Washington State University

Institutional Animal Care and Use Committee

Guidelines for Sterilization of Instruments &

Supplies for Aseptic Surgical Procedures

Survival surgical procedures on all species must be conducted using aseptic technique which requires the use of sterile instruments and supplies. Many supplies such as gloves, surgical blades, and suture materials are commercially available in sterile, ready-to-use packs. However, it is frequently necessary to sterilize (in-house) items such as surgical instruments, drapes, gauze, gowns, and catheters/devices for implant.

In considering methods for sterilization, it is important to differentiate between sterilization and disinfection . Sterilization kills all viable microorganisms, while disinfection only reduces the number of viable microorganisms. High-level disinfection will kill most vegetative microorganisms, but will not kill the more resistant bacterial spores. Commonly used disinfectants, such as alcohol, iodophors, quaternary ammonium and phenolic compounds, are not effective sterilants and, therefore, are not acceptable for the use on items intended to be used in survival surgical procedures.

The preferred methods of sterilization are high-pressure/temperature (e.g. autoclave) for items that can withstand high temperature. For items which are unable to withstand high temperatures and pressure, ethylene oxide gas is the preferred method of sterilization. However, cold chemical sterilization may be used effectively for many items.

The following are approved sterilization procedures:
 

1. High-pressure/temperature steam sterilization using an autoclave* and appropriate monitoring systems to assure sterility.

2. Dry Heat (e.g. hot glass bead sterilizer). These units only sterilize the tip of instruments. Caution: instruments must be cooled before contacting tissue.

3. Gas sterilization with ethylene oxide*, using an approved gas sterilizer and appropriate monitoring systems to assure sterility and personnel safety. All materials sterilized by ethylene oxide require safe airing time.

* Questions regarding the availability of autoclave and gas sterilization services and monitoring systems at WSU may be directed to the IACUC Office at 509/335-6246.

4. Cold chemical sterilization:

A. Effective and proper use of chemical sterilization is dependent on many factors, including:

1) The use of chemicals classified as sterilants. Those classified as disinfectants are not adequate.

2) The physical properties of the item(s) being sterilized. It must be relatively smooth, impervious to moisture, and be a shape that permits all surfaces to be exposed to the chemical sterilant.

3) Exposure

a) All surface, both interior and exterior, must be exposed to the sterilant. Tubing must be completely filled and the materials to be sterilized must be clean and arranged to assure total immersion.

b) The items being sterilized must be exposed (immersed) to the sterilant for the prescribed period of time . Always follow manufacturer's instructions. To prevent corrosion, instruments should not be "stored" in the sterilant.

4) Use of fresh solutions. The sterilant solution must be clean and fresh. Most sterilants come in solutions consisting of two parts that, when combined together, form what is referred to as an activated solution. The shelf life of activated solutions is indicated in the instructions for commercial products. Generally, this is from one to four weeks.

5) Rinsing chemically sterilized items prior to use in the surgical procedures. Instruments, implants, and tubing (both inside and out) must be rinsed with sterile saline or sterile water prior to use to avoid tissue damage to the animal.

B. There are many acceptable commercial sterilants available and their use is encouraged over making up solutions from basic ingredients. Only products classified as sterilants are to be used for sterilizing instruments and implants for surgery. These products must be used according to the manufacturer's recommendations to ensure adequate sterilization. Alcohol is not reliable as a fungicide or virucide and is ineffective against spores. Alcohol is not stable and loses effectiveness through evaporation. As such, alcohol should not be used as a cold sterilant.

 
Following are examples of cold chemical sterilants:

1) Chlorine - Chlorine Dioxide (ClO2 ) requires a minimum of 6 hours of contact time to achieve sterilization. Presence of organic matter reduces activity. Once mixed, there is limited shelf life (<14 days).

2) Aldehydes - Examples of aldehydes are Formaldehyde (6% solution) and Glutaraldehyde. Contact time varies depending on product. Consult manufacturer. Some aldehydes are corrosive and irritating. Consult manufacturer for safety precautions and MSDS information. In regards to Glutaraldehyde, exposure limits have been set by OSHA.