Radiation and Chemical Sterilisation Flashcards
What are some properties of the ideal sterilisation method?
- High antimicrobial activity
- Easily controllable
- Terminal sterilisation
- No hazard to operator
- No toxic residues
- Short processing
- Low cost
Radiation is _____ travelling through space
energy
What are the two main types of radiation? Give examples.
- Electromagnetic: Gamma rays, X-rays, (UV), (IR), microwaves, visible light.
- Particulate: a-particles, b-particles, protons, neutrons.
Standard reference dose for gamma radiation is __ kGy. Items pass in a ___-____ pattern around the source. The wavelength is _____ and is of ____ energy. Exposure times are _____. It is a specialised process with _____ safety control. May or may not cause _______.
25 zigzag short high long high ionisation
Accelerated electrons are better than gamma radiation in terms of process time as the times are _______. Causes ________.
quicker/ shorter
ionisation
Lethal effects:
- Direct ‘hits’ - causes direct alterations to the target (this is usually ____)
- Indirect effects - ____ _____ and peroxide formation
DNA
free-radical
Factors that influence efficacy of sterilisation using ionising radiation include:
- water content
- oxygen levels
- temperature
- size and structural arrangement of DNA in cells
- compounds associated with DNA
- post irradiation conditions
UV radiation is ____ lethal and damaging than ionising radiation. It causes ______ and not ionisation
less
excitation
The typical gamma ray source is:
60Cobalt
Gamma has _____ penetrability whereas UV has _____ penetrability.
good
poor
What are two forms of gaseous sterilisation? (alkylating agents)
- ethylene oxide
- low temp steam formaldehyde
Ethylene oxide max safety limit for humans is __ppm. It also has _____ concerns; potential carcinogen and _______. It works by alkylation which inhibits ______ activities
5
toxicity
mutagen
metabolic
Gas sterilisation is suitable for:
- reusable surgical instruments and medical equipment
- disposable medical devices (those sensitive to radiation
Gas sterilisation is unsuitable for:
- ampules
- impermeable packaging
- products sensitive to high humidity
- soiled products
Advantage of ethylene oxide gas sterilisation?
- Automated sterilisers available
Disadvantage of ethylene oxide gas sterilisation?
- Requires incorporation of biological indicators
- No standard cycles available
- Associated toxicity
- Residual in product which must be removed
- Requires specialist expertise for operation
- Pre-humidification usually required
- No depyrogenation
Advantages of formaldehyde as a sterilising agent
- Automated sterilisers are available
- No explosion risk (unlike ethylene oxide)
- lower cost than ethylene oxide
Disadvantages of formaldehyde as a sterilising agent
Requires incorporation of biological indicators
Associated toxicity –and odour!
Residual in product which must be removed
Requires specialist expertise for operation
Not effective against prions
Not to be used with cellulose containing materials
Does not depyrogenate
Corrosion of some materials
