This text is not intended to cover each and every aspect relating to wounds presented in veterinary medicine. It is, however, designed as a simplified handbook, which will assist members of the veterinary medical team in properly assessing patients and their wounds.
This text is not intended to cover each and every aspect relating to wounds presented in veterinary medicine. It is, however, designed as a simplified handbook, which will assist members of the veterinary medical team in properly assessing patients and their wounds. As you read the following pages, you will find a certain amount of repetition. This is necessary to reinforce key issues and concepts as well as to insure that each section can stand alone as a total reference for that category of wound.
Before examining the management of wounds, it is important to review the fundamentals of wound healing.
Wound healing begins with insult to soft tissue, whether it be surgical or traumatic. This insult sets off a complex sequence of cellular and molecular events, which ends in structural restoration. A fundamental understanding of this process is needed by the veterinarian and technician to provide the necessary environment for normal healing to occur.
Ideally, the goal of wound healing is to fully restore the injured part to its pre-wound condition in a very short time. Unfortunately, this is the exception and not the rule in most of the wounds we encounter. Most healing occurs as a result of epithelial regeneration and fibroplasia. Generally, there is a good compromise between the minimal amount of fibrous tissue needed for structural continuity and tensile strength, and that amount which is excessive and causes beds of granulation tissue, adhesions, strictures, etc. The basic process of this fibroplasia as it relates to wound healing will now be reviewed.
The fibroplastic stage of wound healing occurs in three phases:
* Exudative * Collagen * Maturation
Immediately after insult to soft tissue occurs, whether surgical or traumatic, a state of acute inflammation develops. The insult precipitates the inflammatory response by initiating release of chemical mediators. There are a number of different substances that have been demonstrated or are believed to be important as mediators of inflammation. Some of the familiar ones include histamine, bradykinin, complement, and lysosomal enzymes among others. These mediators bring about the inflammatory response characterized by hemodynamic changes, permeability changes, and leukocytic events. The three events are well underway by two hours. By 8-12 hours, the inflammation has produced an exudate consisting of plasma proteins (especially fibrinigen), polymorpho-nuclear leukocytes, (PMNs), red blood cells, and macrophages. The fibrin clots, and thereby forms an early but very weak bond between the edges of the wound. The numbers of PMNs increase rapidly the first 24 hours but fragment over the next 48 hours. The macrophage population and activity increase between 24 and 72 hours and the cellular debris is phagocytized. Fibroblasts appear at the wound during the first 24 hours and become numerous after 72 hours. In addition to the fibroblasts, newly formed collagen fibrils and numerous capillaries appear. there is a significant increase in the number of fibroblasts at the wound between the third and fifth days. This increase of fibroblasts signals the end of the first phase of healing and the beginning of the second phase.
The collagen phase begins on approximately the fifth day and extends to the fourteenth to sixteenth day. During this time the fibroblasts are laying down collagen. The process of collagen deposition is not firmly understood. It is believed that microfibrils are produced by fibroblasts and that the microfibrils serve as templates for the polymerization of tropocollagen molecules. These molecules then bind themselves in a staggered fashion by cross linkages and chemical bonds in the ground substance to form the collagen fibril. Further aggregation of collagen fibrils into larger fibers produces mature collagen.
At the beginning of the collagen phase, few collagen fibers are present to provide tensile strength. Also, at this time, absorbable suture materials are beginning to weaken and problems can result if excess tension is applied to the wound. This is one reason non-absorbable suture materials are indicated for most skin closures.
By the fifteenth day post-operatively, enough collagen has been laid down to provide approximately the same tensile strength as normal skin. This fact leads to the recommendation of removing most sutures at about the fourteenth day post-operatively.
Once the collagen bed has been laid down, the process of maturation begins. Collagen fibers are turned over and remodeled for weeks to months after the soft tissue insult. During this process, the collagen fibers become thicker and denser, the number of fibroblasts decrease, the fibers develop a definite orientation related to normal tension on wound edges. The scar formed becomes flatter, paler and softens somewhat. It may take months or years for the scar to fully mature.
This stage of epithelial occurs simultaneously with the fibroplastic stage. Most of the strength of wound healing occurs from the fibroplasia stage. This, however, is not the only factor in wound healing. The epidermis serves as a barrier between the body and the environment and is necessary for optimal appearance, function and protection.
This restoration of epithelium begins within hours of the wound. Epithelial cells from the wound margin migrate over the underlying tissues. This initial migration does not show mitotic activity. Mitotic activity is responsible for migration and thickening of the initial layer only after 36 – 48 hours.
There is a period of three to five days after wounding before migratory activity begins across the wound itself. This leads to the suggestion that a bed of granulation tissue is required for epithelialization to occur. In fact, when epithelialization over a defect does occur, the advancing epithelium is bound closely to the bed of granulating tissue. The epithelium advances from each edge of the wound until it meets in the center of the wound with epithelium from the opposite margin. The narrow epithelial covering gradually thickens to result in a flat junction in the line of the wound.
The complexity of healing yields multiple factors interacting for part or all of the healing process. It is not our objective to cover all of them; however, a few of the more important factors are described.
Nutrition. Nutritional factors are probably the most common of all systemic factors which modify normal healing. Protein deficiency has long been known to retard proper healing of tissue. In protein-depleted animals, wound healing time is increased, mature collagen develops more slowly, tensile strength is decreased and spontaneous wound disruption occurs more frequently. It is noted that the amino acid methionine appears to have a sparing effect on wound healing in debilitated animals. Histologically, protein deficient animals produced cellular granulation tissue deficient in collagen fibers. The fibroblasts are arranged irregularly across the wound. There is little difference, however, between wounds in normal animals and those of protein deficient animals on a methionine supplement. Delayed wound healing due to protein deficiency is seen only in severe cases and not with moderate deficiencies.
The presence of chronic anemia has an adverse effect on wound healing as determined by wound tensile strength studies. Uremia induced in the first five days of wound healing causes disruption in every case. After the first nine days, wound healing is not affected by uremia.
In most cases, pituitary, adrenocortical, thyroid and gonadal hormones do not have a specific effect upon wound healing. However, it has been shown that corticosteroids can suppress mitotic activity and the development of tensile strength in the wound. They have the capacity to inhibit not only early phenomena of the inflammatory process but also later manifestations of wound healing. No noticeable impairment of epithelialization in wounds occurs even though dermal elements are drastically reduced.
Wound Trauma. Excessive tissue destruction that is not debrided or is a result of poor tissue handling technique by the surgeon will increase the amount of dead cells in the wound. This results in decreasing the viability of the surrounding tissues and increasing the amount of tissue that the body must remove before eventual healing. The result is increased healing time, decreased tensile strength and increased susceptibility to infection. Careful, meticulous handling of tissue is necessary for a wound to have its best chance for healing. A sharp scalpel should be used for incisions and scissors should be reserved for deep cutting and dissection or where a small amount of crushing is desired for hemorrhage control. Tissue handling with forceps should be done carefully and only with fine toothed forceps such as Adson or other rat-toothed forceps. These forceps hold by separating tissue and not by pressure which results in tissue crushing and cell death as happens with plain thumb forceps. During surgery, tissues should be kept moist and treated with care to preserve viability.
Desiccation occurs when the wound edges are exposed to the atmosphere for too long a period resulting in increased tissue destruction and subsequent delayed healing.
Typically, tissues with a high vascular area heal more rapidly than those areas which are poorly vascularized. This is explained by the need for increased energy by the new tissue, i.e. collagen forming cells have an increased need for oxygen. Blood vascular preservation should be considered in each and every step of any surgical procedure. An example of blood vascular compromise, which many veterinarians fail to realize, occurs during the suturing process. Tight sutures and sutures which incorporate a large amount of tissue can strangulate the tissues and compromise the blood supply.
Invasion of tissues by pathogenic bacteria resulting in infection will always delay or prevent wound healing. The delay can be affected by the virulence of the bacteria, the amount of contamination leading to infection, the degree of hose resistance and the nature of the wound. When infection occurs, there is a mechanical separation of the wound margins and there is an actual cellular disruption by toxins in some infections and vascular interference in others. Management of infected wounds will be discussed later.
When excess bleeding occurs at the wound margins and a clot is formed between the margins, wound healing is delayed. The clot is either absorbed or undergoes liquefaction and remains an excellent medium for bacterial growth. The presence of a hematoma can also cause circulation compromise which can lead to further tissue destruction. The best method of hemostasis is pressure with dry gauze sponges for 45-60 seconds. This will control the majority of the bleeding. Any pumping vessels should be clamped with hemostats ligated with a suture or cauterized.
All foreign materials should be removed. The body reacts to foreign materials and provides a drainage tract to the surface for it. As long as any foreign materials remain, the wound will rarely heal. Non-viable bone is considered a foreign material by the animal's defense mechanisms.
All suture materials constitute a foreign body, however, different suture material produces different body reactions. The knowledge of the types of reactions and their effects upon wound healing is beneficial to the veterinarian. In general, the surgeon wants monofilament suture material or skin clamps for skin closure to provide adequate tension on the wound and to prevent a medium for bacterial growth. Absorbable suture material is required for buried sutures.
The veterinarian is confronted daily with wounds that demand attention. The manner in which these wounds are dealt with may severely affect the outcome of the healing process and the viability and function of the structure involved. This section limits discussion to wounds of the skin and associated soft tissues.
When the veterinarian is presented with a patient with soft tissue insult, he/ she must ask several questions before deciding on the method of repair.
1. What is the condition of the animal? Is the animal in shock and in need of life saving treatment, is the animal toxic, severely ill, anemic, etc.? Wounds may not heal well under these conditions and thus the approach to the case must be different (i.e., permanent buried suture material, support of wound, fluids during surgery, etc.). Therefore, the veterinarian must evaluate the total animal before he begins specific treatment of its wounds. If complications such as the above exist, the veterinarian should stabilize the patient and then treat its wounds. The best surgeon cannot repair a wound on a dead patient.
2. What is the extent of damage that has occurred? Sometimes the smallest wound causes the largest problem. Examine for possible damage to underlying bone and soft tissue structures, including vessels, nerves and superficial organs. Realize that puncture wounds often appear very small at the surface of the skin, but can and often do cause considerable damage that is not always obvious.
3. Where is the anatomical location of the wound? Is there considerable motion of the affected area that would lead to undue stress across the wound? For example, if a wound is located over a joint surface, the normal joint motion can result in tension and suture breakdown. Thus, immobilization with a bandage could moderate this problem.
4. Will the tissue have enough blood supply to survive? Many times wounds may have a skin flap variable in size. A few simple subjective evaluations in regard to the blood supply of the flap can be performed and thus aid in the prognosis of survival. White edges indicate a lack of vascularity and the survival rate is low. However, if the distal edge of the flap is blue, this indicates the capillaries are congested with blood and these flaps have the greatest survival rate. A pink colored distal flap edge has an intermediate survival rate. Another practical test is to blanch the end of the flap with pressure. If there is a rapid return of color, then the flap will probably survive. Research has shown that the width of the flap has no bearing on its survival rate.4
5. What is the duration of the wound? Often the owner will know exactly when the wound occurred. The best time for treatment of wounds is within the first 8 hours. The wound may be contaminated, but not yet infected. Contaminated wounds are considered infected after 8 hours.
6. Miscellaneous considerations:
a. age of the animal; many old animals are compensated chronic interstitial nephritics and the stress of a hospital stay and/or surgery may precipitate renal failure and delayed healing or even death. This is why the author recommends close attention to the renal status of all animals over seven years of age who are hospitalized. Diuresis should be considered in each and every one of these animals.
b. function of the animal; is it a show animal, one that will require a great deal of cosmetic surgery or does the owner just wish a functioning pet?
c. temperament of the animal; will it have to be restrained during the healing phase with the use of tranquilizers, Eliabethan Collars, side braces, etc.?
d. the client; will they follow your instructions and recommendations?
Wounds must first be assessed to determine the manner of healing. The ultimate goal in wound healing is to heal by first intention. As a review, first intention healing is achieved if the wound presented is immediately cleansed and closed. However, wounds will be presented when this is impossible. You may begin to treat the wound so as to allow it to heal by second intention, but once granulation beds are established, surgical intervention is used to promote healing. This process of closing over a granulating bed is described as third intention healing. The least desirable method of healing is by second intention, but there are times that this method may be necessary.
No system of wound classification is complete and all-inclusive. One method of classifying wounds is by cause; that is, punctures, avulsions, lacerations, surgical incisions, abrasions, contusions, burns (thermal and chemical), toxins and crushing. Wounds can be further classified by size and/or the extent of tissue involvement. A planned surgical incision will certainly be expected to present fewer problems than a degloving type injury caused by an auto. Additional factors influencing wound assessment are the extent of contamination and possible infection in a wound. Also important in this assessment is the period of time the wound has been present prior to the time veterinary care is sought.
As a veterinarian, you will want to consider all of the above factors in your assessment of the wound and ultimately, classify the wounds as uncomplicated or complicated, the latter covering both infected or non-infected wounds.
The three basic general considerations of wound care center around cleansing, closing and covering the wound. This is generally referred to as the three "C"s of wound management. In this discussion, wounds will be classified as A) uncomplicated or B) complicated. This type of classification aids the veterinarian in determining the rationale of therapy needed to return the injured skin to maximal function. The return of function must be restored to normal or as close as possible to normal without interference of healing. At the same time, the healing process should not interfere with the function of the injured part. This is the challenge to the veterinarian.
Uncomplicated wounds are those wounds which are planned, relatively simple surgical procedure or unplanned clean lacerations less than 8 hours old. Usually the wounds require a minimum of time and procedures to handle. Your experience and judgment tell you there is an extremely good prognosis or first intention healing.
In any wound management where suturing is utilized, it is important to adequately restrain the animal. Trying to operate on a moving target results in frustrations, an inadequate job and a greater time commitment. General anesthesia is usually the restraint method of choice for most wound suturing.
The management of a simple laceration is accomplished in the following manner. The wound should be protected while the surrounding area is prepared for surgery. A gauze sponge moistened with sterile, water-soluble lubricating jelly is packed into the wound. The hair is clipped around the area and the skin is cleansed with povidone-iodine surgical scrub and rinsed. The gauze packing is then removed and the wound is flushed with sterile 0.9% saline alone or spiked with an aqueous antibiotic or a mild antiseptic solution (not surgical scrub). The area is then surgically draped. Once the drape has been properly placed, the wound edges are excised as necessary to remove dead and devitalized tissue.
The wound edges should be sutured so that strict edge to edge contact is achieved. Slight eversion of the incision is desirable. Skin sutures are placed so that vascular compromise is minimized. This is insured by making certain all sutures are perpendicular to the incision line. The author prefers a simple interrupted stitch alternated with a vertical mattress stitch or sin clamps. This accomplishes slight edge eversion and also helps eliminate suture line tension. A subcutaneous suture is placed if the wound is large and deep.
With the advent of newer suture materials, veterinarians are beginning to utilize different ones in their surgery. The suture material should be selected for the job it is to accomplish. If an absorbable buried suture material is desired, a polyglycolic acid type suture is recommended. These absorbable synthetic suture materials are a significant break-through in suture technology. They are strong, hold knots well and are enzymatically or hydrolytically broken down in the tissues, thus evoking much less tissue reaction than catgut. In the process of re-absorption, an antibacterial agent is released, adding another advantage to the use of this material.
Non-absorbable sutures are many in number ranging from silk to stainless steel wire. The author feels stainless steel wire is the best of the non-absorbables. He uses stainless steel wire for body wall repair when a non-absorbable is required. A swedged-on suture needle is used whenever possible since much less tissue trauma results.
Uncomplicated wounds which have been handled and treated as described previously may not require a dressing. However, the indications for dressing these wounds are to keep them dry and protected and to maintain pressure for dead space obliteration. The principles of dressing wounds will be discussed later.
This category includes wounds which are open at the time of presentation. They usually have a significant amount of tissue damage, destruction or loss. Damage may be superficial or deep. Causes include punctures, avulsions, abrasions, contusions and crushing wounds. There may be a loss of structural integrity as well as soft and hard tissue involvement. Foreign bodies may be present. This type of wound is often encountered in animals hit by cars or involved in fights.
If these wounds can be treated within the first 8 hours after wounding, first intention healing should be attempted if at all possible. The animal is anesthetized and the wound is clipped, cleansed and debrided. Cleansing should be intensive and thorough, since this is the key to achieving a decontaminated wound. The gross dirt, filth and foreign matter can be flushed with slowly running warm tap water. The final flushing should be accomplished with 0.9% saline solution. This final flushing solution can be spiked with aqueous antimicrobial agents or diluted antiseptic solution (i.e. Betadine* solution).
Repair of underlying structures is sometimes necessary. Skin closure in this instance may be difficult or impossible. In these cases, skin flaps may be useful. There are two general types of skin flaps used in veterinary medicine. The first type are those that rotate around a pivot point and the second type are advancement flaps.4, 11 Both of these types can be effectively utilized in veterinary medicine.
If a large subcutaneous dead space is eminent, Penrose drains should be installed and the skin sutured as described. Drains are not only utilized to obliterate dead space and prevent accumulation of wound exudates, but are utilized to aid in the removal of foreign material remaining after wound cleansing. "As a rule of thumb," drains are removed after 4 to 5 days. All wounds which have drains in place should be dressed. The dressing should consist of a non-adherent absorbent pad held in place by a tertiary dressing of your choice. In this instance, the author recommends the use of Telfa dressing covered by a "lift and store" dressing. If an abundant amount of discharge is expected, then the wound should be dressed with a more absorbent dressing system. The dressing should be changed after the first 24 hours and as needed until the drains are removed.
If the wound is over 8 hours old and is grossly infected, necrotic and/or contains ground-in foreign material with loss of skin, second intention healing should be considered. After thorough washing and debridement as described previously, the wound is covered with a sterile wet saline dressing. Hydrasorb dressings are saturated with saline and placed so that they completely cover the wound. It is then covered with a "lift and store" dressing. A tertiary dressing consisting of either a stretch bandage, Kerlix roll or roll gauze is then applied and covered with tape.
All animals in the complicated wound category should be given systemic antibiotics during the initial phase of healing. The author prefers procaine penicillin G at the rate of 50,000 i.u. per pound (s.i.d.) the first two days, dropping to 20,000 i.u. per pound until discontinued. If culture and sensitivity of an infected wound dictates a different antibiotic, the regimen is appropriately changed. If local antibiotics are desired, only aqueous solutions are indicated and these can be placed in the wet saline dressing.
When a healthy granulating bed is achieved (usually in 5-8 days), third intention healing can be attempted. This consists of freshening the wound margins and approximately the skin edges over the granulating tissue. The granulating bed is carefully rinsed with sterile 0.9% saline. It should not be scraped, abraded or mutilated in any way. Third intention healing is the fastest healing possible. Those wounds that cannot be sutured directly can be closed with a cosmetic skin procedure described previously.
If the wound is allowed to heal by second intention, the granulating bed should be covered with a non-adherent Dressing and a "lift and store" dressing depending on the size of the wound. This dressing does not usually need to be changed daily. In some instances only bi-weekly changes are necessary. The end result with second intention healing is a larger scar than either first or third intention. Granulation bed protection is the secret to minimal scar formation.
There are ten primary indications for bandages and dressings: absorption, protection, antisepsis, pressure, immobilization, debridement, packing, information, comfort and esthetics. The aim of this section is to summarize these functions and give indications where and when the veterinarian is most likely to use different kinds of bandages and dressings.
Absorption: The dressing acts as a passageway and storage for wound drainage. This drainage may be serum, blood, purulent exudate or necrotic debris. The aim is to construct a system which absorbs and wicks the exudate up and away from the wound and stores the exudate without allowing strike through to the outside. The contact layer resting next to the wound surface is called the "primary" dressing. It should meet several requirements:
1. It must be sterile.
2. It must remain in contact with the wound and should not be subject to any movement across the wound.
3. It should not adhere to the wound, unless debridement is desired.
4. It should conform to the body surface.
5. It must serve as a passageway for drainage into the storage dressing (secondary dressing) so that it remains dry and does not macerate the skin.
6. It should be non-toxic and non-irritating and should not contain loose material such as powder or lint.
A Hydrasorb dressing soaked in saline is used at times as a primary dressing on open infected wounds; however, this application is used for debriding and redehydration properties and does not fulfill the criteria stated above. Sponges are used as a primary dressing when excessive drainage is anticipated and hydrophilic properties are desired. This material has extremely good hydrophilic properties and will relinquish its absorbed material to a more absorbent secondary dressing such as a "lift and store dressing". This sponge/"lift and store dressing" combination is an excellent dressing system for wounds that have been sutured with Penrose drains in place. Do not use this system on large open surface wounds since the sponge or other gauze-like materials will stick to the wound surface.
The "secondary" dressing component is the absorbent, collection and storage layer.
It must be thick enough to accomplish the job demanded of it and should prevent strike through to the outside of the pad.
For most granulating wounds and sutured wounds without excessive drainage, a combined primary and secondary dressing such as an ABD pad or Hydrasorb are excellent dressings to use. This combination dressing is constructed of a Wet Pruf pad (lift and store) covered with a Telfa sheet. The Telfa sheet is non-adherent and thereby, will not stick to the wound and disturb healing tissues. The pad portion absorbs and stores the wound drainage. However, it is constructed with a wet proof feature so that strike through is prevented. The tertiary component is the outside layer and will be discussed later.
Dressings serve to protect the wound from further trauma, the environment and contamination. The ABD pads not only protects the patient from itself (if fluids can't strike through the dressing, it remains dry on the outside and the animal won't lick it), but also protects the wound from external contamination by helping prevent urine and feces from absorbing through to the wound.
The use of local antibiotics is controversial. It has been shown that some antibiotics harm the cells and interfere with healing. 12 However, aqueous antibiotics associated with wet saline dressings in infected or heavily contaminated wounds may be indicated. Also diluted antiseptic solutions (i.e. diluted povidone-iodine solution – not soap) in wet saline dressings may be used to help control infected wounds. All non-water soluble antibiotic ointments under the dressing should be avoided.
The bandage may exert a slight amount of pressure upon the wound. This is beneficial in reducing the amount of transudate collected in dead space and controlling a minor amount of bleeding, thereby reducing the possibility of a seroma or hematoma which become an excellent culture media for bacteria. The pressure of the bandage will not have much of an effect on the formation of the exudate which is due to the inflammatory process. It is vitally important to remember that excess pressure from the bandage is dangerous. The potential is present to impair arterial inflow, venous and lymphatic out-flow and possibly impinge upon nerves when applying the bandage. Because of these potential problems, the use of a bandage that has two-way stretch is recommended. Daily check distal to the bandage for swelling, coolness, dryness and odor, and have the client do the same. If any change is detected, remove the bandage and assess the situation. Completely bandaging the distal extremities prevents monitoring the degree of pressure exerted by the bandage and therefore is not recommended.
Immobilization places the wound at rest, thereby decreasing the amount of pain present and allows healing to occur without disruption from mechanical trauma. Also in heavily contaminated wounds, the spread of bacteria through non-involved tissue planes is minimized. Reduction of motion also decreases the amount of scar tissue formation. Inadequate immobilization with tendon laceration is common and should not be overlooked.
Wet wound dressings are indicated to decrease the viscosity of the thick wound secretions thus aiding in their removal. The use of wet saline gauze dressings to rid the wound of surface debris is biologically sound. Heating the wet dressing before application produces a more physiological and comfortable environment. The use of hot wet dressings not only stimulates blood flow in underlying tissues but also helps remove wound by-products, and accelerates the local enzymatic processes. Moist heat penetrates to soften hardened tissues and liquefy purulent material to aid in suppuration. Another advantage of using wet saline debriding dressings is that one may saturate the dressing with an agent that is either bacteriostatic or bactericidal.
The wet saline dressings or Hydrasorb soaked in saline are changed as frequently as necessary but should always be covered with an ABD "lift and store" pad. Dressings in general should be removed when they become dry. Excessive necrotic debris on the dressing indicates a more frequent change. As soon as there is no necrotic debris and a minimum of serosanguineous exudate from the wound, it is more efficient to switch to a non-adhering dressing which can be left on for longer periods of time such as a ABD Wet Pruf pad or Hydrasorb.
A disadvantage of wet dressings is skin maceration. If this begins to occur, the dressing should be changed more frequently and stopped as soon as possible.
Deep infected wounds can be packed with antiseptic-soaked (i.e. diluted povidone-iodine solution) gauze. This allows deeper tissues an opportunity to heal and provides an exit for necrotic, purulent debris. Wound packing should be removed a little at a time each day and should not be left in after the infection is under control since it may interfere with wound healing.
Applying a comfortable bandage is quite helpful in keeping the bandage on the animal. The tertiary bandage component is very important since it constitutes a major factor in achieving comfort. The degree of elasticity, if applied properly, can help obtain this comfort goal. Only experience will yield insight into applying a comfortable bandage. Also, care should be taken in changing bandages to minimize patient discomfort and ill feelings. If comfortable, the patient will seldom bother a dressing.
Dressings give information regarding the nature and amount of secretions being produced by the wound. Smell can also be used as a reference to the progression of the wound. Too often, dressings are hastily removed and discarded without careful observation.
By knowing the different functions of dressings, the selection of the right dressing for the current condition of the wound is made with greater ease. The method of choosing and applying the preferred dressing will determine whether desired or harmful results are obtained. Only nature can heal wounds, but veterinarians have the knowledge to properly assist nature for optimal healing to occur.
Primary bandage layer, open wounds:
There are three main types of primary or contact bandaging: adherent, non-adherent semi-occlusive, and non-adherent occlusive.
• Adherent material has wide mesh openings and no cotton filler. A prime example is Versalon. Because the mesh traps loose necrotic tissue and foreign bodies and allows exudate to pass into the absorbent secondary layer and dry, such a bandage can be used on wounds that are not completely debrided. The advantage is that each time the bandage is removed it takes with it adherent necrotic tissue, foreign debris and crust or scan, thus aiding in debridement. The disadvantages include painful removal, viable cell injury, tissue desiccation in dry environments, and tissue maceration or bacteria movement toward the wound from the outer surface if the bandage is too wet.
Adherent material primary bandages are commonly dry-to-dry or wet-to-dry dressings. Use dry-to-dry dressings on wounds with much low-viscosity, non-aggregating exudate. Remove them when the fluid has been absorbed by the primary and secondary layers and dried.
Wet-to-dry dressings are indicated for wounds with viscous exudate, with the gauze either soaked in a sterile saline or 1:40 dilution (0.05%) of chlorhexidine diacetate* wetting solution or place dry sterile gauze on the wound and spray on or pour on the wetting solution. This will dilute the exudate, which will then be absorbed by the bandage layers, and when dry, will be removed with the bandage. (Note that this 0.05% chlorhexidine concentration may not be sufficient for heavy pseudomonas wound infections, yet 0.1% to 0.5% solutions may retard granulation tissue development.)
Change all adherent material dressings at least every day. For patient comfort, moisten the primary layer with 2% lidocaine before removing it.
• Non-adherent semi-occlusive materials are those that stay moist enough to keep tissue from dehydrating and aid epithelialization, yet allow absorption of excess fluid that could cause the wound to macerate. A prime example is Hydrasorb Foam Sponge, a non-adherent, semi-occlusive and highly absorbent bandage equal to the ABD Pad in providing a moist environment for healing. (Note that they are often used in conjunction with Telfa dressings.) These materials replace the need to autoclave gauzes with petrolatum or other solutions to make them non-adhesive, a process that can produce variable impregnation results.
Non-adherent semi-occlusive materials are indicated as a primary bandage for reparative healing wounds with granulating tissue beds, serosanguineous exudate and epithelialized edges. Cover the primary layer with an absorbent secondary layer and a porous tertiary layer. Leave the bandage in place for one or two days, depending on wound drainage.
• Non-adherent occlusive materials are available with a hydrocolloid material on one side that adheres to the skin around the wound, but that over the wound itself absorbs fluids to become a non-adherent occlusive hydrocolloid gel. These bandages are indicated for covering repair stage healing wounds with existing granulation tissue beds, advanced contraction, decreased fluid flow and early epithelialization.
To use hydrocolloid materials, clean and dry the skin surrounding the wound and gently wipe the granulation bed with an antiseptic solution. Warm the dressing package in your hands to soften the material so it will conform to body contours then cut it to the required size and shape. Remove the covering, center the dressing over the wound, and gently press the edges so they adhere to the skin.
Leave the dressing in place for two to three days or until its surface feels like a fluid-filled blister or gel begins to leak. After removing the dressing, wipe the gel from the wound and skin, and apply another dressing unless epithelium covers the wound, in which case the dressing should be discontinued.
Primary bandage layer, closed wounds:
Indications for the primary or contact layer for closed wounds are similar to those for open wounds. When the wound has little or no drainage, a non-adherent dressing displaying some absorptive properties is indicated, such as Hydrasorb Foam Dressing or ABD Pad.
A multipurpose wound dressing:
Non-woven pads made from calcium alginate such as Curasorb* Wound Dressings offer advantages in many different applications including granulating wounds, hemostasis of capillary bleeders, and as a replacement for gel foam in dentistry. Calcium alginate is a natural fiber derived from certain seaweeds. It has strong hydrophilic properties and upon contact with wound exudate will form a soft colloidal gel which covers the wound, protects it, provides mechanical hemostatic action, and enhances formation of granulation tissue and subsequent healing. It does not react with antibiotics or other anti-microbial agents. Curasorb can be easily removed from a wound by irrigation with normal sterile sale, phosphate buffered saline, or 1% sodium hexametaphosphate. This reduces the pain, trauma, and disruption of healing tissue compared to dressings which form an integral matrix with the granulation tissue.
* Trademark of The Kendall Company, Mansfield, MA
This chapter will discuss a quite often misunderstood member of the dressing family, the outer covering or securing agent, the tertiary bandage. Although Webster defines tertiary as "the third in a series," this may or may not be true about tertiary dressings depending on what dressing has been chosen to immediately cover the wound and into what classification the wound has fallen. However, for all purposes, a tertiary bandage is the outer material used to secure the other dressings in place. This bandage material is most often either a surgical adhesive tape or some sort of a gauze bandage roll.
A familiar type of tertiary bandage is the gauze roll. This product is wrapped circumferentially around the patient and is designed to:
1. Hold the other dressings securely in place.
2. Apply mild pressure without constricting.
3. Provide extra cushioning and protection.
4. Immobilize a portion of the patient's anatomy.
There are three major types of bandage rolls – 1) gauze roll or stretch gauze – this is a simple roll of a few plys of normal flat gauze. It is traditionally coarse in texture, quite linty and has no true stretch as we will describe in a tape discussion later. Therefore, this product could cause constriction if swelling has not reached its peak before it is applied. If it is applied while swelling is present and the swelling goes down, the dressing normally becomes loose and is either chewed off or falls off. However, this type of product is effective when used to immobilize a portion of the anatomy or for strapping broken ribs.
Conform stretch bandage:
This product is constructed of synthetic fibers (almost completely eliminating lint) and specially knit, giving it a generous but mild two way stretch. It performs well as a tertiary bandage because it applies mild pressure, yet reduces constriction because it also pulls back as well as stretches out.
Kerlix bandage roll:
This is a special material which has been washed and crinkle-dried resulting in a much softer, loftier and bulkier bandage than gauze. this product performs very well when you want to achieve additional cushioning and protection, maximum conformability and immobilization of a part of the anatomy.
Surgical adhesive tapes:
All too often one type of surgical tape is used to secure all types of dressings. As with the failure of the "one size fits all" concept, the "one surgical adhesive tape for all jobs" theory also fails. There are traditionally five types of tapes: porous, waterproof, elastic and paper and cloth hypoallergenic. The first three find extensive use in veterinary medicine.
Standard porous tape:
The primary feature of this tape is that it allows air to pass through freely. For the average wound, this is not only desirable but is essential. A wound must breathe in order to promote dryness and quicker healing. If a dressing is covered by a non-porous material, it will prevent the wound and adjacent skin from breathing freely and, thus, promote dampness and subsequent skin maceration. Therefore, for most wounds, where the choice for securing the dressing is surgical adhesive tape, a porous tape should be used.
Wet pruf tape:
Occasionally, there will be situations where protecting a wound site from outside moisture is desirable such as bandaging for the treatment of hoof rot or in bandaging horses' legs, etc. Doing a meticulous job cleaning, closing and covering can be negated by choosing the wrong tertiary dressing. In the case of hoof rot, to tape the hoof with a porous tape will only allow water to penetrate and saturate the dressing and promote rather than heal the problem. Therefore, when protecting the wound site from outside dampness is your top priority, a waterproof tape should be used.
Conform Elastic Adhesive Tape:
This is the most widely used but possibly the most misunderstood of the adhesive tapes. Conform tape applies a mild pressure to the wound site because of its elasticity. Of course, because elastic not only stretches out but also pulls back, it is an excellent choice for:
1. Applying mild pressure to a wound site, if used circumferentially.
2. Taping over joints where you wish to achieve conformability, mild pressure and do not want to restrict movement.
3. Situations where you are concerned with swelling or insuring a snug fitting dressing after swelling recedes.
Remember, to achieve true elasticity, the tape must not only create a tensile strength stretching out, but must have constant tensile strength pulling back. If this two way stretch does not exist, you chance constricting the limb or of having the dressing become loose. In summary, choosing the proper product for the specific patient need will greatly improve your patient's recovery time. The tertiary bandage is a very essential part of total wound care. The key questions must be asked before choosing a tertiary bandage are:
1. Do I want to promote or restrict mobility?
2. Is there or will there be swelling associated with this wound; if so, will my dressing of choice compensate safely for this condition?
3. Do I want this wound to breathe or is it more important to keep it protected from outside dampness?
4. Do I need to add additional cushioning and protection?
The application of the tertiary bandage of your choice will complete the covering portion of your wound management program. The proper choice at this critical stage patient care could either enhance or defeat all of the prior steps taken to this point.
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