Ch 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, 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?
- 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
Is tap water hyper-, iso-, or hypotonic?
Hypotonic
What pressure is generally recommended for high pressure irrigation?
How is this best achieved?
5-8 psi
16-22g needle onto a fluid administration set of a 1L bag of fluids under pressure of 300mmHg
List hyperosmotic wound dressings
- Hypertonic saline (20%)
- Honey
- Sugar
List some hydrophilic dressings
- Hydrogel
- Hydrocolloid
- Alginate
Is saline or a balance electrolyte preparation recommended for initial 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 2 braod categories of wound debridement?
- En Bloc Debridement (and then primary closure)
- Layered debridement
What tissues are not well vascularised? How is this overcome?
- Cortical bone - forage
- Excess fat - removed
- Intact fascia - debrided to expose underlying muscle and improve vascularization (fasciotomy or fasciectomy)
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 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
