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WVSOM - Wounds

Wound Healing

QuestionAnswer
Phases of wound healing Inflammatory phase, migratory phase, proliferative phase, late phase scar remodeling
What occurs during hemostasis of the inflammation vascular phase (2-5 days)? Bleeding, vasoconstriction, platelet aggregation, cytokine release, factor XII release (stimulates intrinsic cascade), tissue factor release from injured tissue (stimulates extrinsic cascade)
What occurs during vasodilation of the inflammation phase? Increased permeability releases plasma proteins, RBCs, WBCs; mediated by histamine, leukotaxine, kinins, prostaglandins
Signs of the inflammation phase? Erythema, edema, heat, pain (5-7 days)
What occurs during the inflammation cellular phase? Phagocytosis (macrophages, neutrophils)
PMNs Phagocytic, die within days, part of inflammation cellular phase of wound healing
Monocytes Phagocytic (transform into macrophages), N.B. to chronic inflammation, engulf damaged tissues & digest them, part of inflammation cellular phase of wound healing
Migratory phase Begins 2-3 days after laceration; lasts 2 days-3 weeks; angiogenesis is initiated (neovascularization); epithelialization begins (granulation if too much angiogenesis and epithelialization)
Describe epithelization Marginal basal cells undergo increased mitosis, daughter cells flatten and spread, wound covered in several days
Proliferative phase Begins ~5 days after wounding
What process begins in the proliferative phase of wound healing? Fibroplasia - undifferentiated, extravascular mesenchymal cells transform to fibroblasts stimulated by injury
What hinders fibroplasia? Necrotic tissue, hematoma, infection
When does collagen synthesis begin? 5-7 days
What happens at 5-6 weeks after wounding? Fibroblasts decrease, well-defined capillary network, rate of collagen synthesis decreases
Collagen makes up what percentage of total body protein? 20-30%
Type I collagen makes up what percentage of collagen in the skin? 80-90%
What collagen makes up the remaining 10-20% in the body? Type III
Collagen is made from? What does it require? Fibroblasts; oxygen, ascorbic acid, ferrous iron
How does collagen get its strength? Cross-linking of strands
The role of myofibroblasts Wound contraction
How long does wound contraction take? 12-15 days (or until the wound edges meet)
Does collagen have contractile properties? NO
Late phase scar remodeling (3 weeks) Continued turnover of collagen, continues for 3 weeks-2 years, rate gain of tensile strength plateaus at 6 weeks after injury, cross-linking provides increasing strength, goal = adequate collagen for strength & integrity w/o excessive scarring
What factors affect wound healing? Nutrition, vitamin deficiencies, trace element deficiencies, anemia and hemorrhage, hypoxia, steroids, anti-inflammatory drugs, radiation, cytotoxic drugs, diabetes
What type of wound healing is affected in the severely malnourished? Visceral and cutaneous wound healing
What supplies adequate nutrition? Protein, carbohydrates, fatty acids, vitamins, etc.
When does serum protein become a problem in wound healing? When albumin < 2 grams
Why is ascrobic acid necessary in wound healing? Co-factor for hyrdoxylation of proline and lysine in collagen synthesis
Vitamin deficiencies and fibroblasts Decreases strong cross-linked collagen production
Vitamin deficiencies and vitamin C Deficiency takes months to develop
Overall process of vitamin deficiencies and wound healing New wounds don't heal and old wounds break down due to collagenolysis without synthesis
Zinc deficiency Necessary co-factor for DNA/RNA synthsis; deficiency inhibits cellular proliferation & granulation tissue formation; toxicity inhibits macrophage migration & phagocytosis
Does wound healing occur in the presence of severe anemia? YES (if hypovolemia is not present)
What does hemorrhage do to wound healing? Shuts down microcirculation, decrease oxygen to tissue
Why is oxygen necessary for wound healing? Hydroxylation of proline and lysine; oxygenation requires circulation
What aspects of wound healing do steroids affect? All aspects
What role do steroids normally play? Moderate inflammatory response by inhibiting fibroplasia and neovascularity; impairs epithelization and contraction
What do anti-inflammatory drugs do in wound healing? Inhibit prostaglandin synthesis (typical daily doses do not inhibit wound healing)
Effects of acute phase radiation on wound healing 80% reduction in fibroblast and endothelial cell proliferation
Where are the intermediate effects of radiation on wound healing seen? Endothelial and connective tissue
What do late effects of radiation reflect on wound healing? Total dosage, especially blood vessels, produce avascular scarring and obliterative vasculitis
How do cytotoxic agents affect wound healing? Impair healing primarily through inhibition of cellular proliferation
Key aspect of diabetes and wound healing Infection is 5X more likely in diabetic
How does diabetes affect wound healing? Impaired circulation due to vascular occlusive disease, hyperglycemia inhibits inflammatory response, neuropathy decreases sensation which exacerbates traumatic injuries
Classification of wound closure Primary intention, secondary intention, tertiary intention
Primary intention Surgically clean wound, SUTURED immediately after wounding, granulation tissue minimal, scarring minimal
Examples of primary intention wounds Simple lacerations, surgical incisions, most dog bites, kitchen knife wounds
Secondary intention Loss of soft tissue, contaminated wound left open, considerable granulation tissue, epithelialization and contraction; NO SUTURES!
Examples of secondary intention wounds Puncture wounds, superficial abrasions, most ulcers, snake bites
Tertiary intention Grossly contaminated wound, left open for 4-5 days, delated primary closure
Examples of tertiary intention wounds Uncontrolled hemorrhage (pack and pressure), acute wounds with questionably viable tissue / foreign bodies (wounds embedded with road tar, severely contused tissue), human bites
Steps in wound closure Lidocaine (with/without epi - no epi for finger / toes)->control bleeding->flush wound with saline (0.9%)->apply betadine around skin surface->use sterile field->examine wound->check vessels, tendons, nerves->use appropriate material for close
Materials for wound closure Sutures (used for full / partial thickness wounds), staples (skin), steri strips (partial thickness), tapes (skin), tissue adhesives (usually skin)
Types of sutures Absorbable (plain/chromic cat gut, polyglactin, polyglycolic acid, polydioxanone) vs. non-absorable (nylon, silk, ethibond, polypropylene, wire)
Non-absorable sutures Removable; remain in skin 7-10 days (4-5 days on face); remain in longer in areas of more stress
Created by: JaneO