1 / 87

Wound Healing

Wound Healing. Tulane University Division of Plastic & Reconstructive Surgery. Presentation Overview. Wound H ealing History Phases Factors Influencing Adjuncts to Wound Healing Fetal Wound Care Principles Dressings Abnormal Scarring Exotic Injuries. History of Wound Care.

aloha
Download Presentation

Wound Healing

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Wound Healing Tulane University Division of Plastic & Reconstructive Surgery

  2. Presentation Overview • Wound Healing • History • Phases • Factors Influencing • Adjuncts to Wound Healing • Fetal • Wound Care • Principles • Dressings • Abnormal Scarring • Exotic Injuries

  3. History of Wound Care • Smith papyrus (1700 B.C.) • 7 of 48 case reports dealt with wound healing • Ancient Egypt, Greece, India, and Europe • Gentle wound handling • Foreign body removal • Approximating wound edges • Clean dressings

  4. History of Wound Care • 850 - Gunpowder (change in thought process) • Boiling oil, hot cautery, scalding water • Worse outcomes • 1500 - Ambroise Pare • Rediscovered gentle, clean wound handling during the battle of Villaine • 20th Century – Scientific Method

  5. Phases of Wound Healing • Tissue Injury and Coagulation • Inflammation • Remove devitalized tissue and prevent infection • Early • Late • Fibroproliferative • Balance between scar formation and tissue regeneration • Fibroblast migration • Collagen synthesis • Angiogenesis • Epithelialization • Maturation/Remodeling • Maximize strength and structural integrity • Contraction • Collagen Remodeling

  6. Tissue Injury and Coagulation • Tissue Injury and Coagulation • INJURY (Physical, antigen-antibody reaction, or infection) • Transient (5-10 minute) vasoconstriction • Slows blood flow, aid in hemostasis • Histamine mediated vasodilation and permeability changes • Vessels become lined with leukocytes, platelets and erythrocytes • Leukocyte migration into the wound • Endothelial cells swell and pull away from each other -> allowing serum to enter the wound • Hemostatic factors from platelets, kinins, complement, and prostaglandins send signals to initiate the inflammatory phase • Fibrin, Fibronectin, and plasma help form a clot and stop bleeding

  7. Early Inflammation • Complement Cascade Activation • PMN infiltration • 24-48 hours • Stimulated by: • Complement components (C5a) • Formyl-methionyl peptide products from bacteria • Transforming Growth Factor (TGF)-b

  8. Early InflammationPMNS • Predominant cell type from 24-48 hours • Phagocytosis and debridement • Removal of PMNS does not alter wound healing

  9. Late InflammationMacrophage • Most critical cell type • Predominates after 48-72 hours • Attracted by: • Growth factors (PDGF, TGF-b) • Complement • Clotting components • IgG • Collagen and elastin breakdown products • Leukotriene B4 • Platelet factor IV

  10. Late InflammationMacrophage Functions • Phagocytosis • Primary producer of Growth Factors (PDGF, TGF-b) • Recruitment of fibroblasts (proliferative phase) • Proliferation of extracellular matrix by fibroblasts • Proliferation of endothelial cells (angiogenesis) • Proliferation of smooth muscle cells • This leads to the Fibroproliferative phase

  11. Late InflammationLymphocyte • Appears at 72 hours • Attracted by: • Interleukins • IgG • Complement products • Role yet to be determined

  12. Fibroproliferative • Fibroblasts • Migrate into the wound via ECM • Predominant cell type by day 7 • Collagen synthesis • Begins on days 5-7 • Increases in linear fashion for 2 to 3 weeks • Angiogenesis • Promoted by macrophages (TNF-alpha, FGF, VEGF) • Epithelialization • Mitosis of epithelial cells after 48-72 hours • Modulated by growth factors (EGF, FGF, KGF)

  13. FibroproliferativeExtracellular Matrix • Forms a scaffold for cell migration and growth factor sequestration (fibronectin, proteoglycans, collagen, etc.) • Proteoglycans and Glycosaminoglycans • Proteoglycans are proteins covalently linked to Glycosaminoglycans • chondroitin sulfate • heparan sulfate • keratan sulfate • hyaluronic acid (1st to appear) • Proteoglycans • Create a charged and hydrated environment • Facilitates cell mobility • Viscoelastic properties of normal connective tissue

  14. Collagen • Principle building block of connective tissue • 1/3 of total body protein content • 3 polypeptide chains that wrap around each other to form a collagen unit (tropocollagen) • Filaments ->Fibrils -> Fibers

  15. Collagen Types • Type 1 • Bones, skin, and tendons • 90% of total body collagen • Found in all connective tissues except hyaline cartilage and basement membranes • Type 2 • Hyaline cartilage, cartilage-like tissues, and eye tissue

  16. Collagen Types • Type 3 • Skin, arteries, uterus, abdominal wall, fetal tissue • Association with Type I collagen in varying ratios (remodeling phase) • Type 4 • Basement membranes only • Type 5 • Basement membranes, cornea • Skin • Type 1 : Type 3 ratio is 4:1 • Hypertrophic scars/immature scars ratio maybe as high as 2:1

  17. Collagen Metabolism • Dynamic equilibrium • Synthesis (Fibrosis) vs. Degradation (collagenases) • Collagenase activity • Stimulated: PTH, Adrenal corticosteroids, colchicine • Inhibited: Alpha 2-macroglobulin, cysteine, progesterone • Healing wound • 3-5 weeks equilibrium is reached between synthesis and degradation (no net change in quantity)

  18. Angiogenesis • Formation of new blood vessels throughout inflammatory and proliferative phase of wound healing • Initiated by platelets • TGF-b and PDGF • PMN • Macrophages • TNF-alpha, FGF, VEGF

  19. Angiogenesis • Endothelial Cell • Forms new blood vessels • VEGF(predominant chemotactic stimulator) • Move along the ECM created by fibroblast

  20. Epithelialization • Repithelialization begins within hours of injury • Stimulated by • Loss of contact-inhibition • Growth factors • EGF (mitogenesis and chemotaxis) • KGF, FGF (proliferation) • Dissolution of hemidesmosomal links between epidermis and basement membrane allows lateral movement of epidermal cells • Expression of integrin receptors on epidermal cells allows interaction with ECM

  21. Epithelialization • Epithelium advances across wound with leading edge cells becoming phagocytic • Collagenase (MMP) • Degrades ECM proteins and collagen • Enables migration between dermis and fibrin eschar • Mitosis of epithelial cells 48-72 hours after injury behind leading edge

  22. Maturation/Remodeling • Longest phase: 3 weeks – 1 year • Least understood phase • Wound Contraction and Collagen Remodeling • Wound Contraction • Myofibroblast • Fibroblasts with intracellular actin microfilaments • Uncertain if fibroblasts differentiate into, or if a separate type of cell

  23. Maturation/Remodeling • Collagen Remodeling • Type 3 Collagen degraded and replaced with Type 1 • Collagen degradation achieved by Matrix Metalloproteinase (MMP) activity (fibroblasts, PMNs, macrophages) • Collagen reorientation • Larger bundles • Increased intermolecular crosslinks

  24. Tensile Strength • Collagen is the main contributing factor • Load capacity per unit area • (Breaking capacity- force required to break a wound regardless of its dimensions) • Rate of tensile strength increases in wounds vary greatly amongst species, tissues and individuals • All wounds begin to gain strength during the first 14-21 days (~20% strength), variable then after • Strength PEAKs @ 60 days • NEVER reaches pre-injury levels • Most optimal conditions  may reach up to 80%

  25. Predominant Cell Types

  26. Special Characteristics of Fetal Wound Healing • Lack of inflammation • Absence of FGF and TGF-b • Regenerative process with minimal or no scar formation • Collagen deposition is more organized and rapid • Type 3 Collagen (No Type 1) • High in hyaluronic acid • Area of ongoing research

  27. Factors That Influence Wound Healing • Oxygen • Fibroblasts are oxygen-sensitive • Collagen synthesis cannot occur unless the PO2 >40mmHg • Deficiency is the most common cause for wound infection and breakdown • Hematocrit • Mild to moderate anemia does not appear to have a negative influence wound healing (given sufficient oxygenation) • >50% decrease in HCT • some studies report a significant decrease in wound tensile strength • while other studies find no change

  28. Factors That Influence Wound Healing • Smoking • Multifactorial in limiting wound healing • Nicotine • Vasoconstrictive -> decreases proliferation of erythrocytes, macrophages, and fibroblasts • CO • Decreases the oxygen carrying capacity of Hgb • Hydrogen Cyanide • Inhibits oxidative enzymes • Increases blood viscosity, decrease collagen deposition and prostacyclin formation • A single cigarette may cause cutaneous vasoconstriction for up to 90 minutes

  29. Factors That Influence Wound Healing • Mechanical Stress • Affects the quantity, aggregation, and orientation of collagen fibers • Abnormal tension -> blanching, necrosis, dermal rupture, and permanent stretching • Subcutaneous expansion produces stronger more organized scars • Hydration • Well hydrated wounds epithelialize faster • Environmental Temperature • Healing is accelerated at temperatures of 30 C • Tensile strength decrease by 20% in 12C environment

  30. Factors That Influence Wound Healing • Denervation • No direct effect on epithialization or contraction • Loss of sensation and high collagenase activities in skin -> prone to ulcerations • Foreign Bodies (including necrotic tissue) • Delay healing and prolong the inflammatory phase • Nutrition • Delays increases in tensile strength • Prolonged inflammatory phase and impaired fibroplasia • Edema • May compromise tissue perfusion

  31. Factors That Influence Wound Healing • Lathyrogens • Inhibit the cross linking of collagen bundles • Ex. D-penacillamine • Oxygen Derived Free Radicals • Degrade Hyaluronic acid and collagen • Destroy cell and organelle membranes • Interfere with enzymatic functions • Age • Tensile strength and wound closure rates decrease with age

  32. Factors That Influence Wound Healing • Infection • Prolongs inflammatory phase, impairs epithiliazation and angiogenesis • Increased collagenolytic activity -> decreased wound strength and contracture • Bacterial counts > 105, b-hemolytic strep • Chemotherapy • Decreases fibroblast production and wound contraction • If started 10-14 days after injury, no significant long term problems, but short term decreased tensile strength • Radiation • Stasis and occlusion of small blood vessels • Decreased tensile strength and collagen deposition • Systemic Diseases • DM • Glycosylated RBCs  Stiffened RBCs & Increased blood viscosity • Glycosylated WBCs  impaired immune function • Renal Dz

  33. Factors That Influence Wound Healing • Steroids • Inhibit wound macrophages • Interfere with fibrogenesis, angiogenesis, and wound contraction • Vitamin A and Anabolic steroids can reverse the effects • Vitamin A • Stimulates collagen deposition and increase wound breaking strength • Topical Vitamin A has been found to accelerate wound reepithealization

  34. Factors That Influence Wound Healing • Vitamin C • Essential cofactor in the synthesis of collagen • Deficiency is associated with immune dysfunction and failed wound healing (Scurvy) • Immature fibroblasts and extracellular material • Decreased Alkaline phosphatase • Defective capillary formation -> local hemorrhages • High concentrations do not accelerate healing

  35. Factors That Influence Wound Healing • Vitamin E • Large doses inhibit wound healing • Decreased tensile strength • Less collagen accumulation • HOWEVER • Antioxidant that neutralizes lipid peroxidation caused by radiation  Decreasing levels of free radicals and peroxidases increases the breaking strength of wounds exposed to preoperative radiation

  36. Factors That Influence Wound Healing • Zinc • Deficiency: • Impairs epithelial and fibroblast proliferation • Decreases B and T cell activity • Only accelerates healing when there is a preexisting deficiency

  37. Factors That Influence Wound Healing • NSAIDs • Decrease collagen synthesis an average of 45% (ordinary therapeutic doses) • Dose-dependent effect mediated through prostaglandins

  38. Factors That Influence Wound Healing • Fibrin-based tissue adhesives • Increase breaking strength, energy absorption, and elasticity in healing wounds

  39. Adjuncts to Wound Healing • Hydrotherapy • Whirlpool • Pulsed Lavage • Stimulates formation of granulation tissue • Clean non draining wounds with healthy granulation tissue should NEVER be subjected to hydrotherapy • Water agitation damages fragile cells • Electrostimulation • Imitates the natural electrical current that occurs when skin is injured • Increases migration of neutrophils and macrophages • Promotes fibroblasts • Increased collagen production and tensile strength

  40. Adjuncts to Wound Healing • Ultrasound Therapy • Electrical energy converted to sound waves • Thermal component -> improves scar outcome • Nonthermal component -> cavitation • In animal models • Changes in cell membrane permeability, increase cellular recruitment, collagen synthesis, tensile strength, angiogenesis, wound contraction, fibrinolysis, and stimulates fibroblast and macrophage production • Clinically results are equivocal • LED (Light-emitting diode) • Produces light at multiple wave lengths • Larger area than lasers • Studied by NASA in weightless environments (space station, submarines) • Improved wound healing alone or in combination with hyperbaric oxygen

  41. Adjuncts to Wound Healing • Hyperbaric Oxygen • Increases levels of O2 and NO to the wound • Benefit: Amputations, osteoradionecrosis, surgical flaps, skin grafts • None to minimal benefit with necrotizing soft-tissue infections • Wounds require adequate perfusion • Many off-label uses (Benefit? Financial?) • Acne, Migraines, Lupus, Stroke, MS, and many more • Medicare Coverage • 14 Covered Areas (next slide) • ~1/3 of claims are for problems not covered

  42. Medicare Coverage of HBO • (1)  Acute carbon monoxide intoxication • (2)  Decompression illness • (3)  Gas embolism • (4)  Gas gangrene • (5)  Acute traumatic peripheral ischemia • (6)  Crush injuries • (7)  Progressive necrotizing infections • (8)  Acute peripheral arterial insufficiency • (9)  Preparation and preservation of compromised skin grafts • (10)  Chronic refractory osteomyelitis • (11)  Osteoradionecrosis (ORN) • (12)  Soft tissue radionecrosis (STRN) • (13)  Cyanide poisoning • (14)  Actinomycosis

  43. Adjuncts to Wound Healing • Lasers “Biostimulation” • Excites physiologic processes and increases cellular activity in wounded skin • Accelerates healing of hypoxic and infected wounds when combined with hyperbaric oxygen • Low energy -> promote epithelialization • Different wave-lengths (multiple treatments) • VAC • Bioengineered Matrices

  44. Adjuncts to Wound Healing

  45. Wound Care General Principles • Cleaning and Irrigation • Need at least 7psi to flush bacteria out of a wound • High pressure can damage wounds and should be reserved only for heavily contaminated wounds • Debridement • Most critical step to produce a wound that will heal rapidly without infection • Non-selective: WTD, DTD, WTW,Hydrogen Peroxide, etc. • Useful in wounds with heavy contamination • When starts to granulate, start selective • Selective: sharp, enzymatic, autolytic, or biologic

  46. Selective Debridement • Enzymatic • Naturally occurring enzymes that selectively digest devitalized tissue • Collagenase (Santyl), Papain-Urea (Accuzyme), etc. • Autolytic • Uses the body’s own enzymes and moisture to breakdown necrotic tissue • 7-10 days under semi occlusive and occlusive dressings • Ineffective in malnourished patients • Biologic • Maggots • Calcium salts and bactericidal peptides • Separate necrotic from living tissue making surgical debridement easier

  47. Wound Care General Principles • Fundamentals of Surgical Wound Closure • Incision should follow tension lines and natural folds in the skin • Gentle tissue handling • Complete hemostasis • Eliminate tension • Fine sutures and early removal • Evert wound edges • Allow scars to mature before repeat intervention (2 weeks to 2 months scar appearance is the worst) • Scar appearance depends more on type of injury than method of closure • Technical factors of suture placement and removal are more critical than type of suture used • Immobilization of wounds to prevent disruptions and excessive scarring (Adhesive strips after suture removal)

More Related