Comparative Wound Healing Flashcards
Expectation for stages of wound healing
- Hemostasis - injury/initial bleeding
- Inflammation -
- Proliferation - fill in wound space
- Remodeling
Stages overlap and vary in length
Cell types at each healing stage
Hemostasis - platelets, neutrophils - transition into macro
Inflammation - monocyte/macro
Proliferation - fibroblast
Remodeling - myofibroblasts, lymphocytes
Hemostasis
Platelates are the major cell - responsible for clotting the initial hemorrhage, fibrin clot forms
Vasoconstriction reduce blood loss
Preparation for inflammatory phase
Platelets activated by tissue damage /bleeding
Activated platelets degranulate which release growth factors and cytokines which recruit leukocytes
Inflammation
Purpose of stage is cell recruitment and tissue debridement
Vascular & cellular phase - vasoD, ^^ capillary perm to enable cell migration
stage we can have the most influence - assist w cleaning, antibiotic Tx
Leukocyte emigration
Neutrophils enter the chat in the first 24-48 hrs & phagocytize bacteria, tissue debris & release proteases
Macrophages - 3-5d post injury. Essential for healing, phag necrotic tissue/bacteria, initiate healing process via cytokines & chemoattractant = recruiting fibroblasts, mesenchymal stem cells
Types of tissue trauma & debridement
Blunt vs sharp - loose worse before better
Phagocytosis, enzymatic degradation & mechanical debridement
Proliferation
Main cell type - fibroblasts
Neovascularization - creation of new blood vessels
Granulation tissue formation - very vascular, resistant to infection, disorganized collagen, protects underlying tissue, forms scaffolding
Healing in proliferation
Granulation - filling in wound
Epithelialization (begin to cover defect) - fragile skin
Wound contraction - reduction in wound size
- mediated by myofibroblasts in granulation tissue
Remodeling
Purpose to increase wound function & strength
Main cell type- fibroblasts/myofibroblasts
Collagen reorganization + cross linking = increased collagen, cells rearrange to support more tension
Length of each healing stage
Hemostasis: 0-12 hours
Inflammation: 6h -3-5 days (more w severe wounds)
Proliferation: 4-21 days (more w severe wounds)
Remodeling: 21 days - 2 years
Healing of simple surgical incision
3-4 days: incision weakest, held by suture
7-14 days: ^ tensile but only 10% of normal, dehiscence most likely to occur here
14-21 days: increases to 20% of normal strength
21-42 days: rapid increase 60-70% of normal strength
>42 days: slower increase to ≥ 80% of normal strength
Surgical wound classifications
Clean
Clean contaminated
Contaminated
Dirty
Clean wounds
Infection rate = 0-3.5%
Non traumatic wounds
No inflammation, no breaks in sterility, luminal organs aren’t entered, lumen of GI, GIU or respt aren’t entered
Clean contaminated wounds
Infection rate ~ 4.5%
Enters luminal organs, no sign spillage, resection anastomatosis
Common w gastronomy or cystotomy
Contaminated wounds
Infection rate = 5.8-14.6%
Major breaks in surgery tech, gross spillage of GI, fresh traumatic wounds, enter urinary or biliary tract
Dirty wounds
Gross infection present at time of surgery, traumatic wounds with devitalized tissue, intestinal perforation &/or peritonitis
Types of wound closure
First intention healing & second intention healing
First intention healing
Fresh, uncomplicated surgical incision
- spay, exploratory laparotomy
Clean, a traumatic wound with minimal tissue, <6h old, minimal contamination
Delayed primary closure
Primary wound closure occurs before granulation tissue formation. Will achieve 1st intention healing but delayed by 1-4 days. Common in cases delayed
Steps with treating delayed primary closure
- Lavage
- Gentle debridement
- Fresh bleeding wound margins & underlying subQ tissue
- Wound closure to appose skin edges
1st intention - secondary closure
Secondary would occur after granulation tissue formation
Also achieves 1st int but delayed ≥5 days
Cases presenting for delayed treatment
Severely contaminated wounds or sig tissue trauma
Second intention healing
Wound healing without surgical closure
Significant tissue trauma + contamination
Common with tissue loss/necrosis, exposed bone, tendon, ligament. Granulation tissue bridges the gaps in skin
Wound size in 2nd intention healing
Wound size reduces by contraction & epithelialization
Substantial epithelialization results in large areas of fragile skin - no protection
Contraction stops once tension of skin overtakes the myofibroblasts capacity
Skin grafting may be necessary for success
