Maintaining a Sterile Operating Environment
World Small Animal Veterinary Association World Congress Proceedings, 2014
Martin Kessler, DECVIM (Onc)
Fachtierarzt für Kleintiere, Tierklinik Hofheim, Hofheim, Germany

One of the primary responsibilities of the technical team is to prevent iatrogenic infection of a surgical patient. In humans, infection associated with the hospital care is one of the top 10 leading causes of death today. In a recent study, it was estimated that health care-associated infections are responsible for about 99,000 deaths each year in US hospitals of which 22% are surgical site infections. Systematic studies in veterinary medicine are rare. A few studies have identified a rate of surgical site infections between 3–6% in small animal patients (Eugster et al. 2004; Mayhew et al. 2012) and more than 19% in equines (Ruple-Czernjak et al. 2013). In the operating room, the major reason for iatrogenic microbial contamination are breaks in sterile techniques. It is one of the key responsibilities of the technical staff to recognize and correct breaks in sterile technique made in preparation for and during a surgical procedure and to implement methods to prevent future occurrences.

The goal of asepsis is to prevent the contamination of the open surgical wound by isolating the operative site from the surrounding nonsterile environment. This is achieved by the use of sterile instruments placed on sterile fields, which are created by covering the operating table and instrument trolleys with sterile drapes. All sterile equipment and instruments are placed within the sterile field, and all staff members working within the surgical field have to perform a surgical scrub and wear sterile gowns and gloves. Breaks in sterile technique on the side of the supportive staff can occur with 1) sterilization, 2) setting up and opening the sterile field, 3) scrubbing and drying hands, 4) gowning and gloving, 5) prepping and draping the animal.

1. Sterilisation

Sterilisation is defined as a process that removes or destroys all microorganisms. Without correctly sterilized instruments, there can be no sterile technique. For reusable instruments, this is usually achieved by steam sterilisation. Steam sterilisation requires specific steam chamber temperatures and appropriate exposure times, and it is in the responsibility of the technical staff to ensure that all these parameters are monitored regularly.

Sterility indicator tapes help to ensure that an efficient sterilisation process has been reached by turning a distinctive colour. When packing items for sterilisation, indicator tapes must not be reused after they have gone through a sterilisation cycle, because the turned colour indicator will give the impression that the item is sterile when in fact it is not. Immediately after removing a processed item from the steam sterilizer it must be checked for wet spots, which can occur from condensed steam that has soaked through the sterile package. These wet spots may wick contamination into the package; therefore, these items should not be used and instead need to be re-sterilized. From storage or transportation, small punctures in the packaging can occur. The technician must inspect all sterile items carefully for integrity and a proper sterilisation indicator immediately before they are presented to the surgeon. A packaged item is not considered sterile if there is any indication that the package has become wet, the chemical indicator has not turned colour, or the package shows evidence of crushing or perforation. A package that has been dropped on the floor has to be considered contaminated, since the force that is created when the package hits the floor can cause the sterile barrier to be penetrated by forcing sterile air out and allowing contaminated air and particles into the package.

2. Setting Up and Opening the Sterile Field

The veterinary nurse or other members of the team set up and open the instruments for the surgical procedure. Although routine, this process offers numerous opportunities for breaking sterile technique. All items introduced to the sterile field should be opened, dispensed, and transferred by methods that maintain their sterility.

Sterile drapes establish an aseptic barrier preventing the passage of microorganisms, liquids, and particulate matter from nonsterile to sterile areas. Sterile drapes are used to cover the surfaces were instruments and equipment are placed. Since moisture tends to wick through a drape and contaminate the sterile field, all surfaces must be dry before a sterile drape is placed on them. Dust on the surface to be covered may become airborne and land on the sterile field; therefore, the surface must be cleaned before sterile drapes are placed on it.

When opening a package with sterile contents, the packaging must be opened in a manner which prevents the technician from touching the package contents or the sterile field. Packaged supplies should be opened immediately prior to the start of surgery, since the potential for contamination by particles that are stirred up by movement of personnel and settle on the surfaces, increases with time. When opening a peel package, the nonsterile person opens the package by rolling the wrapper over his or her hands, thus presenting the contents of the package to the scrubbed person. The sterile item has to be presented in a manner that the scrubbed person can grasp the item without contaminating the item or the scrubbed person. Sterile items should be lifted straight up from their packaging and must not be dragged over the packaging edges. For small items, sterile forceps can be used to transfer it out of the package. The sterile boundary of a peel-open package is the inner edge; therefore, peel pouches must not be ripped or torn when opening and contents should never be "pushed" through the peel pouch. Surgical items must not be "flipped" or dropped onto the sterile field, because they could penetrate the drape or roll off the sterile field. Large bundles or packages are opened on a flat surface, because large and/or heavy items tend to be difficult to open aseptically. It is not allowed to reach over the sterile field when presenting a sterile item. When opening wrapped supplies, opening of the package must be done in a way that ensures that the nonsterile person does not reach over the sterile item inside. The nonsterile person should first open the top wrapper flap on the opposite side, then open the flaps to the left and right side. The last wrapper flap is pulled toward the nonsterile person, thus exposing the content. All wrapper edges should be secured to prevent flipping back and contaminating the sterile contents. After a wrapper has been opened, the inside of the wrapper and its contents are considered sterile with the exception of a 3 cm outer edge of the wrapper, which is considered the "margin of safety" between sterile and nonsterile.

A sterile solution must be poured into a sterile receptacle. The scrubbed person holds the saline container away from the table or places it on the edge of the draped surface eliminating the need for the unsterile person to reach across the sterile field. When opening a solution container, the nonsterile person should lift the cap straight up. Only the top rim of the bottle top and bottle contents are considered sterile once the cap has been removed from the bottle. Keep in mind that drapes are considered sterile only at table level, and the drape below the working surface which is not under direct vision of the surgical team is not considered sterile. Any item that falls below the table level has therefore to be considered unsterile. This also applies to the end of the suction tubing which is handed off the sterile field. A 3 cm margin around the borders of the sterile drape is considered unsterile if the drape does not cover the entire surface. When approaching the sterile field unsterile staff has to face the sterile field and it is not allowed to pass through narrow passages between two sterile fields. Likewise, touching the sterile field or leaning over it is not allowed since invisible shedding of skin containing microorganisms may contaminate sterile items or areas. If left unattended, personnel, airborne contaminants, insects, and liquids could contaminate the sterile field. Therefore, once set up, the sterile field needs to be monitored constantly.

3. Cleaning, Scrubbing, and Drying Hands

"The skin can never be rendered sterile, but it can be made surgically clean by reducing the number of microorganisms," (Nicolette 2007).

Especially transient, but also some resident, bacteria can be removed effectively by correct surgical hand antisepsis. Unfortunately, perceived lack of time frequently adversely affects individual hand antisepsis practice. In all areas of the hospital rings, wrist watches or bracelets but also artificial nails should not be worn. Fingernails must always be kept short and clean. If nail polish is worn it must be less than 4 days old and not chipped. Scrubbing hands for surgical procedures is defined as the process of removing as many microorganisms as possible from the hands and forearms by mechanical washing and chemical antisepsis. Before performing a surgical scrub, hair covers and surgical mask must be put on. Washing hands and forearms with soap and running water is necessary prior to the first scrub of the day or if hands are visibly soiled. This prewashing includes cleaning the subungual areas of both hands under running water using a nail cleaner. During the scrub, the hands should always be held above the level of the elbow allowing water to run from the clean to less clean area. After drying the hands, a three- to five-minute, standardized surgical scrub or rub of the hands and forearms using an approved antimicrobial solution from a hands-free dispenser is performed. The goal of hand antisepsis is to reduce microbial bioburden. It is only effective if all surfaces of the hand are exposed to the mechanical cleaning and chemical antisepsis. Alcohol-based surgical hand rubs reduce bacterial count on hands more rapidly than do antimicrobial soaps or detergents. The protocol for their use must follow the manufacturer's instructions. For each hand, one can imagine that each finger, thumb, hand and arm as having four sides. All four sides need to be cleaned effectively, keeping the hands elevated. Particular attention has to be paid to the areas between the fingers. Applying the product has to be repeated as directed by the manufacturer. Contacting the faucet or disinfectant dispenser with hands or forearms must be avoided. Thorough drying of the hands is essential, since moist surfaces allow pathogens to multiply. If performing a scrub with antimicrobial soap, a sterile towel must be used to dry hands. If a surgical hand rub with alcohol-based disinfectants is performed, the product must be completely rubbed in, and hands and forearms must be completely dry before proceeding with gowning and gloving.

4. Gowning and Gloving

A sterile surgical gown and gloves are donned from a waist height surface separate from the sterile field. Only the inner side of a sterile gown can be touched when picking it up, usually at the neck. The folded gown is lifted directly upward, holding it like a book by its binding and attention has to be paid not to touch the wrapper. With the gown still folded the sterile person steps back from the gown table. The neck and armholes are located and the inside front of the gown is held with both hands. When unfolding the gown, the sterile person holds the gown in the armholes with the inside of the gown facing towards the body. The outside of the gown must not be touched with bare hands. As the gown and its sleeves unfold, both arms are extended simultaneously into the armholes. Standing behind the donned person, the nonsterile assistant brings the gown over the shoulders by reaching inside the gown to the shoulder and arm seams. The gown is pulled on, leaving the cuffs of the sleeves extended over the hands. If closed gloving is to follow, the hands should not be pushed through the cuffs. The back of the gown is securely tied by the nonsterile person at the waist first, followed by the neckline.

If the gown is a wraparound style, the sterile flap to cover the back is not touched until the scrubbed assistant has put on gloves. Once donned, the gown's sterility is limited to the portions directly viewed by the scrubbed person. These sterile areas include the gown front, from chest to the sterile field level, and the sleeves from 5 cm below the elbow to the cuff. The neckline, shoulders, under arms, sleeve cuffs and the back are considered unsterile. The white sleeve cuffs of the gown are made of soft, permeable material that is not waterproof. Therefore, cuffs tend to collect moisture and cannot be considered an effective bacterial barrier. Sleeve cuffs are considered unsterile when the scrubbed person's hands pass beyond the cuff. If the surgical gloves do not cover the cuffs, contamination may occur from inside out or from outside in, which is especially dangerous when the surgeon's hands are deep within a body cavity.

There are three methods of gloving: open, closed, and assisted. Since it is difficult not to touch the sterile glove exterior with any part of the skin, the open technique has a higher potential for aseptic breaks and must be performed with care. When the scrubbed person's hands protrude through the sleeve cuffs, the cuffs should be considered contaminated. The open method is used primarily for minor procedures, and it is commonly performed during a surgical procedure when the sterile person discovers a hole in the glove. In this case the perforated glove is pulled off by the nonsterile assistant followed by putting on a new glove using the open method.

In the closed method, the hands are kept inside the cuff at all times during the gowning and gloving procedure. The gloves in their paper wrapper are put on a table surface. The two sides of the glove paper wrapper are opened like a book by grasping the lower inner corners of the bottom fold. Both corners are lifted simultaneously and folded under to ensure that the wrapper remains open during the gloving process. For closed gloving, the right hand is extended with the palm facing upward and with the covered left hand, the right glove is grasped by the cuff from the glove package and lifted straight up. The glove is placed on the right palm with the thumb side down and the glove fingers pointing towards the body. The upper glove cuff is grasped with the cuffed left hand, while the underside of the cuff is held with the cuffed right hand. The cuff of the glove is then pulled over the right cuffed hand until it reached over the end of the sleeve. The sleeve and glove cuff is then held with the left hand and pulled back while wiggling the fingers of the right hand to extend them into the glove. As a result, the hand is in the glove and the glove covers the entire stockinet cuff of the sleeve. Using the gloved right hand, the left glove is picked up and placed with on the palm of the hand in the same manner. The cuff of the glove is grasped with the gloved hand turned over the sleeve and hand of the left hand so that the cuff of the glove is now positioned over the stockinette cuff of the left sleeve with the left hand still in the sleeve. The outside of the glove together with the underlying gown sleeve are now grasped with the gloved hand and pulled onto the left hand.

The assisted method is the safest and therefore most commonly used in human medicine. However, when the scrub person spreads the glove apart, the surgeon's skin or hair may touch the glove exterior as the hand enters the glove. The key is for the person offering the glove to spread the glove cuff as widely and as circumferentially as possible.

Double gloving is becoming increasingly popular. Many surgeons wear two gloves for draping the surgical site, then discard the outer pair of gloves after draping and don new outer gloves before beginning the procedure. This way, a small hole in the outer glove cannot penetrate through the inner glove; however, tactile sensation is somewhat diminished. Gloves should be checked for integrity immediately after donning. Gloves that become contaminated have to be changed immediately. If a hole in a glove is identified, the surgical team has to attempt to isolate all instruments suspected of being contaminated. Once gloving is completed, the wraparound tie of the gown can be handed to the assistant to close the gown.

During the surgical procedure, all sterile personnel stays close to the sterile field and if someone changes positions during the procedure he can move either face to face or back to back, but never turn its back to the sterile field.

5. Prepping and Draping the Animal

Skin cannot be sterilized, but can only be disinfected. The goal of a surgical skin prep is to reduce the risk of a surgical site infection by removing dirt and transient microorganisms from the skin, and decreasing the resident microbial flora to a sub-pathogenic level. In the past, clipping with razors and vigorous washing of the surgical site was recommended, and it was believed that the more intensive the skin was prepped, the better. Today it is believed, however, that using razor blades and performing extensive washing will actually increase microbial flora by damaging the skin and bringing deeper seated bacteria to the surface. It is therefore recommended to clip using electrical clippers followed by a gentle washing of the skin if it is grossly dirty. The basic principles of surgical prepping are to begin at the center (i.e., at the point of the later incision) and prep towards the periphery of the clipped area and never bring a soiled prep paper back over the previously treated surface. After alcohol prep, the skin is sprayed on with an approved disinfectant solution, and the solution is left to dry on its own before draping is started.

Sterile draping of the patient should be done in a manner that it leaves only the incisional site exposed. Only scrubbed personnel should handle sterile drapes. When draping the patient, the drape should be held higher than the patient, and the patient has to be draped from the prepped incisional site out to the periphery. Once the sterile drape has been lowered on the patient and is positioned, it should not be rearranged.

Additional Concerns

Dirt may fall from overhead lights into the surgical field; therefore, lights should always be cleaned before the first scheduled surgical procedure of the day. Everybody in the operating theatre has to cover the skin as much as is practical. Long-sleeved attire and hair coverings are required to prevent bacterial shedding from the head and bare arms. Turbulent airflow in the surgical room is a factor that increases the number of airborne microorganisms. For this reason, the number of people in the operating room and the conversation among people should be kept to a minimum. For the same reason, traffic of personnel in and out of the surgical room should be minimized and doors should be kept shut. Open doors represent conduits for potentially contaminated air, and insects may enter the operating room. If an insect manages to enter into the surgical room, the incision should be covered with a towel followed by efforts to kill the insect or move it out of the room. One trick to minimize increased air turbulence when trying to catch a fly is to turn out all the lights except one that is away from the sterile field to lure the insect to the light. Spraying the insect with alcohol-containing solution immobilizes it and makes it fall down to the floor where it can be killed. Skin can release microorganisms into the air.

If a break in technique has occurred, the surgical procedure has to be stopped and the team members need to communicate the dilemma, discuss options, and identify and implement a solution so the procedure can proceed.


1.  Eugster S, Schawalder P, Gaschen F, Boerlin P. A prospective study of postoperative surgical site infections in dogs and cats. Vet Surg. 2004;33:542–550.

2.  Mayhew PD1, Freeman L, Kwan T, et al. Comparison of surgical site infection rates in clean and clean-contaminated wounds in dogs and cats after minimally invasive versus open surgery: 179 cases (2007–2008). J Am Vet Med Assoc.2012;240:193–198.

3.  Nelson LL. Surgical site infections in small animal surgery. Vet Clin North Am Small Anim Pract. 2011;41:1041–1056.

4.  Nicolette LH. Infection prevention and control in the perioperative setting. In: Rothrock JC, ed. Alexander's Care of the Patient in Surgery. 13th ed. St. Louis, MO: Mosby Elsevier; 2007:75.

5.  Ruple-Czerniak AA, Aceto HW, Bender JB, et al. Syndromic surveillance for evaluating the occurrence of healthcare-associated infections in equine hospitals. Equine Vet J. Epub 2013. doi:10.1111/evj.12190.


Speaker Information
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Martin Kessler, DECVIM (Onc)
Fachtierarzt für Kleintiere Tierklinik Hofheim
Hofheim, Germany

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