Q. What is the difference between sterilisation, disinfection and cleaning?
A. Sterilisation is defined as the complete destruction of living organisms (including spores and viruses). This differs from disinfection, which is a process used to remove most viable organisms, but one which does not necessarily inactivate some viruses and bacterial spores. Cleaning is a process which physically removes contamination but does not necessarily destroy micro-organisms.
Q. How is autoclaving performed?
A. Autoclaving is a process that combines heat and pressure to sterilise instruments. By combining pressure with heat the temperatures of liquids such as water may be raised above their usual boiling points to facilitate the process. The autoclave is thus a form of ‘pressure cooker’. The three variables used in autoclaving are There fore pressure, temperature and time. Typical cycles include 134°C for a ‘hold time’ of 3 minutes, and 121°C for a ‘hold time’ of 15 minutes. The actual timing of the whole process is longer than these figures of course, as the machines need to safely heat up and down.
Q. How is disinfection carried out?
A. Flexible instruments (e.g. flexible cystoscope) would generally be unable to withstand the conditions of autoclaving. ttey are There fore processed by high-level disinfection. ttey are manually cleaned with brushes and detergent, and then disinfected in an automated manner. Ultrasound is used in some devices to facilitate the cleaning process. Automated machines use a cycle whereby the flexible endoscope is disinfected with solutions of chemical such as chlorine dioxide (‘Tristel’).
Q. How do you determine the level of disinfection required for reusable medical instruments?
A. Divided into three classes according to Spaulding Classification: critical, semi-critical and non-critical.
Critical instruments are those that penetrate normally sterile tissue (surgical instruments). They generally require sterilisation before and after use. Semi-critical instruments contact mucous membranes or non-intact skin (cystoscopes). Non-critical items are those that come in contact with only intact skin (blood pressure cuffs).
Q. What do you use for scrubbing and skin preparation, prior to surgery?
A.
Scrubbing
4% Chlorhexidine (Hydrex)
7.5% Povidone iodine (Betadine or Videne)
Skin preparation
Inguinoscrotal: 10% Aqueous povidone iodine (Betadine or Videne)
Genital: Chlorhexidine 0.015% Cetrimide 0.15% (Travasept solution)
Q. What are the ideal climate conditions for an operating theatre?
A. 21°C and 55% humidity.