6 Disinfection and sterilisation Flashcards
What are examples of these medical device classes
- critical/ high-risk items
- semi-critical or high risk items
- low risk items
- minimal risk items
- critical/ high-risk items - come into break of skin/ sterile cavity
- semi-critical or high risk items - come into contact with non-intact skin/ mucus membranes - e.g endoscope
- low risk items - come into contact with intact skin e.g BP cuff
- minimal risk items - e.g flower vase
When considering a method of disinfection, what factors need to be considered?
type of material to be disinfected
level of decontamination required for procedure
likely microogranisms involved
What are different methods of sterilisation?
Dry heat - requires high temperature for much linger exposure periods than moist heat sterilisation
Moist heat - more penetrating that dry heat
Chemical - ethylene oxide
Moist heat sterilisation in an autoclave
What are examples of temperature cycles?
134-138degC 3 mins
121-124degC 15 mins
115 30degC mins
Chlorine based disinfectants are widely available
Hypochlorite is most widely used
What are common examples of these?
actichlor
Ajax - powder
bleach - liquid
hypochlorite inhibits bacterial enzymatic reactions, denaturing of proteins, and inactivation of nucleic acids
first choice for blood spillage
Why do hypochlorite solutions be prepared daily for use?
At high risk of becoming unstable/ ineffective due to:
◆ Presence of heavy metal ions.
◆ Incompatible with cationic detergents.
◆ Its efficiency diminishes with an increase in pH of the solution.
◆ Temperature of the solution.
◆ Presence of biofilms.
◆ Presence of organic matter (particularly if used in low concentrations).
◆ Ultraviolet radiation - degrades in sunlight
◆Corrosive to metal/ plastic container
Using hypochlorite for disinfection
What should the chlorine content ppm be for these scenarios?
- Blood spills
- general environmental disinfection
- routine water treatment
- Blood spills - 10000ppm
- general environmental disinfection - 1000 ppm
- routine water treatment 1ppm
Sodium hypochlorite can release toxic gases
what should it not be mixed with?
ammonia or urine - can release chlorine gas
formaldehyde - gas released is carcinogenic
Phenolic disinfects are oldest disinfectants used by Lister.
What are they useful for?
- Environmental disinfection at low concentration
- Mycobacterial disinfection at higher dose
Cannot be used on items that are to be used on skin/ mucus membranes or food surfaces
Chlorhexidine is a common disinfectant and in available commonly as Hibiscrub
What are its main use?
Antiseptic on intact skin - e.g surgical prep, or MRSA decolonisation
usually combined with alcohol into a solution
Aldehydes include glutaraldehyde and formaldehyde
What are they commonly used for?
glutaraldehyde - disinfect heat-sensitive items such as endoscopes
formaldehyde - gaseous fumigant in infected rooms e.g VHF
can cause irritation to skin/ eyes - need to wear gloves/ apron
Endoscope cleaning
Which bacteria are at risk of transmission if inadequate sterilisation?
Pseudomonas
Mycobacteria
can be present in rinse water
Endoscope sterilisation
Testing rinse water can help ensure we have adequate sterilisation
what standards are set for sampling?
Sampling of the final rinse water for the total viable count (TVC) is recommended to be carried out weekly to ensure the effectiveness of the water treatment system and the machine disinfection cycle. In Europe (EN 15883) the standard states that there should be less than 10cfu/100 mL of final rinse water.
Endoscope sterilisation
what do do if you receive these results in sampling of rinse water
<10CFU
10-100 CFU
> 100 CFU
<10CFU - adequate. No action unless Pseudomonas of Mycobacteria
10-100 CFU - investigate for problem. Disinfect equipment/ processor, consider double strength disinfectant
> 100 CFU - take processor out of service until issue resolved
What are the benefits of “dry cleaning” or “wet cleaning” a surface
- dry cleaning - uses a microfibre cloth to attract dust. Means dust/ bacteria can be retained. However difficult to fully clean the cloth
- wet-cleaning - may spread around the bacteria. Need to ensure washing/ disinfection of mop head
