Chapter 76: Open Wounds Flashcards
What are the 4 phases of wound healing?
- Inflammation
- Debridement
- Repair
- Maturation
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, colonization and infection:
Contamination - The presence of microbes on a surface
Colonization - 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 differ between cats and dogs?
- Open wounds in cats produce significantly less granulation tissue and are more likely to have a peripheral, rather than central, distribution of it
At 21 days after wounding, how does epithelialization and total healing differ in dogs and cats?
Dogs: epithelialization 89%, total healing 98%
Cats: epithelialization 34%, total healing 84%
What are some (8) potential causes of open wounds which fail to progress towards healing?
- Systemic disease (uremia, hepatic disease, Diabetes, Cushings, FIV)
- Malnutrition
- Local tissue hypoxia and ischemia (Normovolemia must be maintained, blood transfusion if anemic)
- Bacterial colonization
- 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
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
Gives you 7-8 psi
List hyperosmotic wound dressings:
- Hypertonic saline (20%)
- Honey
- Sugar
List some hydrophilic wound dressings:
- Hydrogel
- Hydrocolloid
- Alginate
Should you use saline or should you use a balanced electrolyte preparation for initial wound preparation? Why?
Balanced electrolyte prep
- Saline is slightly hypotonic 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 categories of wound debridement?
- En Bloc (and then primary closure)
- Layered debridement
-Nonsurgical (autolytic)
What tissues are not well vascularized? How is this overcome?
Cortical bone - forage
Excess fat - removed
Intact fascia - debrided to expose underlying muscle
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 antimicrobial properties, what other effects of honey 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
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
This facilitates debridement, granulation, and epithelialization
What is typically included in a triple antibiotic ointment?
- Bacitracin zinc
- Neomycin sulfate
- Polymyxin B sulfate
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
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 glucosamine
Reported functions:
- Enhances the action of inflammatory cells
- Increase production of granulation tissue through upregulation of TGF-B, PDGF, fibroblast production and IL-8 production
*works best with silver
What is the recommended porosity of the foam and recommended pressures for negative pressure wound management in small animals?
400 - 600 um pore foam
Recommended -125mmHg for foam-based or -80mmHg for gauze based systems
What are the purported benefits of negative pressure wound therapy?
- Improve wound perfusion
- Reduce edema
- Stimulate granulation tissue formation
- Decrease bacterial colonization
- Remove exudate
Expression of which growth factors/cytokines may be increased 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:
- Stabilization of the graft
- Reduce fluid accumulation under the graft
- Prevent desiccation
- 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
