Chapter 57 - Principles of wound healing

Question 1

3 phases of wound healing

Answer 1

inflammatory (injury - 1 wk)
proliferative (30 min-1mo)
remodeling (3 wk - 1 yr)

Question 2

Under which conditions do wounds heal best?

Answer 2

Adequate metabolic needs (take daily multivitamin)
moist (white petrolatum ointment)
clean
protected

Question 3

When to do scar revision

Answer 3

wait at least 6-12 mo

most scars spontaneously improve within 1-3 years

Question 4

When to time dermabrasion

Answer 4

8-12 wk after inflammatory phase

Question 5

Layers of epidermis/dermis

Answer 5

Corneum
Lucidum
Granulosum
Spinosum
Basale

Papillary
Reticular

Question 6

Healing by secondary intention: risks, when to do

Answer 6

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

Question 7

Tertiary intention

Answer 7

Delayed primary closure

Allow inflammatory phase (phagocytosis contaminated tissue, DEC microbial count), then close primarily

Question 8

Describe inflammatory phase

Answer 8

vasoconstriction (5-10 min)
coagulation cascade - fibrin clot
Activated plt --> chemotactic factors
Vasodilation (histamine)
Cellular - macrophage, neutrophil, lymphocyte infiltration

Question 9

What causes inflammatory phase to prolong

Answer 9

excess nonviable debris

Question 10

When does collagen deposition begin after injury?

Answer 10

After inflammation subsides

Question 11

Describe proliferative phase

Answer 11

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

Question 12

Describe remodeling phase

Answer 12

collagen remodeling, vascular maturation
scars pale, soft, less protruding
Convert III-I collagen, more organized/parallel
Up to 12-18 mo

Question 13

What percentage of tensile strength of normal skin do scars achieve?

Answer 13

Even after remodeling, 70-80%

Question 14

4 local factors that influence wound healing

Answer 14

Oxygenation
Infection
FB
Venous sufficiency

Question 15

Proliferative factors that influence wound healing

Answer 15

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

Question 16

Tenets of Halstead

Answer 16

gentle handle tissue
aseptic technique
sharp anatomic dissection
obliterate dead space
careful hemostasis
avoid tension

Question 17

How does dryness (desiccation) affect healing

Answer 17

Moisture essential esp for re-epitheliazation

dry = slower healing, more expenditure of epithelial cells in wound closure

Question 18

Why does vasoconstriction occur initially in the wound healing process?

Answer 18

The hypoxia is useful only initially as it activates platelets and endothelium

Question 19

Why relaxed skin tension lines matter

Answer 19

Incisions parallel to RSTL close w/ minimal tension
90 degree angle to them –> gape open widely
RSTL determined by collagen matrix, parallel to wrinkles

Question 20

Hypertrophic scar vs keloid

Answer 20

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.

Question 21

Three ways to treat keloid (besides surgery)

Answer 21

intralesional steroid/IFN/Rads

Question 22

Vitamin roles in wound healing (A, C, E, K)

Answer 22

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

Question 23

How does Zinc affect wound healing

Answer 23

cell differentiation, fibroplasia

Question 24

3 characteristics of ideal wound dressing

Answer 24

moist environment
absorb exudate
protect

Question 25

How does smoking affect wound healing? Alcohol?

Answer 25

Smoke- nicotine –> vasoconstriction –> ischemia

Alcohol –> global malnutrition

Question 26

How does Rads affect wound healing?

Answer 26

DEC fibroblast, myofibroblast, endothelial cell prolif; ischemia 2/2 hyalinazation/sclerosis of vessels

Question 27

How vacuum-assisted closure is beneficial

Answer 27

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

Question 28

Describe 5 types of collagen

Answer 28

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