PrinciplesofAsepticTechnique

INTRODUCTION

The regulations promulgated to implement the amended Animal 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 th e 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 principle s 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 ste rilizer 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 tha t are living and reproducing as human or animal 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-or ganism 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 mi cro-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 ant iseptics 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 pa tient 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 wi ll be the recommendations for Aseptic Surgery contained in the Guide for the Care and Use of Laboratory Animals. 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 animals. 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 d esigned 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 surgi cal preparation area for animals. 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 locate d 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 filte rs 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 b e 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 purpo se. 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 animals to hypothermia. T his 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 wit h 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 u nit 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 dur ing 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 pr ocedure.

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 surg eon 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 suctio n 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 veterinarian or surgical supervisor.

Surgical instrumentation and pack prepa ration will vary with the type and complexity of surgery to be performed. Consultation with an institutional veterinarian 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 prepacka ged surgical blades, sponges, saline bowls and miscellaneous catheters.