Wound Flashcards
What are the phases of wound healing?
- Inflammation (day 1-10) 2. Proliferative (day 5-3 weeks) 3. Remodeling (3 weeks - 1 year)
Peripheral nerves regenerate 1 mm/day
What occurs during the inflammation phase of wound healing?
PMN, macrophage, TNF-alpha, IL-1, PDGF
Macrophages are essential for wound healing (release of GF)
What occurs during the proliferative phase of wound healing?
Fibroblasts deposit collagen, neovascularization, granulation tissue, formation of Type III collagen which is then replaced by Type I, epithelialization (1-2 mm/day), PDGF, FGF, EGF
Fibronectin - release by fibroblasts are chemotactic for macrophages
Provisional matrix – mostly fibronectin and hyaluronic acid
Fibroblasts – replace fibronectin-fibrin with collagen
Platelet plug – platelet and fibrin
PDGF, FGF, EGF
What occurs during the remodeling phase of wound healing?
Decreased vascularity, net amount of collagen does not change, cross-linking of collagen, mostly Type I collagen present over Type III
What is the order of cell arrival in wound healing?
Platelet, PMN (0-2 days), macrophages (3-4 days), lymphocytes, fibroblasts (5 days and on)
What is the most important factor in healing open wounds with secondary intention?
Epithelial integrity - Most important factor in healing open wounds with secondary intention
- Migration from hair follicles #1 site, wound edges, sweat glands
- Dependent on granulation tissues in wound
What is the most important factor in healing closed wounds?
Tensile strength - Most important factor in healing closed wound → Primary intention. Depends on collagen deposition and cross linking
D-penicillamine inhibits collagen cross-linking
What is the weakest point for SB anastomosis?
3-5 days
What is the suture removal timeline?
All facial lacerations can be primarily closed if < 24 hours. Use non-absorbable suture, interrupted fashion. Allows drainage
All other lacerations can be primarily closed if < 18 hours
Suture removal- Face: 4 - 7 days.
Other area 2 weeks
What is the role of myofibroblasts in wound healing?
Myofibroblasts are smooth muscle cell fibroblasts that communicate through gap junctions and are involved in wound contraction and healing by secondary intention.
What are the types of collagen and their locations?
I – MC type of collagen. Skin, bone, and tendons,
II – Cartilage
III - increased in wound healing, also in blood vessels (Associated with ANEURYSMS)
IV – Basement membrane, lens of eye
V – found in cornea
What is required for collagen synthesis and hydroxylation?
Alpha-ketoglutarate, vitamin C, oxygen, and iron are required for collagen synthesis and hydroxylation (prolyl hydroxylase) and cross linking of proline residue in collagen
Proline very important for cross linking: Improved wound tensile strength
Zinc needed for wound healing
What is the predominant type of collagen during remodeling?
Type I predominant type during remodeling
By 3 weeks all of Type III Collagen is replaced by type I and maximum collagen accumulation is reached
What is the maximum tensile strength of a wound reached?
By 8 weeks, the wound reaches maximum tensile strength which is 80%
What is essential for wound healing in terms of oxygen measurement?
Transcutaneous oxygen measurement should be > 25 mm Hg
What diseases are associated with abnormal wound healing?
Osteogenesis imperfecta - Type I collagen defect
Ehlers-Danlos – Collagen disorder
Marfan’s – fibrillin defect (connective tissue protein)
Epidermolysis bullosa - excessive fibroblasts Tx: phenytoin
Pyoderma gangrenosum - tx steroids, gets better with colectomy in UC. Associated with hidradenitis
What are the risk factors for wound dehiscence?
Deep wound infection (most significant), poor nutrition, COPD, diabetes, coughers
What are the components of scars?
Scars – Contain a lot of proteoglycans, hyaluronic acid, and water
- Scar revision – wait for one year to allow maturation
- Infants heal with little or no scarring
Scar revision should wait for one year to allow maturation; infants heal with little or no scarring.
What is the effect of denervation and chemotherapy on wound healing?
Denervation has no effect on wound healing; chemotherapy has no effect on wound healing after 14 days.
What is the role of wound vac in wound healing?
Wound vac increases wound contraction, promotes granulation, increases blood flow, and removes edema.
Contraindication to wound vac – Infected wounds, ischemic wounds, malignancy. Fistula is not a CI
What are the key factors in wound healing?
PDGF (chemotactic for inflammatory cells, smooth muscle cells, and fibroblasts), fibroblast growth factor (FGF), epidermal growth factor (EGF), TGF-beta (immunosuppressive)
PDGF: key factor in wound healing. chemotactic for inflammatory cells, smooth mm cells, and fibroblasts. Angiogenesis, epithelialization
Platelet activating factor, PAF: released from endothelium when platelet binds collagen
- Activates platelets, chemotactic to inflammatory cells, increases adhesion molecule expression
- NO Angiogenesis here
Fibroblast growth factor: chemotactic for fibroblasts, angiogenesis, epithelialization
Epidermal growth factor: chemotactic for fibroblasts, angiogenesis, epithelialization
TGF-beta: immunosuppressive
TGF-beta = growth factor – responsible for granulation tissue formation, matrix formation and remodeling
What are the components of platelet granules?
Alpha granule
- Platelet factor 4 – aggregation
- Factor V and VIII
- vWF
- Fibrinogen
- Beta-thrombomodulin – binds thrombin
- PDGF
- TGF-B – modulates above responses
Dense granules – contain adenosine, serotonin, calcium
Platelet aggregation factors – TXA2, thrombin, platelet factor 4
What is the role of selectins and integrins in wound healing?
Selectin – E selectin on endothelial cells bind P selectin (platelet), and L selectin (leukocyte) - involved in rolling adhesion of platelets to initiate platelet plug
Beta-2 integrin – found on leukocytes and platelets. Involved in anchoring adhesion and migration. They bind ICAM and VCAM
ICAM – Found on endothelial cells. Involved in anchoring adhesion and transendothelial migration. Bind Beta 2 integrin
What is the function of CD4 helper cells?
CD4 helper – interacts with MHC class II and releases:
- IL2 release: activates cytotoxic T (CD8) and natural killer cells
- Interferon gamma: activates macrophages
- IL 4 release: increases B cell ab production
What is the best suture technique for wound closure?
A slowly absorbable 2-0 monofilament suture (PDS) with 0.5 cm bite and 0.5 cm distance apart using 4:1 suture to wound length is best.
Ulcers
Diabetic foot ulcers - Usually at charcot’s joint (2nd MTP) and HEEL 2/2 to neuropathy
Leg ulcers – 90% from venous insufficiency tx Compression and wrap
Cartilage
Contains no blood vessels. Get nutrients and oxygen from diffusion
Natural killer cell
Attacks cells with missing MHC expression. Doesn’t use or need MHC complex
MHC 1/2
MHC I – self antigen. Cytotoxic T cells (CD8) recognize and attack non-self MHC I
MHC II – found on APC. CD4 interacts with it.
1ary/ 2ary lymphoid organs
Primary lymphoid organs – liver, bone, thymus
Secondary lymphoid organs – spleen and LN
Reopening a wound
Accelerated wound healing - reopening a wound, results in quicker healing the 2nd time (since healing cells already present)
Sutures
Absorbable sutures: broken down by the body via enzymatic reactions or hydrolysis. Used for deep tissues and tissues that heal rapidly- small bowel anastomosis, suturing in the urinary or biliary tracts, or tying off small vessels near the skin.
Vicryl rapide = 42 days
Vicryl = 60 days
Monocryl = ~100 days
PDS = ~200 days
Non-absorbable sutures: provide long-term tissue support, remaining walled-off by the body’s inflammatory processes (until removed manually if required). Used include for tissues that heal slowly- fascia or tendons, closure of abdominal wall, or vascular anastomoses.
Fascial dehiscence and characteristics of fluid draining from surgical wound
Fascial dehiscence and evisceration (extrusion of abdominal viscera out of wound)= surgical emergency
salmon-color fluid concerning for peritoneal fluid
Risks for wound dehiscense/ incisional hernia: wound infection, obesity, COPD, cardiovascular disease, immunosupression, age, malnutrition, renal failure
Calciphylaxis
-Associated with ESRD on hemodialysis; skin ischemia and necrosis manife
