14 Wound Healing Flashcards
Stages in wound healing: inflammation
Days 1-10
PMNs, Macrophages
Epithelialization
How fast does epithelialization occur?
1-2mm/day
Stage in wound healing: proliferation
5 days - 3 weeks
Fibroblasts
Collagen deposition, neovascularization, granulation tissue formation
Type III collagen replaced with type I
Stage in wound healing: remodeling
3 weeks - 1 year
Decreased vascularity
Collagen cross-linking - remodeling
How fast do peripheral nerves regenerate?
1mm/day
What cells arrive in wounds - what order?
Platelets PMNs Macrophages Lymphocytes Fibroblasts
What cells are essential for wound healing?
Macrophages (release of growth factors, cytokines, etc)
Fibronectin
Chemotactic for macrophages
Anchors fibroblasts
Fibroblasts
Replaces fibronectin-fibrin with collagen
What is the predominant cell type by days 0-2?
PMNs
What is the predominant cell type by days 3-4?
Macrophages
What is the predominant cell type by days 5+?
Fibroblasts
What makes up a platelet plug?
Platelets and fibrin
What forms the provisional matrix?
Platelets, fibrin, fibronectin
Accelerated wound healing
reopening a wound results in faster healing the second time around - healing cells are already present
What is the most important factor in healing open wounds (secondary intention)?
Epithelial integrity
Migration across granulation tissue
Where does epithelization migrate from?
Hair follicles*
Wound edge
Sweat glands
Why do unepithelialized wounds promote bacterial growth?
They leak serum and proteins
What is the most important factor in healing closed wounds (primary intention)?
Tensile strength
Depends on collage deposition and cross-linking of collagen
What is the strength layer of the bowel?
Submucosa
What is the weakest time point for small bowel anastamosis?
3-5 days
Myofibroblasts
Smooth muscle cell-fibroblast
Communicates by gap junctions
Involved in wound contraction and healing by secondary intention
Collagen type I
Most common type of collagen
Skin, bone, tendons
Primary collagen in a healed wound
Collagen type II
Cartilage
Collagen type III
Increased in healing wounds
Blood vessels, skin
Collagen type IV
Basement membranes
Collagen type V
Widespread
Cornea
What are required collagen co-factors?
Alpha-ketoglutarate, vitamin C, oxygen and iron
HYdroxylation and cross-linking of proline residues
What improves the wound tensile strength?
Proline cross-linking
Scurvy
Vitamin C deficiency
What is the tensile strength of a healed wound compared to normal? When?
80%
By 8 weeks
Predominant collagen type synthesized for days 1-2?
Type III collagen
Predominant collagen type synthesized for days 3-4?
Type I collagen
When is type III collagen replaced by type I collagen?
3 weeks
When does a healing wound reach the maximum collagen accumulation?
2-3 weeks
After that, collagen is remodelled, but no extra is added
Effect of d-Penicillamine
Inhibits collagen cross linking
What is essential for wound healing?
Moist environment (avoid desiccation) Oxygen delivery Avoid edema (leg elevation) Remove necrotic tissue
What transcutatneous oxygen measurement do you want for good healing? how do you improve it?
TCOM > 25mmHg Optimize fluids No smoking Pain control Arterial revascularization Supplemental oxygen
What are impediments to wound healing?
Bacteria >10^5/cm2 Devitalized tissue Foreign bodies Cytotoxic drugs Diabetes Albumin < 3.0 Steroids Wound ischemia
How does ____ effect wound healing?
Bacteria
Decreases oxygen content
Collagen lysis
Prolonged inflammation
How does ____ effect wound healing?
Devitalized tissue and foreign bodies
Retards granulation tissue formation and wound healing
How does ____ effect wound healing?
Cytotoxic drugs
5-FU, methotrextae, cyclosporine, FK-506
Impairs wound healing in the first 14 days of healing
How does ____ effect wound healing?
Diabetes
Impedes the earl-phase inflammation response
Hyperglycemia can cause poor leukocyte chemotaxis
How does ____ effect wound healing?
Steroids
Inhibit macrophages, PMNs, and collagen synthesis b fibroblasts
Decrease wound tensile strength as well
How can you counteract the detrimental effects of steroids on healing?
Vitamin A (25,000 IU qd)
How does ____ effect wound healing?
Wound ischemia
Hypoxia
Causes: fibrosis, pressure, poor arterial inflow, poor venous outflow, smoking, radiation, edema, vasculitis
Osteogenesis imperfecta
Type I collagen defect
Ehlers-Danlos syndrome
10 types - all collagen disorders
Marfan’s syndrome
Fibrillin defect (connective tissue protein)
Epidermolysis bullosa
Excessive fibroblasts
Tx: phenytoin
Charcot’s joint
2nd MTP joint
Secondary to neruopathy (can’t feel feet, pressure from walking leads to ischemia)
Also on toes
Most common cause of leg ulcers?
Venous insufficiency
Tx Unna boots (elastic wrap)
Contents of scars
Proteoglycans, hyaluronic acid and water
When do you perform scar revisions?
Wait 1 year to allow maturation
May improve with age
How does cartilage get nutrients/oxygen?
Diffusion
No blood vessels
Impact of denervation on wound healing?
Nothing
Impact of chemotherapy on wound healing?
Inhibits healing
No effect after 14 days
Keloids
Autosomal dominant
Dark skin
Collagen goes beyond original scar
Tx: intra-lesion steroid injection, silicone, pressure garments, XRT
Hypertorphic scar tissue
Dark skinned, flexor surfaces of upper torso
Collagen stays within confines of original scar
Often occurs in burns or wounds that take a long time to heal
Tx: steroid injections, silicone, pressure garments
Platelet - alpha granules
Platelet factor 4
Beta-thrombomodulin
Platelet-derived growth factor
Transforming growth factor beta
Platelet factor 4
Alpha granules
Platelet aggregation
Beta-thrombomodulin
Alpha granules
Binds thrombin
Platelet-derived growth factor
Alpha granules
Chemoattractant
Transforming growth factor beta
Alpha granules
Modulates the response of the other alpha granules
Platelets - dense granules
Adenosine
Serotonin
Calcium
Platelat aggregation factors
TXA2
Thrombin
Platelet factor 4
