Surgery

All surgery must be performed by qualified trained individuals having completed the requisite University of Toronto introductory training modules.  In addition individuals must successfully complete the Anaesthesia Training Module followed by the Surgical Techniques Training module.

The following is the University policy for rodent surgery. Surgery for larger animals such as rabbits, must also conform to acceptable aseptic procedures and be performed in an operating room under sterile conditions as outlined in the Animals for Research Act. Revised Statutes of Ontario, 1980 Chapter 22 and Regulations 16, 17, 18, 19, 1980 November 1985. Refer to relevant Standard Operating Procedures.

University of Toronto Policy on Survival Rodent Surgery

All species undergoing surgery should receive a similar level of care and attention. Recovery surgery in all species of animals should be performed using aseptic technique. (Canadian Council on Animal Care Guidelines)

The argument is still made that aseptic technique is not necessary for rodent surgery because mice or rats often survive surgical procedures performed using less than aseptic technique. However, survival alone is not a valid criterion for judgement of the acceptability of a rodent surgical technique. The criterion for acceptability should be the absence of untoward, unplanned alteration of physiological functions or behavior due to peri-operative infection.

The primary objective of aseptic surgical technique is to reduce microbial contamination of the incision and exposed tissues to the lowest possible practical level.

Prior to undertaking ANY surgical procedure, it is the responsibility of the PRINCIPAL INVESTIGATOR to ensure that staff carrying out those procedures are adequately trained and that provisions are made for post-operative care. DCM has several surgical suites available for use by prinipal investigators or their staff. The Canadian Council on Animal Care recommends that all survival surgery be performed in areas specifically designed for the purpose.

Preoperative Considerations

1. All survival surgeries must be performed in the DCM surgical suites.
2. Surgical instruments must be sterilized using an autoclave.
3. Preparation of the incision site which includes removal of fur and disinfection of skin. The skin is swabbed with two washes each of 70% alcohol and betadine. Avoid spreading prep solutions over a wider area than necessary to minimize heat loss by convection.
4. A surgical drape is a sterile cover draped over all or part of the animal. The drape protects against accidental contamination of surgical instruments.
5. Preparation of the surgeon which includes as a minimum, clean lab coat, hand scrub, mask and sterile surgical gloves.

Post-Operative Considerations

1. Hypothermia is the most common cause of postsurgical mortality. Prevent heat loss during surgery by placing an insulating material underneath the animal (to minimize heat loss by conduction). Post-operative care should include an external heat source while the rodents recover from anesthesia.
2. Fluid replacement by administration of warmed sterile saline or Lactated Ringers solution to rodents by the subcutaneous or intraperitoneal route.
3. There is no requirement for post-operative antibiotics, if proper aseptic technique is followed.
4. Where protocols include the use of narcotic analgesics, it is the responsibility of the Principal Investigator to ensure that analgesics are used and that the records are maintained in the laboratory for perusal by regulatory officials. Analgesics should be administered pre-operatively or peri-operatively to achieve maximally effective pain relief in the post-operative period.

Instrument sterilization

Sterilization kills or renders inactive all microbial organisms. The common methods used are steam heat, ethylene oxide gas or chemicals. Any item used for survival surgery must be sterilized: instruments; materials and devices such as catheters, flow probes, or electrodes; and all fluids used for flushing or injection. Special care is needed to ensure that multi-dose vials of drugs are not contaminated.

Animal preparation

The veterinarian should be consulted as to whether or not the animal should be fasted, and for what time period. There is great variation among species. Regurgitation rarely occurs in rats and fasting may cause life-threatening hypoglycemia.

On the day of surgery, the surgeon and assistants should wash their hands. It is mandatory to wear clean, non-sterile gloves at all times the animal is being handled. Ideally, in a preparation area physically separate from the location where the surgery will be performed, the animal should be anesthetized.

Hair over the surgical site and surrounding area should be clipped and the loose hair picked up by a vacuum system. Hair removal should be done carefully to avoid causing small skin abrasions. Hair should be removed over a liberal area to anticipate any surgical emergency and minimize wound contamination from adjacent areas. After clipping the hair, the skin should be washed with an antiseptic surgical scrub, containing soap, to remove remaining hair and dirt. The surgical area is cleansed two more times with antiseptic scrub and the scrub solution rinsed away with alcohol. A final antiseptic solution (devoid of soap) is sprayed or swabbed along the proposed incision and is not rinsed. The site is covered with clean gauze sponges or cotton, saturated with the antiseptic solution devoid of soap, and the animal transported to the surgical area. The protective gowns (now dirty and covered in hair) should be removed in the animal preparation area. The surgeon and assistants should now put on caps and masks.

When animals are placed directly on metal surgery tables, body heat is lost, therefore insulating materials or warming devices should be placed between the table and the animal. Circulating warm water heating pads or warm water bottles should be used, since electric heating pads are likely to burn. When heat lamps are used, avoid placing the animal in the direct beam. If possible, reflect the heat lamp off of a metal surface and place the animal in the reflected beam.

The surgical site should be draped to isolate the surgical field from the surrounding areas. Drapes are positioned and fixed with towel clamps and should not be dragged across unsterile areas onto the surgical field. Even with rodents and other small animals, the surgical incision site should be draped.

Surgeon preparation

Scrubbing hands prior to putting on sterile gloves is required. There are several acceptable methods but the key components are to use an antiseptic soap and to scrub all surfaces of the fingers, hands, wrists and arms up to the elbows. The dedicated surgical suites operated by DCM have specific procedures that must be followed which relate to staff preparation and traffic flow. However, whenever and wherever a major survival surgery on "higher" warm-blooded vertebrate animals occurs, a surgical cap, face mask, sterile gloves and sterile gown must be worn! Rodent vertebrate survival surgery requires a cap, mask, and sterile gloves, but a clean scrub top may be substituted for the sterile gown.

Principles of Operative Technique

Proper surgical technique is important to prevent wound infection, promote wound healing, and ensure likelihood of a satisfactory outcome to the surgical procedure. Good surgical technique includes:

1. asepsis, asepsis, asepsis
2. gentle tissue handling
3. effective hemostasis
4. maintenance of sufficient blood supply to tissues
5. proper use of surgical instruments accurate tissue apposition
6. appropriate use of monitoring equipment
7. support of vital organ functions
8. expeditious performance of the surgical procedure

Aseptic technique is required at all times and all team members are responsible for monitoring for breaks in aseptic technique. Asepsis is a chain which is only as strong as its weakest link. Potential sources of contamination include the team members, the patient, all articles used in the procedure, the surgical room or area and other personnel entering the surgical area.

Basic Aseptic Principles

1. All articles must be sterilized before use in procedure.
2. If in doubt about sterility of item or person, assume it is not sterile.
3. All persons who touch sterile articles must be sterile.
4. Non-sterile persons never reach across a sterile field.
5. Draped tables are sterile only above the table level.
6. Gown front is sterile only from waist to shoulder level.
7. Moisture causes contamination.

Gentle handling of tissues will help minimize post-surgical pain. Tissues should not be cut or separated without reason and tissue dissection is usually done along fascial planes. Exposed tissue must be protected from drying or contamination. Effective hemostasis and maintenance of blood supply allows visualization of the surgical field while preserving the total blood volume. Hemostasis is achieved by ligation, pressure, electrocoagulation and avoiding damage to major vessels. Only the vessel to be occluded should be incorporated in a ligature or clip. In using electrocoagulation, a high frequency current is applied to a small area of tissue (the bleeding vessel) and electric energy is converted to heat, resulting in coagulation of tissue and sealing of the vessel. To avoid excessive tissue damage, only the vessel to be occluded is in contact with the electrode. Electrocoagulation can be used for minor hemorrhage; large vessels should be ligated. Proper use of surgical instruments minimizes trauma. For example, vascular forceps are used to occlude blood vessels when flow is to be reestablished; hemostatic forceps, which crush, are applied to vessels through which blood will no longer flow.

Accurate tissue apposition enhances healing and promotes rapid return to normal function. Retraction and dissection of tissue can produce pockets known as "dead space". Dead space can delay healing and serve as a site for bacterial growth and fluid accumulation. As tissues are returned to their normal positions, dead space needs to be obliterated by careful suture placement to appose tissue and/or placement of drains to prevent fluid accumulation.

As a procedure is concluded, tissues are replaced to their normal anatomic positions. Most tissues should be apposed with minimal amount of tension and sutures must not devitalize the tissue in which they are placed. Type of suture material and pattern to be used will be dictated by the tissue involved and forces applied to those tissues. Behavior of animals also might influence the choices; some animals are more prone to chew or remove certain types of suture materials or devices such as surgical staples. Most animals will be fully mobile within 1 hour after a surgical procedure and the incision line must be able to withstand the twisting, bending and stretching, which will occur.

Intra operative patient support and monitoring - Accepted medical and veterinary surgical practice requires assessment of the physiologic status of the animal on a regular basis. See relevant Standard Operating Procedures. Vital time for resuscitation can be lost by failure to notice life-threatening physiologic or metabolic problems.

The degree of monitoring sophistication depends on the species, the extent and duration of the surgical procedure, and whether it is a survival or terminal procedure. Monitoring can be qualitative, using the anesthetist's sense of touch, sight and hearing to evaluate the patient; or quantitative, using instruments for periodic measurement of specific vital organ performance.

The anesthetic record provides a detailed account of the course of anesthesia and intra operative events, Blank record forms are available from dcm. It is important to record data from the pre-operative period, the induction period, the anesthetic/surgical period and the immediate post-operative period. Later measurements may be written on the individual animal's chart.

Expeditious performance of the surgical procedure implies that the surgical team will have sufficient training and competence to perform the surgical procedure in the least required amount of time. A rapid response to unplanned or emergency situations is the result of good organization and coordination of team members.

Principles of Postoperative Care

The postoperative period consists of three overlapping phases: anesthetic recovery, acute and long-term postoperative care. Adequate postoperative care enhances the animal's recovery by improving it's physiologic status and minimizing pain and distress. Recovery from anesthesia is the critical time because it is a period of physiologic disturbance during which crises can arise. Frequent observation and monitoring is required. The endotracheal tube should not be removed until the animal is exhibiting an active swallowing reflex. Body temperature needs to be maintained. Heat lamps or supplemental heat are often used. To prevent drowning or aspiration, water and food is withheld.

Animals should be individually caged during this time period. Rodents should not be returned to group cages until each and every individual in the cage has regained normal mobility. In addition to intraoperative analgesia it may be necessary in some cases to provide postoperative analgesia.

Acute postoperative care includes the time the animal is maintained in the recovery area until it is ready to be moved to standard housing. Analgesics, antibiotics and additional fluids might be needed during this time period. Once the animal is fully awake, food and water may be offered.

All animals, including rodents, should be returned to clean cages with fresh bedding to prevent fecal contamination of the fresh surgical incision. If there is danger of injury from other animals, animals should be individually housed.

Long-term postoperative care requires careful observation of body temperature, food intake, locomotion, behavior, and signs indicating pain. Research staff must daily examine the surgical site, monitor for signs of infection, and remove sutures or other devices at the correct time (generally 7-10 days). The surgical site should be observed for signs of infection, incision breakdown (dehiscence), or self-inflicted trauma. At least once a day, catheters should be examined and may need to be cleaned and flushed. Drains, collars, and dressings should be examined daily and changed as needed. Monitoring food and water intake is important to successful recovery. Oral or parenteral supplementation may be necessary to maintain normal hydration and anabolic state. Special diets may be indicated during the recovery period. The quantity and character of urine and feces should be monitored, because changes could indicate complications such as paralytic ileus, acute renal failure, or intestinal hypermotility caused by irritation.

References:

Applying principles of aseptic surgery to rodents. T. C. Cunliffe-Beamer. AWIC Newsletter, Vol. 4, No. 2, Apr-June 1993.

Special report Guidelines for animal surgery in research and teaching. Brown, M. J., Pearson, P. T., and F. N. Tomson. Am J Vet Res, Vol. 54, No. 9, Sept. 1993.