4 wounds classifications. 3 grades of open fracture
Wounds
* Clean: atraumatic surgical
* Clean contaminated: minor aseptic break that is easily removed
* Contaminated: recent traumatic wound with evironmental contamination, or surgical with major asepsis break (GI, urogenital)
* Dirty/infection: older woun with exudate or clear infection. >10^5 organisms per gram of tissue
Open fracture
* Grade 1: <1cm skin break d/t bone penetration, soft tissue moderately contused
* Grade 2: >1cm break associated fracture (Bite, low velocity gunshot)
* Grade 3: extensive soft tissue injury with high comminution of bone (Distal shearing wound, high velocity gunshot)
What about dog and cat skin circulation (vs pigs and humans) makes axial pattern flaps possible (vs grafts)? What about the anatomy of this ciruclation impacts what layers must be included in wound closures?
- They have direct cutaneous arteries and veins, supplying specific sections of skin (huamns/pigs have repeating branches of musculocutaneous artery and vein). Means that one section of skin can be moved elsewhere and maintain viability
- Vessels run through panniculus muscle and form the subdermal/deep plexus: must include it in closure otherwise skin will die as remove its plexus
First healing phase: timeframe and what happens
Inflam and debridement
* 0-5d
* Bleeding, vasocontrction, PLT aggregation
Proliferation
* PLT release WBC attractants: Leukotrienes, PGs, histamine, kinins from WBC vasodilate and allow blood flow to area for more WBC migration to bed
* Neut in 6hr, mono in 12hr (collagen, angiogensis), macro in 24-48hrs (tissue, bacteria, material removal)
Monocyte needed to heal, neuts are not (but might get infection)
List 7 important grwoth factors in phase 1 (debridement specifically)
- Epidermal growth factor: from PLT, macrophage, saliva, urine, plasma
- FIbroblast growth factor: from macrophage, fibroblast, endothelium, mast cells, t-lymphs
- IGF-1: from macrophage, fibroblast, liver
- Keratinocyte growth factor: from fibroblast
- PLT-derived growth factor: from PLT, macrophage, endothelium, epithelium, SMC
- Transofrming grwoth factor beta (TGF-B1, 2, 3): from PLT, t-lymphs, macrophage, endothelium, epithelium, SMC, fibroblast
- VEGF: from epithelium
Second healing phase: timeframe and what happens
Proliferation
* 4d start, for 2-3weeks
* Angiogenesis (VEGF), granulation (PDGF, TGF-b, EGF), epithelialization (fibroblasts proliferate for collagen, capillary bed grows for granulation)
* Epithelium is 4-5days after injury
* Contraction: 5-9d after injury
Rate of granulation formation per day. What are the three base substances for it?
- 0.4-1mm/day
- Collagen, fibronectin, hyaluronic acid
Epithelialization timeframe in sutured and open wounds. Contraction rate per day, and what cell type predominates?
- 24-48hrs sutured, 4-5d open
- 0.6-0.8mm/day
- Myofobroblasts (from fibroblasts), d/t TGF-beta
Depends on O2 tension
Third healing phase: timeframe and what happens
Maturation
* From 17-20d post, for years
* Wound contraction and remodelling
Never as strong: at most is 80%
How long can a tourniquet be placed for? Benefit of LRS over saline for lavage, and method? What pressure is needed in a pressure bag and fluid set to generate adaquate pressure, and what is that pressure?
- 1hr
- NaCl and tap water shown to damage fibroblasts vs LRS
- 18g needle 60ml syringe
- 300mmHg, generates 7-8psi (ideal) from 1L bag
Adherent vs non-adherent dressing change rate. Mechanism of action
- Adherent: 1-3x daily, manual/mechanical debridement of everything
- Non-adherent: 1-3d, autolysis and direct debridement (depending on dressing)
Most common place and injury modality for exposed bone. Hwo can bone be used to aid granulation?
- Carpal and tarsal shearing, from motor vehicle
- Poke into medulla with K-wire or Jacob chuck, don’t wipe away blood. Cover with primary non-adherent dressing at 3-5d intervals
Types of wound closure and indications
- Primary: clean, small containated infected that can be converted to clean
- Delayed primary: 2-5d post, contaminated or large with unknown viability. Wait for healthy granulation
- Secondary closure: >5d post. Dirty/infection. May need to remove granulation and skin to allow closure
- Second intention: normal healing phases. Very large wounds, lots of infection. Note this is successful but can take a while
Drain types.
- Passive: penrose. Secure proximal and distal
- Active: grenad,e vacuum machine, butterfly (negative pressure blood tube), IV tube makeshift (keep 60ml open with needle)
Negative pressure wound therapy indications and contraindications. How much negative pressure? How does it help?
Indication
* skin graft, highly exudative
Contraindication
* necrotic with eschar, osteomyelitis, fistulae, malignancy, exposed vessel/nerve/organ/anastomosis site, active bleeding or disorder
Pressure: -125mmHg
Effect: angiogensis, granulation, reduced wound size
Must ensure no bacterial risk
How does HBOT aid healing? Indications?
- Increases angiogensis, fibroblast proliferation, WBC ROS killing
- Crush, skin graft, anaerobic infection, possible snake bite (Gerkin study)
COld laser therapy mechanism
- Increased mitochondrial ATP (chromophores) via red and near-infrared
- Fibrobalst activation
When are abx not indication for wounds?
- Clean
- Superficial <6hrs
- Contaminated that canbe converted to clean for primary closure
- Mature healthy granualtion bed (note that pseudomonas can cause film over granulation and need topical therapy)
What level of hypoalbuminemia impacts wound healing? Mechanism?
- <2g/dL
- Increases fibrous tissue deposition
Why are cats more at risk of poor healing vs dogs?
- Weaker wound: 7d suture line strength is half that of dog
- Make less granulation tissue, at delayed start (4.5d vs 6.3d), in longer time (8d vs 20d)
- Granulation is peripheral rather than central
Must have SQ tissue. If remove, they will struggle to form granulation and have less lower skin perfusion
Evidence based wound care adjuncts for acute and chronic wounds
Acute
* PRP
* Negative pressure
Chronic
* PRP
* Stem cells
* HBOT
* Laser
* Negative pressure
6 contact layers for wound healing: indication, advantages, disadvantages, how often to change
HTS: MacPhail does at most 2-3 treatments then stops as it is so effective. Use 23.4% undliated
3 types of aliginate and when to use them. What does alginate do to exudate?
- Absorbs it (20-30x weight) and creates ion exchange (makes a hydrogel)
Mortality in dog bite wounds. What steps must be take in abdominal and thoracic bite wounds? When are broken ribs recommended to be removed?
- > 10%
- Imaging and/or exploration
- If displaced
