chemical properties of the surface to be treated may interfere with the method’s activity
Some surfaces are damaged by some methods
Efficacy of Microbial Control
The effectiveness of all microbial control methods depends on the following factors:
Organic debris or other soils
Will dilute, render ineffective or interfere with many control methods
Method of application
Items may be sprayed, swabbed or immersed in disinfectants
Cotton and some synthetic materials may reduce chemical activity
Methods of Microbial Control
Physical Methods
Chemical Methods
Physical Methods
Dry Heat
Oxidation
Moist Heat
Denatures microbial protein
Radiation
Damages cell enzyme systems and DNA
Filtration
Traps organisms that are too large to pass through the filter
Ultrasonic Vibration
Coagulates proteins and damages cell walls
Dry Heat
Incineration
Material or object is exposed to a hot fire
Object must become red hot as in the inoculation loops used in microbiology
Used to dispose of tissue or carcasses
Efficacy: complete sterilization
Dry Heat
Hot Air Oven
Sterility requires 1 hour of exposure @ 170° C(340° F)
Powders and non-aqueous liquids like paraffin or Vaseline
Used in some animal care facilities and useful in domestic applications (e.g. the kitchen oven)
Efficacy: complete sterilization
Dry Heat
Drying
Most organisms require humidity to survive and grow
More commonly used to prevent spoiling and preserve foodstuffs (e.g. raisins)
Efficacy: incomplete sterilization
Moist Heat
Hot Water
Used to clean and sanitize surfaces
Addition of detergents increases efficacy by emulsifying oils and suspending soils so they are rinsed away
Efficacy: incomplete sterilization
Moist Heat
Boiling
Requires 3 hours of boiling to achieve complete sterilization
Boiling for 10 minutes will destroy vegetative bacteria and viruses but not spores
Addition of 2% calcium carbonate or sodium carbonate will inhibit rust and increase efficacy
Useful for field work
Efficacy: may be complete sterilization
Moist Heat
Steam
Similar to boiling because the temperature is the same
Exposure to steam for 90 minutes kills vegetative bacteria but not spores
Efficacy: incomplete sterilization
Moist Heat
Steam under pressure
Pressure increases the boiling point such that the temperature of the water becomes much higher that 100° C (212° F)
The autoclave utilizes steam under pressure to achieve sterilization
This is the most efficient and inexpensive method of sterilization for routine use
Efficacy: complete sterilization
Radiation
Ultraviolet (UV)
Low energy UV radiation is a sterilant when items are placed at a close range
UV radiation has no penetrating ability
Used to sterilize rooms
Very irritating to eyes
Efficacy: may be complete sterilization
Radiation
Gamma radiation
Ionizing radiation produced from a Cobalt 60 source
Good penetrating ability in solids and liquids
Used extensively in commercial preparation of pharmaceuticals, biological products and disposable plastics
Efficacy: complete sterilization
Filtration
Fluid filtration
Forced through a filter with either positive or negative pressure
Filter is most commonly a synthetic screen filter with micropore openings
Used to sterilize culture media, buffers and pharmaceuticals
Pore size of 0.45µm removes most bacteria
Microplasmas and viruses require 0.01µm to 0.1µm
May be used in conjunction with a pre-filter
Efficacy: can be complete sterilization
Filtration
Air filtration
Examples of usage: surgical masks, laboratory animal cages and air duct filters
Fibrous filters made of various paper products are effective for removing particles from air
Efficacy is influenced by air velocity, relative humidity and electrostatic charge
Efficacy: can be complete sterilization
Filtration
Air filtration
HEPA: high efficiency particle absorption filters are 99.97% to 99.997% effective in removing particles with diameters greater that 0.3µm
Filtration
Air filtration
Surgical masks
Designed to protect the patient from the surgeon, not the surgeon from the patient
Special masks are available that are designed to protect personnel from animal pathogens
Masks must fit snugly, stay dry and be changed every 3 to 4 hours to remain effective
Ultrasonic Vibration
Cavitation
High frequency sound waves passed through a solution create thousands of cavitation “bubbles”
Bubbles contain a vacuum; as they implode or collapse, debris is physically removed from objects
Effective as an instrument cleaner
Efficacy: incomplete sterility
Chemical Methods
Many chemicals are available to sterilize, disinfect or sanitize
None is the “ideal” agent
Chemicals penetrate cell walls and react with cell components in various ways to destroy or inhibit growth
Many chemicals are disinfectants with varying levels of efficacy
Some are sterilants
Chemical Methods
Bacteria Viruses
Level Vegetative Acid-fast Spores Lipophilic Hydrophilic
High + + + + +
Medium + + 0 + +/-
Low + 0 0 +/- 0
Examples:
High: Aldehydes, VPHP, Chlorine-dioxide
Medium: Alcohols, Phenols, 7th generation Quats
Low: Quats
Ethylene oxide
Aldehydes
Vapor phase H2O2
Halogens
Phenols
7th generation quaternary
Alcohols
Chlorhexidine
Old generation quaternary
High-cidal
Activity
Low-cidal
Activity
Chemical Methods
Ideal chemical agent
Broad spectrum of activity
Does not stain or damage surfaces
Stable after application
Effective in a short time
Nonirritating and nontoxic to surfaces and tissues
Inexpensive and easy to store and use
Not affected by organic debris or other soil
Effective at any temperature
Nontoxic, nonpyrogenic and nonantigenic
Possesses residual and cumulative action
Chemical Methods
Soaps
Detergents
Quaternary ammonium compounds
Phenols
Aldehydes
Halogens
Chlorine and chlorine releasing compounds
Alcohols
Peroxygen compounds
Ethylene Oxide
Chemical Methods
Soaps
Anionic cleaning agent made from natural oils
Ineffective in hard water
Does not mix well with quats and decreases the effectiveness of halogens
Is not antimicrobial
Minimal disinfectant activity
Chemical Methods
Detergents
Synthetic soaps
Anionic, cationic or nonionic; anionic combined with cationic will lead to neutralization of both
Most are basic; a few are acidic
Emulsify grease and suspend particles in solution
May contain wetting agents
Chemical Methods
Quaternary Ammonium Compounds
Quats: Centrimide, benzalkonium chloride, Zephiran, Quatsyl-D, Germiphene
Effective against gm+ and gm- microorganisms and enveloped viruses
Low toxicity and generally nonirritating
Prolonged contact irritates epithelial tissues
Chemical Methods
Quaternary Ammonium Compounds
Inactivated by organic material, soap, hard water and cellulose fibers
Reduced efficacy in presence of organic debris, soap, detergents and hard water
Ineffective sporocide and fungicide
Bacteria not destroyed may clump together; those inside the clump are protected
Dissolves lipids in cell walls and cell membranes
Chemical Methods
Quaternary Ammonium Compounds
Organically substituted ammonium compounds
More effective in basic pH
Cationic detergent
Deodorizes
Chemical Methods
Phenols
Active against gm+ bacteria and enveloped viruses
Developed from phenol or carbolic acid
Synthetic phenols are prepared in soap solutions that are nontoxic and nonirritating
Prolonged contact may lead to skin lesions
Chemical Methods
Phenols
Toxic to cats because cats lack the inherent enzymes needed to detoxify the compound
May be toxic to rodents and rabbits
Not inactivated by organic matter, soap or hard water
Activity decreased by quats
Chemical Methods
Aldehydes
Active against gm+ and gm-, most acid fast bacteria, bacterial spores, most viruses and fungi
Considered to be a sterilant but may require prolonged contact
Chemical Methods
Aldehydes
Gluteraldehyde (Cidex)
Noncorrosive
Supplied as an acid, activated by adding sodium bicarbonate
Good for plastics, rubber, lenses in “cold sterilization”
Not inactivated by organic material or hard water
Irritating to respiratory tract and skin
Chemical Methods
Aldehydes
Formaldehyde (Formicide)
Aqueous solution 37% to 40% (w/v) formaldehyde
May be diluted with water or alcohol
Irritating to tissues and respiratory tract
A vapor phase surface disinfectant that slowly yields formaldehyde
Chemical Methods
Aldehydes
Biguanide (e.g. chlorhexidine gluconate [Hibitane, Precyde])
Active against gm+, most gm-, some lipophilic viruses and fungi
Efficient disinfectant, used mostly as an antiseptic
Some reduction of activity in presence of hard water and organic material
Immediate, cumulative and residual activity
Precipitates to an inactive form when mixed with a saline solution
Used as a surgical scrub and hand wash
Low toxicity
Chemical Methods
Halogens
Chlorine, iodine, fluorine and bromine
Active against gm+ and gm-, acid fast, all viruses and fungi
Iodine most common
Chlorine and chlorine releasing compounds
Chemical Methods
Halogens
Iodine
Used in solution with water or alcohol
Iodophors: iodine plus carrier molecule that acts to release iodine over time
Surgical scrub (Betadine): iodophor plus detergent
Tinctures and solutions: iodines and iodophors w/o detergent
Nonstaining and nonirritating
Inactivated by organic material
Aqueous forms are staining, irritating and corrosive to metals, especially if used undiluted
Chemical Methods
Halogens
Chlorine and chlorine releasing compounds (e.g. chlorine gas, chlorine dioxide)
Commonly available as sodium hypochlorite
Least expensive and most effective chemical disinfectant
Available chlorine equals oxidizing ability
Damages fabrics, corrosive to metals
Inactivated by organic debris
May require several minutes of contact to be effective
Skin and mucous membrane irritant if not diluted properly or rinsed well
Chemical Methods
Alcohols
Ethyl alcohol, isopropyl alcohol, methyl alcohol
Active against gm+ and gm- bacteria and enveloped viruses
Most effective when diluted to 60% to 70% (isopropyl), 705 to 80% (ethyl)
Chemical Methods
Alcohols
Used as a solvent for other disinfectants and antiseptics
Most commonly used skin antiseptic
Low cost and low toxicity
Chemical Methods
Alcohols
Irritating to tissues and painful on open wounds
Repeated use dries skin
Forms coagulum in presence of tissue fluid
Consists of a layer of tissue fluid whose proteins have been denatured by alcohol
Facilitates survival of bacteria under the coagulum
Fogs lenses, hardens plastics and dissolves some cements
Chemical Methods
Alcohols
Inactivated by organic debris
Ineffective after evaporation
Defatting agent
Chemical Methods
Peroxygen compounds (e.g. Peracetic acid)
Active against gm+ and gm-, acid-fast, fungi.
No virucidal activity
Classified as a sterilant but may not kill pinworm eggs
Chemical Methods
Peroxygen compounds (e.g. Peracetic acid)
Oxidizing agent
Reacts with cellular debris to release oxygen
Kills anaerobes
Applied as a 2% solution for 30 minutes at 80% humidity
Explosive and can damage iron, steel and rubber
Irritating to healthy tissues
Chemical Methods
Ethylene Oxide
Active against gm+ and gm-, lipophilic and hydrophilic viruses, fungi and bacterial spores
Classified as a sterilant
Effective sterilant for heat labile objects
Chemical Methods
Ethylene Oxide
EO is a colorless nearly odorless gas that diffuses and penetrates rapidly
Flammable and explosive
Toxic, carcinogenic and irritating to tissue
Chemical Methods
Ethylene Oxide
Used in a chamber with a vacuum
May be mixed with CO2, ether or freon
Used at temperatures of 21° to 60° C (70° to 140° F)
Works quicker at higher temperatures
Exposure times of 1 to 18 hours
Requires minimum relative humidity of 30% (40% is optimum
Items must be clean and dry and can be wrapped muslin, polyethylene, polypropylene or polyvinyl
Sterilized items must be ventilated in a designated area for 24 to 48 hours to dissipate residual EO
Autoclave
Advantages
Consistently achieves complete sterility
Inexpensive and easy to operate
Safe for most surgical instruments and equipment, drapes and gowns, suture materials, sponges and some plastics and rubbers
Safe for patients and personnel
Established protocols and quality control indicators are easy to access
Autoclave
Disadvantages
Staff may overestimate the ability of the autoclave
Sterility depends on saturated steam of the appropriate temperature having contact with all objects within the unit for a sufficient length of time
Requires a thorough understanding of techniques to ensure that the above occurs
Autoclave
Function
Heat is the killing agent
Steam is the vector that supplies the heat and promotes penetration of the heat
Pressure is the means to create adequately heated steam
Autoclave
Function
Complete sterilization of most items is achieved after 9 to 15 minutes exposure to 121° C (250° F)
Steam at sea level is 100° C (212° F) as pressure is increased the temperature of the steam increases
The minimum effective pressure of the autoclave is 15 pounds per square inch which provides steam at 121° C (250° F)
Many autoclaves attain 35 psi which creates steam temperature of 135° C (275° F)
Autoclave
Function
Exposure times must allow penetration and exposure of all surfaces to 121°C (250° F) steam
Exposure time is decreased by increasing pressure, which increases steam temperature
Steam Sterilization Temperature/
Pressure Chart
Temperature
Pressure(psi) °C °F Time(mins)
0 100 212 360
15 121 250 9-15
20 125 257 6.5
25 130 266 2.5
35 133 272 1
Autoclave
Types
Gravity displacement autoclave
Prevacuum autoclave
Autoclave
Types
Gravity displacement
Water is heated in a chamber
Continued heating creates pressure
Steam displaces air within the chamber forcing it out through a vent
Cycle timing begins when the temperature reaches at least 121°C
Autoclave
Types
Gravity displacement
After sufficient exposure time, steam is exhausted through a vent back into a reservoir
Air that has been sterilized within the jacket and then filtered is admitted back into the chamber to replace the exhausting steam
If the chamber is loaded improperly or there is insufficient steam, there will be air pockets remaining in the chamber that will interfere with steam penetration and result in non-sterile areas
The load must be dried within the autoclave
Autoclave
Types
Prevacuum
Usually a much larger and more costly machine
Equipped with a boiler to generate steam and a vacuum system
Air is taken out of the loaded chamber by means of the vacuum system
Steam at 121°C or more is introduced into the chamber
The steam immediately fills the chamber to eliminate the vacuum
Exposure time begins immediately
At completion of the cycle steam is vacuumed and replaced by hot, dry sterile air
Air pockets are eliminated and processing times are reduced due to the vacuum
Autoclave
Operation
Preparation of the load
Loading the chamber
Autoclave cycles
Autoclave
Operation
Preparation of the load
Linen packs
Pouch packs
Hard goods
Liquids
Contaminated objects
Autoclave
Linen packs
All instruments in packs are scrupulously cleaned and rinsed in de-ionized water
Instruments are disassembled and ratchets are left closed and unlocked
Appropriate lines are in good repair and freshly laundered
Disposable linens are not reused
Autoclave
Linen packs
A chemical sterilization indicator is included in every pack
Chemical sterilization indicators provide verification that the inside of the pack was exposed to appropriate sterilization temperatures for the appropriate length of time
Autoclave
Linen packs
The pack is wrapped using at least two layers of material
The shelf life of the sterilized pack varies with the type of the outer wrapping
Pack is sealed with autoclave tape and labeled with the date, contents and operator
Autoclave tape provides verification that the outside of the pack was exposed to appropriate sterilization temperatures
Autoclave
SHELF LIFE
Wrapper Shelf-life
Dbl wrapped two layer muslin 4 wk
Dbl wrapped two layer muslin 6 mo
heat sealed in dust covers
after sterilization
Dbl wrapped two layer muslin 2 mo
tape sealed in dust covers
after sterilization
Dbl wrapped non-woven barrier 6 mo
materials (paper)
Paper/plastic peel pouches, heat sealed 1 year
Plastic-peel pouches, heat sealed 1 year
Autoclave
Linen packs
Pack should not exceed 30 X 30 X 50 cm (12 X 12 X 20 inches) in size
Pack should not exceed 5.5 kg (12 lb) in weight
Pack should not exceed 115 kg/m3 in density
Autoclave
Pouch packs
Used for single instruments, sponges, etc.
Previous guidelines apply
Pouches are heat sealed or ends are rolled and securely taped with autoclave tape
Labeled as above
Autoclave
Hard goods
Stainless steel or other hard instruments, trays, bowls, laboratory cages and other equipment may be autoclaved without wrapping
Must be physically clean and rinsed in de-ionized water
Syringes and plungers are separated before autoclaving
Autoclave
Liquids
Contained in Pyrex flasks 3 times larger than contents require
Cover loosely with applied lid or paraffin film, or place a needle through the stopper to allow air exchange
Sterility of liquids processed in the autoclave is in question
Removing liquids from the chamber is hazardous to personnel
Autoclave
Contaminated objects
Used before disposal to decontaminate syringes, culture plates, etc., that contain biohazardous waste
Place objects in a container appropriate for disposal
Special autoclavable biohazard bags are available
Autoclave
Chamber loading
Must allow free circulation of steam
Use perforated or wire mesh shelves
Linen packs have 2.5cm to 7.5cm space between
Place multiple packs on edge instead of stacking
Paper/plastic pouches are placed in specially designed baskets that support them on edge with the paper side of each package facing the plastic side of the adjacent package
Solid bowls or basins are placed upside down or on edge
Mixed loads (hard goods and wrapped goods) have wrapped goods on upper shelf
Autoclave
Autoclave cycles
Wrapped goods
Hard goods
Liquids
Autoclave
Autoclave cycles
Wrapped goods
Has “dry” cycle that allows wrapped packs to dry
Used for most surgical packs
Autoclave
Autoclave cycles
Hard goods
Has no dry cycle
Used for trays, bowls, cages, etc. that will not be maintained in a sterile condition
Also used for flash autoclaving to quickly sterilize instruments that are needed immediately
Autoclave
Autoclave cycles
Liquids
Exhausts steam more slowly than other cycles
Used for liquids that would be forced from containers during a faster exhaust cycle
Quality Control
The effectiveness of any method of microbial control must be monitored regularly
Verification of the effectiveness of microbial control should be performed at least monthly
Quality Control
Methods
Recording thermometer
Thermocouple
Chemical indicator
Biological testing
Bowie Dick test
Surface sampling
Serology
Quality Control
Methods
Recording thermometer
Displays the temperature of the autoclave chamber
Operator observes for correct temperature during cycle
Some autoclaves are equipped with printed tape of chamber temperatures during cycle
Quality Control
Methods
Thermocouple
Used in steam and dry heat sterilization chambers
Temperature sensors are placed in the part of a test pack that is most inaccessible to steam penetration
Quality Control
Methods
Chemical indicator
Paper strips impregnated with sensitive chemicals change color when conditions of sterility are met
Used with autoclaves and ethylene oxide systems
Placed deep inside packs before sterilization
Quality Control
Methods
Biological testing
Bacterial spores are exposed to autoclave or ethylene oxide and then cultured
Recommended method for verification of proper autoclave operation in veterinary clinics
Quality Control
Methods
Bowie Dick test
Tests pre-vacuumed autoclaves for complete removal of air and uniform steam penetration
Uses a pack of uniform dimensions with a cross of autoclave tape in the center
Quality Control
Methods
Surface sampling
Surface to be tested is swabbed with a sterile applicator and transferred to a suitable media plate for growth
Surface or item is rinsed with a sterile solution, which is examined for contamination
“Contact plate” of media is touched to the surface and incubated
Recommended method for ensuring proper disinfection of surgical suites in veterinary clinics
Quality Control
Methods
Serology
The presence of viruses in the environment is monitored by serological testing of animals to determine the presence of antibodies
Animals maintained for this purpose are referred to as sentinel animals
Surgical Preparation and Instrument Care.ppt
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