Instrument Selection and Use

Instruments used for rodent surgery are delicate and typically designed for a specific function. Incorrect use of these instruments will damage them and make it difficult, if not impossible, to use them correctly. For example, hemostatic forceps are designed to grasp and hold tissue such as blood vessels or skin. While they can be used to hold a needle for suturing in an emergency, routine use of hemostatic forceps instead of a surgical needleholder is not recommended. These forceps are not designed to securely grasp the needle and using them for suturing will damage the tips making them useless for their intended purpose. Instruments should also be of the appropriate size for rodent surgery. Using instruments that are too large will exaggerate hand motions and decrease surgical precision resulting in poor technique and increased tissue trauma.

It has been reported that repeated use of glass bead sterilizers will make instruments brittle and dull over time. Any instrument that is used frequently, handled roughly or cleaned with abrasive materials can be damaged or dulled. Instruments should be assessed on a regular basis and replaced when necessary. Scissors and other sharp instruments can sometimes be re-sharpened to prolong life. Instruments must be gently cleaned after each use to ensure that all blood and tissue is removed. An ultrasonic cleaner can assist in this process. Proper care will extend the life of your instruments and help preserve your investment.

Reference:
How to Select and Procure Surgical Instrumentation for Rodent Surgical Research. 2012. S Baran, E Johnson, and M Perret-Gentil. ALN Magazine.

Instrument Sterilization

Prior to surgery, instruments and other supplies are placed in a ‘surgical pack’. The surgical pack must not only hold the instruments and supplies during the sterilization process, but also maintain the sterility of the contents until used in surgery. A variety of packing methods exists, including:

• Instruments, with or without an instrument tray, are packed inside a folded cloth or paper wrap and sealed with tape designed to indicate when sterilization has been achieved. Other types of sterilization indicators may be placed inside the pack.
• Peel packs –self-sealing ‘envelopes’ used for steam or gas sterilization. A sterilization indicator is included on the envelope.

Keeping Instruments Sterile During Surgery
Use an extra piece of sterile drape material or the inside of the surgical wrap or envelope as a sterile space to place instruments during surgery. One of the most common errors for an inexperienced surgeon is setting instruments down on an unsterile surface.

Sterilization Procedures

Surgical instruments and other material or equipment that will contact the surgical site must be sterile prior to use.  The process of sterilization kills all forms of life, including bacterial spores and viruses. Chemical disinfection is not the same as sterilization and is not acceptable as the primary method of instrument preparation for surgery. Methods of instrument sterilization include steam (autoclave) and gas (ethylene oxide) sterilization. Dry heat sterilization using a glass bead sterilizer is not acceptable for initial sterilization of instruments prior to surgery but may be used during ‘batch’ surgeries.

Steam Sterilization

• Steam or autoclave sterilization is the most common method of instrument sterilization.
• Instruments are placed in a surgical pack and exposed to steam under pressure.
• A sterilization indicator (required) such as autoclave tape or an indicator strip is used to identify instruments that have been sterilized.

Ethylene Oxide

• Ethylene oxide gas is used to sterilize items that cannot withstand the high temperature and steam of an autoclave.
• Ethylene oxide is highly toxic. Items sterilized with ethylene oxide must be aerated before use to allow the gas to dissipate.

Glass Bead Sterilizers:

• Glass bead sterilizers may be used to re-sterilize instruments during a surgical procedure but are not acceptable as an initial method of sterilization.
• Glass bead sterilizers have a central well filled with glass beads heated to high temperature (approximately 5000F). 
• After removal of blood and tissue, the tips of surgical instruments are placed into the hot glass beads for approximately 10-15 seconds.
• Only the tips of the instruments are re-sterilized in this process.
• Instrument tips become extremely hot and must be cooled before use.
• Glass bead sterilizers may be used between animals when one set of initially autoclaved instruments is used on a group of up to 5 animals.

Reusing Instruments

When surgical procedures are to be performed on multiple rodents, the same set of instruments may be used on more than one animal under the following conditions.

• The instruments must be initially sterilized by autoclaving or gas sterilization.
• Blood and tissue particles on instrument tips must be removed using alcohol before placement in the glass bead sterilizer.

• The tips of instruments must be placed in a hot bead sterilizer between animals.
• A new set of sterile instruments must be used after every 4-5 animals.
• If the instrument tips have become contaminated by contact with a non-sterile surface or non-sterile portions of the body (such as contents of the gastrointestinal tract) a new sterile set of instruments must be used on subsequent animals.

Instrument Tip Technique for Specific Rodent Surgical Procedures

Although challenging, instrument tip technique may be useful for some rodent surgery situations. Generally, this is limited to surgeries in which incisions involve only the skin (no exposure or manipulation of internal organs). Keep the following points in mind when using “tips only” technique:

• Prior IACUC approval is required to use instrument tip technique in research rodents.
• The animal must be maintained in a surgical plane of anesthesia throughout the procedure.
• Begin surgery with sterile instruments and handle them aseptically throughout the procedures.
• The same set of pre-sterilized instruments may be used for up to five similar surgeries provided aseptic technique is followed throughout all procedures.

Sterile surgical gloves do not have to be worn if the following criteria are strictly adhered to:

• Gloves are changed after completing the surgical scrub such that new clean gloves are donned at the beginning of the surgical procedure.
• The gloved hands never touch the working (tip) end of the instruments, the suture, suture needle or any part of the prepped surgical field.
• Only the sterile tips of the instruments are used to handle the animal’s tissues.

Outline of procedures in “tips only” surgery

• The surgeon must wear a mask, and clean lab coat or gown. A head covering (cap or bonnet) is recommended.
• Place the anesthetized and surgically prepped animal on a warming device that has been covered with a clean paper bench towel.
• Open your sterile surgical pack and any other sterile equipment needed (e.g., suture material) without touching or handling the sterile contents.
• Disinfect your hands with hand sanitizer or wash your hands with soap and water. After hands are dry, put on clean examination gloves.
• Drape the surgical site with a large sterile drape. The surgeon must handle the drape only by its edges so that it does not become contaminated. (The drape should contain a ‘pre-cut’ opening that allows access to the surgical site as it will be difficult for the surgeon to cut an opening without contaminating the drape.) A new sterile drape must be used for each animal.
• After a surgical instrument is handled by the surgeon, only the tip of the instrument is considered sterile. If the surgeon lays the instrument down, the sterile tip must be placed on a sterile gauze sponge or drape. The instrument handle should not come in contact with the sterile surface to avoid contamination of that surface.
• If the tip of a surgical instrument becomes contaminated, the tips may be re-sterilized by rinsing away blood or tissue using alcohol or sterile water and placing the tips in a hot bead sterilizer.
• Keep in mind that the surgeon cannot touch the instrument tips, suture material or wound clips, suture needle or any part of the prepped surgical field with his/her hands during the surgery.
• Gloves should be rinsed with 70% alcohol between surgeries. If you must handle another mouse to anesthetize and prep it, you must change gloves before performing the next surgery.