Equine Wounds

Question 1

how long does the inflammatory phase last

Answer 1

several days

Question 2

what occurs to maintain hemostasis in the inflammatory phase

Answer 2

1. reflex vasoconstriction
2. platelet aggregation
3. fibrin deposition

platelet and fibrin are activated by thrombin, leading to clot formation

Question 3

what protects against infection during the inflammatory phase

Answer 3

leukocyte migration

granulocytes first (neutrophils) –> peak at day 2

macrophages later –> starting from 24 hours, lasts days to weeks

Question 4

what does the inflammatory phase do

Answer 4

provides substrate and cellular signals for later stages of healing

synthesis and release of growth factors by macrophages initiates proliferation phase

Question 5

when does the proliferation phase occur

Answer 5

active by 3rd day and continues for several weeks

Question 6

how is angiogenesis initiated by

Answer 6

low O2 tension, high lactate concentration and low pH

capillary endothelial cells grow at 0.4-1mm per day

Question 7

what are the major cell type by the 4th day

Answer 7

fibroblasts –> peak numbers by 7-14 days

recruited from adjacent tissue, undergo local proliferation and transform from local stem cells

initially –> proliferate and migrate –> later on: synthesis and re-organize

Question 8

how is collagen deposited

Answer 8

fibroblasts produce collagen in a haphazard arrangement

begins slowly on 3rd day, peaks within 1-3 weeks

Question 9

what is epitheliazation

Answer 9

slow process, first apparent 4-5 days after wounding

Question 10

what occurs during the epithelialization during proliferation phase

Answer 10

migration and proliferation of basal keratinocytes

interaction of fibroblasts and keratinocytes –> further keratinocyte proliferation

migration of keratinocytes only occurs over a healthy granulation tissue

Question 11

what is contact inhibition

Answer 11

occurs when keratinocytes meet in the middle of the wound

Question 12

when does contraction occur

Answer 12

starts in 2nd week, lasts several weeks

Question 13

what is the purpose of contraction

Answer 13

reduces surface area of wound by 40-80%

Question 14

what occurs during contraction

Answer 14

differentation of fibroblasts into myofibroblasts

process slows and ceases when wound edges meet and/or when skin tension surrounding the wound becomes too high

Question 15

when does the remodelling phase occur

Answer 15

begins during 2nd week and ends scar tissue 1-2 years later

Question 16

what are the features of scar tissue

Answer 16

10-15% weaker than original tissue

Question 17

how does wound activity slow

Answer 17

fibroblast proliferation and migration stops

growth factors signal decline

Question 18

what is collagen re-arrangement

Answer 18

randomly orientated collagen fibres are re-arranged into bundles, cross-linked and aligned along lines of tension by fibroblasts –> gradual increase in would strength

Question 19

when does wound strength improve

Answer 19

20% by 3 weeks

50% by 3 months

70-80% at conclusion of maturation

Question 20

what are the differences between ponies and horses

Answer 20

ponies heal faster –> quicker and more intense inflammatory response, less dehiscence, less bone sequestra

Question 21

why do body wounds heal faster

Answer 21

differences in rate of epithelialization and contraction

Question 22

what causes exuberant granulation tissue

Answer 22

prolonged inflammatory response + excessive proliferation phase (proud flesh)

exuberant granulation tissue characterized by abundance of capillaries surrounded by collagen

Question 23

what factors affect wound healing (11)

Answer 23

1. systemic health and medications
2. necrotic tissue
3. tissue deficit
4. Iatrogenic factors
5. poor tissue oxygenation
6. infection
7. neoplastic formation
8. foreign body
9. loss of blood supply
10. local factors
11. continued trauma

Question 24

how does concurrent disease/immunosuppression affect wound healing

Answer 24

pituitary pars intermedia dysfunction (PPID or Cushings) –> high endogenous cortisol –> decrease inflammation –> delayed healing +/- increase in change of wound infection

lymphosarcoma

viral disease

Question 25

how does concurrent drug therapy affect wound healing

Answer 25

oral predisolone for asthma

Question 26

how does malnutrition affect wound healing

Answer 26

protein is required for wound healing hypoproteinaemia --\> alterations in fibroplasia, angiogenesis, remodelling alteration in wound healing will be effective well in advance of clinical evidence of hypoproteinaemia, weight loss, etc

Question 27

what causes acute disruption to vasculature

Answer 27

arterial venous capillary occlusion of vasculature by swelling

Question 28

how does anemia affect wound healing

Answer 28

due to major hemorrhage --\> decrease oxygen carrying capability --\> local tissue hypoxia local tissue hypoxia can also occur with inappropriate bandaging

Question 29

how is angiogenesis affected by O2 tension

Answer 29

vessels forming in low O2 environments are immature and bleed easily vessels forming in high O2 environments mature and form faster

Question 30

what other wound healing processes affected by O2 tension

Answer 30

fibroblastic replication and migration and development of collagen wounds with low O2 tension are more susceptible to infection as leukocyte activity is slowed

Question 31

what areas of the wound are most commonly affected by necrotic tissue

Answer 31

skin margins and subcutaneous tissues

Question 32

what occurs when bone is exposed

Answer 32

susceptible to necrosis when the wound has exposed bone and/or disrupted periosteal blood supply leads to sequestrum formation which acts like a foreign body sequestra are more likely to occur if wound is infected

Question 33

what is tissue deficit

Answer 33

skin most commonly affected can also affect subcutaneous tissues --\> dead space blood vessels --\> impaired blood supply soft tissues --\> dead space +/- alteration of function

Question 34

what occurs during infection of a wound

Answer 34

very common inhibitor of healing mainly bacteria but can also be fungi and parasites (biofilms) usually characterized by purulent exudate

Question 35

what can be done to minimize infection

Answer 35

1. cleaning with antiseptics 2. lavaging with isotonic fluids 3. debridement 4. choice of wound dressing 5. debridement 6. use of antibiotics

Question 36

how does movement affect wound healing

Answer 36

between skin and deeper tissues as a result of normal anatomical structures during walking within the wound bed

Question 37

what can be done to minimize movement

Answer 37

1. bandaging 2. splints 3. casts 4. restricted movement

Question 38

what local factors affect wound healing

Answer 38

1. dead space 2. cold/heat 3. desiccation/maceration 4. pH variations 5. tension

Question 39

how does continued trauma affect wound healing

Answer 39

1. distal limb wounds --\> almost always require bandaging 2. harness/tack --\> need time off from working 3. recumbency --\> especially in weak/emaciated horses 4. self inflicted trauma --\> not as common as dogs/cats

Question 40

how do neoplastic transformations affect wound healing

Answer 40

1. equine sarcoid --\> most common 2. squamous cell carcinoma --\> both can appear similar to granulation tissue

Question 41

what iatrogenic factors affect wound healing

Answer 41

1. neglect by owner 2. mismanagement (errors of managment, over treatment, aggressive tissue insults)

Question 42

what are wound characteristics

Answer 42

1. location 2. age 3. type 4. contamination 5. stage of healing

Question 43

what are the types of contamination in wounds

Answer 43

1. clean: surgical wound created under aseptic conditions 2. clean-contaminated: surgical would where the respiratory, alimentary or urogenital tract has been entered under controlled conditions 3. contaminated: surgical wound with major break in aseptic technique or any open, acute, accidental wounds 4. dirty or infected: old with devitalized tissue or gross contamination with foreign material