Wounds Flashcards
6 steps of wound healing
Coagulation Inflammation Collagen synthesis Angiogenesis Epithelialization Contraction
4 “phases” = hemostasis/inflammation, proliferation, maturation, remodeling
Coagulation
Coagulation and complement cascades activated and platelets form a plug. Release of inflammatory mediators from activated platelets set everything off.
Impaired by: Anticoagulants Antiplatelets Coag factor deficiency Chronic liver disease Uremia
Inflammation
Signs = pain, swelling, heat, erythema, loss of function
Happens bc wound is invaded by PMNs (through first 48h) and macrophages (peak at 24h)
Macrophages are ESSENTIAL for healing
Bacteria, cell debris, dirt, other foreign material also cleared from wound site by macrophages and PMNs
Impaired by:
Steroids
Immunosuppressants
Congenital/acquired immune deficiency
Collagen synthesis
Occurs by fibroblasts in vicinity of wound in response to growth factor peptides
Amino acids hydroxyproline and hydroxylysine are parts of collagen. Their synthesis and hydroxylation is dependent on Fe, alphaKG, and ascorbate (C)
Angiogenesis
“Granulation”
Occurs in response to peptide growth factors such as vascular endothelial growth factor (VEGF)
Presence of these new vascular networks is what gives granulation tissue its characteristic beefy-red appearance.
Presence of granulation tissue is reassuring that healing is under way. At one month postinjury the wound is at 85% ultimate cohesive strength.
Epithelialization
Happens with migration of epithelial cells over the wound defect.
Integrity of basement membrane restored (type 4 collagen and other matrix components deposited)
Foreign bodies like suture material and necrotic tissue remain separated from wound by migrating epithelial cells
Once this happens, the wound is waterproof
This step is done usually 24-48h after surgical wounds that were closed primarily.
Contraction and remodeling
Surrounding uninjured skin is pulled over the wound defect and the size of the scar is reduced
Made possible by myofibroblasts which have a contraction mechanism similar to muscle cells
Takes many months to complete
Wound contraction is NOT scar contracture. SC happens after wound repair is stopped and can lead to undesirable effects since architecture of surrounding tissue may become distorted.
Maturation of scar occurs over next 9m to 2y. Cross linking of collagen and clinical flattening of scar.
What is a clean wound?
Wound created in sterile, nontraumatic way in area free of preexisting inflammation
Resp, alimentary, genital, urinary tract non entered
All people involved in case maintained aseptic technique
Risk of infx = 2%
What is a clean-contaminated wound?
Resp, alimentary, genital or urinary tract entered BUT no significant spillage of its contents and there was no established local infection
Only minor break in aseptic technique
Risk of infx = 5%
What is a contaminated wound?
Gross spillage from GI tract
GU and biliary tracts entered in presence of local infection (cholangitis)
Wound was result of recent trauma
Major break in aseptic technique
Risk of infx = 15%
What is a dirty/infected wound?
Wound result of remote trauma and contains devitalized tissue and/or purulent material
Established infection or perforated viscera prior to procedure
Risk of infx = 35%
What types of healing involve sutures?
primary and delayed primary intention
Primary intention
Seen following closure of clean surgical wounds or traumatic lacs in where there is minimal devitalized tissue
Edges of wound are approximated with sutures or staples
Very small defect so re-epithelialization is fast and healing time is short overall
Dressings changed after 24-48h to less bulky one
Wound strength max at 3m and is 70-80% of normal skin
Secondary intention
Healing following closure of wounds not approximated with sutures
Reason for no sutures is:
Wound edges cannot be apposed bc defect is large (donor site skin graft) OR surgeon chooses to not close bc of high infection risk
Pack these wounds loosely with moist gauze and cover with sterile dressing. Assess daily for development of granulation tissue and presence of infx
Wound closes by contraction and then epithelialization. Contraction is from edges inward. Then epithelialization at 1mm per day also edges inward. Granulation tissue generated at center of closing wound.
Third (delayed primary intention)
Following closure of wounds in which there is obvious gross contamination at incision site
Following removal of rupture appendix in which there was leakage of pus into peritoneal cavity. Parietal peritoneum and fascial layers closed. ABx given. Skin and subq not sutured until 3-5d later after bacterial contamination is less.
