Vett 111 Week 8 - Notes

The three phases of wound healing are

Inflammatory, proliferative, and maturation Distinct characteristics overlap in the time line of healing

Degloving Injury

Injury - typically to the distal limb - in which a large section of skin is torn off the underlying tissue in a glove-like fashion

Skin forms an important protective barrier against

Insults from the environment

Velpeau Sling

Non-weight-bearing forelimb sling that flexes the entire limb; primarily used for medical shoulder luxation

Bite Wounds

Often cause extensive injury to deeper tissues that is not apparent on inspection of the skin due to skin's elasticity. Along with tissues being crushed and lacerated, bite victims are often shaken, which adds to separation of tissues and creation of dead space. Always considered contaminated Management includes exploration, lavage, and debridement. Type of closure depends on the ability to remove contaminated and damaged tissue. Drains are commonly used in bite wounds with extensive dead space Projectile injuries (e.g., bullets) and impalement injuries (e.g., sticks) are treated similarly

Degloving Injuries

One in which a large section of skin is torn off the underlying tissue in a glove-like fashion. Common in dogs that jump off or fall out of a moving vehicle and are dragged along the pavement Can lead to severe loss of tissue, usually involving the distal limbs. Abrasion of bones and exposure of joints are also common. Require weeks to months of wound care - tend to be heavily contaminated with foreign debris and have varying amounts of devitalized tissue Aggressive wound lavage and debridement precede granulation tissue formation. Because of lack of loose skin for wound contraction, large defects require skin graphing.

Contraction begins about ___ after injury and cal last for ___ weeks

One week / Several

Wound Factors Influencing Wound Healing

Origin of wound - surgically created tends to have much more predictable healing compared to traumatically induced Contamination of wound (including suture or drains) Increased production of wound exudate - leads to fluid accumulation within tissues and separation of tissue planes, further hindering wound healing Tension on wound edges or movement of surrounding tissues will interfere with proliferative phase

Tertiary Layer of Bandage

Outer, protective layer which keeps the other layers in place, and determines the appropriate amount of pressure and support to be applied. This final layer must not be occlusive, or moisture will accumulate within the bandage

Collagen

Proteins that make up most of the skin, bone, cartilage, tendons, and other connective tissues

Primary intention wound healing

Healing of a wound across a surgically closed incision

Second Intention Healing

Healing of a wound by granulation tissue formation, epithelialization, and contraction

Third Intention Wound Healing

Healing of a wound that has already formed granulation tissue and undergone secondary closure

Luxation

A joint dislocation, also called luxation, occurs when there is an abnormal separation in the joint, where two or more bones meet. A partial dislocation is referred to as a subluxation.

Non-occlusive

A state in which the teeth of the upper and lower mandibles do not mesh with one another Not impermeable to moisture

Wound Infection

A wound is considered infected when the bacterial count is greater than 100,000 (10^5) organisms per gram of tissue Signs: Swelling, heat, redness surrounding tissue Healthy wounds may exude serosanguineous clear fluid Discharge from infected wounds can be copious and of varying consistency, color, and odor. With severe infection, systemic signs such as lethargy, pain associated with wound, and changes in appetite and drinking may occur. Signs of infection should resolve within 2 - 3 days of treatment

Secondary Layer of Bandage

Absorbs and holds exudate (if present) and provides some immobilization and support. If a large amount of exudate is produced, the secondary layer must be thicker to allow absorption of fluids into the bandage without causing strike-through into the tertiary layer

Patient Factors Influencing Wound Healing

Age - concurrent health problems that may alter healing capabilities Chronic viral infections & Endocrinopathies - delay wound healing / Diabetes mellitus - alters tissue perfusion and release of oxygen / Hyperglycemia - interferes with defense against infection Orthopedic & Neurologic - may lead to periods of prolonged recumbency Poor nutritional status delay wound healing and alter wound strength Obesity - Associated with increased risk of wound infection and dehiscence because decreased vascularization of fatty tissue leads to a decreased capacity for healing

Semi-occlusive

Allowing air and moisture through. Used in reference to bandage materials. A semi-occlusive primary layer is used for moist wound healing

Abrasions

An area of skin that has been superficially scraped, creating a wound - also, tooth wear associated with chewing on objects such as rocks, ice cubes, toys, and bones Partial-thickness dermal wounds that are common in animals after vehicular injury Due to preservation of parts of the dermis, these wounds heal well by re-epithelialization Maintaining a moist wound environment will speed epithelialization and is preferred.

Immediate Wound Care

Apply a water-soluble lubricant to catch hair falling into the wound / Use scalpel blade or scissors to carefully shave hair from the wound edges Gently clean surrounding skin with antiseptic, but avoid applying soap to the wound, because it is cytotoxic to the cells. Lavage to remove any water-soluble lubricant and, more important, any foreign or loose necrotic debris (8 - 12 pounds per square inch)

Modified Robert Jones Bandage

Bandage similar to a Robert Jones Bandage but with a much thinner secondary layer

Principles of Bandaging

Bandages are applied for two main reasons: Management of soft tissue wounds and stabilization of bone and joint injuries - postoperative bandages help to decrease hemorrhage and edema, eliminate dead space, increase patient comfort, and protect the wound from the patient and the environment Three layers of bandages: Primary, secondary, and tertiary

Casts & Splints

Casts are used to provide stability for joint injuries or fractures, for temporary support until surgery, as a means of definitive treatment, or as an adjunct after surgical stabilization Only used for injuries below to elbow or stifle joint Encircle the entire limb - casting tape is overlapped 30% - 50% over a Modified Robert Jones Bandage, being careful not the touch the skin Bivalving insists of using an oscillating cast saw to create halves, which are kept together by elastic gauze or tape - recommended in case of the need for fast removal of cast in an emergency, although it weakens stability of cast. A variety of prefabricated splints made of plastic or aluminum are available (lateral and spoon splints) - fiberglass casting tape or thermoplastic material can also be used to make custom splints Most forelimb splints are applied to the caudal limb surface - rear limb splints are applied laterally, unless only the metatarsi and foot are splinted (caudal splint) Schroeder-Thomas splint - immobilize distal femoral fractures that otherwise were not able to be bandaged. Suspends the limb in a rigid metal frame fashioned to match the outline of the leg - NOT RECOMMENDED to treat fractures because it causes muscle contracture with permanent loss of limb function Spica Splint - maintains forelimb or pelvic limb in extension through application of a soft-padded bandage and addition of a strong lateral support splint that curves over the shoulder or pelvis. Most commonly used in forelimb after elbow luxation reduction. Prolonged immobilization must be avoided to prevent muscle contracture and joint damage

Fibroblasts

Cells that are recruited into a wound during the proliferative phase of wound healing that help form granulation tissue

Burns

Classified on the basis of how deep into the tissues the injury reaches and how large the affected area is. Can be caused by accidental or deliberate injury in the animal's environment, most often caused by accidental inappropriate use of heating blankets, lamps, hair dryers, and poorly grounded electrocautery units. First-Degree Burns: Superficial and are confined to the outermost layer of the skin - skin will be reddened and painful but recovers in a few days without treatment Second-Degree Burns: Result of partial-thickness dermal injury, and may form fluid-filled blisters or show discoloration of part of the dermis, similar to third-degree. Full extent of damage may not be known until several days after injury. Can often be managed by second intention healing with re-epithelialization Third-Degree Burns: Full-thickness injuries characterized by a thick, leathery, often black layer of dead dermis (eschar). Treatment requires removal of the eschar and wound debridement. If left to heal by second intention, these wounds must contract and re-epithelialize. Larger burns may require skin grafts to cover the defect. Fourth-Degree Burns: Involved deeper tissues apart from the dermis and require surgical reconstruction if large Animals with extensive burns are critically ill and require intensive care to survive

Active drains

Closed-suction drains Work by creating a vacuum within the wound and allowing wound fluid to be removed via a rigid fenestrated drain into an external collection container More expensive than passive Play an important role in management of more extensive wound

Wound exudate

Combination of WBCs and fluid leaked from blood vessels and lymphatics

The first objective must be to prevent further ___ of the wound while avoiding contamination of the ___ with pathogens from the wound

Contamination / Environment

Wound healing is a ___ process that starts at the ___ of injury and lasts up to ___ thereafter

Continuous / Moment / Months

Wound Drainage

Depending on quantity of wound exudate and disrupted soft tissues causing dead space, passive or active wound drains may be used in conjunction with wound closure Dictated by location of wound and amount of drainage Removed when amount of wound fluid decreases (usually around 3 - 5 days) because simple presence of a drain will stimulate some fluid production

Decubitus Ulcers & Pressure Sores

Develop over bony prominences as the result of skin compression on hard surfaces during long periods of recumbency Patients with orthopedic or neurologic problems, extremely obese animals, and large and giant breeds with little soft tissue coverage over these bony prominences are at a particular risk. Most common location: elbow (lateral or caudal surface of the olecranon) Prevention includes housing on soft, clean, and dry surfaces. Use of pressure-relieving sleeves. Rotating recumbent patients periodically. Surgical closure usually fails if wound continues to be exposed to the surface - advanced reconstructive surgery is required in large ulcers that have failed to respond to conservative treatment Inappropriate or prolonged periods of bandaging can need to pressure necrosis of the skin (olecranon, calcaneus, and bony prominences of the feet) Prevention: do not add more padding to susceptible areas - use doughnut shaped bandage material. Signs include reddening of the skin with hair loss. White, purple, or black color changes indicate severe damage to the dermis, which usually leads to sloughing and an open wound Most pressure sores are treated by second intention healing after the splint or cast has been modified or removed

Bandage, Cast, Splint, and Sling Application in Small Animals

Distal Limb Bandages are often applied to protect wounds and stabilize bone or joint injuries Casts, Splints, and Slings are used to provide further stability to orthopedic injuries or to prevent weight bearing Only injuries below the elbow or stifle joint can be effectively immobilized.

Robert Jones Bandage

Distal limb bandage for which a large amount of rolled cotton is used; aids in immobilization of fractures. Rigid material can be incorporated into this bandage

Slings

Ehmer Sling - non-weight-bearing sling applied to pelvic limb to protect the hip joint after injury. Used primarily after closed reduction of craniodorsal hip luxation and selectively after surgery associated with coxofemoral joint - will internally rotate and abduct femur, forcing femoral head into the acetabulum and maintaining reduction. Broad elastic tape is used to make a "figure-of-eight" loop around the stifle and hock while both joints are held in flexion and hock is externally rotated - tape may be wrapped around abdomen in rare occasions to reduce movement at hip joint. To prevent slippage of the sling over the cranial aspect of the stifle joint, care must be taken to apply adhesive tape as far proximally on the femur as the flank fold will allow. Irritation can occur around flank fold and inguinal area because of the tape. Limb must be inspected daily due to chance of swelling of the foot (sling must be altered or removed if swelling occurs). Non-weight bearing slings should not be maintained for longer than 2 - 3 weeks to prevent muscle and joint contracture. 90/90 Flexion Sling - non-weight bearing sling that consists of a simple loop of adhesive tape wrapped around the stifle and hock while both joints are held at about 90 degrees of flexion - applied immediately after repair (critical in puppies after repair of distal femoral fractures - prevents quadriceps tie-down or contracture by keeping affected muscles stretched) and maintained for 2 - 3 days until post-operative pain and swelling decrease Velpeau Sling - non-weight bearing sling for forelimb that is used to immobilize all joints of the affected leg. Mainly applied after reduction of medial shoulder joint luxation or after reconstruction of tenuous fractures. Forelimb is flexed and brought up agains the thoracic wall, soft-padded bandage is applied to keep it in place. Care must be taken not to impair breathing as this bandage encircles the chest Carpal Flexion Sling - non-weight bearing forelimb sling that is applied with the carpus in flexion. Prevents weight-bearing, allows movement of elbow and shoulder joint. Can be used to relieve tension on carpal flexor tendons after injury or surgical repair - if used for inappropriate length of time, contracture of carpal flexor tendons is possible. Hobbles - prevent abduction of the pelvic limbs and are used after reduction of ventral hip luxations. Can be applied at level of stifle joints or at metatarsi - May not protect entirely against reluxation and patients must be supported with an abdominal sling and kept on non-slippery flooring.

Moist Wound Healing Environment

Enhances cell migration and cleanup and is preferred over allowing a wound / scab to dry out

Any scabs covering a wound are ___ underneath until the scab falls off

Epithelialize

Exuberant granulation tissue

Excessive formation of vascularized fibrous tissue (granulation tissue) in an open wound. Granulation tissue is considered exuberant when it grows above the level of the skin - Also referred to as proud flesh

Inflammatory Phase

First phase of wound healing - characterized by formation of a blood cloth within the wound, release of growth factors, and recruitment of macrophages and neutrophils to clean up the wound and to modulate healing Begins immediately - lasts for three to five days As injury occurs, blood is released into the wound via the injured blood vessels Platelets aggregate and form fibrin clot within wound (aids in control of bleeding and stabilizes wound edges), clot also allows growth factors to be released as part of clotting cascade. Within a few hours, wound microphages and neutrophils are recruited and modulate wound healing by releasing more growth factors - help to remove bacteria and cellular debris from the wound Often called lag phase - wound strength is at its lowest

Carpal Flexion Sling

Forelimb sling used in small animals that flexes the wrist joint and is used to protect flexor tendon repair and prevent weight bearing while allowing movement of the elbow and shoulder

Spica Splint

Full-limb bandage, including a lateral splint that reaches over the shoulder or hip that is used to aid in immobilization

Passive drains

Function by allowing fluid flow along the drain surface as a result of capillary action Must exit in a dependent location so that fluid can gravitate toward the exit skin incision Must be covered with sterile bandage while in place - provide a direct avenue for ascending infection

Hypertonic

Having an osmolality higher than that of blood

Isotonic

Having the same osmolality as that of blood

Occlusive

Impermeable to moisture - used in reference to bandage materials. An occlusive primary layer is used for moist wound healing

Non-adherent Primary Layer

In direct contact with wound bed but does not adhere to it. Used once granulation tissue has formed or epithelialization has begun, to protect and promote second intention would healing Semi-occlusive non-adherent primary layer is permeable to air and fluid and allows exudate to be absorbed by the secondary layer An occlusive non-adherent primary layer is impermeable to air and retains moisture (primary layer of choice) Much less painful when changed and allows longer intervals between bandage changes once the wound is in the proliferative phase Moist wound healing environment enhances cell activity and improves granulation tissue formation and epithelialization.

After Care for Bandages, Splints, Casts, and Slings

Length of time that a bandage should be on depends on the underlying condition Prolonged immobilization leads to muscle atrophy, contracture of soft tissues, and joint changes; therefore, any type of bandage should be removed as soon as possible. Bandage changes are required because complications under the bandage are not obvious, often once or twice a day - once healthy granulation tissue occurs or the wound is in the epithelialization phase, bandage changing can be decreased to every 2 - 3 days. If there is no wound (fracture, joint injury) the bandage should be changed weekly. Limit exercise to short bathroom walks on a leash until bandage is removed - activity poses a risk for shifting of bandage, development of chaffing or sores, and complications during healing Monitor of distal limb bandages include daily inspection of toes for swelling (increased distance between toenails) or decrease viability (decreased warmth or abnormal color) Bandage must be kept dry and clean when the animal goes outside Elizabethan collars might be necessary to prevent animal from chewing on the bandage Watch for sudden behavioral changes such as increased lameness, biting at the limb, and also foul odor from the bandage, which could indicate that complications are occurring. Good Client Education is highly important

A ___ infection rate is seen with moist wound healing

Lower However, bacteria may be trapped underneath the occlusive layer if it is not applied correctly and changed at appropriate intervals

Moist Wound Healing

Maintaining a moist wound environment by using an occlusive or semi-occlusive primary bandage layer

Extracellular matrix

Meshwork-like substance attached to the outer cell surface that provides support and anchorage

Primary Layer of Bandage

Most important for wound protection and healing because it directly influences the wound environment - may be adherent or non-adherent and may be non-occlusive, semi-occlusive, or occlusive. Type depends on phase of wound healing and the amount of exudate present.

Ehmer Sling

Pelvic limb sling used in small animals that prevents weight bearing and helps force the femoral head into the acetabulum by abduction and internal rotation of the femur

Inguinal

Pertaining to the groin area

Healthy granulation tissue is ___ in appearance because of the abundance of capillaries; poor quality granulation tissue is ___ because of lack of appropriate blood supply

Pink / Pale

Decubitus Ulcers

Pressure sores (bed sores) that develop when an animal lies on a bony prominence for too long

Wound closure has to occur before granulation tissue has formed to be called ___

Primary closure

Non-adherent Dressing

Primary layer that does not adhere firmly to the wound surface

Second intention wound healing refers to

Process of healing by contraction and epithelialization. Except for surgical debridement, surgical closure is not performed Often performed in areas with little skin (e.g., distal limb). Can produce contraction over joints, muscles, or tendons with impaired function and may not be desirable. Newly epithelialized wound is often friable and easily traumatized.

Epithelialization

Process of wound coverage by epithelial cells during the final stage of the proliferative phase of wound healing Usually begins 4 - 5 days after the injury and occurs from the wound edges, moving toward the center. Cells advance in a single layer across the wound until they meet in the middle New epithelial cells are formed at the wound margins to replace keratinocytes and supply more cells for migration, thereby thickening the epithelial layer New epithelium tends to be friable and to bleed easily

Concurrent Treatment Factors Influencing Wound Healing

Radiation therapy - can lead to tissue fibrosis and vascular scarring Certain types of chemo therapy - can suppress bone marrow function and decrease resistance to infection Corticosteroids - decrease body's inflammatory response and delay all phases of wound healing

Re-epithelialization

Regrowth of epithelial cells over a wound. Cells advance in a single layer across the wound until they meet in the middle when migration stops as the result of contact inhibition

Debridement

Removal of foreign matter and dead tissue from a wound Goal: removal of obviously contaminated, devitalized, or necrotic tissue and elimination of foreign debris from the wound Surgical debridement: under anesthesia under aseptic conditions - fastest and most effective. Careful wound exploration is performed, enzymatic agents can be used to break down debris Mechanical Debridement: using an adherent primary bandage layer (wet-to-dry) can be performed for initial management of highly contaminated wounds. Wet-to-dry can cause several undesirable effects. Maggots of a special fly may also be used.

Distal Limb Bandages

Robert Jones Bandage can be used to temporarily immobilize limbs distal to the elbow or stifle joint - relies on extremely thick secondary layer (sounds like a ripe melon when tapped, once finished). Not often used in small animals Modified Robert Jones Bandage - most commonly applied to distal limb of small animals - uses much thinner secondary layer and is often referred to as "Soft-padded Bandage". Tertiary layer must not be overly tightened or pressure necrosis may occur.

Proliferative Phase

Second phase of wound healing; characterized by invasion of fibroblasts, formation of granulation tissue, deposition of collagen, epithelialization across healthy granulation tissue, and wound contraction by myofibroblasts Overlaps with the inflammatory phase Begins 2 - 3 days after injury and can continue for several weeks depending on size and type of wound Marked by fibroblasts and endothelial cells entering the wound. Growth factors released into the wound stimulate proliferation and recruitment of these cells, as well as production of an extracellular matrix As cells migrate into the wound, new vessels are formed by angiogenesis to supply oxygen and nutrients to newly forming tissue Granulation tissue begins to fill the wound 3 - 5 days after injury, creating a barrier against infection and a surface for re-epithelialization - consists of myofibroblasts, endothelial cells, inflammatory cells, and new blood vessels, all connected by extracellular matrix Fibroblasts deposit collagen into the wound, increasing wound strength Fibroblasts decrease in number and are replaced by tissue rich in collagen once granulation tissue covers the wound bed. Epithelial cells can migrate across healthy granulation tissue to reestablish a barrier between the wound and environment. Once keratinocytes cover the wound, a new basement membrane is formed and cells begin to differentiate to re-epithelialize skin. Wound contraction of the full-thickness skin edges occurs as a result of contraction of myofibroblasts within the granulation tissue. It helps reduce the size of the wound, sometimes considerably.

Lacerations

Sharp cut or tear through skin and possibly deeper tissues Produced by tearing of skin and deeper tissues. Tissues are relatively sharply incised and trauma to surrounding area is minimal Fresh lacerations with minimal contamination can be lavaged, debrided, and closed primarily. More chronic lacerations can be excised en bloc and closed primarily if small enough. Secondary closure may be performed if wound is heavily contaminated

Dead Space

Space between tissues created by a wound, allowing accumulation of fluid

___ of the patient must take precedence over any definitive wound care

Stabilization

Primary Closure

Surgical closure of a fresh, clean wound, leading to primary intention healing

A ___ ___ ___ should be applied quickly to protect the wound until it can be properly managed

Temporary clean bandage

Contralateral

The opposite side

Maturation Phase

The third and final phase of wound healing - During this phase collagen fibers remodel and align, and there is a final gain in wound strength Final phase of wound healing - begins approximately 3 weeks after injury, continuing for weeks to months, even years. Characterized by remodeling and realignment of collagen fibers along tension lines. Wound tissues gain the most strength during this phase, but will never be as strong as normal tissue.

Myofibroblast

The type of fibroblast with contractile properties similar to those of smooth muscle cells, which are responsible for wound contraction

Bandages for other locations

Tie-over bandage can be applied to locations on the body where traditional limb bandages cannot be used or would be impractical - axillary and inguinal areas, around the pelvis. Uses suture loops that encircle wound edges and are used as anchor points for bandage material. Wound is covered with protective primary and secondary layer. A protective tertiary layer is used to cover the bandage - layers are then held in place by strands of large suture or umbilical tape that crisscross over the bandage from one suture loop to another - skin suture loops are maintained while umbilical tape is cute for removal of bandage. Adhesive drapes can be used instead of tie-over skin sutures to hold primary and secondary layers in place Three-layer soft padded bandages - encircle the respective body part (head, chest, abdomen, tail). Elastic materials can be used to hold primary and secondary layers in place Head-bandage: applied immediately after surgery with the animal still under general anesthesia. Must monitor for respiratory compromise due to bandage or corneal abrasions "Figure-of-eight" bandages around the abdomen must ensure that urination and defecation are not impaired Tail bandages often require a small strip of adhesive tape applied to the skin at the proximal end to keep the bandage from slipping off

Modified Thomas Splint

Traction splint constructed of rods; used to stabilize long-bone fractures in large animals

External Coaptation

Use of rigid external devise such as a bandage, splint, or cast to align fractures

Granulation tissue

Vascularized fibrous tissue that covers a full-thickness skin wound if the wound is left to heal by second intention

Adherent Primary Layer

Wet-to-dry bandage uses an adherent primary layer for nonselective debridement Moist, sterile gauze is placed onto the wound bed and is covered by a relatively thick absorptive secondary layer. Moisture of the wound surface helps dilute exudate and debris, which then are wicked into the dry secondary layer. As the gauze dries it adheres to the wound bed, at which time the bandage should be removed. Mechanical debridement occurs when the adhered dried gauze is pulled away from the wound, taking with it superficial tissue and foreign material - this will also remove healthy tissue (e.g., new granulation tissue) and delay the healing process. Often causes bleeding and pain when the gauze is removed, necessitating proper analgesia or sedation.

The physiologic phases of wound healing begin

When injured - either by trauma or a purposeful insult (surgical incision)

Secondary Closure

Wound that has formed healthy granulation tissue and is then closed by apposing the skin over the granulation tissue

Wound Closure

Wounds are classified on the basis of whether they are surgically or traumatically created, their level of contamination, and expected number of organisms within the wound. These all dictate the type of wound management and closure to be used Surgically created wounds can be closed by direct apposition and will heal by primary wound closure. Clean traumatic cuts may also undergo primary closure after wound lavage. Small wounds with contamination can be excised en bloc and closed primarily Wounds with questionable degree of contamination or excess drainage may require a 2 - 3 day period of open wound management before they undergo delayed primary closure (allows elimination of contamination and improved wound health) In wounds requiring a longer period of open wound care such as heavily contaminated wounds, secondary closure can be performed - these wounds are allowed for form a healthy bed of granulation tissue, which is then folded onto itself with closure of the skin. Also referred to as third intention wound healing