Chapter 57 - Principles of wound healing Flashcards
3 phases of wound healing
inflammatory (injury - 1 wk)
proliferative (30 min-1mo)
remodeling (3 wk - 1 yr)
Under which conditions do wounds heal best?
Adequate metabolic needs (take daily multivitamin)
moist (white petrolatum ointment)
clean
protected
When to do scar revision
wait at least 6-12 mo
most scars spontaneously improve within 1-3 years
When to time dermabrasion
8-12 wk after inflammatory phase
Layers of epidermis/dermis
Corneum Lucidum Granulosum Spinosum Basale
Papillary
Reticular
Healing by secondary intention: risks, when to do
ADV: low infection risk, high healing rate, surveillance if cancer incompletely excised
DIS: greater contracture
works best in concavities (temporal fossa, medial canthus, alar groove), good with forehead/scalp
Tertiary intention
Delayed primary closure
Allow inflammatory phase (phagocytosis contaminated tissue, DEC microbial count), then close primarily
Describe inflammatory phase
vasoconstriction (5-10 min) coagulation cascade - fibrin clot Activated plt --> chemotactic factors Vasodilation (histamine) Cellular - macrophage, neutrophil, lymphocyte infiltration
What causes inflammatory phase to prolong
excess nonviable debris
When does collagen deposition begin after injury?
After inflammation subsides
Describe proliferative phase
re-epitheliazation (completed in 24 hr in primary closure)
Fibroblasts day 2 proliferate, produce III coll, elastin, ECM
Wound contraction via myofibroblasts, centripetal, maximal at 10-15d
Describe remodeling phase
collagen remodeling, vascular maturation
scars pale, soft, less protruding
Convert III-I collagen, more organized/parallel
Up to 12-18 mo
What percentage of tensile strength of normal skin do scars achieve?
Even after remodeling, 70-80%
4 local factors that influence wound healing
Oxygenation
Infection
FB
Venous sufficiency
Proliferative factors that influence wound healing
GH- fibroblast prolif
EGF- from platelets. epithelial/fibrob prolif/migrate, activate fibroblast, vascular form
PDGF- chemoattractant for PMN/mac/fibroblast
FGF- from macrophage/mast/lymphocytes/endothelial cell/fibroblast…prolif vascular endothelial cells
TGF- prolif epithelial cell, fibro
IGF-1 via liver/plasma/fibroblasts, proliferation fibro, ECM
TNF- from macrophage/mast/lymphocyte, promote fibroblast prolif
Tenets of Halstead
gentle handle tissue aseptic technique sharp anatomic dissection obliterate dead space careful hemostasis avoid tension
How does dryness (desiccation) affect healing
Moisture essential esp for re-epitheliazation
dry = slower healing, more expenditure of epithelial cells in wound closure
Why does vasoconstriction occur initially in the wound healing process?
The hypoxia is useful only initially as it activates platelets and endothelium
Why relaxed skin tension lines matter
Incisions parallel to RSTL close w/ minimal tension
90 degree angle to them –> gape open widely
RSTL determined by collagen matrix, parallel to wrinkles
Hypertrophic scar vs keloid
Hyper: remain within boundary of injury, regress with time, wavy/randomly organized collagen, parallel to epithelial surface
Keloid: cross boundary, may enlarge, thick fibers closely packed together.
Three ways to treat keloid (besides surgery)
intralesional steroid/IFN/Rads
Vitamin roles in wound healing (A, C, E, K)
A- reepithelialize, collagen synth, cross-link
C- lysine/proline hydroxylation in collagen synth antioxidant (reductant in free radical formation), PMN fxn
E- reduces collagen production to decrease wound tensile strength
K- clotting factors
How does Zinc affect wound healing
cell differentiation, fibroplasia
3 characteristics of ideal wound dressing
moist environment
absorb exudate
protect
How does smoking affect wound healing? Alcohol?
Smoke- nicotine –> vasoconstriction –> ischemia
Alcohol –> global malnutrition
How does Rads affect wound healing?
DEC fibroblast, myofibroblast, endothelial cell prolif; ischemia 2/2 hyalinazation/sclerosis of vessels
How vacuum-assisted closure is beneficial
skin grafts
remove fluid secretions that prevent revascularization/imbibition of graft
promote granulation in infected wounds healing by 2 intention
Never use with nasal, oral, tracheal, blood vessels or neoplastic sites
Describe 5 types of collagen
I- skin/bone/tendons/connective tissue
II- cartilage, cornea stroma, vitreous humor…shock abs/joint mobile
III- formation of fibrous elements, ubiquitous
IV- basement membrane, scaffold for filtration
V- cytoskeleton…ubiquitous
