Hot Bead Sterilisers

The text on this page is taken from an informal compilation of opinions of contributors to the online VOLE List. As such, they are not peer reviewed and may contain differences of opinion. Those wishing to contact the list may contact Adrian Smith.

Does anyone have any Guidance of Use, or SOPs, along the lines of: "if you are going to use a Hot Bead Sterilisers, at least use it properly in this way...", that they would be happy to share, please? Unfortunately we're having some persistent pushing to want to use them.

Or, if anyone has a really good rebuttal statement/policy that they also wouldn't mind sharing, that too would be very gratefully received!

I use as guidelines the 3rd video on this site (Procedures with Care) http://www.procedureswithcare.org.uk/aseptic-technique-in-rodent-surgery-tutorial

Here is an example of a standard procedure:

5. PROCEDURE

5.1. Hygiene and Safety

5.2. Appropriate PPE must be worn.

5.3. Local safety rules pertaining to electrical equipment must be followed.

5.4. Caution must be applied when placing instruments into, and removing them from, the bead steriliser to avoid burns. Hollow instruments must not be placed in the bead steriliser, as they may explode.

5.5. Switch off and unplug the bead steriliser after use. Report any faults or problems to the line management immediately.

5.6. General considerations

5.7. Use of a hot bead steriliser does not replace autoclaving or other validated methods of sterilisation for instruments. Bead sterilisers will only sterilise the tips of the instruments, leaving the possibility that the stem and handles are contaminated, thereby contaminating the surgeon’s sterile gloves and the drapes.

5.8. Bead sterilisers do not clean the instrument, so a system of working must be employed that incorporates cleaning before insertion into the beads.

5.9. Bead sterilisers are only suitable for sterilising metal instruments that have relatively long handles. Prolonged contact with heat may degrade some instruments (e.g. fine tips, certain metals).

5.10. Technique

5.11. The bead steriliser should be powered on at least 20 minutes before it is required, to allow time for the beads to reach operating temperature. Most steriliser models have a light which illuminates when the correct temperature has been achieved. The bead cover (if present) can then be opened/ slid back.

5.12. The steriliser casing is not sterile and should be placed away from the surgical area, away from sterile drapes, instruments and the draped animal.

5.13. Instruments must be sterilised by a validated method (e.g. autoclaving) at the start of the procedure.

5.14. Instruments must be cleaned and dry before placement in the beads, to prevent ‘baking on’ of tissue debris.

5.15. Instruments must be placed one at a time into the beads to enable adequate sterilisation and prevent cross-contamination. Care must be taken neither to allow the handles, nor the surgeon’s hand, to touch the outside of the steriliser casing.

5.16. The top 1cm of beads may not be at required temperature, so instruments should be placed 2-3cm deep into the beads and allowed to sterilise for 15 seconds before removal. Note that larger instruments may require a longer sterilisation time.

Holdridge et al state that the Germinator instructions specify a 4-cm dip for 60 seconds.--JR2315 (talk) 18:46, 5 January 2023 (UTC)

5.17. Instruments must be cooled (e.g. in sterile saline or placed on a sterile drape) and checked for any adhering glass beads before contact with the animal.

5.18. The glass beads should be stirred periodically to ensure even heating.

5.19. Switch off the bead steriliser after use and replace the sliding cover (if present) at the top. Always keep the steriliser casing upright, to prevent loss of beads.

How many times can instruments be bead sterilised before a full clean and autoclave? I do see a set of instruments being used across a cage of rodents sometimes and when I attended a surgery course some years back they had a five times in beads then full clean policy (not sure how evidence-based this was). I'm interested to hear if anyone has a limit for how many times bead sterilisers should be used on the same kit.

Holdridge et al determined that the efficacy of sterilisation decreases with subsequent uses, depending on how contaminated the tips were. Comparing strict aseptic technique, a brief run through the fur, and a dip in caecal contents, the probability that the instruments were sterilised by the hot bead device dropped by 4% with each subsequent fur-contaminated series, and 11.5% with each subsequent caecal-contaminated series. Therefore, they decided that if only minor fur contamination occurs between surgeries, they could use the same set of instruments for up to 5 surgical procedures before the probability of sterility dropped below 80%. It should be noted that they followed the Germinator instructions, which specify dipping the instruments 1.5" (4cm) into the beads for 60 seconds, which differs from the above recommendation.--JR2315 (talk) 18:46, 5 January 2023 (UTC)

It's also worth designating zones on the sterile instrument field, to keep tips and handles in separate areas. This also applies for procedures where the surgeon's hands may become contaminated (the typical example being a sole operator using a stereotaxic frame and drill etc).

In terms of the "designated fields", I've seen open petri dishes being used for that purpose.  The instruments are laid down with their handle on the drape outside the dish, resting against the edge of the dish, and the tip of the instrument hanging in mid-air over the dish.  The demarcation line between the clean and dirty fields couldn't be clearer.