Radiation and Chemical Sterilisation

Question 1

What are some properties of the ideal sterilisation method?

Answer 1

• High antimicrobial activity
• Easily controllable
• Terminal sterilisation
• No hazard to operator
• No toxic residues
• Short processing
• Low cost

Question 2

Radiation is _____ travelling through space

Answer 2

energy

Question 3

What are the two main types of radiation? Give examples.

Answer 3

• Electromagnetic: Gamma rays, X-rays, (UV), (IR), microwaves, visible light.
• Particulate: a-particles, b-particles, protons, neutrons.

Question 4

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 _______.

Answer 4

25
zigzag
short
high
long
high
ionisation

Question 5

Accelerated electrons are better than gamma radiation in terms of process time as the times are _______. Causes ________.

Answer 5

quicker/ shorter

ionisation

Question 6

Lethal effects:

• Direct ‘hits’ - causes direct alterations to the target (this is usually ____)
• Indirect effects - ____ _____ and peroxide formation

Answer 6

DNA

free-radical

Question 7

Factors that influence efficacy of sterilisation using ionising radiation include:

Answer 7

• water content
• oxygen levels
• temperature
• size and structural arrangement of DNA in cells
• compounds associated with DNA
• post irradiation conditions

Question 8

UV radiation is ____ lethal and damaging than ionising radiation. It causes ______ and not ionisation

Answer 8

less

excitation

Question 9

The typical gamma ray source is:

Answer 9

60Cobalt

Question 10

Gamma has _____ penetrability whereas UV has _____ penetrability.

Answer 10

good

poor

Question 11

What are two forms of gaseous sterilisation? (alkylating agents)

Answer 11

• ethylene oxide

- low temp steam formaldehyde

Question 12

Ethylene oxide max safety limit for humans is __ppm. It also has _____ concerns; potential carcinogen and _______. It works by alkylation which inhibits ______ activities

Answer 12

5
toxicity
mutagen
metabolic

Question 13

Gas sterilisation is suitable for:

Answer 13

• reusable surgical instruments and medical equipment

- disposable medical devices (those sensitive to radiation

Question 14

Gas sterilisation is unsuitable for:

Answer 14

• ampules
• impermeable packaging
• products sensitive to high humidity
• soiled products

Question 15

Advantage of ethylene oxide gas sterilisation?

Answer 15

• Automated sterilisers available

Question 16

Disadvantage of ethylene oxide gas sterilisation?

Answer 16

• 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

Question 17

Advantages of formaldehyde as a sterilising agent

Answer 17

• Automated sterilisers are available
• No explosion risk (unlike ethylene oxide)
• lower cost than ethylene oxide

Question 18

Disadvantages of formaldehyde as a sterilising agent

Answer 18

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