Integument

Question 1

List 6 common wound pathogens

Answer 1

Staphylococcus, Streptococcus, gram negatives E coli, Enterococcus, Proteus, Pseudomonas

Question 2

List common pathogens in dog bite wounds (4)

Answer 2

Pasteurella multocida, anaerobes: Bacillus, Clostridium, Corynebacterium

Question 3

Name the four major approaches to wound closure. List specific indications for each approach, including factors related to the amount of time that has passed since the injury.

Answer 3

1. Primary wound closure (first intention healing)
   - Wounds edges apposed and allowed to heal by first intention. Appositional healing or by graft soon after injury.
   - Indications: clean, sharply incised wounds, minimal trauma/contamination.
   - Timing: Within 6 hours, or up to 12 if wound contamination and tissue trauma is minimal.
2. Delayed primary wound closure
   - Appositional closure within 3-5 days post wounding. BEFORE granulation tissue produced in wound bed.
   - Indications: Mildly contaminated, minimally traumatised wounds that require some cleaning, debridement and open wound management prior to closure. Class 2 wounds.
   - Allows for manipulation of environment of wound bed to ensure microbial contamination is reduced and tissue health maximised.
3. Healing by contraction and epithelialisation (second intention healing)
   - wound is left to heal by contraction and epithelialization, producing a continuous epithelial surface.
   - Indications: Dirty, contaminated and traumatised wounds while cleansing and debridement necessary but primary closure is prohibited. - - Opportunities to close the wound during open wound management (secondary closure) should be considered to expedite process.
4. Secondary wound closure (also called third intention healing)
   - Appositional closure of a wound 3 to 5 days after wounding, after granulation tissue has formed
   - Indications: severely contaminated, traumatized wounds that require ongoing open wound management and manipulation of the wound environment to reduce microbial contamination +/- treat infection +/- improve tissue health.
   - Granulation tissue provides a microbial resistance, vascular substrate that facilitates healing. Some debridement may be necessary for closure to be performed over granulation tissue.

Question 4

What are 3 classes of wounds?

Answer 4

Class 1 = 0-6 hours old, minimal contraction and tissue trauma = golden period (insufficient replication of microorganisms to cause infection)
Class 2 = 6-12 hours old, replication of bugs has occurred but have not reached critical level, could be considered to be in golden period
Class 3 >12 hours, microbial replication may have reached levels consistent with infection

Question 5

Describe the phases of wound healing.

Answer 5

IDPM
1) Inflammatory
- initial 5 days of injury
- Immediately post trauma - hemorrhage caused by disruption of vessels then vasoconstriction and platelet aggregation to limit bleeding.
- Vasodilation follows within 5-10 mins, allowing fibrinogen and clotting elements to leak from plasma into the wound, forming a clot and eventually a scab.
- clot serves as a scaffolding for neutrophils, monocytes, fibroblasts, endothelial cells
- plasma contains inflammatory mediators e.g. histamine, prostaglandins, leukotrienes, complement, growth factor

2) Debridement
- simultaneously with the inflammatory phase
- Marked by entry of WBC into the wound
- Neutrophils first to appear (~6 hours post injury): remove extracellular debris via enzyme release and phagocytosis.
- Monocytes appear 12 hours after trauma. Become macrophages in 48 hours. Monocytes stimulate fibribolastic activity, collagen synthesis, angiogenesis. Macrophages remove necrotic tissue, bacteria, foreign material.

3) Proliferative
- Begins 3-5 days after injury, lasts 2-4 weeks
- Dramatic healing phase - characterized by angiogenesis, granulation tissue formation, epithelialization
- New epithelium - 4-5 days after injury
- Wound contraction first noted 5-9 days after injury and continues into maturation phase

4) Maturation
- 17-20 days after injury - may continue for years
- Adequate collagen deposition present
- wound contraction and remodeling of the collagen fibre bundles
- Healed wounds never as strong as original tissue, scars 80% as strong

Question 6

Define necrotising soft tissue infections (NSTI)

Answer 6

Soft tissue infections associated with virulent bacterial or fungal organisms involving skin, SQ tissue, muscle, fascia that cause vascular occlusion, ischemia and necrosis.

Question 7

Define Toxic Shock Syndrome (TSS)

Answer 7

Acute, severe and systemic inflammatory response from microbial infection at a normally sterile site, usually Staphylococcus or Streptococcus (exotoxin-releasing)
- Acute, early occurrence of circulatory shock and MODS + rash

Question 8

Key pathologic process of NSTI

Answer 8

microbial invasion associated with localised thrombosis leading to liquefactive necrosis of the superficial fascia and soft tissue

Question 9

Rule of 9s for estimating %BSA in burn patients

Answer 9

Head and neck - 9
Each forelimb - 9
Each rear limb - 18
Dorsal trunk - 18
Ventral trunk - 18
Total = 99