Sterilisation

Question 1

What is the Spaulding classification regarding instruments for sterilisation?

Answer 1

• Critical - Associated with high risk of infection if they become contaminated as they come into contact with the bloodstream or sterile tissue
• Semi-critical - Come into contact with mucous membranes or non-intack skin
• Non-critical - Contact only intact skin

Question 2

What is toxic anterior chamber syndrome (TASS)

Answer 2

Severe inflammation in the anterior chamber of the eye following ophtho procedures and seems to be related to instrument processing

Question 3

What are the main options for cleaning of surgical instruments prior to sterilisation?

Answer 3

• Manual cleaning with enzymatic cleaners or detergents (no bubbles)
• Mechanical cleaning of surgical instruments (preferred method) -
• • Ultasonic cleaning with cavitation, washer decontaminators, washer disinfectors and washer sterilisers. Instruments must be thoroughly rinsed after cycle is complete

Question 4

What is the only approvel method for drying instruments prior to steilisation?

Answer 4

Filtered, medical grade compressed air

Question 5

What are the ideal properties of a wrapping material?

Answer 5

• Prevent microbial penetration
• Permeable to the sterilising agent
• Resistant to heat
• Allow for aeration
• Resistant to physical damage and moisture penetration
• Possess minimal wrap memory
• Long shelf-life with sufficient strength and durability
• Free of toxic ingredients and dyes
• Provide a barrier to microorganisms and fluid

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Question 6

What is the most common wrap material? What are its downsides?

Answer 6

Cotton muslin wrap
- Can generate lint
- Not moisture resistant
- Requires a double layer

Question 7

List the types of available sterilisation

Answer 7

• Liquid chemical germicides (cold sterilisation)
• Steam sterilisation
• Ethylene oxide sterilisation
• Ozone sterilisation
• Plasma sterilisation
• Vapourised Hydrogen Peroxide
• Sterilisation by radiation

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Question 8

List some options for cold sterilisation. What are the problems with cold sterilisation

Answer 8

• Glutaraldehyde 1-1.5%
• Orthophthalaldehyde (Cidex)
• Hydrogen peroxide 7.5%

Should be considered high level disinfectants rather than sterilisation. Gluteraldehyde is irritation to skin and mms and can decrease pulmonary function. It is acidic and requires buffering prior to use. Cidex is less irritating and does not require a pH adjustment.

Question 9

How do steam sterilisers work?

Answer 9

Kill microorganisms through coagulation and denaturation of proteins by moist heat
- Water serves as a catalyst and allows lower temperatures to be used

Question 10

What are the 2 types of steam sterilisers?

Answer 10

• 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

Question 11

What are the temperature and time options for gravity-displacement autoclaves

Answer 11

• 121C for 30 minutes with 15-30mins drying
• 132C for 15 minutes with 15-30mins drying

Question 12

What are the potential causes of wet packs after steam sterilisation?

Answer 12

• Improper loading
• too large metal mass
• Overloaded tray
• Lack of absorbent materials
• Insufficient cooling time

Question 13

What is the recommended temp and time for dry heat sterilisation? When is this indicated?

Answer 13

• 160C for 120 mins
• Certain sharp instruments, glassware and powders can be damaged by moisture

Question 14

What are the guidelines for flash sterilisation of a metallic, unwrapped, nonporous item in a gravity-displacement autoclave?

Answer 14

135C for 3min with 1min drying

Question 15

What are the safety concerns surrounding ethylene oxide?

Answer 15

Carcinogenic, mutagenic and neurologic hazards

Question 16

What is ozone sterilisation used for? What is the recommended temp and time?

Answer 16

• Good option for moisture and heat-sensitive items.
• 30-35C for 4 hours

Question 17

What is plasma sterilisation?

Answer 17

• 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

Question 18

What is used for radiation sterilisation?

Answer 18

Cobalt 60 gamma rays or electron accelerators

Question 19

What are the 6 classes of sterilisation indicators?

Answer 19

• 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

Question 20

What biological indicator is used for steam sterilisation (as well as plasma and ozone)

Answer 20

• Geobacillus Stearothermophilus
• One study found 12% failure rate on biological indicators, none of which were detected by simultaneous chemical indicators

Question 21

What are the ideal conditions for storage of sterilised materials?

Answer 21

• 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