Purpose
To provide information on standard methods for sterilization of critical items, explain the advantages and disadvantages of those methods, offer guidance on what information to include in IACUC protocols, and provide reference information on accepted liquid chemical sterilants.
Definitions¹
- Critical items:
- Objects that enter sterile tissue or the vascular system and thus confer a high risk of infection if contaminated with microorganisms. This includes surgical instruments, implants, cardiac and urinary catheters, and items that enter the brain through a chamber.
- Semi-Critical Items:
- Objects that contact mucous membranes or non-intact skin. This category includes anesthesia equipment and gastrointestinal endoscopes. These medical devices should be free from all microorganisms, however a small number of bacterial spores are permissible.
- Sterilization:
- A process that destroys or eliminates all forms of microbial life, including bacterial spores.
- High-Level Disinfection:
- A process that eliminates many or all pathogenic microorganisms, except for a small number of bacterial spores.
- Cleaning:
- Removal of visible soil (e.g., organic and inorganic material) from objects and surfaces, normally accomplished manually or mechanically with detergents or enzymatic products.
Background
Devices, instruments, and equipment which contact sterile body tissues or the vascular system are called “critical items” and generally require sterilization prior to use. Critical items do not include items that only contact non-sterile mucous membranes (e.g. gastric or colonic endoscopes). These are termed “semi-critical items” and require, at minimum, high-level disinfection.1
The Guide for the Care of Use of Animals (The Guide) states that “aseptic technique should be followed for all survival surgical procedures.” This includes preparation of the surgical site and the surgeon, and sterilization of instruments, supplies, and implanted materials. The sterilization of instruments used in survival surgeries is required by the Animal Welfare Act (2013).
Steam sterilization (autoclaving) is the recommended method to sterilize the majority of critical items, as it is reliable, consistent, effective, rapid, and easily monitored. In addition, it penetrates through packing devices. Ethylene oxide (ETO) gas sterilization has similar advantages and is useful for heat-sensitive and/or moisture-sensitive medical equipment, but ETO is toxic and requires appropriate engineering controls to minimize occupational exposure. Hydrogen peroxide gas plasma is a newer alternative technology to ETO, although it has lower penetration and is not appropriate for long catheters. For those items which cannot withstand increased heat, and when low temperature processes (i.e. low temperature ethylene oxide gas or hydrogen peroxide gas plasma sterilization) are not available, cold liquid chemical sterilants can be used. Certain cold sterilants have been cleared by the FDA for use to sterilize medical devices.2
Liquid chemical sterilants are not ideal for sterilization, as their use requires a longer contact time, is difficult to monitor, involves toxic chemicals in many cases, and requires immersion of the device in the sterilant. Attention to contact time is crucial, as the contact time is what determines if a chemical is acting as a high level disinfectant or as a sterilant. Proper rinsing in sterile water prior to use is essential. Occupational health recommendations for each chemical must be followed carefully in order to minimize personnel exposure.
In the case of non-survival surgeries, The Guide states that sterilization and aseptic technique may not be required, “but, at a minimum, the surgical site should be clipped, the surgeon should wear gloves, and the instruments and surrounding area should be clean.” Additionally, “for nonsurvival procedures of extended duration, attention to aseptic technique may be more important in order to ensure stability of the model and a successful outcome.”
Regarding the use of alcohol as a disinfectant, The Guide upholds the position that “alcohol is neither a sterilant nor a high-level disinfectant but may be acceptable for some procedures if prolonged contact times are used.” According to the CDC, alcohols are not recommended for sterilization because they lack sporicidal action and cannot penetrate protein-rich materials.1 The IACUC is tasked with evaluating the use of alcohol on a case-by-case basis.
Guideline
Critical items used for survival procedures must be sterile, and the method(s) of sterilization should be described in the IACUC protocol.
Non-survival procedures do not require that critical items are sterile, but, at a minimum, critical items must be clean. The use of non-sterile items should be described in the IACUC protocol along with assurance that the items are clean. The duration of a non-survival surgery will be considered by the IACUC when assessing the importance of aseptic technique.
Methods of Sterilization
Items must be cleaned prior to sterilization. The preferred method for sterilization of critical items is autoclaving. Low temperature gas/plasma/vapor sterilization is the next preferred option, if available. If those preferred options are not available or suitable for the application, liquid chemical sterilization may be employed using agents and conditions that have been FDA-cleared for sterilization.2
Agents classified as high-level disinfectants, and alcohol (which is considered neither a sterilant nor a disinfectant), do not meet requirements for sterilization and are generally not acceptable for the preparation of critical items for survival procedures. Exceptions require approval by the IACUC, and require A) justification that the above sterilization methods are not appropriate, and B) demonstration that the selected method effectively sterilized the item.
Table 1 and Table 2 provide examples of common sterilants with required contact times and maximum reuse periods. Some of these sterilants are FDA-cleared for sterilization of medical devices (see reference 2) and some have been used based on scientific evidence of efficacy (see reference 3). Prior to using liquid chemical sterilants, Environmental Health and Safety should be consulted to discuss and address any safety concerns.
Hot bead sterilization is a quick method for re-sterilization of the working end of instruments. This method is appropriate for certain procedures, but is not intended as an initial means of sterilization. Instruments must be allowed to cool before contacting tissue.
Guidance for IACUC protocols
- The method of sterilization of critical items should be described in the IACUC protocol.
- If steam autoclave is not appropriate for the research application (e.g. heat-sensitive and/or moisture-sensitive items), that justification should be provided in the IACUC protocol.
- If liquid chemical agents are used, the IACUC protocol should include:
- Specific chemical or chemicals used
- Duration of exposure (contact time)
- Temperature
- Rinsing method
- Agents classified as disinfectants, or alcohol, may only be used if:
- The IACUC protocol justifies why steam autoclave, low temperature gas/plasma/vapor sterilization, and FDA-cleared sterilants are not appropriate for the research application
- References and/or data are provided to demonstrate the efficacy of the selected method in producing functional sterility for that research application
Table 1. Liquid Chemical Sterilants
| Agent | Brand name, company | Contact time for sterilization | Reference | Maximum reuse period |
| Povidine Iodine (10%) | 24 hrs | 3, not FDA | Povidine Iodine (10%) | |
| Hydrogen peroxide, 7.5% | K970230 Sporox Sterilizing & Disinfection Solution, Reckitt &Colman Inc. | 6 hr at 20 ˚C | 2 | 21 days |
| 7.25% hydrogen peroxide0.23% peracetic acid) | K972708 EndoSpor Plus Sterilizing and Disinfecting Solution, Cottrell Limited | 3 hrs at 20 ˚C | 2 | 14 days |
| 1.0% hydrogen peroxide/0.08% peracetic acid | K960513 PeractTM 20 Liquid Sterilant/Disinfectant, Minntech Corp | 8 hrs at 20°C | 2 | 14 days |
| 3100-3400 ppm peracetic acid | K091210 Acecide-CHigh Level Disnfectant and Sterilant, Best Sanitizers Inc. | 2 hrs at 20°C | 2 | 5 days |
| 1.12% glutaraldehyde1.93% phenol/phenate | K003087 Sporicidin Sterilizing and Disinfecting Solution, Sporicidin International | 12 hrs at 25°C | 2 | 14 days |
| Glutaraldehyde, >2% | See associated table for specific products | 10 hrs | 2 |
Table 2. Glutaraldehyde (>2%), FDA-cleared for sterilization2
| Brand name, company | Contact time for sterilization | Maximum reuse period |
| K060618 Cidex Activated Dialdehyde Solution, Advanced Sterilization Products | 10 hrs at 25°C | 14 days |
| K924434 Cidex™ Activated Dialdehyde Solution, Johnson and Johnson Medical Products | 10 hrs at 25°C | 14 days |
| K924334 Cidex Formula 7™ Long-Life Activated Dialdehyde Solution, Johnson and Johnson Medical Products | 10 hrs at 20-25°C | 28 days |
| K923744 Cidex PlusTM 28 Day Solution, Johnson and Johnson Medical Products | 10 hrs at 20-25°C | 28 days |
| K012889 Banicide Advanced for Sterilization and High Level Disinfection, Pascal Company, Inc. | 10 hrs at 25°C | 30 days |
| K993042 Rapicide High Level Disinfectant and Sterilant, MediVators, Inc. | 7 hrs 40 min at 35°C | 28 days |
| K974188 °Cetylcide-G Concentrate and Diluent Concentrate, Cetylite Industries, Inc. | 10 hrs at 20°C | 28 days |
| K932922 Procide 14 N.S., Cottrell Limited | 10 hrs at 20°C | 14 days |
| K932922 OmnicideTM Long Life Activated Dialdehyde Solution, Cottrell Limited | 10 hrs at 20°C | 28 days |
| K932922 OmnicideTM Plus, Cottrell Limited | 10 hrs at 20°C | 28 days |
| K931592 Metricide Plus 30 Long-Life Activated Dialdehyde Solution, Metrex Research, Inc. | 10 hrs at 25°C | 28 days |
| K931052 Metricide 28 Long-Life Activated Dialdehyde Solution, Metrex Research, Inc. | 10 hrs at 25°C | >28 days |
| K930284 Metricide Activated Dialdehyde Solution, Metrex Research, Inc. | 10 hrs at 25°C | 14 days |
| K914749 Wavicide – 01, Wave Energy Systems | 10 hrs at 22°C | 30 days |
| K974062 MedSci 3% Glutaraldehyde, MedSci, Inc. | 10 hrs at 25°C | 28 days |
| K113015 Aldahol V High Level Disinfectant, MIcrochem Laboratories, Inc.(Glutaraldehyde with 20.1% isopropanol) | 8 hrs at 20ºC | 14 days |
| K041360 Aldahol III High Level Disinfectant, Healthpoint LTD(Glutaraldehyde with 26% isopropanol) | 10 hrs at 20° C | 14 days |
References
- Rutala WA, Weber DJ, the Healthcare Infection Control Practices Advisory Committee (HICPAC). 2008. CDC Guideline for Disinfection and Sterilization in Healthcare Facilities. Available: Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008 (PDF)
- FDA-Cleared Sterilants and High Level Disinfectants with General Claims for Processing Reusable Medical and Dental Devices. 2015. Available: FDA-Cleared Sterilants and High Level Disinfectants with General Claims for Processing Reusable Medical and Dental Devices
- Callahan BM, Hutchinson KA, Armstrong AL, Keller LS. 1995. A comparison of four methods for sterilizing surgical instruments for rodent surgery. Contemp Top Lab Anim Sci. 34(2):57-60.
Approval/Review Dates
Originally Approved: 06/15/2017
Last Reviewed/Revised by the IACUC: 11/13/23 (OAW)