Ch 11 Sterilisation Flashcards
sterilization
process of destroying all microorganisms (including bacteria, viruses, spores, fungi, and prions)
through chemical or physical means
disinfection
disinfection is anything less than sterilization
High-level: any microorganisms present, with the exception of large numbers of bacterial spores.
Intermediate-level: not kill bacterial spores
low-level: kill most vegetative bacteria, as well as some fungi and viruses
classification scheme developed by Spaulding
Critical, semicritical, and noncritical.
critical: high risk for infection because they come in contact with the bloodstream or sterile tissues.
surgical instruments, catheters, needles, and implants, all of which should be sterilized.
Semicritical: contact with mucous membranes or nonintact skin, such as endotracheal tubes
options for cleaning of surgical instruments prior to sterilisation? (2)
**Manual cleaning **
enzymatic cleaners or detergents (no bubbles)
**Mechanical cleaning **
Ultasonic cleaning with cavitation, washer decontaminators, washer disinfectors and washer sterilisers. Instruments must be thoroughly rinsed after cycle is complete
What is the only approvel method for drying instruments prior to steilisation?
Filtered, medical grade compressed air
What are the ideal properties of a wrapping material? (8)
Prevent microbial penetration
Permeable to the sterilising agent
Resistant to heat
Allow for aeration
Possess minimal wrap memory
Long shelf-life with sufficient strength and durability
Free of toxic ingredients and dyes
Provide a barrier to fluid
Does not exist
What is the most common wrap material? What are its downsides?
Cotton muslin wrap
- Can generate lint
- Not moisture resistant
- Requires a double layer
List the types of available sterilisation (7)
Liquid chemical germicides (cold sterilisation)
Steam sterilisation
Ethylene oxide sterilisation
Ozone sterilisation
Plasma sterilisation
Vapourised Hydrogen Peroxide
Sterilisation by radiation (gamma)
List some options for cold sterilisation. What are the problems with cold sterilisation
Glutaraldehyde 1-1.5%
Hydrogen peroxide 7.5%
Should be considered high level disinfectants rather than sterilisation.
Gluteraldehyde is irritation to skin and can decrease pulmonary function.
It is acidic and requires buffering prior to use.
agents that combine acceptable efficacy (especially against spores) with low levels of user, instrument, and environmental toxicity have proved elusive. Additionally, these products suffer from decreased ability to access microbes in the interiors or crevices of items when compared with thermal methods of sterility.
How do steam sterilisers work
Kill microorganisms through coagulation and denaturation of proteins by moist heat
- Water serves as a catalyst and allows lower temperatures to be used
2 types of steam sterilisers?
Gravity-displacement (steam rises to the top and cool air is removed though a valve at the bottom)
Prevacuum type - A pump is used to remove air before steam is admitted to allow for very rapid and uniform steam distribution
121C for 30 minutes with 15-30mins drying
What are the potential causes of wet packs after steam sterilisation? 5
Improper loading
too large metal mass
Overloaded tray
Lack of absorbent materials
Insufficient cooling time
What is the recommended temp and time for dry heat sterilisation? When is this indicated?
160C for 120 mins
Certain sharp instruments, glassware and powders can be damaged by moisture
guidelines for flash sterilisation of a metallic, unwrapped, nonporous item in a gravity-displacement autoclave?
135C for 3min with 1min drying
safety concerns surrounding ethylene oxide?
Carcinogenic, mutagenic and neurologic hazards
ozone sterilisation used for?
Good option for moisture and heat-sensitive items.
What is plasma sterilisation?
Use of electromagnetic energy to create a plasma phase from a vapour of hydrogen peroxide, oxygen or peracetic acid/h2o2mix
Rapid and cost effective
45-59C for 28-75min
useful for moisture- or heat-sensitive items
What is used for radiation sterilisation?
Cobalt 60 gamma rays or electron accelerators > high energy photons act as sterilant by breaking down bacteria dna, high penetration capability, cold process therefore use on sensitive and packaged goods.
Items such as suture and certain implants are often sterilized by radiation.
Expensive, damage material, radiation exposure to workers
What are the 6 classes of sterilisation indicators?
Class 1 - Indicates the pack has been processes but limited info regarding parameters met - eg external tape
Class 2 - Test for air removal (“Bowie-Dick test”)
Class 3 - React to a specific parameter
Class 4 - React to more that 1 parameter
Class 5 - React to all parameters which are important for a certain type of sterilisation
Class 6 - Monitor more specific guidelines for unique parameters eg combatting prior infection
Recommended to always use a class 1 indicator as well as an additional indicator in the deepest part of the pack
What biological indicator is used for steam sterilisation (as well as plasma and ozone)
Geobacillus Stearothermophilus
One study found 12% failure rate on biological indicators, none of which were detected by simultaneous chemical indicators
ideal conditions for storage of sterilised materials?
Temp should not exceed 24C
Humidity should not exceed 70%
4 air exchanges per hour
As long as the sterile wrap remains sealed, undamaged and dry, internal sterility should be maintained indefinitely
Efficacy of vaporized hydrogen peroxide for repeated sterilization
of a single-use single-incision laparoscopic surgery port
Scharf 2019
This study suggests that a single-use single-incision laparoscopic port
and its associated components can be effectively sterilized after multiple simulated uses by using VHP.
Influence of multiple reuse and resterilization cycles on the
performance of a bipolar vessel sealing device (LigaSure)
intended for single use
Kuvaldina 2018
Conclusion: Repeated use and resterilization resulted in failure of the vascular seal
due to inadequate tissue apposition after a minimum of 10 cycles
low-temperature hydrogen peroxide sterilization unit
Influence of closed glove exchange on bacterial
contamination of the hands of the surgical team
Biehl 2023
Prospective experimental study
Closed glove exchange did not increase bacterial hand contamination
over baseline levels.
baseline, contamination was found on 17/200
dominant hands and 13/200 nondominant hands (8%)
Andrade et al. found that the most common source of wound contamination was the hands of the surgical staff
In human patients, glove exchange prior to wound closure has been shown to reduce the risk of SSI
Preoperative skin asepsis protocols using chlorhexidine
versus povidone-iodine in veterinary surgery:
A systematic review and meta-analysis
Marchionatti 2022
Systematic meta-analytical review
This study showed that asepsis protocols using chlorhexidine
were comparable to povidone-iodine in preventing postoperative SSI and
reducing skin bacterial colonization.
more high-quality randomized controlled
trials are needed to confirm these conclusions.
Comparison of hydroalcoholic rubbing and conventional
chlorhexidine scrubbing for aseptic skin preparation in dogs
Asimus 2019
Experimental study.
Animals: Healthy dogs (n = 6) with no clinical signs of skin disease.
no difference
between sites on any animal or for any method. Colony forming units were not
detected at any time on any site in any dog after antiseptic application.
Rubbing with hydroalcoholic (HA) solution was as effective as CHXG
and prevented bacterial growth for at least 3 hours
currently no known resistance to HA solution
Recent articles
in both human and veterinary medicine have reported that HA
solutions are more efficient than traditional medicated soaps for
the presurgical hand antisepsis of surgeons
Emergence of resistance to CHX has been observed
Alcohol-based hand
rubs are now the norm for hand hygiene prior to a surgical
procedure because they are more effective, are less irritating
to the hands, and require less time than hand washing with
antimicrobial soap
