Wound Healing Flashcards
What are the roles of platelets in wound healing? (Hemostasis Stage - Stage 1)
PLT becomes activated and begin degranulation (hematoma forms) : release of cytokines at site of injury and signals the start of inflammatory phase
Wound healing: 1 = hemostasis phase, 2= inflammatory phase, 3 = proliferative phase, 4 = remodeling phase
Describe the Inflammatory Stage (stage 2) in Wound Healing
INFLAMMATORY (≥ 3-5 days)
1. Chemotaxis of neutrophils (response to cytokine signal)
2. Vasodilation (increased BF to site of injury)
3. Increased permeability of microvasculature @ site of injury (to allow for diapedeis of plasma proteins & neutrophils)
4. Tissue debridement via phagocytosis by neutrophils
ALSO STAGE WHERE VETS CAN HAVE GREATEST IMPACT ON HEALING — TISSUE DEBRIDEMENT!!
Chemotaxis: in response to stimuli (cytokine release)
Diapedesis: transmigration of leukocytes across endthelium (of blood vessels)
Plasma proteins: Membrane Attack Complex (MAC) = “straw through cell”
Neutrophils dominate in phagocytes in wound healing (versus macrophages)
Describe the Proliferative Stage (stage 3) in Wound Healing
PROLIFERATIVE = repair! (4-21 days)
1. Chemotaxis of fibroblasts => synthesize collagen & proteoglycans (granulation tissue), forming a scaffold / “core” of the wound
2. Neovascularization occurs
3. Wound begins to contract (reduced wound size), mediated by the myofibroblasts -> Especially important in SECOND intention healing!! (non-surgical closure)
4. Epithelial migration / granulation tissue over contracted wound
Granulation tissue only forms into scaffold in SECOND INTENTION (or secondary closure in First intention) WOUND CLOSURE b/c the margins are NOT closed via surgical closure (sutures)
Describe the Remodeling Stage (stage 4) in Wound Healing
REMODELING = wound maturation! (21 days to 2 years)
1. Goal = achieve maximum tensile strength via collagen reorganization, degradation (of excess)
2. Wound contraction peaks // wound closes (scar)
First intention wound closure = minimal scarring (no granulation b/c of suture)
Second Intention wound closure = wider, more visible scar (granulation over contracted wound margin)
Post-operatively, when is peak tensile strength acheived by? When is it weakest?
Peak = > 42 days; may only reach 80% of normal
Weakest = 3-4 days post-op
21- 42 days: rapid increase in wound strength, up to 60-70% of normal
What timeframe post-op is wound dehiscence most likely to occur?
7-14 days
Wound dehiscence is a surgery complication where the incision reopens :(
What are the 4 surgical wound classifications?
1. Clean :))
- no break in aspetic technique; non-traumatic/non-inflammed (e.g., biopsies, laparoscopies)
- ≤ 3.5% infection rate
2. Clean-Contaminated :)
- luminal organs entered W/OUT spillage of contents
- 4.5% infection rate
3. Contaminated :(
- break in aseptic technique
- fresh trauma wounds
- gross spillage of GI contents into wound
- 5.8 - 14.6% infection rate
4. Dirty-Infected :((
- major break in aseptic technique
- abscessed or foreign material present
- older wounds (>4 hours) // devitalized tissue
- intestinal perforation (wound contaminated with fecal matter)
First versus Second Intention wound healing
First = healing with surgical closure (rapid + minimal scar) -> 1º, delayed 1º, or 2º closure
Second = healing WITHOUT surgical closure (or minimal) -> significant tissue trauma; contaminated or dirty wound
- Proliferation and Remodeling wound healing stages
When is primary closure used in First Intention?
fresh, clean/uncomplicated surgical incisions; minimal bacterial contamination; < 6 hours old
When is delayed primary closure used in First Intention? How does secondary closure differ?
Delayed Primary Closure = contaminated wounds or devitalized tissue (e.g., lacerations)
- wound lavage + debridement in clinic -> WAIT 1-4 days -> surgically close
- close BEFORE granulation tissue forms (which occurs ≥ 3-5 days)
Secondary Closure = severely contaminated wounds and/or substantial tissue trauma
- same as delayed, but surgical closure is performed AFTER GRANULATION TISSUE FORMS
Recall: Granulation tissue only forms into scaffold in SECOND INTENTION (or secondary closure in First intention) WOUND CLOSURE b/c the margins are NOT closed via surgical closure (sutures)
Indications for Second Intention wound healing?
- Significant tissue trauma; severely contaminated or diry wound
- tissue loss / necrosis
- exposed bone, tendon, ligament, etc.
Recall: in SECOND INTENTION, granulation tissue deposits and forms scaffolding / “wound core” for wound contraction+++
