Basic wound management Flashcards
What are the 3 main phases of wound healing?
- Lag/inflammatory
- Repair
- Remodelling
How long does each phase of wound healing last?
Lag/inflammatory = 1-5 days Repair = 6-16 days Remodelling = from 2-3 weeks to several months
What signs will a wound show during the lag/inflammatory phase?
Classic signs of inflammation: heat, pain, redness, swelling
Describe the lag/inflammatory phase
- Immediate response to injury is haemostasis
- Cells and fluid exit blood vessels and platelets trigger the formation of a fibrin clot
- Neutrophils are attracted to the wound by chemotaxis
- Monocytes enter the wound where they differentiate to macrophages
What are the roles of neutrophils in the lag/inflammatory phase
Degrade necrotic tissue
Control infection by destroying bacteria
What are the roles of macrophages in the lag/inflammatory phase
Remove degenerate neutrophils, necrotic tissue and debris by phagocytosis
Secrete growth factors that regulate wound healing
What are the 3 components of the repair phase?
- connective tissue repair
- wound contraction
- epithelialisation
Describe the processes involved in connective tissue repair
- mesenchymal cells in the wound edges differentiate into fibroblasts
- fibroblasts create a new collagenous extracellular matrix
- capillary growth follows fibroblast migration: combination forms granulation tissue
How does granulation tissue become a paler scar?
By day 7-14 after injury the collagen content of the wound stabilises, fibroblasts undergo apoptosis and the new capillaries undergo apoptosis resulting in acellular tissue
Describe the process of wound contraction
- specialised myofibroblasts proliferate the wound and attach to the matrix and contract
- contraction continues until the wound edges meet and contact inhibition occurs
Describe the process of epithelialisation
- Epithelial cells from the wound edges and any remaining hair follicles migrate across the wound to form a monolayer
- Proliferation occurs to increase thickness
How does epithelialisation differ in partial thickness and full thickness wounds?
Partial: begins immediately
Full: requires an adequate granulation bed so begins 4-5 days post injury
Describe the remodelling phase
- The collagen content and strength of the wound increase rapidly over the first 14-16 days
- After this the cellular content of the granulation tissue reduces and collagen bundles reorganise by thickening, cross-linking and reorienting across lines of tension
Give examples of local factors affecting wound healing
- Wound perfusion
- Tissue viability
- Wound fluid accumulation
- Infection
- Pressure, motion, tension
Give examples of systemic factors affecting wound healing
- immunosuppression: disease (FIV, hyperadrenocorticism), glucocorticoid administration
- neoplasia: residual disease, cytotoxic drugs