WOUND HEALING

Fontano, Michael JeffGagtan, MajelleGarcia, Kristina Fatima Louise

PHASES OF WOUND HEALING Hemostasis and Inflammation

Proliferation

Maturation and Remodelling

HEMOSTASIS AND INFLAMMATION Exposure of subendothelial collagen to platelets

results in platelet aggregation, degranulation, and activation of the coagulation cascade

Platelet -granules release a number of wound-active substances platelet-derived growth factor (PDGF) transforming growth factor beta (TGF) platelet-activating factor, Fibronectin serotonin

HEMOSTASIS AND INFLAMMATION

HEMOSTASIS AND INFLAMMATION fibrin clot

scaffolding for the migration into the wound of inflammatory cells such as polymorphonuclear leukocytes (PMNs, neutrophils) and monocytes

PMNs first infiltrating cells to enter the wound

site Peak: 24 to 48 hours.

HEMOSTASIS AND INFLAMMATION• Neutrophil

― phagocytosis of bacteria and tissue debris― major source of cytokines early during inflammation (TNF)― release proteases such as collagenases (participate in matrix

and ground substance degradation in the early phase of wound healing)

― implicated in delaying the epithelial closure of wounds

• Stimulants for Neutrophil migration― increased vascular permeability― local prostaglandin release― presence of chemotactic substances, such as complement

factors, interleukin-1 (IL-1), tumor necrosis factor alpha (TNF-), TGF, platelet factor 4, or bacterial products

HEMOSTASIS AND INFLAMMATION Macrophages

achieve significant numbers in the wound by 48 to 96 hours postinjury and remain present until wound healing is complete

wound débridement via phagocytosis c contribute to microbial stasis via oxygen radical

and nitric oxide synthesis activation and recruitment of other cells via

mediators (cytokines and growth factors) as well as directly by cell–cell interaction and intercellular adhesion molecules

regulating angiogenesis and matrix deposition and remodeling

PROLIFERATION days 4 through 12 tissue continuity is re-established Fibroblasts and endothelial cells

last cell populations to infiltrate the healing wound

strongest chemotactic factor for fibroblasts is PDGF

PROLIFERATION Endothelial cells

proliferate extensively during this phase of healing

participate in the formation of new capillaries (angiogenesis),

MATURATION AND REMODELLING begins during the fibroplastic phase characterized by a reorganization of

previously synthesized collagen wound strength and mechanical

integrity in the fresh wound are determined by both the quantity and quality of the newly deposited collagen

MATURATION AND REMODELLING Deposition of matrix

Fibronectin and collagen type III- early matrix scaffolding

glycosaminoglycans and proteoglycans- next significant matrix components

collagen type I is the final matrix.

MATURATION AND REMODELLING Scar remodeling continues for many (6

to 12) months postinjury, gradually resulting in a mature, avascular, and acellular scar.

The mechanical strength of the scar never achieves that of the uninjured tissue.

DRESSINGS

DRESSINGS Provides ideal environment for wound

healing Mimics the barrier role of epithelium

and prevents further damage Provides hemostasis and limits edema Controls the level of hydration and

oxygen tension within the wound Allows transfer of gases and water

vapor from the wound surface to the atmosphere

DESIRED CHARACTERISTICS OF WOUND DRESSINGS

Promote wound healing Conformability Pain control Odor control Non allergenic and non irritating Permeability to gas Safety Nontraumatic removal Cost efffectiveness convenience

CLASSIFICATION OF DRESSINGS1. Primary – placed directly on the wound

and may provide absorption of fluids and prevent dessication, infection, and adhesion of a secondary dressing

2. Secondary – placed on a primary dressing for further protection, absorption, compression and occlusion

ABSORBENT DRESSINGS Absorb without getting soaked Designed to match the exudative

properties of the wound and may include cotton, wool, and sponge.

NONADHERENT DRESSINGS Impregnated with paraffin, petroleum

jelly, or water soluble jelly for use as nonaddherent coverage

Secondary dressing must be placed on top to seal edges to prevent dessication and infection

OCCLUSIVE AND SEMI OCCLUSIVE DRESSINGS

Provide good environment for clean, minimally exudative wounds

Waterproof and impervious to microbes, but permeable to water vapor and oxygen

HYDROPHILIC AND HYDROPHOBIC DRESSINGS

Components of a composite dressingHydrophilic – aids in absorptionHydrophobic – waterproof and

prevents absorption from light to heavy wounds

HYDROCOLLOID AND HYDROGEL DRESSINGS

Combination of occlusion and absorbency Form complex structures with water and fluid

absorption occurs with particle swelling, which aids in atraumatic removal of dressingHydrocolloid - for light to moderate acute and chronic woundsHydrogel - for burns(including those caused by radiation) skins tears, surgical wounds, and pressure ulcers.

ALGINATES From brown algae with polysaccharides

containing mannuronic and glucoronic acid Polymers gel, swell and and absorb great

deal of fluid Used when there is skin loss, in open

surgical wounds with medium exudation and on full thickness chronic wounds

for moderate to heavy wounds, because of their superior absorption ability

MEDICATED DRESSINGS Used as drug-delivery system, agents

like benzoyl peroxide, zinc oxide, neomycin, and bacitracin-zinc

Shown to increase epithelialization by 28%

Used depends on the amount of wound drainage

Alginates

Hydrogel Hydrophili

c

Nonabsorbent

Absorbent

Hydrocolloid

Hydrophobic

Semi occlusive

Occlusive