Surgical site infections
ORLANDO, FL – All surgical wounds become contaminated with bacteria during surgery. The goal is to minimize that contamination and prevent surgical site infection (SSI), an avoidable complication in veterinary surgery occurring in about 2-5% of clean surgical procedures. Potential causes of wound infection in dogs and cats go far beyond surgical techniques and sterilization procedures, explained Steve J. Mehler, DVM, DACVS, speaking at the North American Veterinary Association Conference.
Known risk factors for surgical site infection:
- Older animals
- Obesity
- Endocrinopathy increases infection rates as much as 8.2x in surgical wounds
- Distant site of infection
- Surgery sites clipped before anesthetic induction are 3x more likely to become infected
- Use of propofol for induction increases the infection rate 3.8x in clean procedures
- Anesthesia lasting longer than 60 minutes
- Duration of surgery longer than 90 minutes
- Number of people in the operating room
- For each minute of anesthesia above 60 minutes there is a 0.5% increase in infection rate, or for every additional hour the infection rate goes up 30%
Definitions
1. Sterilization is the complete destruction of all living organisms, including vegetative forms of bacteria and spores. Sterilization of surgical equipment, implants, linens, and attire is one of the basic requirements of aseptic technique.
Methods of sterilization routinely used in veterinary medicine include steam, chemicals, plasma, and radiation. Steam is most commonly used; proof that sterilization has occurred requires culturing a biologic indictor at least weekly, after a steam sterilization cycle is performed.
Ethylene oxide sterilization is dangerous and a major health hazard. Plasma sterilization is safe and effective but is still relatively expensive. Radiation involves the use of Cobalt60 and is the form of sterilization used with most prepackaged sterile items.
Cold chemical “sterilization” is more of a disinfection process that utilizes 2% glutaraldehyde. Items must be clean of organic material, completely disassembled, and dry prior to immersion in chemical sterilization baths. Instruments coming out of cold chemical baths must be thoroughly rinsed in sterile water and dried with sterile towels to prevent damage to patient’s tissues.
2. Disinfection is the destruction of most pathogenic organisms on inanimate objects.
3. Antisepsis is the destruction or inactivation of most pathogenic organisms on animate objects. Antiseptics are used on patient skin preparation and surgical scrubbing.
4. Asepsis is a condition free from germs, infection, and any form of life.
5. Sanitization is the reduction of microbial populations to safe levels as determined by public health requirements.
Other facts to consider
Dr. Mehler recommends a dose of a first generation cephalosporin at the time of induction and then every 120 minutes while under anesthesia when a clean procedure (e.g. skin mass removal) or a clean-contaminated procedure (e.g. enterotomy or cystotomy) is being performed.
It is important to consider that clean/clean-contaminated wounds with no perioperative antibiotics have a 4.4% infection rate; clean/clean-contaminated wounds with antibiotics (30 minutes prior to wounding, given every 90-120 minutes, and not more than 24 hours post operatively) have an infection rate of 2.2%; clean/clean-contaminated wounds with antibiotics used inappropriately (more than 24 hours after wounding) have infection rates of 6.24%. Finally, animals with clean wounds receiving any antibiotic more than 24 hours postoperatively have been shown to have infection rates of 8.2%, which is much higher than without antibiotics.
Aseptic technique
Since it is impossible to eliminate all microorganisms from the surgical field, the goal is to limit the numbers to a level that the patient can handle, by following the rules of aseptic technique:
- The surgery team remains within the sterile area until the procedure is completed
- Talking is minimized
- Movement within the sterile area is minimized
- Non-scrubbed personnel do not reach over or walk between the sterile fields
- Scrubbed team members face each other and the sterile field at all times
- Equipment, instruments, drapes, and sutures used during surgery must be sterile
Preparation of the surgeon and team
There are several key points to remember to help reduce SSIs. They include wearing a clean set of scrubs every day, covered with a gown or lab coat when out of the immediate surgery area. Scrubs should not be worn to work, and every team member should wear separate street clothes and shoes to work and then change into clean scrubs. Aprons or protective gear should be worn when prepping patients, scrub tops should always be tucked into scrub pants, and long-sleeved shirts should not be worn under the scrub top. Dr. Mehler said that since shoe covers have not demonstrated a reduction in SSI rates, a dedicated, easily cleaned pair of clogs should be worn.
Head covers should always be worn by all personnel in the surgery suite, surgical preparation area, and during the packing of surgical packs, and a hood should be worn if there is significant facial hair.
Masks should be worn whenever entering a sterile area and must fit snugly to the face to prevent venting laterally or downwards.
Finally, fingernails should be short and clean with all nail polish removed prior to surgery. No artificial nails, rings, or watches should be worn during surgery, and hands should be washed with soap and rinsed well before the surgical scrub.
Patient preparation
All fur, at least 3 cm from any potential incision, should be clipped before entering the operating room using a sharp #40 blade, or a #10 blade for dense coats. Ensure that the fur is vacuumed from the patient, the gurney, the floor, and the personnel before entering the operating room.
Surgical Scrub
The goal is to mechanically remove dirt and oils, to reduce the number of transient bacterial populations, and create a residual depression of resident bacterial flora.
Drapes and draping
Drapes act as a barrier to prevent movement of debris and bacteria into the surgical field from non-sterile areas. The two main types of drapes are reusable woven fabrics and disposable nonwoven fabrics.
Nonwoven fabrics, made from regenerated cellulose, wood pulp, polyesters, synthetic polymers, or combinations of these materials, are the standard of care in most human operating rooms and are rapidly replacing woven products in veterinary medicine.
Other important rules
- Scrubbed personnel are the only people who should handle sterile items
- If you are not sure that an item is sterile, treat it as contaminated
- Sterile tables and hands should always stay above the waist
- Surgical gowns are sterile only from mid-chest to the waist, and to the elbow
- Any sterile item or packaging that is wet or damaged is treated as contaminated
Consequences of a break in aseptic technique
When aseptic techniques are not followed, or if significant breaks occur, recognized or otherwise, the consequences can be devastating. Routine complications associated with breaks in aseptic technique include:
- The contamination of tissue with pathogenic bacteria
- Infection
- Increased post-operative pain
- Delayed wound healing
- Increased costs and hospitalization times
- Poor cosmetic result
- Loss of client
- Loss of patient Dr. Mehler concluded by saying that when it comes to preventing SSIs, honesty saves lives. It is everyone’s responsibility to speak up and let the team know if you think that something is contaminated or if a break in aseptic technique occurred.CVT
