Comparative Wound Healing

Question 1

Expectation for stages of wound healing

Answer 1

1. Hemostasis - injury/initial bleeding
2. Inflammation -
3. Proliferation - fill in wound space
4. Remodeling
   Stages overlap and vary in length

Question 2

Cell types at each healing stage

Answer 2

Hemostasis - platelets, neutrophils - transition into macro
Inflammation - monocyte/macro
Proliferation - fibroblast
Remodeling - myofibroblasts, lymphocytes

Question 3

Hemostasis

Answer 3

Platelates are the major cell - responsible for clotting the initial hemorrhage, fibrin clot forms
Vasoconstriction reduce blood loss

Question 4

Preparation for inflammatory phase

Answer 4

Platelets activated by tissue damage /bleeding
Activated platelets degranulate which release growth factors and cytokines which recruit leukocytes

Question 5

Inflammation

Answer 5

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

Question 6

Leukocyte emigration

Answer 6

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

Question 7

Types of tissue trauma & debridement

Answer 7

Blunt vs sharp - loose worse before better
Phagocytosis, enzymatic degradation & mechanical debridement

Question 8

Proliferation

Answer 8

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

Question 9

Healing in proliferation

Answer 9

Granulation - filling in wound
Epithelialization (begin to cover defect) - fragile skin
Wound contraction - reduction in wound size
- mediated by myofibroblasts in granulation tissue

Question 10

Remodeling

Answer 10

Purpose to increase wound function & strength
Main cell type- fibroblasts/myofibroblasts
Collagen reorganization + cross linking = increased collagen, cells rearrange to support more tension

Question 11

Length of each healing stage

Answer 11

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

Question 12

Healing of simple surgical incision

Answer 12

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

Question 13

Surgical wound classifications

Answer 13

Clean
Clean contaminated
Contaminated
Dirty

Question 14

Clean wounds

Answer 14

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

Question 15

Clean contaminated wounds

Answer 15

Infection rate ~ 4.5%
Enters luminal organs, no sign spillage, resection anastomatosis
Common w gastronomy or cystotomy

Question 16

Contaminated wounds

Answer 16

Infection rate = 5.8-14.6%
Major breaks in surgery tech, gross spillage of GI, fresh traumatic wounds, enter urinary or biliary tract

Question 17

Dirty wounds

Answer 17

Gross infection present at time of surgery, traumatic wounds with devitalized tissue, intestinal perforation &/or peritonitis

Question 18

Types of wound closure

Answer 18

First intention healing & second intention healing

Question 19

First intention healing

Answer 19

Fresh, uncomplicated surgical incision
- spay, exploratory laparotomy
Clean, a traumatic wound with minimal tissue, <6h old, minimal contamination

Question 20

Delayed primary closure

Answer 20

Primary wound closure occurs before granulation tissue formation. Will achieve 1st intention healing but delayed by 1-4 days. Common in cases delayed

Question 21

Steps with treating delayed primary closure

Answer 21

1. Lavage
2. Gentle debridement
3. Fresh bleeding wound margins & underlying subQ tissue
4. Wound closure to appose skin edges

Question 22

1st intention - secondary closure

Answer 22

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

Question 23

Second intention healing

Answer 23

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

Question 24

Wound size in 2nd intention healing

Answer 24

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