Sterilization and disinfection Flashcards
(31 cards)
Costs associated with hospital acquired infections in the UK
- Leading cause of preventable diseases
- > 5000 deaths/year
- > £1bn / year
Decontamination
= the process whereby pathogens are removed, inactivated of destroyed
Involves
* Thorough cleaning: essential before high-level disinfection and sterilization because inorganic and organic materials that remain on the surfaces of instruments interfere with the effectiveness of these processes
* Then disinfection and/or sterilization
Differences between sterilization vs disinfection vs cleaning
**Sterilization **
* = the complete elimination or destruction of all forms of microbial life
* Physical or chemical processes
Disinfection
* = a process that eliminates many or all pathogenic micro-organisms on inanimate objects with the exception of bacterial spores
* Usually using liquid chemicals
**Cleaning **
* = removal of visible soil (organic or inorganic) from objects and surfaces. Physical removal of the infectious material, or organic matter, on which organisms thrive.
* Usually manual or mechanical means using water with detergents or enzymatic products
Spaulding categories of instruments/items for patient care
3 categories based on risk of infection involved. Used to plan methods for disinfection or sterilization
Critical: e.g. surgical instruments, urinary catheters, needles
* Enter normally sterile tissue or the vascular system or through which blood flows
* High risk of infection
* Should be sterilized
Semi-critical: e.g. laryngoscope blades
* Touch mucous membranes or skin that is not intact. I
* Intermediate risk of infection (intact mucous membranes are generally resistant to infection)
* Require high-level disinfection: kills all micro-organisms except high numbers of bacterial spores
Non-critical: e.g. bedpans, BP cuffs
* Touch only intact skin - low risk of infection.
* Require low-level disinfection
Sterility assurance value (SAL): definition, what is the SAL of a sterile device?
Represents the probability that a device remains contaminated after it has gone through a sterilization process.
A sterile device has a SAL of 10^-6 i.e. probability of organism surviving on that device is 1 in a million
What influences efficacy of disinfection and sterilization?
- Cleaning of the object
- Organic and inorganic load present
- Type and level of microbial contamination
- Concentration of, and exposure time to, sterilant
- Nature of the object
- Temperature and relative humidity
Sterilization methods: types, uses
- High temperature: Steam (most common), dry hot air (not used in hospitals - higher temp than most medical devices can withstand, relatively inefficient and lengthy)
- Low temperature: ethylene oxide, hydrogen peroxide gas plasma, peracetic acid immersion, ozone, ionizing radiation
Most medical and surgical devices are made of heat stable materials -> sterilised by heat, primarily steam sterilization
Some materials e.g. plastics require low temperature sterilisation -> e.g. ethylene oxide gas used for heat and moisture sensitive medical devices
Steam sterilization: equipment, parameters, minimum exposure period for wrapped healthcare supplies
Moist heat (in form of steam under pressure) is **most widely used method of sterilization. **
Uses an autoclave (basic setup shown in picture)
Four parameters:
* Steam
* Pressure
* Temperature
* Time
Principle = expose each item to direct steam contact at required temp and pressure for specified time
Recognised common minimum exposure periods for sterilization of wrapped healthcare supplies:
* 30 mins at 121 degrees C in a gravity displacement sterilizer
* 4 minutes qt 132 degrees C in a prevacuum sterilizer
Steam sterilisation: advantages and disadvantages
Advantages:
* Rapidly micobicidal
* Least affected by soils
* Penetrates medical packing and device lumens
* Non-toxic
* Rapid cycle time
* Easy control or monitor of cycle
* Inexpensive
Disadvantages:
* Adverse for heat liable items
* Potential for burns
Ethylene oxide gas sterilisation: what is it, temperature, advantages/ disadvantages
- Flammable colourless gas at temperatures above 10.7 degrees C
- Smels like ether at toxic levels
- Low temperature sterilant
Advantages:
* Very effective at killing micro-organisms
* Penetrates medical packaging and many plastics
* Compatible with most medical materials
* Cycle easy to control and monitor
Disadvantages
* Expensive (c.f. steam)
* Lengthy cycle/ aeration time: up to 24h (c.f. steam)
* Potential hazard to patients + staff
Hydrogen peroxide gas plasma sterilization: advantages and disadvantages
Advantages:
* Used for heat and moisture sensitive items
* Compatible with most medical devices
* Fast-cycle time 28-52 minutes, no aeration necessary
* Simple to operate, install and monitor
* Safe for environment and health care worker: no toxic residuals
Disadvantages:
* Cannot process cellulose (paper), linens and liquids
* Endocopes or medical device restrictions based on lumen internal diameter and length
* Requires synthetic packaging and special container tray
* Small sterilization chamber
Ozone sterilisation: what is ozone, effectiveness, mechanism
- Ozone = a gaseous molecule containing 3 oxygen atoms.
- Manufacturing: oxygen subejected to an intense electrical field that separates oxygen molecules (O2) into atomic oxygen (O), which combines with other ozygen molecules to form ozone (O3).
- Fresh ‘spring rain like’ scent, bluish color
Function
* One of the most powerful microbicides known: inactivates or kills even the most resistant pathogens
* Metastable: tendes to revert back to its original state, oxygen
Ionizing radiation sterilization: mechanism, uses
- Uses gamma rays from cobalt-60 to produce sterility
- Widely used in industry: Ideal for pre-packed, heat labile, single use items e.g. needles and face masks
Sterilization monitoring: parameters, examples of biological monitors for steam, dry heat, ETO, plasma sterilization, peracetic acid
- ** Physical:** cycle time, temperature, pressure
- Chemical: heat or chemical sensitive inks that change color when germicidal-related parameters are present
- **Biological: **bacillus spores that directly measure sterilization
Biological monitors:
* steam: geobacillus stearothermophilus
* dry heat, ETO: B. atrophaeus
* plasma sterilization, peracetic acid: G. stearothermophilus
Routine decontamination methods for:
* airway
* breathing system tubing
* laryngeal masks
* self-inflating bags
Airway: single use disposable airways only: do not reprocess or reuse
Laryngeal masks: after use, send reusable masks to the sterile services department to be reprocessed. Should not be used >no. of times recommended by manufacturer (usually 40). Or use single-use devices instead.
Breathing system tubing: protect tubing with filters. Discard disposable single use tubing after each session of use. Ideally send reusable tubing to Sterile Services Department for cleaning and sterilization after each patient use
** Self inflating bags**: replaced by single use self inflating bags. For reusable: detergent and warm water after use.
Routine decontamination methods for: laryngoscope, laryngoscope blades
Laryngoscope: cleaning then autoclaving
Laryngoscope blades: disposable blades preferred -> discard single use blades into appropriate sharps containers.
Routine decontamination methods for: suction tubing, suction equipment
Suction tubing: discard disposable suction tubing after 24h continuous use, when visibly soiled, and between patients
Suction equipment: Use disposable liners and discard them when full, and between each patient, in a designated rigid container. Change suction equipment that is in use (i.e. has fluid in the container) every 48 h. Change jars after each patient. Reusable jars are for single patient use only -> rinse, clean, decontaminate using thermal disinfection or sterilization
Routine decontamination methods for: BP cuff, tympanic thermometer, pulse oximeter
BP cuff: if reusable, wipe or clean with warm water and detergent between patient use
Tympanic thermometer: dispose single use earpiece covers after each use. Clean outer case with warm water and detergent or alcohol wipe
Pulse oximeter: warm water and detergent after each use
Cleaning: definition, processes
= physical removal of the infectious material, or organic matter, on which organisms thrive.
Process may be manual or mechanical:
Manual:
* immersion in a diluted detergent at 35 degrees
* non-immersion for electrical equipment: wipe with cloth soaked in cleaning solution
Mechanical:
* can be part of thermal or chemical disinfection
* ultrasonic cleaning: used in areas that are difficult to reach. Ultrasonic waves create small bubbles on the surface. Bubbles increase in size until they cavitate and collapse -> producing areas of vacuum which dislodge the contaminants
Commonly used methods for disinfection (4)
- Thermal washer disinfection
- Pasterurization (or low temperature steam)
- Boiling water disinfection
- Chemical disinfection
Thermal washer disinfector: mechanism, suitable for, effectiveness
Mechanism
* Cleans devices by spraying them with water and detergent
* Initial clean at or below 35 degrees. Then hot water disinfection rince where surface temperature of devices reaches 71 degrees C for 3 minutes, 80 for 1 minute, or 90 for 1 second
Suitable for:
* Devices must be able to withstand repeated exposure to wet heat at temperatures of approx 80 degrees
* NOT suitable for hollow and porous devices unless a special adaptor is available
Effectiveness:
* Most organisms are inactivated except for bacterial spores, some heat-resistant viruses, and cryptosporidia
Pasteurization: method, unsuitable for
- Aka low temperature steam
- Method of disinfection: >70 degrees C for 30 minutes.
- An alternative to chemical disinfection. Not a sterilization process: purpose is to destroy all pathogenic micro-organisms with the exception of bacterial spores
- Unsuitable for oily or greasy items or those with sealed cavities
