国外医学院烧伤和治疗.pptVIP

* Rate- depends on tissue- buttock- loose tissue, contracts more than scalp tissue * * Remodelling- turnover of collagen- old collagen broken down and new collagen is synthesused in a denser, more organised fasion., with increaing intermolecular cross links. Water quantitiy decreases, changes in texture, thickness and color These factors will affect the process of healing ?? Divided into immediate and delayed Immediate ?? Skin – fluid retention ‐ Protection from infectious agents Fluid loss ‐ haemoconcentration and poor vascular perfusion of the skin and viscera – shock and acute tubular necrosis * Delayed ?? Poor perfusion – infections and sepsis ?? Scar tissue – lack elastic properties – contractures If the burns are 30% released cytokines and inflammatory mediators lead to systemic effects: 1. CVS – increased capillary permeability – fluid into interstitial space, peripheral and splanchnic vasoconstriction, decreased myocardial contractility all lead to hypotension and end organ hypoperfusion * Late wound healing events Collagen synthesis 3 helical polypeptide chains Lysine and proline hydroxylation Required for cross-linking Late wound healing events Collagen synthesis 3-5 days post injury Primarily by fibroblasts Maximum synthesis rate 2-4 weeks Declines after 4 weeks Type 1 collagen most common ( 80-90% of skin collagen) Type 3- seen in early phases of wound healing Wound contraction Centripetal movement of the wound edges toward the center. ( 0.6-0.7 mm/day) Begins at 4-5 days Maximal contraction 12-15 days Trivial component in closed incisional wounds, significant for closure of open wounds Rate- depends on tissue Circular wounds- slower closure but avoid stenosis Wound contraction Mechanism- cell mediated processes, not requiring collagen synthesis Myofibroblasts- fibroblasts with myofilaments in cytoplasm Appear in wound day 3-21 Located in periphery- pull wound edges together. Contractures- contraction across joint surface Termi