L06: Wound Healing "Flesh and Bood" (Case) Flashcards
skin functions
- maintain hydration and thermoregulation
- defense against pathogens and chemicals
- vitamin D synthesis
- sensory (e.g. mechanoreceptors)
- storage (H2O, electrolytes, fat, proteins)
- insulation
chars. of Epidermis
- superficial
- cuboidal/stratified epithelium
- avascular (completely reliant on underlying blood supply)
- variable thickness depending on location
chars. of Dermis
- below epidermis
- collagen/elasticity
- vascular plexus, lymphatics, nerves
- hair follicles, glands
- vessels susceptible to collapse under too much tension
chars. of Hypodermis
- assoc. with dermis
- mostly fat/CT
- contains panniculus
- contains subdermal plexus and direct cutaneous artery and vein, which runs PARALLEL in dogs/cats**
5 stages of wound healing and length of time for each**
Coagulation (<5 min) Inflammation (0-24hrs) Debridement (2-5d) Proliferation (Repair) (4-21d) Maturation (21d-2 years)
main players of primary coag. (formation of platelet plug)
platelets
vWF
subendothelial collagen
Describe process of inflammation
- vasodilation (redness, heat)
- egress of leukocytes and serum (swelling)
- fibrin cross-links through platelet plug
- neuts come first to engulf bacteria, release proteases, and prepare wound for macs (24-48hrs)
- macs engulf dead neut debris and clean up wound (2-5d)
- platelets»_space;cytokines
1st and 2nd phases of wound healing
1st: inflammatory
2nd: proliferative
Describe process of debridement
- removal of necrotic tissue and debris by macs
- aka lag phase
lag phase
critical period when wound is becoming weaker and you must rely solely on suture technique to hold it together
-duration dependent on: amt. of necrotic tissue, tissue type (presence of collagenase, metalloproteinase? what pH?)
Describe process of proliferation
- influx of fibroblasts (max @ 7-10d) signaled by mac after adequate debridement has occurs
- random, rapid deposition of type 1 collagen
- rapid gain in tensile strength “log phase”
- angiogenesis
- granulation tissue formation
- cytokine dependent
- pink, glistening
- epithelialization as myofibroblasts contract edges of wound
describe process of maturation
- collagen remodeling
- “second lag phase”
- linearization
- cross-linking
- continues for weeks to years
at how many days is tensile strength of tissue relatively equal to strength of tissue?
7-14 days
intrinsic wound factors
hypoproteinemia anemia malnutrition uremia DM hyperadrenocorticism infection
Extrinsic wound factors
mechanism (shear, crush, laceration, etc.)
foreign material
irradiation
antiseptics
T?F:steroids will delay collagen formation and wound healing
T
3 classes of wounds based on TIME and CONTAMINATION***
1) class 1: 0-6hrs, minimal contamination, 1ary closure common
2) 6-12 hrs, moderatie contamination, may use 1ary closure in some cicumstances
3) >12 hours, gross contamination, never use primary closre
What is a “clean” wound?
wound created by surgery, not entering GI or respiratory tract. No contamination or break in asepsis. (ie spay/neuter; SSI 5%)
irradiation and steroid effect on wound healing
delay wound healing
What is a “clean-contaminated” wound?
GI or resp. tract entered, minor break in asepsis.
ie. enterotomy or lung lobectomy; SSI = 10%
What is a “contaminated” wound?
> GI with gross contamination, inflammation, major break in aspepsis (ie enterotomy with spillage; SSI = 30%)
What is a “dirty” wound?
devitalized or necrotic tissue, gross debris, pus. (ie. infected bite wound)
Abx use in Class 1 and clean wounds
rarely necessary, unless systemically unhealthy.
-exceptions: time, foreign material
Abx use in Class 2-3 and clean-contaminated, contaminated, dirty
Should use broad spec penicillin or cephalosporin.
- takes 3-5days to do culture and sensitivity testing
- monitor well if wound based
