Surgery is defined as any procedure that exposes tissues normally covered by skin or mucosa. Experimental surgery has great potential for causing pain or distress to animals if not performed properly. Surgery can result in pain, damage to tissue and post-operative infections. Therefore stringent guidelines for training, surgical facilities, asepsis, surgical preparation, anesthesia, intra-operative records, analgesia, surgical technique, and post-operative monitoring have been established.
Surgery is classified in several ways. There are different requirements depending on the type of surgery being performed.
Surgery is major if it enters a body cavity (thorax, abdomen, calvarium), or has the potential for having significant complications. Included would be orthopedic procedures and extensive cannulation procedures.
Other surgery is classified as minor. Minor procedures include peripheral vessel cannulations and skin incisions.
Surgery is also classified as survival vs. nonsurvival. Asepsis and sterility are not required for non-survival procedures, unless the procedures are of sufficient duration to allow bacterial infections to affect the outcome of the study.
There are also slightly different requirements for surgery performed on large animals such as rabbits, dogs, pigs and monkeys versus rodents and non-mammals.
Surgical facilities used for survival surgery must be designed and maintained in such a way that they help prevent the development of post-procedural infections. Design features include:
Separation of the preparation areas from the surgery area
Minimization of personnel traffic flow through the surgery area
Air flow should be away from the surgery area (e.g. positive room pressure, use of filtered, laminar flow air). It may be desirable to have HEPA filtered air for high-risk procedures
Room surfaces should be non-porous and easily sanitized
A regular room cleaning and disinfection schedule should be established (i.e. daily cleaning of floors and work surfaces, weekly to monthly cleaning of walls and cabinets)
The surgery area should be free of all equipment and materials not necessary for the procedure. Any stored items should be in cabinets or drawers.
How these goals are achieved will vary somewhat depending on the type of surgery.
An approved surgery suite is needed for large animal major survival surgery, with separate rooms for preparation of the patient, preparation of the surgeon, the operating room and a recovery of the animal from anesthesia.
Non-survival surgery, minor surgery or rodent/non-mammal surgery may be performed in a dedicated work area. This is a room or bench top which from which all materials are removed at the time of the surgery. The same concepts described above are important for a dedicated area.
The IACUC will review and approve all surgical areas.
Asepsis is defined as preventing exposure to microorganisms and prevention of infection. Three things that are extremely important in achieving asepsis are the reduction of time, trauma and trash.
Time of surgical procedure is an important factor, as the longer a procedure takes the greater the possibility of contamination and therefore infection.
Trauma that is sustained by the tissue as a result of rough handling, drying out upon exposure to room air, excessive dead space, implants or foreign bodies or non-optimal temperatures will contribute to infections.
Trash refers to contamination by bacteria or foreign matter.
It may be possible to follow slightly different procedures for achieving asepsis when performing surgery on small patients such as rodents, birds, reptiles and amphibians. Typically, surgical times are short, incisions are small and the amount of tissue trauma is minimal. These all minimize the risk of infection.
Preparation: Surgeon, Patient, Instruments and Supplies
It is essential that anything that will contact the subcutaneous tissues of an animal be appropriately sterilized to prevent post-procedureal infections. These will be discussed below. Videos on many of these techniques are available from the central animal facilities and the University library system. The RAR veterinary staff can provide training as well. Other aspects of preparation include pre-operative fasting, if necessary, a decision about prophylactic antibiotics, appropriate anesthesia of the patient, and a plan for post-operative pain control and supportive care.
Preparation of Instruments and Supplies
Surgical instruments and supplies must be sterilized before they are used for survival surgery. There are a number of ways that this can be achieved.
Durable instruments and supplies may be autoclaved. This an extremely reliable and cost-effective method for sterilization. The disadvantage is the time that it takes to perform (from 15 minutes to 1 hour). Normally a wrapped "pack" of instruments is prepared and is opened the day of surgery. Packs may be stored if they are kept away from moisture. A preparation date should be put on each prepared pack and packs should not be used if they are more than six months old.
Instruments and less durable supplies may be sterilized by ethylene oxide. This is also a reliable method for sterilization. However, it is more costly than autoclaving and also takes time to perform (overnight). Ethylene oxide is hazardous and must be performed using appropriate procedures and equipment. The Fairview-University hospital Fairview Sterile Stores service can provide this service (672-4234 or 672-7181).
Instruments and some materials may be sterilized in a cold sterilant solution. There are several acceptable commercial sterilants available. Only products classified as sterilants are to be used for sterilizing instruments and implants for surgery and they must be used according to the manufacturer's recommendations for sterilization. Following are examples of four commercial products listed by brand names: Cidex ? active ingredient: 2% glutaraldehyde; Sporicidin ?active ingredients: phenol 7.05%, glutaraldehyde 2%, Sodium phenate 1.2%; Alcide ?active ingredient: sodium hypochlorite; and Sporclenz - for a minimum of 6 hours. active ingredient: hydrogen peroxide. Non-commercial solutions that are acceptable include: glutaraldehyde 2% for a minimum of 10 hours; 8% formaldehyde + 70% ethyl alcohol for 18 hours. All surfaces, 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 in the sterilant to assure total immersion. The items being sterilized must be exposed to the sterilant for the prescribed period of time. The sterilant solution must be clean and fresh. Most sterilants come in solutions consisting of two parts that when added together form what is referred to as an "activated" solution. The shelf life of activated solutions is indicated on the instructions for commercial products. Rinsing chemically sterilized items. Instruments, implants, and tubing (both inside and out) should be rinsed with sterile saline or sterile water prior to use to avoid tissue damage. Note: chemicals classified only as disinfectants (for example, 70% alcohol) are not adequate.
Instruments can be sterilized in a hot bead sterilizer. This device is appropriate for performing rodent and non-mammal surgery. The efficacy of the sterilization is high and it sterilizes in a very short time (10 sec.) However, only the tips of the instruments are sterilized. It is necessary to allow the instruments to cool before handling tissue to prevent thermal injury. [Ref: Callahan, et. al, 1995. A comparison of four methods for sterilizing surgical instruments for rodent surgery. Contemp. Top. Lab. Anim. Sci, 34:2, 57-60.]
Instruments and materials are often available pre-sterilized. The packages should have an expiration date on them. Surgical supplies may not be used for survival surgery when they have passed the expiration date.
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