Surgical Instruments and Aseptic Technique

SCALPEL

The scalpel is the best instrument for incising tissues with minimal trauma. A variety of disposable blades are designed to fit several different scalpel handles (Figure 28-1). The Bard-Parker No. 3 handle uses detachable blade Nos. 10, 11, 12, and 15 and is the most useful for small animal surgery. The Bard-Parker No. 4 handle is larger and uses detachable blade Nos. 20, 21, and 22. This handle is most commonly used for large animal surgery.

BIOMEDICAL LASERS

Surgical lasers may be used to cut or ablate (destroy) tissue. There are many different types of lasers. The most commonly used in veterinary medicine are carbon dioxide (CO₂) and neodymium:yttrium-aluminum-garnet (Nd:YAG) lasers. Advantages of incising tissue with a laser include some hemostasis and possibly less postoperative swelling and pain as compared with cutting with a scalpel blade. Disadvantages include delayed wound healing and safety issues associated with the use of lasers. Special glasses must be worn by everyone in the room, and care must be taken to prevent ignition of combustible materials. Smoke evacuators and laser-safe surgical masks should be used to reduce the amount of particulate debris inhaled from the smoke plume.

ELECTROSURGERY

Electroscalpels can be used to cut or coagulate tissue and help to minimize bleeding. They work by passing a high-frequency alternating electrical current through the tissue (Figure 28-2, A). Cutting or coagulation can be performed through the same handpiece, and the surgeon can activate it by a switch on the sterile handpiece or by a foot switch (Figure 28-2, B). However, the power level must be adjusted by a nonsterile technician. In monopolar electrosurgery, current passes from the handpiece (Figure 28-2, C) through the patient to a metal ground plate (Figure 28-2, D) that is placed under the patient. Poor contact between the patient’s skin and the ground plate can burn the patient at the site of the ground plate. In bipolar electrosurgery, the current passes between two tips on the handpiece (Figure 28-2, E), which grasp the tissue. No ground plate is needed for bipolar electrosurgery.

SCISSORS

Specific scissors are designed to cut tissue, suture, wire, or bandage material (Figure 28-3). There are many types of dissecting scissors, made for precise cutting and dissection of tissue. Operating scissors vary by the type of blades (straight or curved), the type of points (blunt-blunt, blunt-sharp or sharp-sharp), and the cutting edge of the blades (plain or serrated). Mayo dissecting scissors are heavy scissors used for cutting tough tissue, such as heavy connective tissue. The blades may be straight or curved. Metzenbaum dissecting scissors are fine, curved scissors used for cutting delicate tissue, such as fat or thin muscle. Metzenbaum scissors are preferred for most soft tissue dissection. They should never be used for cutting suture because this dulls the edges and causes the blades to separate and lose effectiveness. Stitch scissors or Littauer suture removal scissors are used to cut all sutures except wire sutures. Wire-suture–cutting scissors can cut wire suture. Lister bandage scissors are available to cut bandage material. One blade of the Lister scissors has a blunt end to facilitate sliding under a bandage without poking the skin. To prolong the life of any scissors, it should be used only for its intended purpose.

NEEDLE HOLDERS

Needle holders are designed for holding curved suture needles during suturing and for performing instrument suture ties. Mayo-Hegar and Olsen-Hegar needle holders are two commonly used needle holders (Figure 28-4). The Olsen-Hegar needle holder has built-in suture scissors, which negates the need for an assistant to cut suture. It allows the surgeon to work alone and cut suture without switching instruments. The potential disadvantage of this needle holder is that the suture may be accidentally cut during suture placement.

Needle holders consist of a set of jaws, a hinge or box lock, and handles with a ratcheted locking device (Figure 28-5). The size and design of these components vary greatly, depending on the intended use. The jaws commonly have tungsten carbide inserts that provide excellent grip. The tungsten carbide insert is hard, resistant to wear, and can be replaced when worn, thereby prolonging the life of the instrument. Worn inserts can result in improper closure of the jaws or sharp edges that inadvertently cut suture. Needle holders are available in different sizes, depending on the needle sizes they are designed to hold. Improper use of needle holders (such as using a needle holder that is too small for the size of the needle or using the needle holder to bend or twist wire) may not only damage the jaws, but may also spring the box lock and ratchet.

THUMB FORCEPS

Thumb forceps are special tissue forceps designed to hold and easily release tissue with a simple finger motion (similar to tweezers). They have a spring action, and the jaws are opposed by compressing the two metal handles together. Several different jaw surfaces are available and are designed for use with various tissues (Figure 28-6, A to C). Brown-Adson thumb forceps have multiple intermeshing teeth with a broad tip, providing good tissue and needle handling. They are commonly used during suturing and wound closure. Rat-tooth thumb forceps have large interdigitating teeth and are primarily used for skin or fascia. Adson thumb forceps have delicate intermeshing teeth (“rat toothed”) that provide a good, atraumatic grasp of delicate tissues. They are commonly used during dissection. Cooley and DeBakey thumb forceps have long, narrow jaws with multiple delicate sets of teeth that are especially good for vascular surgery. Russian thumb forceps have a broad curved surface good for needle handling, but are traumatic when used to hold tissues. Dressing thumb forceps do not have teeth and are used for applying and removing dressings. They are not designed to grasp tissue and are undesirable for this use because the surgeon must squeeze hard and crush the tissue to grasp it. Thumb forceps are available in a variety of sizes, depending on the intended surgery. For example, thoracic forceps have long handles to enable the surgeon to reach tissues deep within the chest, but these same forceps would be too cumbersome and awkward to use on the skin.

TISSUE FORCEPS

Tissue forceps are locking instruments that clamp tissues (Figure 28-7, A). Different teeth patterns allow them to grip various types of tissues without slipping. Allis tissue forceps securely grasp tissue, but also crush it (Figure 28-7, B). Therefore they are considered to be traumatic and should only be used on tissue that is being removed. Babcock forceps are shaped similarly to the Allis forceps, but are less traumatic because they have a smoother grasping surface and less tip compression (Figure 28-7, B). The Doyen intestinal tissue forceps (Figure 28-7, A) is a more delicate instrument used to occlude and hold intestine. The disadvantage of less traumatic tissue forceps is that they are less secure on the tissues.

Towel clamps are forceps used to attach towels and drapes to the patient. These forceps have pointed tips that curve and join like ice tongs. They are available in different sizes (see Figure 28-7, A). Backhaus towel clamps and Roeder towel clamps are two common designs. The Roeder towel clamp has a metal bead or ball stop attached to the jaws that prevents deep tissue penetration and prevents the towel from slipping toward the box lock of the forceps.

HEMOSTATIC FORCEPS

Hemostatic forceps are tissue forceps used to stop bleeding by crushing blood vessels (Figures 28-8 and 28-9). They are available in different sizes and may be straight or curved. Most hemostatic forceps have transverse grooves on the inside surface of the jaws to better grasp the tissue. Halsted mosquito hemostats are small and designed to occlude small vessels (see Figure 28-8, A). When using hemostatic forceps, the tips of the forceps should be used to grasp only as much tissue as necessary. Crile forceps and Kelly forceps (see Figure 28-8) are larger hemostatic forceps and are used on larger vessels. The jaws of the Crile forceps are transversely grooved for the entire length, but only the distal halves of the Kelly forceps are grooved. Rochester-Péan forceps are large, transversely grooved forceps that are used to clamp tissue bundles and large vessels (see Figure 28-9). Rochester-Ochsner forceps are similar to the Rochester-Péan forceps, but have interdigitating teeth at the tips (see Figure 28-9) that aid in grasping the tissue. Rochester-Ochsner forceps are used most commonly in orthopedic or large animal surgery. Rochester-Carmalt forceps are large crushing forceps with longitudinal grooves and cross-grooves at the tip to provide more traction (see Figure 28-9). These forceps are used for clamping across tissue containing vessels. The Rochester-Carmalt forceps are commonly used to crush the vessels of the ovarian pedicle or the body of the uterus during an ovariohysterectomy (spay) operation. When clamping across vessels, the forceps should be applied with the concave surface facing upward to facilitate tying the ligature. Refer to Chapter 29 for more information on the use of hemostatic forceps.

RETRACTORS

Properly placed retractors do not interfere with the surgery yet provide good visibility of the surgical site and allow more room for the surgeon to work. Retractors may be handheld or self-retaining. A surgical assistant is needed to maintain the position and tissue tension of a hand-held retractor. The Army-Navy retractor and the Senn retractor are double-ended hand-held retractors commonly used to retract skin, fat, or muscle (Figure 28-10). The Army-Navy retractor has smooth blades, whereas the Senn has one smooth blade and one blade with three sharp or blunt prongs. The malleable retractor is made of thin metal that is easily bent to the desired shape (Figure 28-10). It is commonly used to retract abdominal organs. The Snook ovariohysterectomy hook is a specialized type of hand-held retractor used to expose the horn of the uterus during an ovariohysterectomy (see Figure 28-10). The Hohmann retractor consists of a single blade and a handle that are used to lever tissues out of the way for better visibility (see Figure 28-10). It is used almost exclusively in orthopedic surgery and can provide good visibility in certain joint surgeries.

Self-retaining retractors are maintained in the desired position by some type of locking mechanism on the retractor handle. The advantage of the self-retaining retractors is that the surgeon and the assistant have their hands free for other tasks. The Balfour retractor provides increased exposure of the abdominal cavity (Figure 28-11). The two wirelike blades are used to distract the abdominal incision, and the solid spoonlike blade is hooked onto the sternum to distract it cranially. The Finochietto rib spreader retracts the ribs to expose the surgical field within the thoracic cavity (see Figure 28-11). The ratcheted part of the retractors is positioned at the dorsal aspect of the thoracic incision so that it does not interfere with the surgeon. Gelpi retractors and Weitlaner retractors (Figure 28-12) are self-retaining retractors commonly used for muscle retraction, especially in orthopedic and neurologic surgery. Refer to Chapter 29 for more information on retraction techniques.

SUCTION TIPS

Several different suction tips are commonly used (Figure 28-13). The Poole tip is used primarily in the abdominal or thoracic cavity because it has an outer sleeve with small holes to prevent tissue, such as fat, from becoming entrapped in the tip. The Frazier tip is most commonly used in orthopedic and neurologic surgery. The Yankauer tip is a general-purpose suction tip. The suction tip is attached to a long, sterile suction tube. The other end of the suction tube is connected to a nonsterile suction canister. Refer to Chapter 29 for more information on the use of suction.

MICHEL SKIN CLIPS

Drape material is often attached to the incised skin edge during surgical procedures to minimize contamination of the surgical field by the surrounding skin. The use of Michel skin clips is one method of attaching the drape to the wound edges (Figure 28-15). One end of the Michel clip-applying-and-removing forceps grips the clip. When the handles are squeezed, the clip bends to pinch the edges of the drape and the skin together. The other end of the forceps has jaws that remove the clip by bending it backward and disengaging it from the incision edge. There are alternatives to Michel clips, including the use of suture, “scalp clips,” towel clamps, and adhesive drapes.

RONGEURS

Rongeurs have sharp cupped tips that are used to cut small pieces of dense tissue, such as bone, cartilage, or fibrous tissue (Figure 28-17, A). Rongeurs have a double-action or single-action mechanism (Figure 28-17, B). Double-action rongeurs have a smooth cutting action and are mechanically stronger than single-action rongeurs, but they are also larger. Double-action rongeurs are preferred for removing large amounts of dense tissue. Single-action rongeurs are more commonly used in confined areas, as in removing bone to perform spinal surgery. Kerrison rongeurs have a gun-shaped appearance and are useful for spinal surgery. Bone-cutting forceps are similar to rongeurs, but have paired chisel-like tips. They are used for cutting bone and should not be mistaken for wire cutters (Figure 28-18).

BONE-HOLDING FORCEPS

Bone-holding forceps are designed to hold bone and bone fragments in alignment while orthopedic implants (screws, pins, wires, or plates) are applied (Figure 28-19). Most bone-holding forceps are self-retaining. A Kern bone-holding forceps has a ratcheted handle that allows it to be clamped securely on the bone. The self-retaining bone-holding forceps, also known as speed locks, has a nut that tightens against one handle to squeeze the handles together.

CURETTES

Curettes are used to scrape hard tissue, such as bone or cartilage. Curettes are designed with a small cuplike structure at one or both ends of a handle (similar to an ice cream scoop). The cup has a sharp cutting edge and is available in various sizes (Figure 28-20). A common use of bone curettes is to retrieve cancellous bone from the medullary cavity (tibia, humerus, ilium) for use as a bone graft. Cancellous bone grafts are often used during fracture repair.

PERIOSTEAL ELEVATORS

Periosteal elevators are instruments that are used to pry periosteum or muscle from the bone surface. They have a bladelike structure at one or both ends of a handle. The blades have sharp or blunt edges and are available in various sizes (Figure 28-21).

OSTEOTOMES AND CHISELS

Osteotomes and chisels are used to cut bone. Osteotomes and chisels are used by pounding on the flared end of the handle with a mallet (Figure 28-22, A). The cutting edge of the osteotome is tapered on both sides, whereas the chisel is tapered only on one side (Figure 28-22, B).

GIGLI WIRE

Gigli wire is used to cut bone by placing the wire around the bone and drawing it back and forth in a sawing fashion. T-shaped handles hook onto the wire to give the surgeon a firm grasp of the wire.

TREPHINES

Trephines are T-shaped tubular instruments with a cylindrical cutting blade (Figure 28-23). Trephines are usually used to remove a core of bone for biopsy.

POWER EQUIPMENT

Some power equipment is commonly used in orthopedic and neurologic surgery. Although some drills are electric or battery powered (Figure 28-24, A and B), many orthopedic drills and saws are powered by nitrogen gas that is supplied via a sterile hose (Figure 28-24, C). The Hall air drill is a specialized high-speed bur that grinds bone (Figure 28-24, D). It is most commonly used for spinal surgery.

BONE PINS

Bone pins vary in diameter, length, and the type of points. Steinmann pins are smooth, stainless steel pins ranging in diameter from to ¼ inch. Three different types of pin points are available, including chisel, trocar, or threaded trocar. Some pins have threads, similar to a screw. A power drill or a Jacobs hand chuck is required to insert the pin into bone, and a pin cutter is necessary to cut it to the proper length (Figure 28-25). Steinmann pins may be called intramedullary (IM) pins because they are often placed in the medullary cavity of long bones for fracture fixation. Kirschner wires (K-wires) are similar to Steinmann pins, but are smaller and can be used to pin small bone fragments. The available sizes are 0.035-inch, 0.045-inch, and 0.062-inch in diameter.

INTERLOCKING NAILS

Interlocking nails are similar to IM pins, but have preplaced holes through the pin that allow screw placement. Interlocking nails have more rigid fixation than IM pins. Equipment is similar to that required for pins, but specialized equipment is needed for screw placement.

ORTHOPEDIC WIRE

Stainless steel orthopedic wire is supplied on spools (Figure 28-26). The common sizes used in small animal surgery are 22 gauge, 20 gauge, and 18 gauge (Table 28-2). It is most commonly applied in a cerclage fashion by encircling the bone or bone fragments and twisting the ends in a “twist-tie” manner. Orthopedic wire is often used for fracture repair in combination with pins or bone plates.

EXTERNAL FIXATORS

External fixation is a means of stabilizing fractures using pins placed through the skin and bone. The pins are held rigid by a metal or acrylic connecting bar that is attached to the pins several centimeters from the skin (Figure 28-27). The metal apparatus uses special clamps to attach a metal connecting bar to the pins. Acrylic (methyl methacrylate) connecting bars are often made from dental acrylics or hoof-wall–repair acrylics because they are less expensive than surgical grades of acrylic. The acrylic connecting bar is more versatile and lighter than the metal apparatus. Ring fixators use special wires instead of pins in the bone. Several metal rings encircle the limb and are fixed in alignment using rods. Each bone wire is clamped to one of the rings.

BONE SCREWS

The two basic screw types are cortical and cancellous screws. Cortical screws are fully threaded screws that are designed for dense (cortical) bone. Cancellous screws are either partially threaded or fully threaded and are made with wider threads to have a better grip in the softer cancellous bone (Figure 28-28).

The general steps of screw placement include drilling a hole in the bone, measuring the hole with a depth gauge to determine the proper screw length, using a bone tap (a screwlike instrument with sharp threads) to cut a screw path in the bone, and inserting the screw with a specialized screwdriver. Bone screws may be used alone or in conjunction with a bone plate or interlocking nail.

Bone screws are named by both the screw length and thread diameter (in millimeters). Commonly used screws in small animal surgery are 2.7- and 3.5-mm diameter cortical screws and 4.0-mm diameter cancellous screws. All of these screws have hexagonal heads and are driven by the same hexagonal screwdriver. Smaller screws (1.5- and 2.0-mm diameter) have cruciate heads and require a small, cruciate screwdriver. Larger screws (4.5-, 5.5-, and 6.5-mm diameter) are used in large animal surgery. These screws use a large hexagonal screwdriver.

BONE PLATES

There are many different types of bone plates (Figure 28-29). Bone plates are named by the number of screw holes and by the screw diameter size that best fits the plate. For example, a seven-hole, 3.5-mm plate would use seven, 3.5-mm diameter screws. Bone plates must be bent to match the curve of the bone and fastened to it with bone screws. Instrumentation required to apply a bone plate is highly specialized and includes drills, drill bits, drill guides, depth gauges, bone taps, tap sleeves, screws, screwdrivers, and plate benders (Figure 28-30). Although bone plating is more complex than other types of orthopedic fixation, plate fixation is much more stable in most cases.

TOTAL HIP PROSTHESIS

Replacement of the hip joint with a prosthesis may be done in some dogs with severe arthritis. This procedure is done by highly trained veterinary surgeons and requires much specialized orthopedic equipment in addition to the prosthesis itself. The femoral prosthesis consists of a long stem that fits inside the proximal femur and a ball that replaces the femoral head. A special cup replaces the acetabulum.

ARTHROSCOPE

There is a selection of different arthroscopes that have been developed with various diameters and viewing angles. For example, there is a 5-mm-outer-diameter (OD) arthroscope with either a 10-degree, 25-degree, or 70-degree lens angle; a 4-mm OD with a 10-degree, 30-degree, 70-degree, or 110-degree lens angle; a 2.7-mm OD with a 5-degree, 30-degree, or 70-degree lens angle; and a 1.9-mm OD with a 5-degree or 30-degree lens angle. A 4-mm OD, 25-degree or 30-degree angled lens scope is generally used by most equine surgeons (Figure 28-31), whereas a 2.7-mm OD, 30-degree angled lens scope is commonly used for canine arthroscopy. Most arthroscopes have a television camera permanently coupled to them, which allows the surgeon to view the joint on a television monitor (Figure 28-32). A television monitor has the advantage of a larger image. This greatly improves visualization of the intraarticular space compared with direct viewing through the eyepiece of the arthroscope. This method also provides better aseptic technique because the surgeon’s face is not near the surgical field, and an assistant can operate the camera-scope unit, allowing the surgeon more freedom. A monitor also allows several persons to observe the procedure simultaneously, and a videotape record can be made for future replay.

ANCILLARY ARTHROSCOPIC EQUIPMENT

Along with the arthroscope come various instruments used to introduce the scope into the joint. Stab incisions are made in the skin over the joint space once the site is surgically prepared through which the arthroscope and hand instruments will be inserted once the animal is positioned for surgery.

FLUID DELIVERY SYSTEMS

Fluid, usually a balanced electrolyte solution, is infused into the joint under pressure to maintain distention of the joint capsule, which is essential for visualization of the intraarticular space. Gas insufflation, using CO₂ or nitrous oxide, has also been used as a method of distending the joint. However, a special system with a pressure-regulating device is required. One disadvantage of gas is that it does not allow for lavage of the joint space if osteochondral chip fragments become detached in the joint. The fluid is infused into the joint space through the sleeve, around the arthroscope. The sleeve has at least one stopcock that is used as an ingress port to connect a sterile fluid line (Figure 28-39).

HAND INSTRUMENTS FOR ARTHROSCOPIC SURGERY

Numerous hand instruments of various types are available or have been adapted for arthroscopy. They are used to remove or retrieve osteochondral chip fragments, débride articular cartilage or subchondral bone, or probe cartilage or cartilage lesions. The instruments are inserted into the joint through a separate stab incision, and the arthroscopic operation is performed via a technique called triangulation. Only the most commonly used instruments are discussed here.

RADIATION

Some materials that would be damaged by other methods of sterilization can be safely sterilized by radiation. Radiation destroys microorganisms without causing any significant temperature elevation. Gloves and some suture materials are sterilized by radiation during the manufacturing process.

THERMAL ENERGY

The most common method used for sterilization is heat. The mechanism by which heat destroys microorganisms is not completely understood, but it is believed that death is the result of protein denaturation. This is probably a gradual process and may be reversible during the early stages of sterilization. The thermal susceptibility of microorganisms is influenced by several factors, including inherent resistance, individual variation, and age (young bacteria are more susceptible). There is no one temperature at which all microorganisms are killed instantly because death of bacteria and spores is a function of temperature and duration of heat.

The two basic types of heat sterilization are moist heat and dry heat. Dry heat is used to sterilize materials that cannot tolerate moist heat, but can withstand high temperatures. Oils, powders, and petroleum products are most effectively sterilized by dry heat, whereas rubber, fabrics, and some metals may be damaged by the high temperatures. An advantage of dry heat is that it will not rust or corrode needles or sharp instruments. Dry heat is more difficult to control than moist heat, and the sterilization time is longer.

Both dry and moist heat destroy bacteria through protein denaturation; however, dry heat kills by protein oxidation, whereas moist heat kills by coagulation of critical cellular protein. Moisture facilitates the coagulation of protein; thus moist heat kills bacteria and spores at lower temperatures and shorter exposures than dry heat.

Moist heat sterilization is accomplished by either boiling water or by steam under pressure. Boiling water at ambient pressures is not a reliable means of sterilization because of its relatively low temperature. The bactericidal effect of boiling water can be enhanced by alkalinization with sodium hydroxide (0.1 g/dl) or sodium carbonate (2 g/dl). The addition of these agents reduces instrument corrosion, but they cannot be used with glassware or rubber goods. Boiling water probably results in disinfection rather than sterilization and is rarely used.

The most common method of sterilization is saturated steam under pressure. Increased pressure causes steam to achieve a higher temperature. Materials to be sterilized in this manner must be penetrable by steam and not damaged by heat or moisture. Sterilizers that employ steam under pressure are called autoclaves (Figure 28-52).

ETHYLENE OXIDE

Ethylene oxide is a colorless gas at room temperature. It is flammable, explosive, and toxic. It can cause skin burns, respiratory irritation, vomiting, headaches, and birth defects (see Chapter 6). The manufacturer’s guidelines should be followed carefully to prevent injury to hospital personnel and patients. Ethylene oxide penetrates paper and plastic film packaging. The item to be gas sterilized is wrapped in plastic packaging (polyethylene, polycoated paper, and Mylar) and heat sealed before sterilization (see Figure 28-53).

Ethylene oxide destroys metabolic pathways within the cells by alkylation, and it is capable of killing all microorganisms. Effective sterilization with ethylene oxide is dependent on the concentration of gas, exposure time, temperature, and relative humidity. Ethylene oxide activity is enhanced by increasing the temperature or the gas concentration. Ethylene oxide sterilizers usually operate at temperatures between 21° C and 60° C (70° F and 140° F). The activity of ethylene oxide approximately doubles with each 10° C increase in temperature. Doubling the ethylene oxide concentration decreases the sterilization time by approximately one half. Moisture is necessary for the lethal action of ethylene oxide, and optimum relative humidity for sterilization with ethylene oxide is 40%. Exposure time varies from 48 minutes to several hours, but 12 hours of exposure is commonly used when sterilizing at room temperature.

After ethylene oxide sterilization, materials should be quarantined in a well-ventilated area for a minimum of 7 days or in an aerator for 12 to 18 hours. Recommended aeration time varies with the type of material and other factors. Color-coded chemical sterilization indicators are commonly placed within the packs when using ethylene oxide sterilization (see Figure 28-55). Biologic indicators are available for ethylene oxide sterilization and are the only truly reliable test for sterility. Since results are unavailable for several days, biologic indicators are most commonly used to evaluate the sterilization system and not individual packs. External tape can be used to indicate exposure to gas sterilization (Figure 28-56).

HYDROGEN PEROXIDE GAS PLASMA

Gas plasma sterilization has been replacing ethylene oxide because it is safer for the environment and personnel. It can inactivate mycobacteria, bacterial spores, fungi, and viruses and can be used to sterilize most items. Items that cannot be sterilized with this method include linen, wood or paper, endoscopes, some plastics, liquids, and tubes or catheters that are long (greater than 12 inches) or of small diameter (less than 3 mm). Items to be sterilized are wrapped in nonwoven polypropylene fabric or plastic (Tyvek-Mylar) pouches and placed in the sterilization chamber. A vacuum is drawn, and hydrogen peroxide is injected and is vaporized. After 50 minutes, the pressure is lowered, and radio waves are applied to the chamber, creating a gas plasma. This creates free radicals, which kill the microorganisms. The process takes about an hour and requires no aeration. A biologic indicator is used to test for sterility, and a chemical indicator is used to show that hydrogen peroxide was present.

CHEMICAL DISINFECTION

A disinfectant is an agent that destroys bacteria or inactivates viruses. Disinfectants are chemical agents that are applied to inanimate objects to destroy the vegetative form of bacteria, but not necessarily the spore forms. Disinfectants that are capable of destroying vegetative bacteria plus spores, tubercle bacilli, and viruses may be used as chemical sterilizers.

Disinfection time is the time required for a particular agent to produce its maximal effect. It is influenced by many factors, including the nature of the material disinfected, the degree of soil and microbial contamination, and the concentration and germicidal potency of the disinfectant.

Antisepsis is the prevention of infection by inhibiting the growth of infectious agents. Antiseptic agents, such as iodine or chlorhexidine, are substances used on living tissue to effect antisepsis. A glossary of key terms used in describing aseptic technique may be found in Box 28-1.

ANTISEPTIC AND DISINFECTANT COMPOUNDS

COLD STERILIZATION

Cold sterilization refers to soaking instruments in disinfecting solutions, such as chlorhexidine or glutaraldehyde. Metal trays used to soak instruments in disinfectant are called cold trays (Figure 28-57). Since sterility cannot be guaranteed, cold-sterilized instruments should be used only for minor procedures (superficial lacerations, dental procedures) or for equipment that cannot tolerate other forms of sterilization, such as endoscopic equipment. Exposure times should exceed 3 hours, and the equipment must be rinsed thoroughly before use.

STERILIZATION OF ARTHROSCOPIC EQUIPMENT

Most hand instruments and ancillary equipment can be steam sterilized. They can also be gas sterilized with ethylene oxide or cold sterilized using a glutaraldehyde-based solution (CidexPlus, Johnson & Johnson Medical Inc.). Cold sterilization affords the ability to use the equipment more than once in a single day, unlike steam and gas sterilization in most situations. The arthroscope, light cable, and camera can be gas sterilized or cold sterilized, but not steam sterilized.

With cold sterilization, the instruments are soaked for a minimum of 20 minutes in the Cidexplus just before surgery. The electrical plug of the camera cable is not submerged in the cold sterilization solution, which would damage it. The end is draped out over the top of the container with the Cidexplus. The surgeon or assistant double gloves and removes the instruments from the solution. The instruments are then placed in a sterile autoclave tray containing sterile water. Once the instruments have been submerged in the sterile water, each piece is gently agitated, individually removed from the tray, rinsed with sterile water by a scrub nurse or other assistant, and transferred to the instrument table. The surgeon or assistant removes his or her outer gloves and dries the instruments. It is important that the Cidexplus be thoroughly rinsed from the instruments. Glutaraldehyde can cause a chemical synovitis and is injurious to chondrocytes. A double rinse further reduces the amount of glutaraldehyde residue remaining on the instruments.

SKIN PREPARATION—SURGICAL CLIP

The surgical site is usually prepared after the animal is anesthetized. The hair is first clipped in the same direction as the hair growth. Then it is clipped against the direction of growth to achieve the closest shave possible (using a No. 40 clipper blade). A wide region of skin is clipped around the proposed surgical incision. A general rule is to shave at least 2 to 4 cm in every direction from the proposed incision, depending on the size of the animal and location of the incision. For abdominal procedures, the clip should extend several centimeters cranial to the xyphoid, caudal to the pubis, and lateral to the nipples. For orthopedic procedures, the entire circumference of the limb is clipped from the foot up onto the body. Long hair growing near the periphery of the clipped area should be cut short enough that it cannot hang over the clipped area. Sterile, water-soluble lubricant may be placed in open wounds before clipping around them. The lubricant will collect hair, allowing it to be rinsed away before the surgical scrub. Areas that appear to be infected should be clipped last so that the clippers do not spread infected material. After clipping, a vacuum cleaner may be used to eliminate loose hairs on the skin. The surgical clip should be thorough but gentle. Unnecessary roughness will result in inflamed or traumatized skin, which can cause greater postoperative complications.

SKIN PREPARATION—SURGICAL SCRUB

Initial skin preparation is done in the preparation room to remove gross contamination. Before scrubbing the abdomen of a male dog, the prepuce should be flushed with an antiseptic solution. Examination gloves are worn to decrease contamination from the hands. The surgical scrub is performed by alternating an antiseptic scrub (such as povidone-iodine or chlorhexidine scrub) with alcohol or sterile saline. (Remember not to use alcohols or detergents in open wounds, eyes, or mucous membranes.) Scrubbing should begin over the proposed incision site and extend outward in a spiraling pattern, never going back toward the center with the same gauze sponge (Figure 28-58). The sponge is replaced with a clean one, and the process is repeated until no dirt is visible on the discarded sponges.

The sterile surgical scrub is done once the animal is properly positioned on the operating table. Sterile gloves should be worn, and sterile sponges are used. If the sterile surgical scrub is performed by alternating povidone-iodine with alcohol, the total contact time of the povidone-iodine should be at least 5 minutes. After the final povidone-iodine scrub, a 10% povidone-iodine solution should be sprayed or painted on the skin. Alternatively the sterile surgical scrub may be performed by alternating chlorhexidine gluconate with either alcohol or sterile saline. Either chlorhexidine or sterile saline may be left on the skin at the end of preparation. Both povidone-iodine and chlorhexidine are effective scrub solutions, but the contact time for chlorhexidine is less critical than for povidone-iodine.

Several skin preparations are now available that enable a “one-step prep” (Table 28-6). The solution is packaged in a small plastic bottle that is directly attached to an applicator sponge. After squeezing the bottle to activate solution flow, the sponge is used to “paint” a single uniform coat of the solution on the skin, starting at the incision site and working outward in a circular motion (Figure 28-59). It requires a 30-second application time and dries within 2 to 3 minutes, so the preparation time is much faster than the traditional alternating scrub described earlier. They contain isopropyl alcohol, which is a broad-spectrum antimicrobial with rapid onset of activity. The other substances in these preparations result in further antimicrobial action and the formation of a film that adheres strongly to the skin and provides long residual activity. These solutions should be applied to clean, dry skin. However the skin should not be scrubbed beforehand with Betadine or Hibiclens scrub because residues may prevent the one-step preparation from adhering appropriately. These one-step preparations should be applied to intact skin and are not appropriate for open wounds because of the high alcohol content (70% to 74%). These preparations enhance the skin adherence of incise drapes. The region will be flammable until it dries. Alcohol-free solutions are being developed.

There are many modifications to the surgical preparation technique. For example, in preparation for feline orchiectomy (castration), the scrotal hair is plucked rather than clipped. Feline onychectomy (declawing), tail docking, and dewclaw removal of neonatal puppies are commonly performed without clipping the hair. The surgical site is soaked or gently scrubbed with detergent and swabbed with alcohol or antiseptic solution. Bovine and porcine castrations are performed without clipping the hair, and an alcohol or antiseptic wash is usually used. Equine castrations may be prepared with three thorough washes using dilute chlorhexidine or povidone-iodine solution.

PATIENT POSITIONING

There are several common positions in which to place an animal for surgery. The position of the animal is described by the region of the body that contacts the table. For example, right lateral recumbency means the animal is lying on its right side, dorsal recumbency means the animal is on its back, and sternal recumbency means the animal is on its belly. Maintaining patient positioning is facilitated by the use of adjustable surgical tables, portable tabletop V troughs, sand bags, or vacuum-activated “beanbags.”

In orthopedic surgery, the affected leg is often suspended from an overhead support or intravenous (IV) stand during skin preparation and initial surgical draping. The advantage of hanging the leg is that it allows aseptic preparation of the entire circumference of the limb, so the surgeon can manipulate it during surgery. To hang the leg, the distal limb is wrapped (using gauze or an examination glove covered with tape) to cover any unclipped areas, and strips of tape (“stirrups”) are extended from the end of the foot. The leg is suspended by these stirrups (Figure 28-60). The entire limb circumference is clipped and scrubbed from the foot to the level of the inguinal or axillary region. The skin preparation usually extends to the dorsal and ventral midlines of the body.

PATIENT POSITIONING

Positioning of the equine patient for surgery can be quite an involved process. It requires more personnel compared with small animals. In most situations, the minimum number of persons required to position a horse on a surgery table is three. There are various ways in which a horse is moved or transported to the surgical suite and ultimately onto the surgical table. This is determined by the physical setup of the surgical facility. An overhead hoist system greatly facilitates the lifting and positioning of the horse onto the surgery table. As an example, the horse is walked into a padded induction room and anesthetized by using several persons pushing the horse against one of the walls during the induction of the anesthesia. As the animal becomes anesthetized, it is allowed to collapse to the floor and then roll into lateral recumbency. At that point, the horse is positioned in the center of the moveable floor that rolls into the surgical suite. Nylon leg bands are strapped to the front and rear feet, and an overhead chain hoist is hooked to the bands (Figure 28-61). The horse is raised off the floor and moved onto the surgical table by way of a rail system that the chain hoist moves on. Once the animal is over the surgical table, it is gently lowered onto the table in the desired recumbency. If the horse is to be in dorsal recumbency, it is maintained in this position by the use of side poles with pads wedged between the poles and the horse (Figure 28-62). Once the horse is positioned on the table, the leg bands are removed, and the legs may be secured to the positioning poles or table to reduce shifting of the horse during surgery. The chain hoist is rolled away, and the rolling floor is pushed back into the padded induction room, and the surgical doors are closed. Large examination gloves or obstetrical (OB) sleeves are used to cover the feet of the horse to reduce contamination of the surgical suit (Figure 28-63). As with proper technique, the personnel remaining in the surgical suite must wear proper surgical attire, including caps and masks. The surgical nurse should take charge to make sure that all personnel in the surgery suite are following protocol. During this preparation time, an anesthesiologist or anesthesiology technician is often placing arterial catheters in the hind limb or facial artery, attaching the ECG monitor, and attaching fluid lines to the IV catheters.

SKIN PREPARATION

For some equine surgical procedures, particularly abdominal surgeries, it is difficult to clip the hair and perform an initial skin preparation before the horse is anesthetized. A wide area of hair at the intended surgical site is removed with electric clippers (Figure 28-64). An initial skin preparation is performed using chlorhexidine or povidone-iodine scrub with a rinse and wipe down of alcohol. During the initial preparation, the opening of a male horse’s sheath (gelding or stallion) is packed with gauze sponges and sutured closed. This prevents urine and smegma from contaminating the surgical field (Figure 28-65). With female horses, it is imperative that the mammary area is cleaned thoroughly. Next a sterile skin preparation is performed with sterile gloves and sterile sponges (Figure 28-66). Three to five surgical scrubs alternating with the chlorhexidine and alcohol are performed, starting at the center of the surgical site and moving outward in a circular fashion (Figure 28-67). Preparation is complete when the sponges no longer collect visible dirt. Then the surgical area is sprayed with a chlorhexidine solution, which is left on the skin (Figure 28-68).

ATTIRE

Proper surgical attire and proper scrubbing, gowning, and gloving procedures are important aspects of aseptic technique. Street clothing, especially shoes, are a major source of contamination and should not be worn into the operating room. Ideally, each person should have a pair of shoes designated for use only in the operating room. Disposable shoe covers may be worn in the operating room and discarded upon leaving the room. Lint-free scrub suits should be worn in the operating room. The shirt should be tucked into the pants to reduce the amount of skin debris dispersed into the room. Outside the operating room, scrub suits should be protected by a laboratory coat to reduce contamination.

During surgery, surgical caps and masks are worn by all persons who are in the room. The surgical cap covers the hair to reduce airborne contamination. Different types of surgical head covers are available to cover short hair, long hair, or beards (Figure 28-69). The mask protects the wound from saliva droplets, primarily by redirecting air flow out the sides of the mask. Masks are effective for relatively short periods and should be changed between procedures.

HAND SCRUB

Scrubbing of the hands and arms, followed by gowning and gloving, is performed by all personnel who will be in close proximity to the surgical site. Surgical gloves may have tiny holes, so they cannot be solely relied upon to prevent contamination from the hands. The purpose of scrubbing the hands and arms is to remove dirt and decrease the concentration of bacterial flora. The surgical cap and mask must be donned. The gown pack may be opened before scrubbing (Figure 28-70). All jewelry is removed from hands and arms before beginning the sterile hand scrub, and fingernails should be short and free of polish or artificial nails. Once the scrubbing has begun, the hands and arms should not touch nonsterile objects. If this occurs, the scrub is started over.

While scrubbing, the hands are always held above the level of the elbows so the water drains off the elbows. Soap is applied to a sterile brush, and a systematic scrub is begun. Scrub all four sides of each finger, with special attention to the fingernails (Figure 28-71, A). The back, both sides, and the palm of the hand are scrubbed. Next the wrist and forearm are scrubbed, working toward the elbow (Figure 28-71, B). After both hands and arms have been scrubbed, they are rinsed in running water (Figure 28-71, C). The entire scrub process is then repeated.

The two basic methods of surgical scrubs are the counted brush strokes and the timed. The counted brush strokes method is performed by counting the number of brush strokes used on each skin surface. Ten to 25 brush strokes are made on each surface of the fingers, hands, and arms before rinsing. This is performed four times. The timed method is more commonly used. This is done by repeatedly scrubbing and rinsing for a set period of time. The initial scrub of the day should last about 5 minutes. For subsequent scrubs during the day, 2 to 3 minutes is adequate.

Waterless hand antiseptics are now available that are at least as effective as the traditional hand-scrub technique described earlier and cause less skin trauma. These antiseptics contain an alcohol solution, which provides a rapid antimicrobial kill of a broad spectrum of microorganisms. They also contain a lotion to prevent drying of the skin. Hands must be clean and dry, but scrubbing is not necessary. The solution is rubbed briskly and evenly over one hand and forearm; a second application is applied to the other hand and forearm. A final application is applied to both hands and allowed to air-dry. The waterless antiseptics are fast, effective, easy to apply, and nonirritating.

GOWNING AND GLOVING

The hands and arms are thoroughly dried with a sterile towel (Figure 28-72) before gowning (Figure 28-73) and gloving.

The two methods for gloving yourself are closed gloving and open gloving. The risk of contamination is minimized with closed gloving (Figure 28-74) because the outside of the gloves never contacts skin. There is a much higher risk of contamination during open gloving (Figure 28-75), and it is generally reserved for minor procedures when a gown is not worn (e.g., sterile patient scrub, urinary catheterization). If it is necessary to replace gloves during surgery, it is preferable to have a nonsterile assistant remove the old gloves and simultaneously pull the gown sleeve so that the hands remain inside the sleeves (Figure 28-76). If the old gloves are removed in this manner, new gloves can be put on by the closed gloving method or by assisted gloving (Figure 28-77).

MAINTAINING STERILITY

It is important for the entire surgical team to be conscious of sterility, even if they are not “scrubbed in” (i.e., gowned and gloved). Nonsterile personnel should only touch nonsterile items or areas and should not lean over or reach across sterile fields. Those who are scrubbed in should only touch sterile items or areas and should always face the sterile field. Only sterilized items can be placed on a sterile field. If anyone on the surgical team notices a potential source of contamination or “break” in sterile technique, it should be mentioned immediately so that steps can be taken to reduce the risk of further contamination. To reduce contamination, only essential personnel should be present in the operating room, and excessive movement should be avoided. Conversation should be kept to a minimum.

THE PATIENT

Sterile surgical drapes are used to maintain a sterile field around the surgical site. Draping is performed by personnel who have scrubbed in. First, four small towels (cloth or paper) are placed to surround the area where the surgical incision will be. These are called quarter drapes and they are secured to the skin using towel clamps. During this procedure, one must be careful not to brush the front of the surgical gown against the surgical table. Then a large drape is placed over the animal, surgical table, and instrument stand to provide one continuous sterile field. Cloth drapes have an opening or “fenestration,” which is positioned over the surgical site. If a disposable paper drape is used, the appropriately sized hole may be cut after the drape has been placed. Because skin preparations do not sterilize, but only disinfect, the skin, plastic incise drapes may be used to provide a sterile surface at the start of surgery. These are translucent, adherent plastic drapes that are used to completely cover any visible skin after the barrier drapes have been applied. Incise drapes are often impregnated with an antiseptic. The surgeon can cut through the incise drape simultaneously with the skin incision. Refer to Chapter 29 for more detail on draping procedures.

If a limb has been suspended in preparation for an orthopedic procedure (as described under Patient Positioning), the quarter drapes are placed on the body, around the base of the limb. The distal limb is then held with a sterile wrap while a nonsterile assistant cuts the stirrups. The nonscrubbed, distal portion of the limb is covered with a sterile towel or sterile Vetrap. A sterile cotton stockinette or adhesive incise drape may be used to cover the entire leg. Finally the limb is passed through a hole in the large sterile drape that covers the entire animal.

After draping is completed, sterile instrument packs, light handles, suture material, and other sterile equipment may be opened. Draped tables and instrument trays are considered to be sterile only on the top of the draped surface, so if part of a sterile item slips below the level of the tabletop, it is considered to be contaminated and should no longer be touched by the surgeons.

OPENING STERILE ITEMS

Nonsterile assistants must open all sterile items for the surgeons. Nonsterile assistants can only touch the outside of sterile packs and should never reach over a sterile field. Large or heavy packs, such as an instrument pack, may be set on a table to be opened. The four folded edges of the outer wrap are opened one at a time, while never extending the hand and arm over the top of the pack (see Figure 28-70, A). If the pack can be placed on a Mayo instrument stand, this can be accomplished by moving around the stand and pulling each fold away from the center. The inner wrap may be opened by the surgeon or by a nonsterile assistant. Once the instrument tray is exposed, the surgeon can pick it up and set it on the draped instrument stand.

A smaller wrapped pack may be opened while holding it in one hand (Figure 28-78). As each corner of the pack is unfolded, it is grasped by the hand that is holding the pack. This prevents the edges of the wrap from contaminating the contents of the pack. The exposed item may be grasped by the surgeon or carefully set on the sterile field.

To open a plastic or paper pouch, scalpel blade, or suture package, the edges of the wrapper should be peeled back slowly and symmetrically, keeping the package opening directed away from the body. Some items may be dropped onto the sterile field; be careful not to lean or reach across the sterile field (see Figure 28-70, B). If the item is small or awkward to handle, the surgeon can grasp it with a gloved hand or sterile instrument. The item should not be allowed to touch the peeled edges of the pouch because the edges are considered contaminated.

Sterile saline may be poured into the sterile saline bowl. To avoid reaching over the sterile field with the saline container, the surgeon may hold the bowl away from the instrument tray or position it on the tray at the edge of the sterile field. The lip of the saline container should be a few inches above the rim of the bowl to reduce the risk of touching it, but not so high that the saline splashes as it is poured. If drapes or gowns (especially those made of cloth) become wet with saline or blood, they may no longer be impermeable to bacteria and are said to have “strike-through.”

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