Ch 76 open wounds Flashcards
What are the four ‘steps’ of wound healing
- Formation of fibrin-platelet plug
- Recruitment of WBCs to protect from infection
- Neovascularisation and cellular proliferation
- Tissue remodeling
What are the most common locations of a decubital ulcer?
Greater trochanter
Lateral elbow
Lateral hock
Define contamination, colonisation and infection
Contamination - The presence of microbes on a surface
Colonisation - Surface microorganisms are replicating
Infection - Invasion and replication of microorganisms within the tissue
What microbial burden has been associated with a higher rate of infection? What time does it typically take to reach this level?
10^5 CFU/g
Within 6 hours
What is a more relevant calculation of microbial burden?
Microbial burden = (Number of microorganisms x Virulence) / Host Resistance
How does the production of granulation tissue of cats differ to that of dogs?
Open wounds in cats produce significantly less granulation tissue and is more likely to have a peripheral, rather than central, distribution
At 21 days after wounding, how does epithelialisation and total healing differ in dogs anc cats?
Dogs: epithelialisation 89%, total healing 98%
Cats: epithelialisation 34%, total healing 84%
What are some potential causes of open wounds which fail to progress towards healing (8)?
- Systemic disease (uraemia, herpatic dz, DM, cushings, FIV)
- Malnutrition
- Local tissue hypoxia and ischaemia (Normovolaemia must be maintained, blood transfusin if anaemic)
- Bacterial colonisation
- Altered cellular and stress response
- Repetitive trauma
- Presence of necrotic tissue
- Tension
What are some options to improve wounds which are incapable of forming granulation tissue?
- Omental flaps
- Muscular flaps
- Vascular skin flap for closure
Immediate Wound Care
aimed at reducing the microbial burden and preventing further contamination.
- irrigation
- antimicrobial (topical, systemic if wound infected > exit tissue culture after wound debridement)
- protection
Is tap water hyper-, iso-, or hypotonic?
Hypotonic
What pressure is generally recommended for high pressure irrigation?
How is this best achieved?
16-22g needle onto a fluid administration set of a 1L bag of fluids under pressure of 300mmHg
Topical antimicrobial agents suitable for immediate wound management
- antimicrobial ointments,
- silver-based dressings,
- hyperosmotic dressings (20% hypertonic saline, honey, sugar)
List hyperosmotic wound dressings
Hypertonic saline (20%)
Honey
Sugar
definitive wound care involves (5):
- wound prep
- debridement
- moist environment
- topical ab’s
- NPWT
Is saline or a balance electrolyte preparation recommended for wound preparation? Why?
Balanced electrolyte prep
- Saline is slightly hypoosmolar and is cytotoxic to fibroblasts
What antiseptics can be used in the wound
0.05-0.1% chlorhexidine
0.1 - 0.01% povidone-iodine
No detergents! (Cytotoxic)
Why is debridement important?
Presence of contaminants causes inflammation and devitalised tissue acts as a medium for microbial growth
What are the 3 braod categories of wound debridement?
- En Bloc Debridement (and then primary closure)
- Layered debridement
- non-surgical
aspetic, Exploration and exposure of the deeper levels
Layered debridement
- sequential removal of devitalized tissue at the surface of the wound, progressing to the wound depths.
- intent of debridement is to have a well-vascularized wound bed
- cortical bone (“forage”) allows the vascular medullary canal to communicate with the wound bed
- Excess fat should be removed
- intact fascia debrided to expose underlying vascular muscle tissue
What tissues are not well vascularised? How is this overcome?
Cortical bone - forage
Excess fat - removed
Intact fascia - debrided to expose underlying muscle
Nonsurgical Debridement
- topical application of enzymatic or chemical agents that dissolve collagenous tissue and cause superficial sloughing of debris and devitalized tissue
- enzymes; take time to have an effect, can be expensive, are nonselective > indicated in chronic, indolent, or nonhealing wounds
Honey
- antimicrobial effects that are not explained by hyperosmolality alone or by hydrogen peroxide
- inhibin number is the amount of dilution to which the honey will retain its antibacterial activity
- eduction of inflammation because of antioxidant
- facilitation of wound healing by stimulation of B- and T-lymphocyte proliferation, phagocytic activity
wet-to-dry
- Mechanical debridement
- require more intense wound care sp dpn’t get too dry
- are nonselective and will debride normal tissue
- never be applied to a healthy granulating wound.
maggots
- secrete digestive enzymes to dissolve necrotic tissue.
What substances do most enzymatic debridement agents contain?
Trypsin
Collagenase
Papain
Urea
How do nonenzymatic debridement dressings work?
What are some examples?
- Draw exudate and accompanying debris out of the wound
- Dehydrate microorganisms and have a cidal and inhibitory effect
- Hypertonic saline dressings. Sugar-, Honey- and Dextran-soaked dressings
How is hydrogen peroxide produced by honey? At what concentration?
Hydrogen peroxide is produced by the action of glucose peroxidase (within the honey) on glucose.
Forms at a very low concentration of 0.003%
What antimicrobial effects are provided by Honey?
What is the inhibin number of medical grade Honey?
Hydrogen peroxide production
Oxygen-derived free radicals
Phytochemicals (phenols and organic acids)
Acidic pH (3.2 - 4.5)
The inhibin number is the amount of dilution to which the honey will retain its antibacterial activity
Other than is antimicrobia properties, what other effects of Honet may enhance wound healing?
Reduction of inflammation due to anti-oxidant content
Stimulation of B- and T-lymphocyte proliferation
Stimulation of phagocytic activity
Stimulation of cytokine release from monocytes
What type of maggots are used for wound debridement?
Maggots of the green blow fly Lucilia Sericata
Can destroy healthy epithelium - MUST be protected
Moist Wound Healing
- fostering a moist wound environment to facilitate debridement, granulation tissue formation, and epithelialization
- facilitates autolytic wound debridement
- Dry to minimally exudative > hydrogel dressing
- Mild to moderately exudative > hydrocolloid sheet, polyurethane foam dressing
- Heavily exudative > colloidal dressings (alginate) or hypertonic saline
What is the underlying prinicple of moist wound healing?
Application of a hydrophilic (moisture retentive) dressing to maintain the cellular and cytokine-rich exudate at the wound surface
What is typically included in a triple antibiotic ointment?
Bacitracin zinc
Neomycin sulphate
Polymixin B sulphate
How does incorporation of silver into alginate dressing effect its function?
- Increased antimicrobial activity
- Improved binding affinity for elastase, MMP-2, TNF-a, and IL-8
- Further inhibited production of free radicals
silver
- Use of 1% silver sulfadiazine is fast being replaced by newer nanoparticle slow-release, silver-impregnated dressings
- silver dressings may result in a surface exudate > similar to that seen with Pseudomonas infections.
- After the exudate has been removed with wound irrigation, the true color of the underlying wound bed can be evaluated.
How do bioscaffolds work?
What wounds are they recommended for?
Provides a substrate for extracellular matrix formation
Stimulates matrix deposition, angiogenesis and epithelialisation due to collagenous and growth factor content
Recommended for use with chronic, indolent ulcers
What is chitosan?
What are its reported functions?
Chitosan is a lineal copolymer of linked Beta glucosamine and N-acetly-D-glucosamine
Reported functions:
- ENhance the action of inflammatory cells
- Increase production of granulation tissue through upregulation of TGF-B, PDGF, fibroblast production and IL-8 production
List 2 growth factor-containing agents which coulf be used in wound management?
rhPDGD-BB
Autologous PRP
What is the recommended porosity of the foam and recommended pressures for negative pressure wound management in small animals?
400 - 600 mcm pore foam
Recommended -125mmHg for foam-based or -80mmHg for gauze based systems
What are the purported benefits of negative pressure wound therapy? (5)
Improve wound perfusion
Reduce oedema
Stimulat granulation tissue formation
Decrease bacterial colonisation
Remove exudate
Expression of which growth factors/cytokines may be increases in negative pressure wound therapy?
VEGF and FGF-2 (experiment on rats)
IL-8 and VEGF (humans)
How may NPWT be beneficial for skin grafting? Used at what pressure?
Benefits:
- Stibilisation of the graft
- Reduce fluid accumulation under the graft
- Prevent dessication
- Possibly prevent bacterial contaminations
Pressure -65 to -75mmHg
What are the effects of NPWT on bacterial burden?
Unclear….
- Upregulation of IL-8 and IL-1B may trigger accumulation of neutrophils and thus accelerate bacterial clearance
Negative-Pressure Wound Therapy
- local application of subatmospheric pressure across a wound
- occlusive dressing, mechanical unit that applies constant negative pressure (suction).
- Controlled experimental studies in dogs show positive and negative effects
- alter the interstitial fluid gradient reduce edema, potentially increasing dermal perfusion (how this exactly acheved is unclear)
- tissue perfusion can decrease with increasing suction and increased tissue pressure
- STUDY: pressures from −75 to −100 mm Hg might effectively stimulate blood flow while minimizing marginal hypoperfusion
- granulation tissue formation thought to result from stress and strain created in the extracellular matrix, altering the proliferative response > likely modulated by molecular mechanism (VEGF, IL8, FGF).
- Intermittent suction appeared to have a greater effect than continuous suction and may promote vascular proliferation within the wound
In vitro evaluation of a hybrid negative pressure system for
wound therapy
Jack S. Davey 2024
A commercial NPWT device (control) and three homemade-NPWT devices (wall suction)
commercial NPWT device produced an average pressure
variance of 3.02 mmHg, and the h-NPWT produced average variances of 4.38
The h-NPWT system achieved negative pressures that were comparable
to those of a commercial control NPWT device
CHRONIC AXILLARY
WOUNDS IN CATS
Pathophys
- in one case report, bacterial biofilm was shown to be present upon
- presence of foreign material
- poor local blood supply in the area leads to poor granulation
- high mobility
- tension
histopathological analysis of a chronic non-healing pressure wound in a dog
- For long-term resolution of an axillary
wound, antimicrobial therapy is important (infection is one of the
most common complications observed) - tissue sample recommended for ab stewradship
- wound management first (irrigation, debride, tie-over)
definitive TX
- simple closure: complications after initial wound closure leading to suboptimal outcomes and further treatment have frequently been reported in the literature
- omental pedical graft: before primary closure,blood supply and lymphatic tissue, as this assists with controlling infection achieved positive results in 70% of the wounds presented, and the average healing time was 24 days.
- elbow skin flap: can function as an
axial pattern flap, is created by detaching the skin from the trunk to allow cranial advancement
- APF: thoracodorsal and lateral thoracic artery axial pattern flaps and the omocervical flap, provide full-thickness skin coverage, resistance to infection and early immobilisation and neovascularisation,
- complications associated with skin flaps is seroma formation, which may lead to infection > active suction drains
- in one study combining omentalisation and a thoracodorsal
axial pattern flap, 100% of the wounds had healed within 14 days and only 20% required minor revision surger
Studies comparing a superficial swab with deep tissue culture for microbial
culture and sensitivity testing, both in human and veterinary medicine
- these showed no clear advantage of one technique over the other.
- the Levine technique, where a swab is pressed on 1 cm2 of healthy tissue in the wound until fluid is obtained, is suitable
- One advantage of tissue biopsy is that the resulting sample can also be
sent for histopathological analysi
Treatment of moderate grade dog bite wounds using
amoxicillin–clavulanic acid with and without enrofloxacin:
a randomised non-inferiority trial
NJ Kalnins 2021
AVJ
Of the 24 dogs in treatment group A, 1 required the
addition of enrofloxacin at re-examination. None of the 26 dogs
in group B required alteration of antimicrobial coverage.
Twenty-one different organisms were identified:
Staphylococcus pseudintermedius, Neisseria spp., Pasteurella
multocida and P. canis were the most common. Over 90% of
gram-negative and gram-positive isolates were susceptible to
amoxicillin–clavulanic acid.
Amoxicillin–clavulanic
acid is an appropriate empirical antimicrobial choice for moderate
DBW in South East Queensland.
Heald 2022 – electroceutical dressing for management of chronic (>6m) wounds in a dog and a cat
- electroceutical → bacterial inhibition by interrupting bacterial adhesion, generation of
hypochlorous acid + may stimulate angiogenesis, keratinocyte proliferation and migration- reduction in wounds in treated cases that previously failed other treatments
There is a plethora of modern wound dressings available, but
unfortunately there is insufficient data on the application of these in dogs and cats to make evidence-based recommendations.12,17
- only two studies are available that have investigated the effect of different dressings in cats. The rest are mainly case-reports
- consdier using NPWT in cats
The effects of a proprietary Manuka honey and essential oil
hydrogel on the healing of acute full-thickness wounds
in dogs
Raphael L. Repellin 2021
stanley
acute, full-thickness wounds in dogs.
Study design: Prospective, controlled, randomized, experimental study
no difference of infection
rate between the two groups (superficial, did not require Tx, 17%)
This study did not provide evidence to support the application of
HoneyCure® in small, acute wounds in healthy dogs > wounds in both groups healed in the
same amount of time.
However, application
may be beneficial in the early proliferative stage of wound healing and in wounds that would benefit from early, robust epithelialization.
Comparison of bacteriologic culture results
for skin wound swabs and skin wound biopsy specimens
Stokes 2021
52 client-owned dogs
Culture results of swab and tissue biopsy specimens were identical in 11/52
(21.2%) cases. Tissue biopsy specimen and swab cultures yielded positive
results for 44 (84.6%) and 40 (76.9%) wounds, respectively
In 7/52 (13%) wounds, the observers would have treated the patient
differently on the basis of the results of the 2 cultures
swab collected by the Levine technique
is an appropriate noninvasive alternative to culture of a tissue biopsy specimen.
A negative result obtained from culture of a swab is likely to be reliable.
Disagreement between the results of swab and tissue biopsy specimen
cultures is likely of low clinical importance
Rationale for hyperbaric oxygen therapy in traumatic injury and wound care in small animal veterinary practice
D. M. Levitan 2021
could improve short- and long-term outcomes in complicated wounds.prospective studies for the various clinical situations described
due to lack of compelling data from well-designed studies in the veterinary peer-reviewed literature
best applied in situations where healing is
impaired, such as with severe swelling, infection, crush injury,
radiation scars and hypoxic tissue > chronic oxygen deficiency and the local oxygen tension is not
optimal for healing
patient breathes 100% oxygen while inside a pressurised chamber,
benefits
- Vasoconstriction and reduced inflammation
- HBOT enhances the function of leukocytes
- antibacterial and antifungal effects of HBOT
- Reduction of ROS in ischemia/reperfusion injury
- Neovascularisation
indicated for: reperfusion injury (spinal), graft, necrotizing wounds, burns
Pretreatment aerobic bacterial swab cultures to predict
infection in acute open traumatic wounds: A prospective
clinical study of 64 dogs
Lauren E. Hamil 2020
Prospective clinical trial.
Animals: Sixty-four dogs
Initial swabs were taken from each wound prior to and after lavage
and debridement
Fewer bacteria were cultured from postlavage than from prelavage
swabs in 43 of 50 (86%) acute wounds
Postoperative infection was subsequently
diagnosed in 14 of 64 (22%) dogs; 13 of these dogs had positive culture
results. Bacterial species
present in the initial wound swab did not correlate with those subsequently
cultured from infected tissues.
Routine bacterial culturing of acute wounds is not
likely to help predict subsequent wound infection, nor is it likely to accurately
guide early selection of antimicrobials to treat wounds that become infected.
Comparison of Negative Pressure Wound
Therapy and Silver-Coated Foam Dressings in
Open Wound Treatment in Dogs: A Prospective
Controlled Clinical Trial
Nolff 2018
Prospective randomized clinical study
Materials and Methods Dogs (n = 26)
shorter time to closure (14.2d) vs foam dressing (28.6d)
- greater reduction in total wound area at all time points
- less progression of local infection
NPWT-treated wounds showed faster closure, improved macro-deformation
and less local signs of infection.
The available experimental and retrospective clinical trials
in dogs and cats demonstrated faster granulation, effective
local infection control and improved closure rates
resulted in
faster closure using NPWT compared with foam during the
first 9 days: faster reduction in both the wound area and
volume occurred. To understand these effects, several factors
must be considered. As thewoundswere ultimately surgically
closed whenever possible, the exact duration of open treatment
is notwithout bias.
One potential drawback is the increased time of hospitalization,
as well as the increased time needed for dressing changes
as well as the need for anaesthesia during dressing changes
HUMANS
Several recent trials report that tap water (TW) of drinkable quality is as safe and effective as normal saline for the cleansing of acute traumatic wounds, odds of infection equivical
Stanley 2017 – review
- cycling of pressure → increased blood flow (oxygenation and nutrient supply) alternating
with decreased blood flow (hypoxia → stimulation of angiogenesis
and fibroplasia)
Mauer 2021 – acellular fish skin grafts for wounds in 11 dogs, 4 cats
treated FSG maintains omega-3 fatty acids, collagen, elastin, laminin, lipids, fibrin, proteoglycans and glycosaminoglycans
- omega-3 → anti-viral, anti-bacterial and anti-inflammatory properties
- anti-bacterial for up to 24-72 hours in human wounds
- 3D microporous structure of FSG homologous to mammalian extracellular matrix
- incorporated into would within 7-10 days
- no risk of autoimmune reactivity (vs mammalian grafts) and no communicable disease
- number of applications: dogs: median 2 (1-4), cats: 1-2
- time between each application: dogs 4-21 days
- closure by second-intention by median 71 days (26-145) in 10/11 dogs, 3/4 cats
- failure to heal in 1 dog, 1 cat
