Wounds

Question 1

Abrasion

Answer 1

Partial thickness epithelial injuries secondary to shear forces. Rapid healing is expected via re-epithelialisation.

Question 2

Puncture wounds

Answer 2

Sharp force penetrating injury. Deep tissue injury and contamination occurs and usually involves a much larger area or volume than initial wound appearance suggests e.g. bit wounds, penetrating trauma, gunshot/ other projectiles

Question 3

Laceration

Answer 3

Sharply incised wounds involving epidermis, dermis +/- deeper tissues including muscles and tendons. Depending on the nature of the wounding object, some potential for necrosis of wound edges exists. Some authors include incisions as lacerations or separate them into a separate group.

Question 4

Degloving injuries

Answer 4

Anatomic or physiologic. Anatomic degloves result in the loss of skin at the time of trauma. In physiologic degloves, the skin is initially intact but deprived of the underlying vascular supply resulting in necrosis and dehiscence (wound ruptures along surgical suture) which may only become apparent after 5-7 days. These injuries result from shear forces and may induce large amount of soft tissue and bone loss either directly or indirectly secondary to loss of vascular supply.

Question 5

What are the phases of wound healing?

Answer 5

1. Inflammation and debridement
2. Proliferation and repair
3. Remodelling/ Maturation

Question 6

Inflammation and debridement

Answer 6

• Characterized clincally by erythema and oedema of wound edges
• Immediate from time of tissue injury–> 1-3 days
• Haemorrhage
• Haemostatic and inflammatory mechanisms
• smooth muscle contraction- vasoconstriction
• wound enlargement
• primary haemostatic plug stabilized by fibrin
• activated platelet products
• vasodilation
• leukocyte migration

Question 7

Neutrophil function

Answer 7

kill bacterial species via the release of active oxygen species to phagocytose them. Process requires sufficient partial pressure of oxygen within the wound and is impaired by wound hypoxia. Neutrophils also breakdown and phagocytosis of ECM via proteolytic enzymes and cytokine production prolonging inflammatory phase

Question 8

Clean

Answer 8

Wound does not enter a hollow viscous or lumen of the body e.g. fresh laceration

Question 9

Clean- contaminated

Answer 9

Wound enters or penetrates into a colonized viscous or cavity of the body, but under elective and controlled circumstances (e.g. ovariohysterectomy; enterotomy without spillage of luminal content)

Question 10

Contaminated

Answer 10

Gross contamination is present at the surgical site in the absence of obvious infection e.g. penetrating injury to the abdominal cavity with intestinal perforation. Wound should never be closed

Question 11

Dirty

Answer 11

Active infection is already present e.g. long-standing open wounds > 6 hours, abscess). Wound should never be closed.

Question 12

Chemokine

Answer 12

Cytokines mediating chemotaxis

Question 13

Cytokines and chemokines

Answer 13

Initiate, mediate, and sustain activity within the healing wound
* are ligands for cell surface receptors stimulating intracellular signalling mechanisms

Question 14

Macrophage function

Answer 14

Phagocytosis (neutrophils, bacteria, ECM)

Cytokine production- the controllers of wound healing

Question 15

Proliferation/ Repair

Answer 15

• Day 4-12
• End of lag (wound strength)
• Wound closure and tissue replacement- capillary ingrowth from surrounding existing vessels/ fibroblast proliferation and migration (fibroblasts produce collagen)
• collagen production: rapid gains in wound strength

Question 16

Granulation Tissue

Answer 16

Appears between 3-6 days

• compose of fibroblasts, capillaries, macrophages and collagen with macrophages and granulocyte patrolling the surface
• Provides a mechanical barrier and biologic barrier against microbial infection to deep tissues

Question 17

Wound contraction

Answer 17

Result of fibroblasts–> myofibroblasts

• extend feet which adhere to extracellular matrix, produce smooth muscle filaments, they contract
• no new skin is produced wound is just being pulled in- will continue until wound is closed unless there is too much tension in the other direction
• wound contraction commences about 5 days after wounding
• intussusceptive stretch in surrounding skin

Question 18

Epithelialisation

Answer 18

• epithelial proliferation/ migration
• migrate across the wound surface
• stratification and thickening occurs
• only happens if granulation surface is okay. If poor, than migratory function doesn’t work very well
• ideally moist wound environment- otherwise dry slows the process down
• requires absence of infection

Question 19

Maturation/ Remodelling

Answer 19

• Increases the strength and stability of the healed wound
• Type III collagen initially produced is remodelled
• Remodelling process- balance between collagen and synthesis and lysis
• never returns to normal strength- likely around 80% after about 3 months (1 week 3% wound strength; 3 weeks- 30%)
• process is ongoing- months to years

Question 20

Sutured wounds

Answer 20

Idential mechanisms occur- process occurs more rapidly- less distance, optimised wound environment (after debridement), wound contraction not required

Question 21

Differences with cat wound healing?

Answer 21

• Cats only 50% as strong as dogs at day 7
• Slower granulation, slower epithelialisation, slower wound contraction
• therefore delay suture removal (despite healed appearance)

Question 22

Impediments to wound healing- systemic factors

Answer 22

• Immunodeficiencies (ie. diabetes mellitus, obesity, malnutrition, hyperadrenocorticism)– because they affect white cell function)
• Neoplasia
• Age
• Hypoproteinaemia
• Therapeutic agents- corticosteroids, cytotoxic chemotherapy, radiation therapy

Question 23

Impediments to wound healing- local factors

Answer 23

• Wound perfusion/ blood supply (O2 delivery)- surgeons need to preserve vasculature as much as possible near wounds
• Tissue viability
• Foreign material
• Fluid accumulation (Seroma, haematoma)- increases distance for diffusion (relative hypoxia) and cell migration; inhibits host immune response, medium for bacterial growth
• infection (prolongs and intensifies inflammatory phase of wound healing/ bacterial toxins and enzymative damage from the host response to tissues can be non-specific)
• mechanical factors

Question 24

En-bloc debridement

Answer 24

Removing all of the tissue

Question 25

Debridement

Answer 25

The process of removing nonliving tissue from pressure ulcers, burns, and other wounds.

Question 26

Moist wound healing

Answer 26

* Cell proliferation and migration maximized * Cell function in inflammatory and debridement phases maximized * Leukocytes remain in wound- selective autolytic debridement * Growth factors and cytokines preserved in wound fluid

Question 27

Primary layer- dressing

Answer 27

Interacts with wound surface

Question 28

Secondary layer- dressing

Answer 28

Absorbs wound fluid

Question 29

Tertiary layer- dressing

Answer 29

fixes wound in place, pressure

Question 30

Foam Dressings

Answer 30

More absorbent- highly exudative wounds, favourable moist wound environment, increased cost of dressings, less frequent dressing changes

Question 31

Film dressings

Answer 31

Absorbent layer and 1 or 2 film layers, pores allow fluid and gas exchange, absorptive capabilities are limited (minimally exudative wounds or frequent bandage changes)

Question 32

Alginates

Answer 32

Kelp extract, ion exchange forms gel, very absorbent, promotes haemostatisis and granulation, promote epithelialization, odour and purulent appearance

Question 33

Hydroactive dressings

Answer 33

Insoluble polymers/ gels, hydrophilic and absorb wound exudates, autolytic debridement, preserve serum growth factors

Question 34

Negative pressure wound therapy

Answer 34

* controlled sub-atmosphere pressure to wounds * constant suction so they are less likely to pull their dressing off * increases blood flow and O2 delivery to the tissues, exerts tension stress which upregulates cytokines and intracellular mechanisms that regulate cellular proliferation, it might remove more bacteria from the wound * on the wound for maybe 3-5 days * have to go back to surgery to dig the foam out

Question 35

Timing wound closure

Answer 35

*assess tissue viability & degree of contamination

Question 36

Tension lines

Answer 36

incisions parallel to tension lines, closure parallel to tension lines

Question 37

Presuturing

Answer 37

2-3 days before surgery, mechanical creep

Question 38

Undermining

Answer 38

Around the wound edges, deep to the panniculus carnosis muscle (present on trunk and head- not on the limbs) because of the vascular supply of dogs

Question 39

Releasing incisions

Answer 39

Staggered parallel incisions about 1 cm long, relieves some tension