The regulations promulgated to implement the amended Welfare Act require that all survival surgery be performed using aseptic procedures. This includes the use of surgical gloves, masks, sterile instruments and aseptic technique.
In this chapter, the Principles of Aseptic Technique will be discussed with the emphasis on the practical application of these principles in the laboratory set ting. In centralized experimental surgeries, a well-trained staff should be available to advise those who use such facilities and oversee its operation to ensure the maintenance of an aseptic environment for survival surgery. When survival surgery is conducted outside such an environment, it is the principal investigator's responsibility to ensure that appropriate aseptic conditions and practices are maintained. This chapter will provide the necessary information to carry out this responsibility.
Prior to discussing the specific principles of aseptic surgery a brief review of pertinent terminology is necessary.
TERMINOLOGY
Antimicrobial - An agent or action that kills or inhibits the growth of micro-organisms.
Antiseptic - A chemical agent that is applied topically to inhibit the growth of micro-organisms.
Asepsis - Prevention of microbial contamination of living tissues or sterile materials by excluding, removing or killing micro-organisms.
Autoclave - A steam sterilizer consisting of a metal chamber constructed to withstand the pressure that is required to raise the temperature of steam to the level required for sterilization. Early models were termed "autoclaves" because they were fitted with a self-closing door.
Bactericide - A chemical or physical agent that kills vegetative (non-spore forming) bacteria.
Bacteriostat - An agent that prevents multiplication of bacteria.
Commensals - Non-pathogenic micro-organisms that are living and reproducing as human or subject parasites.
Contamination - Introduction of micro-organisms to sterile articles, materials or tissues.
Disinfectant - An agent that is intended to kill or remove pathogenic micro-organisms, with the exception of bacterial spores.
Pasteurization - A process that kills nonspore-forming micro-organisms by hot water or steam at 65-100oC.
Pathogenic - A species that is capable of causing disease micro-organism in a susceptible host.
Sanitization - A process that reduces microbial contamination to a low level by the use of cleaning solutions, hot water or chemical disinfectants.
Sterilant - An agent that kills all types of micro-organisms.
Sterile - Free from micro-organisms.
Sterilization - The complete destruction of micro-organisms.
Since the pioneering work of such surgeons as Joseph Lister, who introduced the use of carbolic acid antiseptics in 1865, and William Halstead, who advocated the use of surgical gloves in 1898, surgeons have strived to eliminate surgical infections through the use of aseptic technique. Potential sources of contamination are well defined. They include the patient and the surgical environment: the surgeon and support staff, the instruments, sutures, drapes and all other equipment which can have contact with the surgical field.
FACILITIES
The basis for this discussion about facilities will be the recommendations for Aseptic Surgery contained in the Guide for the Care and Use of Laboratory subjects . The Guide states:
"Functional areas for aseptic surgery should include a separate support area, a preparation area, the operating room or rooms and an area for intensive care and supportive treatment of subjects. The interior surfaces of this facility should be constructed of materials that are impervious to moisture and easily cleaned. The surgical support area should be designed for storing instruments and supplies for washing and sterilizing instruments. Items that are used on a regular basis, such as anesthetic machines and suture materials, can be stored in the operating room."
"There should be a separate surgical preparation area for subjects. An area equipped with surgical sinks should be close to, but apart from, the operating room. A dressing area should be provided for personnel to change into surgical attire."
The surgical facility should be located outside normal facility traffic patterns. This can help to minimize the potential for surgical suite contamination by the movement of personnel and equipment. Personnel access to these areas should be restricted to essential surgical support staff.
Ideally, the operating room ventilation system should provide a net positive pressure with respect to the surrounding facilities. The system should be regularly monitored. Maintenance work should be performed when the surgery is idle. Ventilation filters should be inspected and cleaned or replaced at regular intervals. If explosive anesthetics agents are to be used, the Guide recommends that floors should be conductive and electrical outlets should be explosion-proof and located not less than 5 feet off the floor. Dedicated surgical facilities should be used for aseptic surgeries and the storage of essential surgical equipment, not as general storage space.
EQUIPMENT
The equipment in areas used for aseptic surgery should be easy to clean and portable to simplify sanitization of the area. The operating table should be con structed with a durable surface material impervious to moisture which can be readily cleaned. Plastic or stainless steel is frequently used for this purpose. Other useful table design features which assist patient positioning include height and tilt adjustments, V-trough configuration and restraint strap cleats. A disadvantage of stainless steel construction is that it predisposes subjects to hypothermia. This can be corrected by the routine use of a heating pad placed under the surgical patient. Reusable, easy to clean vinyl heating pads which recirculate hot water are frequently used for this purpose. Inexpensive short-term alternatives include hot water bottles or heat lamps. Any heat source should be used with caution to prevent patient burns.
Instrument tables provide the surgeon ready access to the surgical instruments and minimize the risk of sterilized instrument contamination by contact with non-sterile fields. Commercially available instrument tables, such as Mayo stands, consist of a stainless steel tray supported by a pedestal base with a foot-operated height adjustment device, but any tray arrangement may be used for this purpose. The unit should be easy to clean and simple to operate. The drapes in an instrument pack frequently include impervious table covers which can minimize instrument contamination and allow the surgeon to reposition the table without breaking aseptic technique during the procedure. Surgical buckets on wheels (kick buckets), which can be readily positioned with the feet, are another recommended piece of equipment. They should be easy to clean and lined with a plastic bag which should be changed at the end of the procedure.
Adequate lighting is essential for performing surgical procedures. A variety of fixtures can be used to provide sufficient light. The commercially available surgical light fixtures may be ceiling or wall-mounted or free standing. Surgical lights are often positioned above the operative area and should be regularly wiped with a moist towel prior to use to minimize potential contamination of the sterile field below. Light fixtures designed with detachable sterilizable handles allow the surgeon to adjust the beam during surgery. Wheeled, height-adjustable intravenous drip stands should be available when conducting major surgery. Care should be taken to assure that the I.V. tubing does not contaminate the sterile fields. Positioning the I.V. tubing along the heating blanket helps warm I.V. solutions before infusion.
Surgical suction is another useful accessory. Sterilized tubing and suction tips are provided for use in the aseptic field. The tubing is connected to a non-sterile suction bottle which in turn is connected to a built-in vacuum line. If built-in vacuum lines are not available, portable electric vaccum pumps are commercially available.
Ancillary equipment such as respirators, electrosurgical units and ECG monitors should be portable and included with the light fixtures in a routine equipment cleaning schedule. Specific details on such devices could be obtained from an institutional personel or surgical supervisor.
Surgical instrumentation and pack preparation will vary with the type and complexity of surgery to be performed. Consultation with an institutional personel or surgical supervisor could be helpful when selecting the appropriate surgical instruments necessary to perform a proposed procedure. Instrument packs should be double wrapped. Various commercial materials are available for this purpose. Although pack instrument preparation will be discussed later, as many sterilizable items as possible should be included. These might include prepackaged surgical blades, sponges, saline bowls and miscellaneous catheters.
Personnel
Aseptic technique requires careful attention to a series of steps which begins with patient and instrument preparation and ends at final wound closure. Failure at any one step may result in wound infection which could compromise the subject's health and the experimental data derived from the subject. Aseptic technique designs all actions and motions to protect the sterile field from contamination. The surgeon and surgical support staff must be adequately trained to perform each step correctly. Acquiring and developing the necessary skills to maintain aseptic technique requires practice. Personnel should receive instruction on the indications for aseptic technique, the sources of potential contamination, patient, instrument and equipment preparation, sterilization systems, gowning and gloving techniques, and intraoperative aseptic management. Once this theoretical knowledge is gained, trainees can rapidly learn by observing the aseptic management techniques of a well-trained surgical support staff. Trainees should practice each step until correct techniques become second nature.
Assistance with employee training may be available from the institutional personel, a member of the subject care staff and/or a member of a hospital surgery staff.
STERILIZATION
Sterilization is the process that is intended to kill or remove all types of micro-organisms. There are two principal sterilization methods:
1) Physical (dry heat or saturated steam)
2) Chemical (ethylene oxide gas or chemical liquids).
Factors which determine the method to be used are the type of micro-organisms involved, the nature of the article to be sterilized and the time available for sterilization.
Physical Methods (Steam)
Steam sterilization (frequently referred to as autoclaving) depends on the use of steam above 100oC. Temperatures ranging from 121-134oC at pressures of 15-30 psi are generally recommended. The biocidal action of moist heat is a denaturation of major cell constituents. Many sterilizers are designed to provide an automatic sterilization cycle. In the first stage of the cycle, air is evacuated and the chamber brought to the pre-set sterilizing temperature, which is maintained for a holding period sufficient to kill all microbial contaminants. Minimum holding times for the sterilization of medical equipment are 15 minutes at 121oC, 10 minutes at 126oC, and 3 minutes at 134oC. The steam is then removed and instrument packs are allowed to dry or liquids cool. The drying stage may be adjusted to suit the load.
The chamber is then pressure by the introduction of filtered air.
The recommended periods of exposure vary with the nature of the article to be sterilized and the method used to wrap the article. Specific details are available from the references at the end of the chapter.
Steam sterilization has the advantage of rapid penetration of wrapped materials with the destruction of all viruses and bacteria, including the most resistant spores. The sterilization of different supplies is more readily controlled than in other types of sterilizers. However oils, grease and powdered substances cannot be sterilized by this method. The steam autoclave must be maintained in good repair and operated correctly in order to perform to specifications. Sterilization failure can occur when machines are not regularly serviced.
Steam autoclave function should be monitored continuously using one or more of several commercially available indicator systems. The color change on a chemical dye impregnated indicator strip placed within the pack can provide a convenient and rapid visual check that the appropriate sterilization conditions were reached. Function should also be monitored on a regular basis using commercially available biological indicators. Spore strips of Bacillus stearothermophilus are placed within the wrapped article prior to sterilization. After sterilization the strip is incubated at 57oC for 48 hours. The absence of growth indicates effective sporicidal autoclave action.
Chemical Methods (Gas)
Ethylene oxide gas is effective against all types of micro-organisms. The biocidal action of this gas is considered to be alkylation of nucleic acids. It is non-corrosive and safe for most plastic and polyethylene materials. However, it is not applicable to liquids or to articles in impervious packaging material. It cannot be used to sterilize subject diets due to the potential toxic effects of this gas. It can also be a toxic hazard for subjects receiving prosthetic implants which have been sterilized by this gas. The operating pressures and temperatures (45-60oC and 10-12 psi) of ethylene oxide sterilizers are considerably less than for steam units. Articles should be well aerated prior to use to minimize the potential for tissue toxicity. Aeration should be done in a manner which minimizes exposure of personnel.
This can be accomplished through the use of self-aerating sterilizers or separate aeration cabinets.
Ethylene oxide gas is a potential carcinogen and mutagen and represents a potential occupational health hazard for personnel operating sterilizers. Operation of gas sterilizers and aerators should be in strict conformance with manufacturers' recommendations and institutional policies. Personnel exposure should be minimized by appropriate ventilation of exhaust gas. A regular monitoring program for personnel should be in place.
Gas sterilizer function should be monitored continuously using one of several commercially available indicator systems. The color change on a chemical dye-impregnated indicator strip placed within the pack can provide a convenient and rapid visual check that the appropriate sterilization conditions were reached. Function should also be monitored on a regular basis using a commercially available biological indicator such as spore strips of Bacillus subtilus which are placed within the wrapped article prior to sterilization. After sterilization the strip is incubated at 37oC for 24 hours. The absence of growth indicates effective sterilization.
Temperature-sensitive adhesive tape used to secure packages prior to sterilization only indicates that the package has been exposed to the sterilizer; this tape does not monitor sterilizer function.
Chemical Methods (Liquids)
The use of chemical solutions as a sterilization technique for surgical equipment is frequently employed, but it should be stressed that most solutions only disinfect and do not guarantee sterility. When the necessity for maintaining sterility is a critical factor, as in the implantation of prosthetic devices, indwelling catheters or vascular access ports, disinfection in chemical solutions is not recommended. Such prostheses should be thoroughly sterilized by either gas or steam. Chemical solutions, however, offer the advantages of safety for delicate and thermolabile plastics.
Other limitations of chemical solutions should also be appreciated. Equipment must be thoroughly cleaned before immersion, as chemical action is ineffective in the presence of proteins or fats. There are currently no indicators commercially available to monitor the effectiveness of this sterilization method.
Alcohols are neither sporicidal nor viricidal. They are not stable and lose effectiveness through evaporation. Alcohols cannot be used for instruments that have plastic or cemented parts.
The chlorine compounds exert their biocidal action by oxidization. The for mulations which require the mixing of acid and base components with water to generate chlorine dioxide, offer the advantages of wide spectrum biocidal action and a safe alternative to the more hazardous phenols or formaldehydes. The active shelf life of mixed chemicals is reported to be 24-48 hours.
If chemical sterilization of instruments is the method to be used, it can be performed in covered trays containing fresh solutions. A two-tray system, one each for even-numbered and odd-numbered days, will ensure that instruments have a full 24-hour contact time.
PREPARATION OF A SURGICAL PACK
A well-organized and consistent surgical pack preparation system can avoid errors and facilitate surgery. Instruments can be cleaned by hand or with an ultrasonic cleaning unit. After cleaning, each instrument should be inspected to ensure that all debris has been removed. After physical cleaning, instruments can be dipped in a commercial protective lubricant solution and allowed to drain dry. Items should be assembled on a tray and arranged in a consistent order. Materials should be placed in sequential order so that items used first are placed on top. Packs should not be too densely packed in the autoclave to allow for adequate steam or gas penetration. Indicator test strips can be placed deep within the pack. Packs should be double wrapped, and the outer wrap should be secured with adhesive indicator tape on which is recorded the date of sterilization. When applicable, the type or contents of pack (e.g., laparotomy, thorocotomy) can also be noted on the tape.
Note the following points when opening a sterilized surgical pack. The sterilization date should be checked; the shelf life of wrapped instruments is generally considered to be up to 6 months. The adhesive indicator tape should be noted for the appropriate color change and the pack description should be checked, when applicable. Packs should be placed on a dry instrument tray and the outer wrapping carefully unfolded by touching only the corners of the outside drape surface. The operator should avoid reaching over the pack. The packs should not be opened too early. The surgeon working without assistance should open the pack immediately before scrubbing. Any other sterilized supplies which can be opened onto a sterile field should be made ready at this time.
PREPARATION OF THE SURGEON
In a laboratory setting, the extent of surgeon preparation will depend on the facilities and the need for strict attention to aseptic technique. Well-equipped surgical facilities, in which sophisticated survival procedures are performed, generally require surgeons to wear appropriate surgical clothing and to scrub, gown and glove. Instruction in such procedures should be done on a one-to-one or small group basis in appropriately designed scrub rooms. To augment the actual hands-on approach or when necessary a video tape demonstration or pictorial diagrams can be used. Readers are advised to consult the references quoted at the end of the chapter for instructional details.
To minimize wound contamination potential, the surgeon should change into surgical scrubs and shoes or wear shoe covers. Head covers and face masks should cover all facial hair. Remove all rings, jewelry and wrist watches before scrubbing. Finger-nails should be trimmed short and cleaned with a disposable nail cleaner. Scrub sinks equipped with leg or foot-operated faucets are ideal. Regular faucets must be turned on, adjusted and not touched again. The hands and forearms are washed for 30 to 60 seconds with a surgical scrub soap. Then a sterile brush is used to methodically scrub all surfaces of the hands, fingers and forearms down to the elbows. Both arms are rinsed and the process repeated starting with fingertips working down to the elbows. The definition of a "complete surgical scrub" is controversial. However, contact times of 3 to 15 minutes and/or 5 to 20 strokes per surface are frequently recommended.
After rinsing, the hands are held together high and rinse water allowed to drip from the elbows. This minimizes the contamination of hands by water dripping from the non-sterile upper arm areas. The surgeon should avoid touching anything at this stage except to dry the hands with a sterile towel. Next the sterile gown is carefully removed from the pack to avoid touching the outside of the gown. It is held away from the body and shaken out. The sleeve hole is located and each arm inserted in turn. Correct gowning requires an assistant to tie the back of the gown at the neck and waist (being careful to touch only the inner gown surface).
Sterile surgical gloves are packaged with the cuff of each glove turned down. This allows the gloves to be put on without the bare hands ever touching the outside surface of the glove. One glove is picked up by the turned-down cuff and pulled onto the hand with the cuff left turned down. Using the gloved hand, pick up the remaining glove by inserting the fingers into the cuff and pulling it onto the opposite hand. Then the glove cuff is lifted over and onto the gown cuff and the process repeated on the other hand. This technique is known as "open gloving." An alternative and more difficult method is closed gloving, descriptions of which can be found in general surgical texts. Remove the powder on the outer glove surface by wiping the gloved hands with a damp sterile gauze. Arms and hands should be held above the waist at all times. Aseptic technique is maintained when the gowned and gloved surgical team only touches sterilized equipment within the sterile field.
The surgeon working alone faces logistical problems when attempting rigid aseptic protocol as defined above. A proposed practical sequence of steps to minimize errors is presented as follows:
1. Assemble all sterilized supplies.
2. Change into scrubs.
3. Set up table, heat pads and gas machines, check equipment.
4. Weigh subject, induce anesthesia. Prepare subject by hair clip and shave, catheters placed as required.
5. Position and secure subject on the table.
6. Connect to gas machine, connect accessory monitors. Start I.V. lines as required.
7. Make certain that a stable anesthetic plane is attained.
8. Put on cap, mask. Open sterile instrument and prep packs.
9. Using one sterile glove, prepare surgical site with scrub solutions.
10. Put on new sterile glove and drape patient.
11. Remove gloves. Recheck stable anesthetic state. Open glove and gown packs if not included in instrument pack.
12. Perform surgical scrub.
13. Put on gown and gloves.
14. Start surgery.
SUMMARY
The practice of aseptic technique, when performing
survival surgical procedures, minimizes the chances that subject health or experimental
data will be compromised by post-surgical infections. Aseptic techniques require
that appropriate facilities and equipment be available and that the personnel
involved be adequately trained. The key element in maintaining an aseptic environment
is well-trained personnel who understand the principles of aseptic technique
and utilize this knowledge on an ongoing basis.
aseptic404.net