Proper instrument sterilization is a critical component to preventing infection and ensuring successful outcomes in survival surgery. True sterility is achieved when all microorganisms, including bacterial spores, are destroyed. A variety of sterilization methods are commonly employed, including high heat (i.e., autoclave), gas (i.e. ethylene oxide), and chemical. Autoclaving is a known gold standard to achieve sterility but other methods of high-heat sterilization are routinely used. Hot bead sterilization is a regular practice for rodent surgeries in many facilities, especially when a large batch of surgeries must be completed.

Hot bead sterilization is a quick and convenient method. Windeler et al. (1975) demonstrated sporicidal effects of hot beads when the instrument was immersed for 15 seconds at 218 C. However, several considerations must be made when using hot bead sterilization for batch surgeries. First, there is a risk of thermal tissue injury if instruments are not granted enough time to cool (The Guide, 2011). Second, there is no indication that the instrument has reached the necessary temperature to become sterile and the surgeon must guess the appropriate time to remove the instrument. A third factor, and perhaps the most important, is that cross-contamination may occur among surgical patients because the handles of the instruments used are not sterilized, and this may increase the incidence of infection.

All animals are susceptible to infection if sterility is broken; thus, every surgical patient should be treated with the highest standards of aseptic technique. Infection has serious implications for animal welfare and surgical success, and may confound the results of the study. Additionally, if the implant becomes infected due to cross-contamination, the only way to rid the animal of the infection is to remove the device. This ultimately results in an increase in necessary sample size and a likely increase in study cost.

To avoid these complications, DSI recommends adhering to strict aseptic technique for all rodent surgeries. Multiple instrument packs may be autoclaved or gas-sterilized so a fresh pack is available for each animal. Alternatively, instruments may be fully immersed in a cold chemical sterilant for a time period recommended by the manufacturer between each surgery. These methods ensure that the entire instrument is sterilized, not just the tips, and mitigates the risk of cross-contamination and subsequent infection via instrument handles. As the Dutch philosopher Desiderius Erasmus so eloquently stated, “Prevention is better than cure”.

References:

Baines, S. (1996). Surgical asepsis: principles and protocols. In Practice, 18(1), 23-33. doi:10.1136/inpract.18.1.23.

National Research Council. 2011. Guide for the Care and Use of Laboratory Animals: Eighth Edition. Washington, DC: The National Academies Press. doi:https://doi.org/10.17226/12910.

Standards of Practice for the Decontamination of Surgical Instruments. Retrieved from http://www.ast.org/AboutUs/Sterilization_and_Disinfection/.

Vinay, P., MDS, Giridhar Reddy, Y., Nikhilanand, H., & Priyadarshini. (2011). Sterilization Methods in Orthodontics--A Review. International Journal of Dental Clinics, 3(1), 44-47.

Windeler, A. S., & Walter, R. G. (1975). The sporicidal activity of glass bead sterilizers. Journal of Endodontics, 1(8), 273-275. doi:10.1016/s0099-2399(75)80040-9.