Asr-Sterilants, Disinfectants, & Antiseptics

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Sterilization

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The physical or chemical destruction of all microbial life including highly resistant bacterial spores

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Disinfection

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The inactivation of most pathogenic organisms except for some highly resistant forms (spores) on inanimate surfaces and implies the destruction of the vegetative forms of bacteria but not spores

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Antiseptic

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A substance that inhibits or destroys microorganisms on or in living tissue

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Asepsis

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A state of freedom from infection

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Aseptic Technique

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The steps required to prevent contamination of the surgical site with infectious agents

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5 Methods of Sterilization

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1. Filtration
2. Radiation
3. Thermal
4. Liquid Chemical
5. Gas Chemical

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Filtration Sterilization

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• May be used for gasses or liquids
• Involves the separation of particulate matter of known sizes using a membrane
• Commonly used for pharmaceutical liquids
• Useful for heat sensitive media, offers high through-put, and provides absolute sterilization
• Unable to differentiate between similarly sized particles
  

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Radiation Sterilization

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• Usually gamma radiation from Cobalt 60
• Provides penetration through relatively impervious materials (i.e., metal and plastic)
• Leaves no chemical residue
• Can start a structural change in materials, especially some polymers, that may continue to develop over months
• Usually used by manufacturers due to cost of the process
  

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2 Types of Thermal Sterilization

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1. Dry Heat
2. Wet Heat

Most common form of sterilization. Believed to denature bacterial proteins

Sterilization is a function of time and temperature

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Dry Heat Sterilization

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• (i.e. hotbead sterilizer) used on moisture sensitive materials such as oils, powders, and petroleum products
• Causes protein oxidation which requires longer exposure or higher temperatures

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Wet Heat Sterilization

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(boiling water and autoclave) kills bacteria via the coagulation of critical proteins

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Boiling Water Sterilization

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• A poor sterilant at ambient pressure
• Has a relatively low temperature
• May be enhanced by the addition of sodium hydroxide or sodium carbonate
• Destructive to instruments, especially glassware and rubber
  

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Autoclave Sterilization

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• Involves superheated steam under pressure to allow higher temperatures than normal steam can provide
• Requires materials and wrapping that are not damaged by heat, moisture, and pressure and are permeable to the steam.
• Requires complete saturation of the surgical pack for effective sterilization
• i.e., 121 degrees C for 13-15 minutes (5-10 minutes plus 3-8 minutes as a safety margin)
• Larger or denser packs require more time for adequate saturation with steam
• Time for the autoclave to reach temperature and saturate the pack is the heat-up time
• Pre-vacuum autoclaves achieve this heat-up time in 12 minutes
• Can be used for emergency “flash” autoclaving
• Also reach higher temperatures and so require shorter exposure times (131 degrees C for 3 minutes)
• Loads should be vented for ~10 minutes following a cycle to prevent condensation
  

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Liquid Chemical Sterilization

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• Sterilants are designed to kill all microorganisms, disinfectants are not
• Chemical sterilants are regulated by the FDA as medical devices, EPA involved as well
• Approved chemical sterilants will say on the bottle that they are sterilants
• Cold sterilants work by contact, care should be taken that all surfaces are in contact with the solution
• Flush sterilant through catheters, open all latches, etc.
• Cold sterilants are tissue irritants and require complete rinsing (sterile water or saline) of sterilized objects to remove all chemicals prior to tissue contact
  

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Chemical Disinfectants

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• Disinfectants are NOT adequate for instrument and implant/catheter sterilization
  
• Nonsterilant chemicals will have disinfectant written on the bottle and should not be used for instrument or device sterilization
  

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4 Types of Chemical Sterilants

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1. Glutaraldehyde
2. Formalin or formaldehyde
3. Hydrogen Peroxide
4. Peracetic Acid 35%

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Glutaraldehyde

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• Requires >12 hours of full immersion for sterilization of resistant spores
• Noncorrosive
• Activated solutions have less than 2 week shelf life
• Toxic to skin, eyes, respiratory tract
• Glutaraldehyde solutions come in different strengths
• Only those classed as a sterilant should be used for instrument or device sterilization
  

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Formaldehyde/Formalin

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• 37% aqueous formaldehyde
• Requires > 24 hours of full immersion for sterilization of resistant spores
• Toxic to skin, eyes, respiratory tract
  

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Hydrogen Peroxide

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• 6% aqueous solution with >30 minute exposure may kill some resistant spores in addition to less hardy microorganisms
• Potentially explosive at high concentrations
• Corrosive
• Irritant to skin and eyes
  

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Peracetic Acid (35%)

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• Steris System 1
• Automated process suitable for endoscopic equipment
• Fast (30-45 minutes) and has environmentally friendly byproducts
• Useful only for small loads of instruments and provides no sterile packaging, must be used immediately upon cycle completion
  

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2 Types of Gas Sterilization

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1. Ethylene Oxide (ETO)
2. Hydrogen Peroxide

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Ethylene Oxide Sterilization

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• Colorless gas
• Flammable, explosive, toxic, and irritating to skin and mucus membranes
• Destroys metabolic pathways by alkylation
• Typically requires 12 hours of exposure
• Time is inversely proportional to pressure
• Requires ~24 hours of ventilation after cycle
  

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Hydrogen Peroxide Sterilization

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• Safer than ETO to the user
• Requires little ventilation and shorter exposure times
• Cannot be used with absorbent materials such as paper or cloth
• Will condense into water and soak the packaging, preventing gas contact and allowing post-sterilization “wicking” of microorganisms through the packaging
  

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Chemical Disinfection

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• Primarily chemical
• High-level disinfectants used for instrument disinfection between rodent procedures, some oral procedures, and for delicate endoscopic equipment that cannot be sterilized
• Intermediate and some low-level disinfectants should be used for cleaning surfaces in surgery
• Disinfectants rated as high, intermediate, or low based on efficacy against microorganisms
  

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High-Level Disinfectants

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Used for instrument disinfection between rodent procedures and for critical surface cleaning

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6 Types of High Level Disinfectants

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1. Aqueous Iodine
2. Aldehydes
3. Sodium Hypochlorite (bleach)
4. Phenol Compounds (carbolic acid)
5. Iodophors (Povidone iodine)
6. Chlorhexidine

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Aqueous Iodine

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• Contains higher levels of free iodine
• Cytotoxic
• Stains surfaces
• 30 minutes of exposure for disinfection
  
• high level disinfectant

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Aldehydes

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• 30-45 minutes of exposure for disinfection
• high level disinfectant
  

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Sodium Hypochlorite (bleach)

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• Toxic
• Corrosive
• 3,000 ppm for 45-60 minutes for disinfection
• high level disinfectant

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Phenol Compounds (Carbolic Acid)

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• No longer commonly used
• 30 minutes for disinfection
• Intermediate-level Disinfectants
• Used for cleaning surfaces
• high level disinfectant
  

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Iodophor (Povidone iodine)

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• Iodine complexed with surfactants or polymers for slower release of free iodine
• Dilution lowers cytotoxicity and increases bactericidal activity
• Rapidly deactivated in the presence of organic matter
• Residual activity of 46 hours
• May be mildly irritating
• high level disinfectant
  

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Chlohexidine

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• Rapid onset and long residual activity (8-12 hours)
• Not deactivated by organic matter
• Nonirritating
• Considered superior to Iodophors due to residual action even when dried
• high level disinfectant
  

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2 Types of Low Level Disinfectants

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1. Alcohols (Isopropyl)
2. Quaternary Ammonium (Quat, Zephiran)

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Alcohol (Isopropyl)

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• Bactericidal
• Ineffective against most spores and fungi
• Minimal residual effects and inhibited by organic debris
• Cytotoxic
• Degreaser
• 30 minutes exposure for surface decontamination
  

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Quaternary Ammonium (Quat, Zephiran)

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• Bactericidal
• Work by dissolving outer coatings on some pathogens
• Some bacteria, including Staphylococcus aureus and Pseudomonas, have common resistant strains
• Ineffective against spores and some viruses
• May support growth of some types of bacteria
• Per CDC, is not an appropriate sterilant
• Low toxicity in stable solutions
• 10-30 minutes for surface decontamination

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Antiseptics

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• Commonly used for surgical site preparation on the patient and for surgeons to scrub hands and forearms prior to gowning and gloving
• Intermediate level disinfectants are often acceptable antiseptics
  

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3 Types of Antiseptics

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1. Chlorhexidine
2. Iodophors
3. Alcohol

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Chlorhexidine

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• Considered more effective than the Iodophors
• Available as tinctures, solutions, and detergents
• Works by contact time, requires sufficient skin contact duration for effect
  

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Iodophors

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• Available as tinctures, solutions, and detergents
• Works by contact time similar to chlorhexidine
• Principal antiseptics
  

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Alcohol

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• Useful for low-level antisepsis
• Has minimal residual effects
• Evaporates rapidly and leaves no residue
• Inhibited by organic debris
• Not sufficient as the primary antiseptic per standard human and veterinary surgical texts
• Useful in conjunction with Iodophors or chlorhexidine
• Breaks up surface oils and surface tension