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
what to use for debridement and lavage
sterile saline 0.9%, liberal volume. (betadine can kill fibroblasts if too high conc.)
wet to dry bandage
use physiologic/hypertonic saline and gauze as primary layer to suck moisture out of wound
-honey, sugar, antiseptics unnecessary
negative pressure bandage
- use porous sponge with subatmospheric pressure
- continuous removal of bacteria, exudate and edema fluid
- improves perfusion and granulation tissue
nonadherent dry to dry bandage
-indicated following debridement, to protect wound, encourage moist healing and epithelialization
semiocclusive nonadherent dry to dry bandage
- has evaporative fluid loss
- doesn’t harm wound bed
- ie. telfa and Ca alginate
types of drains
Active (preferred, creates vacuum in wound to remove exudative fluid and eliminate dead space; Jackson-Pratt)
Passive (relies on gravity and appropriate use to work; Penrose)
drains are always temporary - 3-5d max because presence of tube keeps debridement phase active, even though it is allowing drainage
Types of wound closure
Primary (immediate, 6hrs but before granulation 2d) Second intention (no sx closure, dependent on wound healing)
