Rodent Surgery

Survival surgical procedures must be carefully planned and performed to avoid post-operative complications (pain, distress, infection, etc.). The following guidelines are applicable to all rodent surgeries performed as part of research or teaching activities, and should be followed unless specific exceptions are approved by the Institutional Animal Care and Use Committee (IACUC). Recently shipped animals should be acclimated before surgical intervention. General practice is to allow an acclimation period of 5 days. If post-surgical housing is planned to be changed (i.e. single housing), it is best to acclimate the animals to the change prior to surgery. Surgeries should be performed by, or under the supervision of an appropriately trained individual with experience in the respective technique(s). It is the responsibility of the Principal Investigator to ensure that appropriate training has been provided. Surgical procedures can be classified as survival vs. non-survival, and major vs. minor. In survival surgery, animals recover from anesthesia following the procedure, while in non-survival procedures the animals are euthanatized before recovery from anesthesia. Major surgical procedures penetrate or expose a body cavity, or have the potential to produce substantial impairment of physical or physiologic functions. Minor survival procedures do not expose a body cavity and cause little or no physical impairment. No animal is to be used in more than one major survival operative procedure unless the procedures are approved by the IACUC.

All rodent surgeries may be performed in laboratories with areas that are able to be sanitized and are free of unnecessary items. During surgeries, activities unrelated to the surgical procedure are discouraged in the vicinity of the operative procedure to minimize the occurrence of aerosol contamination of the surgical site. Prior to use, the work surface should be disinfected and/or covered with a clean drape and cleaned at the conclusion of the operative procedure.

Pre-operative fasting is not routinely necessary because rodents, unlike many other species, cannot vomit and therefore are not at risk of aspiration while under anesthesia. However, pre-operative fasting may be necessary to help evacuate the gastrointestinal tract prior to its surgical manipulation. For survival surgical procedures, the hair or fur should be removed from the surgical site in an area remote from where the surgical procedures will be performed. Following hair removal, the skin should be disinfected with an antiseptic solution (ex. povidone iodine scrub or chlorhexidine scrub). Sterile drapes may be used to protect from inadvertantly contacting unsterile areas. Ideally, the drape will cover the entire animal with only the site of surgery exposed. Attempts should be made to maintain the animal's normal body temperature by minimizing heat loss and/or providing supplemental heat. Maintenance of normal body temperature minimizes cardiovascular and respiratory disturbances caused by anesthetic agents. Because some anesthetics inhibit blinking, ophthalmic ointment should be applied to both eyes to protect against corneal drying and ulceration.

If nonsurvival surgery is performed, the instruments must be clean but do not have to be sterile. If survival surgery is performed, all instruments and supplies having contact with the surgical site or sterile field must be sterile. Some supplies are commercially available in a sterilized form (ex. suture material, scalpel blades, needles, drapes, etc.). Specific sterilization methods for unsterile items may be selected on the basis of physical characteristics of materials to be sterilized. Regardless of the sterilization method used, sterilization indicators should be used to identify materials that have undergone proper sterilization and dated to indicate when sterilization was done. It is recommended to re-sterilize any materials for which it has been 8 weeks or longer since the date of in house sterilization.

Autoclaving is a common effective sterilizing method that may be used on heat and moisture resistant materials. Liquid chemical sterilants may be used on moisture resistant/heat labile materials. When using liquid chemical sterilization, the manufacturer's recommendations for contact time should be used and the material should be rinsed with sterile saline or sterile water before contacting animal tissue. The chemical sterilant should be replaced when contaminated with blood or other body fluids. Note, alcohol is neither a sterilant nor a high-level disinfectant and should not be used as the sole agent for sterilizing materials. Gas sterilization (ethylene oxide) may be used on moisture and heat labile materials; however, ethylene oxide sterilization is not currently unavailable at Southern Illinois University at Carbondale.

Provided the instruments are handled appropriately and have not contacted non-sterile surfaces, a single set of sterilized instruments may be used on up to 5 animals before the instruments must be re-sterilized when performing serial rodent surgeries. To ensure the potential for microbial contamination has been reduced to the lowest practical level, it is recommended that the instruments be placed in either a glass bead sterilizer or liquid chemical sterilant between animal surgeries. If a glass bead sterilizer is used, care should be taken to ensure the instruments are not overly hot before reusing. If liquid chemical sterilants are used, the instruments should be rinsed with sterile saline or sterile water before reusing.

When non-survival surgery is performed, the surgeon should wear gloves but the gloves do not have to be sterile. If survival surgery is performed, the surgeon should wear sterile gloves. A clean laboratory coat or scrub suit, face mask and hair coverings are recommended but not required. If working alone, the surgeon should have all non-sterile procedures (ex. anesthetizing and positioning animal for surgery, preparing all instruments/supplies such that they may be used aseptically) completed before scrubbing. The face mask and/or hair covering (if used) should be donned and the packs of sterile gloves and towel should also be opened before scrubbing. The surgeon should scrub with an antiseptic scrub preparation (ex. povidone iodine or chlorhexidine). After scrubbing both hands, rinse with water, then use a sterile towel to dry. Don the sterile gloves, making sure not to contaminate the outer surfaces of the gloves in the process by contacting non-sterile surfaces. If the glove(s) contact non-sterile areas, they should be changed with sterile replacements.

Aseptic techniques should be used to reduce the microbial contamination to the lowest possible practical level. Antibiotics should not be considered as a replacement for aseptic procedures and are not recommended to be given routinely following surgery. However, if a nonsterile part of an animal such as the gastrointestinal tract is to be surgically exposed or if a procedure is likely to cause immunosuppression, pre and post-operative antibiotics may be appropriate. The abdominal and/or thoracic body wall should be closed with absorbable suture material. The skin should be closed with staples/wound clips or a monofilament suture material. Silk or other braided suture material should not be used when closing skin incisions due to the potential for wicking bacteria contaminated moisture into the surgical site.

It is the responsibility of the investigative staff to monitor the animals during the anesthetic recovery period and each day during the post-operative clinical recovery period, including weekends and holidays. Animals should be recovered from anesthesia in a clean, dry, warm environment separated from other animals not recovering from anesthesia where they can be frequently observed by trained personnel. During anesthetic recovery, particular attention should be given to thermoregulation, and postoperative pain or discomfort. If the anesthetic recovery period is prolonged, it may be necessary to rotate the animal approximately every 30 minutes from lateral recumbency on one side to lateral recumbency on the other side to avoid hypostatic congestion of the lungs. Animals can be returned to their animal housing room after they are able to ambulate relatively normally.

After anesthetic recovery, during the post-operative clinical recovery period the intensity of monitoring necessary will vary with the procedure performed. During this period, the animals should be accessed for signs of pain or discomfort and general well being, and the surgical site monitored for normal healing progression and signs of post-surgical infection. Supportive care should be provided as needed. If the procedures produce or are expected to produce more than momentary or slight pain to the animals, appropriate analgesic agents should be administered unless it is described to be contrary to the goals of the study for scientific reasons in the animal use protocol. Clinical signs of discomfort can vary but may include abnormal posture, reluctance to move or to be handled, vocalizing, poor appetite or unthrifty appearance. The animal may also be monitored for adequate intake of food and water and ability to urinate and defecate normally. Additionally, parenteral fluids for maintenance of water and electrolyte balance may be needed during this period. Monitoring and supportive care normally continues for 7-10 days or until the skin sutures or staples are removed. The attending veterinarian may be contacted with any post-operative complications or concerns.

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