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Eq ACVS Phase 1 > Ch.5 Wound Healing > Flashcards

Ch.5 Wound Healing Flashcards

1
Q

Which wounds are clean, clean contaminated, contaminated and dirty

A

Clean - created under aseptic conditions
<1 x 10^5 (100,000) bacteria/g tissue

Clean contaminated - Surgical wounds of respiratory/ailimentay/urogenital entered under controlled conditions w/o min contamination
<1 x 10^5 (100,000) bacteria/g tissue

Contaminated - open, acute, accidental, major break in aseptic technique
>1 x 10^5 (100,000) bacteria/g tissue

Dirty - old, devitalized tissue, gross contamination, foreign debris

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2
Q

Describe the 3 classes of wounds

A

Class 1 <6hrs duration w min contamination
Class 2 6-12hrs duration w significant contamination
Class 3 >12hrs duration w gross contamination

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3
Q

What are the phases of the healing process?

A

1 - Inflammatory or lag phase - hemostasis and acute inflam

2 - Proliferative phase - tissue formation

3 - Remodeling phase - healing tissue regains strength

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4
Q

When is a delayed primary closure performed

A

Clean contaminated w edema/questionable tissue viability
2 - 5 days after injury

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5
Q

When is a secondary closure performed

A

Contaminated or infected wound
At least 5 days after injury

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6
Q

What are the functions of PMN (polymorphonuclear cells) in tissue repair

A
  1. Phagocytosis of microbes
  2. Macrophage activation
  3. Amplify inflammatory response
  4. Stimulate repair process
  5. Mediators - reactive oxygen species, cationic peptides, eicosanoids, proteases
    TNF Alpha
    IL-1Beta IL-6
    VEGF, IL-8
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7
Q

What are the functions of macrophage in tissue repair

A
  1. Phagocytosis of PMN, damaged tissue and microbes
  2. Amplify repair process
  3. Stimulate angiogenesis and fibroplasia
    Fibrolysis
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8
Q

What is the early wound clot known as

A

Provisional wound matrix

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9
Q

Activated platelets within the provisional wound matrix direct and amplify the early inflammatory phase of healing through the release of what

A

Wound repair mediators most importantly
1) PDGF - Platelet derived growth factor
2) TGF-Beta - Tissue growth factor Beta

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10
Q

What activates Leukocyte migration into the wound?

A
  1. Exposed collagen
  2. Elastin breakdown products
  3. Complement factors
  4. Cytokines
  5. Changes in mechanical tension
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11
Q

What are the first cells to enter the wound in large numbers and are the hallmark of acute skin injury

A

PMNs polymorphonuclear cells

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12
Q

On what day do PMN polymorphonuclear cells numbers peak

A

Day 2 and decline as debris is cleared from the site

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13
Q

What are the roles of the neutrophils in the wound

A
  1. Remove damaged tissue and bacteria by phagocytosis
  2. Release chemoattractant to further augment the early cellular inflammatory response
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14
Q

At what stage after injury do circulating monocytes enter the wound and differentiate into macrophages

A

24 hours

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15
Q

What proteinases are released by the macrophages in the wound

A

Elastase
Collagenase
Plasminogen activator

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16
Q

What initiates the proliferative phase of wound repair

A

Tissue growth factors released by macrophages

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17
Q

After how long is the proliferative phase of wound repair active

A

Day 3

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18
Q

What is the proliferative phase of wound repair characterised by

A
  1. Angiogenesis
  2. Fibrous and granulation tissue formation
  3. Collagen deposition
  4. Epithelialization
  5. Wound contraction
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19
Q

What initiates the process of angiogenesis

A

Decreased oxygen tension
High lactate levels
Low pH

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20
Q

The endothelial cells at the tips of capillaries adjacent to the wound grow at what rate

A

0.4 - 1.0 mm/day

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21
Q

What growth factors play a significant role in neovascularization?

A

VEGF - Vascular Endothelial Growth Factor
bFGF - basic Fibroblast Growth Factors

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22
Q

What do MMPs (matrix metalloproteinases) do?

A

Reduce migration and proliferation of endothelial cells

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23
Q

When do fibroblasts arrive in the wound

A

Day 2

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24
Q

What are the major cell type in the wound bed by day 4

A

Fibroblasts

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25
On what day does the fibroblast number peak
7-14 days
26
What regulates fibroblast migration and proliferation
PDGF - platelet derived growth factor TGF-Beta - transforming growth factor bFGE - basic fibroblast growth factor
27
What do fibroblasts synthesise and release
1.Collagen 2. Glycosaminoglycans - hyaluronan 3. Glycoproteins - fibronectin and laminin 4. Elastin 5. Proteoglycans 6. Proteases including MMPs (matrix metalloproteinases)
28
When does collagen production begin in a wound
Day 2-3
29
When does collagen production reach peak production
1-3 weeks
30
Which type of collagen do wound fibroblasts produce
Type 1 collagen
31
30-40% of collagen found in the acute wound will be what type of collagen
Type III
32
Why is the relationship between keratinocytes and fibroblasts important
Keratinocytes stimulate fibroblasts to synthesize and release growth factors and cytokines which in turn stimulate keratinocyte proliferation
33
How do keratinocytes clear a path across the wound surface
They synthesize and release collagenases, MMPs and plasminogen activator
34
How long before new epidermis is evident at the wound edges
4-5 days
35
How does new epidermis differ from that found in uninjured skin
It lacks retepegs which anchor it to the underlying connective tissue matrix In full thickness wounds it lacks a dermal layer without which there is a loss in tissue strength and elasticity
36
When does contraction begin in full thickness wounds
2nd week following injury
37
How much does contraction reduce the wound surface in full thickness wounds
40-80%
38
What is the rate of contraction in areas with loose skin
0.75mm/day
39
What is responsible for fibroblasts to form myofibroblasts
TGF-B1 released from macrophages and keratinocytes
40
What signifies the change from fibroblast to myofibroblast
Acquisition of an alpha smooth muscle actin microfilament system
41
Function of the actin microfilament system
Wound contraction
42
How does scar tissue strength compare to original tissue strength
15 - 20% weaker
43
What does the remodelling and maturation phase begin with
Begins with the replacement of Hyaluronan in provisional matrix by proteoglycans in the ECM
44
when does the remodelling and maturation phase begin and end
Begins 2 weeks after injury - continues for 1-2 years
45
What is the strength of scar tissue at 3 weeks vs original tissue
20%
46
At what stage is scar tissue 50% of original tissue strength
3 months
47
What % of wounds closed by primary intention are thought to dehisce
59-74%
48
How does wound healing in horses differ greatly from other species
Marked diff btw species ie horse vs pony Varied healing rate depending on location Exuberant granulation tissue
49
How does wound healing in ponies differ from horses
Faster More intense inflammatory response - less infection Myofibroblasts are organised and orientated parallel to the wound surface for optimal healing at 2 weeks Less bone proliferation In exp study 7-9 week repair in pony vs 12 in horse
50
What is the reported rate of re-epithelialization in distal limb wounds in horses
0.09mm/day
51
What is the reported rate of contraction in distal limb wounds in horses vs body
Distal limb .2mm/day Body 0.8 - 1mm/day
52
Contamination with how many microorganisms in the presence of soil can result in infection
100
53
What are the most common wound isolates
Pseudomonas aeruginosa Staphylococcus spp
54
What is believed to be the cause of exuberant granulation tissue in horses
PMNs stay higher in horses for a longer period of time resulting in chronic inflammation - imbalance of mediators released from PMNs - tumour necrosis factor alpha, IL-1, IL-6, PDGF, TGF-B and bFGE contributes to profibrotic state. TGF-B1 enhances migration and proliferation of fibroblasts and subsequent collagen production and delays fibroblast apoptosis
55
Why more excessive granulation tissue in distal limb
Tissue hypoxia as a result of microvascular occlusion of the small capillaries within the granulation tissue found to be 3 times higher in distal limb Potentially bandaging - lowers cutaneous temp due to dc blood flow - stimulates angiogenesis and wound debris on bandage provides constant source of inflammatory mediators.
56
Wound dressing guidelines
Occlusive dressing in clean wounds until healthy bed of granulation tissue develops then switch to semi occlusive Dirty wounds - adherent hydrophilic or antimicrobial dressings until healthy granulation tissue forms then switch to semi-occlusive
57
Effect of shockwave on distal limb wounds
Decreases TGF-B1
58
How does protein deficiency delay wound healing
Suppresses fibroblast proliferation, angiogenesis, collagen synthesis and remodelling
59
Role of Vit E in wound healing
Antioxidant Augments antimicrobial action against MRSA
60
Role of B Vitamins in wound healing
Important cofactors in collagen cross linking reactions
61
How should fluids be applied to a wound for debridement
At an oblique angle Pressure of 7-15lbs per square inch 1L bag - pressurised to 300mmHg - 16-22G needle
62
How is autolytic debridement achieved
Placing an occlusive dressing over the wound, trapping the body's own proteases within the wound to liquefy necrotic tissue
63
What are the ingredients in Granulex used for chemical debridement
Trypsin Peruvian balsam Castor oil
64
Which fly larvae are used in maggot debridement
Lucilia sericata
65
How much necrotic tissue can maggot consume per day
75mg
66
Suture tension above what pressure leads to tissue necrosis
>30-40mmHg (above capillary pressure)
67
How dilute should chlorohex be to use on wound
0.05% Add 25ml of 2% chlorohex to 975ml saline
68
How dilute should povidone-iodine be to use on wound
0.1-0.2% 10-20ml of 10% Pov-Iod to 980/990ml saline
69
What % hydrogen peroxide is toxic to fibroblasts
3% but 1%cream - faster healing
70
What additional benefits does SSD possess over triple abx
Effective against pseudomonas and fungi
71
Draw backs of nitrofurazone
Decrease epithelialisation Decrease wound contraction Carcinogenic
72
Benefits of honey on wound healing
Efficacious against 10 common pathogens inc MRSA Decrease distal limb wound retraction Improves wound healing up to day 21
73
Which growth factor has been approved for topical use
PDGF -Platelet derived growth factor
74
What does PRP contribute to wound healing
Rich in: TGF-B PDGF -platelet derived growth factor Epidermal growth factor Transforming growth factor alpha VEGF - vascular endothelial growth factor Serotonin Histamine Secrete: fibrin, fibronectin vitronectin which act as a matrix providing a surface for epithelial migration
75
Benefit of using Acemannan
Active ingredient of aloe vera accelerates the production of granulation tissue over exposed bone
76
What proregenerative cytokines are secreted from stem cells
VEGF, EGF, KGF, IGE

Eq ACVS Phase 1 (72 decks)

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