Equine Wounds Flashcards
how long does the inflammatory phase last
several days
what occurs to maintain hemostasis in the inflammatory phase
- reflex vasoconstriction
- platelet aggregation
- fibrin deposition
platelet and fibrin are activated by thrombin, leading to clot formation
what protects against infection during the inflammatory phase
leukocyte migration
granulocytes first (neutrophils) –> peak at day 2
macrophages later –> starting from 24 hours, lasts days to weeks
what does the inflammatory phase do
provides substrate and cellular signals for later stages of healing
synthesis and release of growth factors by macrophages initiates proliferation phase
when does the proliferation phase occur
active by 3rd day and continues for several weeks
how is angiogenesis initiated by
low O2 tension, high lactate concentration and low pH
capillary endothelial cells grow at 0.4-1mm per day
what are the major cell type by the 4th day
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
how is collagen deposited
fibroblasts produce collagen in a haphazard arrangement
begins slowly on 3rd day, peaks within 1-3 weeks
what is epitheliazation
slow process, first apparent 4-5 days after wounding
what occurs during the epithelialization during proliferation phase
migration and proliferation of basal keratinocytes
interaction of fibroblasts and keratinocytes –> further keratinocyte proliferation
migration of keratinocytes only occurs over a healthy granulation tissue
what is contact inhibition
occurs when keratinocytes meet in the middle of the wound
when does contraction occur
starts in 2nd week, lasts several weeks
what is the purpose of contraction
reduces surface area of wound by 40-80%
what occurs during contraction
differentation of fibroblasts into myofibroblasts
process slows and ceases when wound edges meet and/or when skin tension surrounding the wound becomes too high
when does the remodelling phase occur
begins during 2nd week and ends scar tissue 1-2 years later
what are the features of scar tissue
10-15% weaker than original tissue
how does wound activity slow
fibroblast proliferation and migration stops
growth factors signal decline
what is collagen re-arrangement
randomly orientated collagen fibres are re-arranged into bundles, cross-linked and aligned along lines of tension by fibroblasts –> gradual increase in would strength
when does wound strength improve
20% by 3 weeks
50% by 3 months
70-80% at conclusion of maturation
what are the differences between ponies and horses
ponies heal faster –> quicker and more intense inflammatory response, less dehiscence, less bone sequestra
why do body wounds heal faster
differences in rate of epithelialization and contraction
what causes exuberant granulation tissue
prolonged inflammatory response + excessive proliferation phase (proud flesh)
exuberant granulation tissue characterized by abundance of capillaries surrounded by collagen
what factors affect wound healing (11)
- systemic health and medications
- necrotic tissue
- tissue deficit
- Iatrogenic factors
- poor tissue oxygenation
- infection
- neoplastic formation
- foreign body
- loss of blood supply
- local factors
- continued trauma
how does concurrent disease/immunosuppression affect wound healing
pituitary pars intermedia dysfunction (PPID or Cushings) –> high endogenous cortisol –> decrease inflammation –> delayed healing +/- increase in change of wound infection
lymphosarcoma
viral disease
how does concurrent drug therapy affect wound healing
oral predisolone for asthma
how does malnutrition affect wound healing
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
what causes acute disruption to vasculature
arterial
venous
capillary
occlusion of vasculature by swelling
how does anemia affect wound healing
due to major hemorrhage –> decrease oxygen carrying capability –> local tissue hypoxia
local tissue hypoxia can also occur with inappropriate bandaging
how is angiogenesis affected by O2 tension
vessels forming in low O2 environments are immature and bleed easily
vessels forming in high O2 environments mature and form faster
what other wound healing processes affected by O2 tension
fibroblastic replication and migration and development of collagen
wounds with low O2 tension are more susceptible to infection as leukocyte activity is slowed
what areas of the wound are most commonly affected by necrotic tissue
skin margins and subcutaneous tissues
what occurs when bone is exposed
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
what is tissue deficit
skin most commonly affected
can also affect subcutaneous tissues –> dead space
blood vessels –> impaired blood supply
soft tissues –> dead space +/- alteration of function
what occurs during infection of a wound
very common inhibitor of healing
mainly bacteria but can also be fungi and parasites (biofilms)
usually characterized by purulent exudate
what can be done to minimize infection
- cleaning with antiseptics
- lavaging with isotonic fluids
- debridement
- choice of wound dressing
- debridement
- use of antibiotics
how does movement affect wound healing
between skin and deeper tissues
as a result of normal anatomical structures
during walking
within the wound bed
what can be done to minimize movement
- bandaging
- splints
- casts
- restricted movement
what local factors affect wound healing
- dead space
- cold/heat
- desiccation/maceration
- pH variations
- tension
how does continued trauma affect wound healing
- distal limb wounds –> almost always require bandaging
- harness/tack –> need time off from working
- recumbency –> especially in weak/emaciated horses
- self inflicted trauma –> not as common as dogs/cats
how do neoplastic transformations affect wound healing
- equine sarcoid –> most common
- squamous cell carcinoma –> both can appear similar to granulation tissue
what iatrogenic factors affect wound healing
- neglect by owner
- mismanagement
(errors of managment, over treatment, aggressive tissue insults)
what are wound characteristics
- location
- age
- type
- contamination
- stage of healing
what are the types of contamination in wounds
- clean: surgical wound created under aseptic conditions
- clean-contaminated: surgical would where the respiratory, alimentary or urogenital tract has been entered under controlled conditions
- contaminated: surgical wound with major break in aseptic technique or any open, acute, accidental wounds
- dirty or infected: old with devitalized tissue or gross contamination with foreign material
