Revision 5, wounds Flashcards
Blood supply of the (canine and feline) skin and clinical importance
- The epidermis and dermis
- Different from humans (musculocutaneous vessels) → different reconstructive
techniques - Direct cutaneous arteries (dogs and cats, most of the skin)
- Parallel to the skin in the hypodermis
- Arise from perforator arteries
- Musculocutaneous arteries
- Perpendicular to the skin surface
- Supply small portions of the skin
- Subdermal plexus is of major importance
Importance of subdermal plexus
Primary Blood Supply:
The subdermal plexus is the main network of blood vessels supplying the skin in dogs and cats.
Surgical Significance:
Skin Flaps:
When creating skin flaps for surgery, it’s crucial to include the subdermal plexus to ensure the flap gets enough blood and doesn’t die.
Incision Planning: Surgeons need to be careful with their cuts to avoid damaging this vital blood supply, which helps in healing.
Wound Healing:
The subdermal plexus provides the necessary blood flow for skin healing. If it’s damaged, healing can be slow and problematic.
Classification of wounds
Open wounds:
- Surgical incision
- Laceration
- Abrasion
- Avulsion
- Puncture
- Burn
- Pressure sores
- Cast- & bandage related
Closed wounds:
- Contusion
- Hematoma
- Crush injury
- Hygroma
Open wounds
* Surgical incision and laceration
- Surgical/traumatic
- Edges generally clean and free from tissue damage
- Tend not to get infected
- Minimal contamination
- Sufficient bleeding to decrease tissue colonization
- Rarely significant damage to surrounding tissue - Deep wound – physical exploration/imaging!
- Surgical management
Open wounds:
Abrasion
- Superficial damage not extending beyond the dermis
- Frictional forces when moving parallel to a rough surface, usually at speed
- Combination of graze (scratch), abrasion and avulsion
- Generally heavily contaminated
- Severe abrasions with ongoing tissue necrosis might become
avulsions - Surgical vs open wound management
Open wounds:
Avulsion
The separation of tissue from their deeper attachments (usually including muscle)
Defects often extensive and complex
May be initially free of bacterial contamination, but without
appropriate wound management rapid colonization and infection of necrotic tissue will occur
Degloving:
- Skin and deeper tissues torn from an extremity, just as a
glove is removed from the hand (mechanical vs physiological) - Degloved skin should be preserved where possible
- Surgical/open wound management/in combination
Shearing:
- Usually involve loss of deeper tissues
- Including skin, tendons, muscle, possibly bone - The joints of the distal limb frequently exposed
- Heavily contaminated with bacteria and debris
- Extremely prone to infection
- Need for orthopedic surgery
- Open wound management
Open wounds:
Puncture
Caused by any sharp object that pierces the skin to create a
relatively small deficit or hole
Damage assessment! Possible perforation of a cavity without a skin wound
Risk of abscessation
Bite/sting, insect, tick
Firearm wounds (lead!?)
Open wounds:
Burn
Caused by extreme temperature (hot or cold) or by contact with a chemical substance, electricity or radiation
May require prolonged treatment, monitoring (inpatient)
Treatment depends on the case
- Thermal
- Chemical
- Electrical
- Radiation
Open wounds:
Pressure sores
- Caused by pressure typically on the elbow and hocks of large dogs
- Open or closed wounds
- Open sores prone to infection (bones and joints)
- Hygromas (best treated medically)
- Medical/surgical treatment
Open wounds:
Cast- & bandage related wounds
Iatrogenic wounds are common
- Ischemic injury due to overtight application of bandaging
- Inadequate padding of vulnerable areas
- Excessive exercise, allowing bandage slippage
- Wet or dry bandages (higher risk of bacterial strikethrough
and infection)
Serious wounds may result in the loss of digits or limbs
Phases of wound healing
- Acute inflammatory phase
- Debridement phase (breakdown)
- Proliferation phase
- Maturation phase (remodelling)
Acute inflammatory phase
- Characterized by (5): redness, pain, heat, swelling, loss of function
- Lasts approximately 5 days
After wounding:
1. Filling with blood and lymph
2. Immediate vasoconstriction of the damaged vessels
3. Vasodilation
4. Epithelial cells begin to migrate from the wound periphery onto the
exposed tissue
5. The blood clot dries to form a scab
6. White blood cells leaking into wounds initiate the debridement
phase
Debridement phase (breakdown)
- Approximately 6-12 hours after injury
- Formed inflammatory exudate provides all the necessary phagocytic cells and proteolytic enzymes to deal with the demarcation
- An exudate (of WBC, dead tissue, wound fluid) forms on the wound
- Necrotic tissue impedes wound healing
- Phase ends with the rejection of nonvital tissue
- Sometimes combined with inflammatory phase
Proliferation phase (reparation)
- Repair phase
- Approximately 3-5 days after injury
- Signs of inflammation subside
- Neovascularizarion (uudissuonittuminen)
Divided into 3 processes:
Granulation :
1. Red irregular surface
2. Fragile tissue
3. Functions as a barrier to infection and a scaffold for migrating epithelial cells
4. Capillary network occurs through sprout formation of capillary endothelial cells on the wound surface
5. Granulation tissue formed at each wound edge at a rate of
0.4 to 1 mm/24h
Wound contraction :
1. Surface & cavity of wound become smaller
2. Adjacent skin pulled closer to the centre of the wound
3. Especially loose skin
4. Begins 5-9 days after wounding
5. Stops when edges connected/tension too high
6. Risk of contracture
7. Thinning of the surrounding skin (temporary)
Epithelialization
1. Proliferation of basal epithelial cells from the adjacent skin
edges and their moving over and adhesion to the surface of wound
2. Prevention of excessive formation of granulation tissue
3. Total duration from days to weeks
4. Surface of wound that has become epithelialized is
known as the epithelial scar (thin and fragile)
Maturation phase (remodeling)
- Increasing strength of the scar as a result of remodelling of tissue
- The newly formed collagen is arranged parallel to the tension lines of the skin
- Total duration can range from weeks to a year or even longer
- No or insufficient hair follicles, sweat and sebaceous glands, poor movability and elasticity and an absence of pigment
- The healed wound will never regain skin’s original strength
Wound healing differences in canines and felines
- Research predominantly in dogs
- Intact skin of cats less perfused vs dogs
- Breaking strength of a wound 50% less in cats 7 days after primary closure
- Formation of granulation tissue takes longer in cats and first appears only at the wound edges
- Pseudohealing more common in cats
- More research warranted
Protocol for wound management (traumatic wounds)
Many will heal naturally, some need intervention
- Stabilization of the patient
- Stopping the bleeding (pressure, special dressings for minor wounds
(adrenaline-soaked gauzes etc.)) - Reduction of the level contamination, clipping the area (up to 4-6hours after
wounding to prevent bacterial infection)
- Use a clean room and aseptic technique
- Obtain a complete medical history of the patient
- Obtain information about the cause and age of the wound
- Make a complete assessment of the wound
- Debride necrotic tissue
- Remove contamination
- Choose the appropriate method of closure
- Choose the appropriate dressing
- Make regular assessments to monitor the progression of wound
healing - When dealing with chronic wounds not responding to normal
wound management, consider using an advanced technique
Open wound management
- Due to wound characteristics/financial reasons/until surgical closure
- Superficial wounds
- Dressing, bandage?
- Wound-healing enhancers used
- Healing process often time-consuming
- Might need some surgical intervention
Wound closure options (depending on the time of closure)
PRIMARY CLOSURE
- Clean wounds, surgical wounds that are contaminated (been debrided)
- Less than 6 hours old
- Direct closure of the wound after lavage and debridement
- Leads to a more anatomical and functional recovery than others
- Sutures removed in 1-2 weeks
- If level of contamination, tissue viability, depth of tissue damage or vascular supply is questionable → other options
Wound closure options (depending on the time of closure)
DELAYED PRIMARY CLOSURE
- Wound management as an open wound until it is clean and no formation of granulation tissue → then closed
- Closure 3-5 days after the emergency of the wound
- Allows drainage of the wound, a decrease in contamination and the
development of a clear demarcation line between viable and necrotic tissue prior to surgery
Wound closure options (depending on the time of closure)
SECONDARY CLOSURE
- Closure of the wound after the formation of granulation tissue
- Contaminated or infected wounds
Two methods:
- Leaving the existing granulation tissue intact, only separating the
edge of the skin from the granulation tissue bed and advancing it over the wound - Excision of the granulation tissue bed followed by primary closure
- Second method used preferrably
1. Wound edges more mobile
2. Incidence of infection lower
3. Cosmetic reasons
Functions (goals) of wound dressings/bandages
- Provide a moist environment
- Provide a warm environment
- Protect from trauma
- Protect from external contamination
- Application of topical medication
- Immobilization of the wound
- Support of the wound edges
- Absorb exudate
- Prevent or reduce oedema
- Provide an aesthetic appearance
