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.

 

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, ie. instruments, catheters, flow probes, or electrodes and fluids used for flushing or injection must be sterilized. Special care is needed to ensure that multi-dose vials of drugs are not outdated or contaminated. Packs of sterile instruments or materials that are to be stored for more than a week, should be double wrapped in packaging which is impermeable to water. The date of sterilization should be clearly marked on the outer wrapper. Expiration dates vary with packaging materials, but a general guideline is 2 months from the date of sterilization. Commercially available plastic dust covers will extend the shelf life to 6-12 months.

 

Available methods of sterilization include steam heat, ethylene oxide gas, glass bead, and chemical agents. Glass bead sterilizers will sterilize only the portion of the instrument placed in the beads. Chemical agents include glutaraldehyde, phenols, and chlorine dioxide but all have serious drawbacks: glutaraldehyde is mutagenic, phenols are corrosive and both require special disposal procedures; chlorine dioxide has a short sterilizing useful life (1 day) and is corrosive to metals. All chemical agents require rinsing with sterile solutions prior to tissue contact. The effectiveness of chemical sterilizing agents is currently under review by various government agencies and it appears that the manufacturers' recommendations will change.

 

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; whereas, prolonged fasting in ruminants will reduce bloat and the risk of regurgitation and pulmonary aspiration. Bathing some animals may be necessary to remove excess dirt and hair and is best done the day before the scheduled surgery.

 

On the day of surgery, the surgeon and assistants should wash their hands. It is advisable to wear clean, non-sterile gloves at all times the animal is being handled. It is preferable to wear a clean (not sterile) gown over the scrub suit while preparing the animal.

 

In a preparation area physically separate from the location where the surgery will be performed, the animal should be anesthetized and intubated. In general, intubation is recommended for all warm-blooded vertebrates, since the endotracheal tube minimizes the potential for aspiration of stomach contents. In addition, the endotracheal tube allows for positive pressure ventilation should emergency resuscitation be required.

 

Hair over the surgical site 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. Because anesthetized rodents experience excessive heat loss, a much smaller area should be clipped - only the hair directly over the surgical site. 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 suite operated by the Office of Animal Care, has specific procedures which 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 and cold-blooded vertebrate survival surgery requires a cap, mask, and sterile gloves, but a clean scrub top may be substituted for the sterile gown.

 

Dispelling the myth about rodent surgery! It was once believed that rodents, by virtue of species adaptation to surviving in contaminated natural environments wre resistant to infection, not requiring sterile surgical technique. This is absolutely not true. To assist in dispelling this myth, it is illegal in the State of New York to perform rodent survival surgery without aseptic procedures. Specifically, New York State indicates the necessary components of aseptic techniques in rodents to include sterile instruments, sterile gloves, caps, masks, scrub tops for surgeons and separate surgical and animal prep areas. It is often not possible to have a fresh pack of sterile instruments available for repetitive rodent surgeries. Thus, resterilization or decontamination procedures must be available. A well accepted method is the use of the glass bead sterilizer for instruments combined with "the no touch" surgical technique.

 

  1. All instruments used in survival rodent surgeries must be steam sterilized (this can be done by Animal Care staff for a fee) prior to each group of surgeries (biological indicator monitoring of sterilizer effectiveness is advisable).
  2. Instruments must be kept on sterile non-porous drapes during use.
  3. Instruments must be cleaned of blood and debris by brushing or wiping with sterile water or saline and sterile gauze sponges between surgeries.
  4. If contamination has occurred, instruments must be placed in a chemical agent or a glass bead sterilizer for the appropriate period of time for the method used to be effective (or the instrument pack replaced by a new sterile instrument pack).
  5. If a chemical agent is used, instruments must be rinsed with sterile water or saline before being used on the next animal.
  6. Surgical gloves and blades should be changed between each animal or after contamination.
  7. Following surgery all instruments must be thoroughly cleaned and preferably placed in an ultrasonic cleaner and rinsed.

 

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:

 

"Asepsis is a chain which is only as strong as its weakest link." Aseptic technique is required at all times and all team members are responsible for monitoring for breaks in aseptic technique. 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

 

Gentle handling of tissues will help minimize postsurgical 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. Tissues are replaced to their normal anatomic positions with minimal amount of tension by sutures to prevent tissue devitalization. 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. Because physicians normally work with cooperative human patients, they must re-evaluate surgical materials and methods to be used with animals.

 

Most animals will be fully mobile within 12 hours after a surgical procedure and the incision line must be able to withstand the twisting, bending, and stretching which will occur!

 

Intraoperative patient support and monitoring - Accepted medical and veterinary surgical practice requires assessment of the physiologic status of the animal on a regular basis. 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 intraoperative events, Blank record forms are available from the Animal Care Office. Whether you use one of these forms, or one of your own design, 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.

 

Support of vital organ functions is an integral part of any surgical protocol. Many devices are available but they may not be practical or applicable for all species.

 

  1. Body temperature - This can be measured via rectal or esophageal thermometers. Every effort should be made to combat hypothermia by use of circulating warm water blankets, warm water bottles, heat lamps, or application of insulating materials such as drapes.
  2. Respiratory system support - This can be as simple as appropriate positioning of the animal to ensure an unobstructed airway, endotracheal intubation, or providing supplemental oxygen.
  3. Cardiovascular function - A variety of techniques may be used for assessment: capillary refill time, heart rate monitoring, Doppler Flow probes, EKG, palpation of pulse, and use of esophageal or conventional stethoscopes.
  4. Cardiovascular support - includes fluid therapy and availability of defibrillators (if necessary) and cardioactive drugs.
  5. Hydration Status - Monitoring rate and amount of urine production, as well as subjective assessment of blood loss, and capillary refill time of the oral mucus membranes can indicate adequacy of fluid volume. There are many possible choices for fluid replacement, but normal (0.9%) saline or balanced electrolyte solutions such as lactated Ringer's are common. Intravenous (IV) administered fluid therapy is best for larger animal species, but can be difficult in smaller animals; Subcutaneous (SQ) or Intraperitoneal (IP) fluids may be appropriate for these species. Warming fluids is recommended.

Required Components of a Perioperative Record:

 

References used for this module: