20 Wound Healing

Question 1

Hemostasis

Answer 1

1º: Formation of platelet plug
2º: production of fibrin clot; intrinsic (8,9,10,12) and extrinsic (7) pathways-> common->coagulation phase

Intrinsic: APTT
Extrinsic: PT
Common: TT

Question 2

Inflammation cells

Answer 2

Neutrophils: first cells (24-48h), cytokines (TNF), proteases
Macrophage: activate and recruit other cells, chemoattractants, 48-96h
T lymph: bridge, strengthen scar formation (collagen), 1wk

Question 3

Proliferation

Answer 3

Day 4-12

Granulation tissue

Question 4

Proliferation important cells

Answer 4

Endothelial cells: mediated by TGFB, TNFa, VEGF; migrate and form new BV
Fibroblasts: ECM; mediated by PDGF

Question 5

Proliferation ECM

Answer 5

1 Structural proteins: collagen (type I [mature, 90%], type III [repair, 9%]; elastin
2 Proteoglycans: dermatan sulfate, chondroitin sulfate; forms ground substance, provide lattice for collagen
3 Adhesive proteins: fibronectin, laminin
4 Hyaluronic acid: fluid environment

Question 6

Reoganization

Answer 6

Type III -> I
ECM deposition (3 mo)

Question 7

Wound tensile strength

Answer 7

2 wk: 20%
3 wk: 30%
10-12 wk: 70-80% (max)

Question 8

Scar remodeling

Answer 8

12-18 mos

1-1.5 yrs = scar revision

Question 9

Epithelialization

Answer 9

Establish tissue integrity

Superficial = reepithelialization (24-48h, waterproof)

Question 10

Wound contraction

Answer 10

Contracture: inc contraction due to myofibroblasts
Myofibroblast: a-smooth muscle actin in thick bundles (stress fibers)

Question 11

Stratification of bacterial burden

Answer 11

Contamination (no multiply)
Colonization (multiply, no host response)
Infection (host response)

Question 12

Primary intention healing

Answer 12

Clean wounds
Mechanical apposition (sutures, tape glue, staples)

Question 13

Secondary intention healing

Answer 13

Reasons: infection, extensive tissue loss
More extensive healing (contracture)
Close spontaneously

Question 14

Tertiary intention healing

Answer 14

Potentially contaminated

Monitor for several days (clean, 3-5d)

Question 15

Systemic factors that affect wound healing

Answer 15

1 Age: physiologic changes, underlying diseases, medications
2 Nutrition: malnutrition (more infection, less collagen), vit C (no collagen, inc infection), vit A (inc inflammatory response), vit E, zinc (cofactor)
3 Metabolic disorders: DM (dec inflammation, angiogenesis, collagen; growth factors), uremia
4 Steroids: anti-inflammatory, prevents epithelialization and contraction
5 Chemo drugs: attenuates inflammation, delay 2 wks post-op
6 Smoking: vasoconstriction -> hypoxia

Question 16

Local factors affecting wound healing

Answer 16

1 Ionizing Radiation Therapy
2 Low Oxygen tension: hypoperfusion (low BV/cardiac failure; local causes), need for collagen synthesis; low BP = arterial insufficiency and vasoconstriction
3 Wound infections: >10^5 microorganisms per gram of tissue (high risk); staphcoccus

Question 17

Class I: clean wounds

Answer 17

clean: no 3 tracts (respi, GI, GU),

Class ID: prosthetic devices

Question 18

Class II: clean contaminated

Answer 18

entry into 3 tracts, done in elective procedures

Question 19

Class III: contaminated

Answer 19

contaminated by not infected

no time to prepare patient

Question 20

Class IV: dirty/infected

Answer 20

inflammatory reaction and frank infectious process

Question 21

Antibiotic prophylaxis

Answer 21

Only in class 2 and 3
Must be given before surgery (30 mins)
Know the half-life of antibiotics or double the usual dose

Cefazolin

Question 22

Acute wound (normal)

Answer 22

Predictable and result is well-healed wound

Standard inflammation, proliferation, remodeling

Question 23

Chronic wound (impaired)

Answer 23

Does not heal for 4 wks
Due to local/systemic factors

Delayed wound: dec strength but gets same integrity as normal wound; cause by reversible factors
Impaired healing: no mechanical strength; pts with compromised immune system

Question 24

Chronic wounds

Answer 24

Etiology: repeated trauma, excess inflammation, poor oxygen
Causes: GF breakdown, no synthesis of GFs

Question 25

Ischemic arterial ulcer

Answer 25

Arterial stenosis -> obstruction -> peripheral vascular resistance (claudication)

Diagnosis: distal portion of extremities, absent pulse, poor granulation, ankle-brachial index

Treatment: revascularization -> wound care

Question 26

Venous stasis ulcer

Answer 26

Aging -> venous stasis -> incompetent superficial/deep venous system -> ulceration
Chronic: incompetence of deep venous system

Diagnosis: shallow wound + lipodermatosclerosis (RBC leaks out)

Treatment: compression therapy

Question 27

Diabetic wounds

Answer 27

Neuropathy: sensory and motor loss = unrecognized injury, charcot foot
Peripheral vascular disease

Treatment: control DM

Question 28

Pressure injury

Answer 28

Excess pressure -> capillary collapse, muscle wasting
Supine: scarum
Wheelchair: ischial tuberosity

Treatment: prevention (turning schedule), wound care

Question 29

Stages of pressure ulcers

Answer 29

1 = intact skin
2 = partial thickness skin loss
3 = full thickness skin loss
4 = with fascia and bone
unstageable = eschar

Question 30

Hypertrophic scars

Answer 30

In confines of original wound
4 wks after trauma
Occur when not following relaxed skin tension lines (Langer’s lines)

Question 31

Keloid scars

Answer 31

Extend beyond border
Does not extend into subcutaneous
Common: earlobe, deltoid, parasternal, upper back

Question 32

Treatment of excess healing

Answer 32

intralesional corticosteroid injections: for younger scars, cannot remove scar just reduce; keloid > HTS; no systemic effects

silicone sheets: 24h/day for 3 mos

excision/surgery: HTS > keloid

radiation: destroys fibroblasts, for older adults
pressure: collagen maturation and flattening; for HTS after burns; pressure garment is worn 23-24 hrs for >1 yr