LA Wounds and Septic Arthritis

Question 1

what are the 4 stages of wound healing?

Answer 1

1. hemostasis: injury to vessel and exposure of endothelium kicks off coagulation cascade, leading to blood clot formation, matrix formation, and platelet activation; exposure of endothelium also kicks off arachidonic acid pro-inflammatory pathway, leading to vasoconstriction and hypoxia
2. inflammation:
   -initiated by hemostasis
   -has early and late stages: neutrophils peak 1-2 days post injury and monocytes differentiate into macrophages later on
   -extended chronic inflammation can result in exuberant granulation tissue (wound edges can’t heal over this, must intervene)
3. proliferation: starts 3-5 days after wounding
   -provides tissue to fill the void
   –granulation tissue: started by macrophages which start to form fibroblasts (replace fibrin clot with collagen matrix)
   –blood vessels (angiogenesis) then capillary regression near the end
   –epithelialization starts
4. maturation/remodeling:
   -regain strength and function
   -wound contraction via myofibroblasts
   -gain in strength: now at 60-70% of normal tissue strength (no wound heals to 100% strength)

Question 2

describe angiogenesis in wound healing

Answer 2

1. growth factors and cytokines secreted in the inflammatory phase induce ECM scaffold for endothelial cells
2. sprouting off capillaries for new vascularization
3. regression one tissue has filled in; switch from red to pale pink color = more mature granulation tissue bed

Question 3

describe epithelialization

Answer 3

1. requires granulation tissue
2. starts 24-48 hours after wounding
3. VERY slow! 0.5mm/week in distal limb wound of horse

Question 4

describe steps for wound evaluation

Answer 4

1. history: who (signalment), what (regions), where, when, how/why, vaccination status (TETANUS!!)
2. physical exam:
   -whole horse: TPR, MM color and CRT, auscultation (need to stabilize before move further with wound?)
   -wound: location, contamination, tissue loss
3. sedation! when dictated by physical exam findings

Question 5

what physical exam findings indicate need of stabilization before further dealing with a wound?

Answer 5

1. evidence of significant blood loss: pale MM, slow CRT, elevated HR, +/- increased respiratory rate
2. evidence of shock

Question 6

describe stabilization if there is acute blood loss/shock

Answer 6

1. stop the bleeding!!
   -tourniquet, pack it with something
2. replace circulating volume:
   -IV fluids, blood transfusion

Question 7

how do you deal with contamination of a wound?

Answer 7

1. clean up what is there and prevent further contamination
2. provide optimal environment for wound to heal
   -proper moisture, clean, bandage, needs oxygen

Question 8

describe wound evaluation

Answer 8

1. clip and clean; keep hair out!
2. protect the wound to prevent further contamination with hair and debris
3. now that wound is clean, palpate wound to determine depth and extent
   -gloved finger
   -sterile probe/hemostat
4. diagnostic imaging/procedures
   -radiographs
   -ultrasound: gas artifacts can make challenging
   -advanced imaging
   -other: synoviocentesis
5. synovial structure evaluation if applicable:
   -for any wound close to a synovial structure!
   -radiographs: stick a probe to follow the tract and inject contrast
   -synoviocentesis: into joint, but away from where wound is! get a sample; inject fluid and see if comes out the wound; if does= contamination
   -synovial fluid analysis: color, clarity, components (distrib of white cells, appearance of cells, bacteria), lactate, serum amyloid A

Question 9

describe wound cleansing

Answer 9

1. solution to pollution is dilution!
2. isotonic solution for wound lavage:
   -gross contamination: hose
   -8-15 psi (to not push stuff deeper in wound)
   -2 tsp table salt per liter of tap water

Question 10

describe use of antiseptics

Answer 10

1. non-selectively cytotoxic
2. broad spectrum antimicrobial activity
3. PI (iodine) activity inhibited by organic debris
4. use to clean around wounds!! not inside wound bc will kill healthy tissue trying to heal

Question 11

compare and contrast septic arthritis in adults versus foals

Answer 11

adults:
-most commonly traumatic (wound/puncture)
-very rarely iatrogenic or hematogenous

foals:
-most commonly hematogenous!! lots of unclosed off vasculature
-or traumatic

Question 12

what are the 3 types of hematogenous septic arthritis in foals?

Answer 12

1. synovial (type S): vessels in synovial membrane
2. epiphyseal (type E): may look like a rat chewing away on the bone
3. physeal (type P): vessels in physis; bacteria get lodged there

Question 13

what are prognostic factors for septic arthritis in adults versus foals

Answer 13

adults:
1. bone involvement or tendon involvement if tendon sheath/bursa: worse
2. acute versus chronic
3. contra-lateral limb effects (support limb laminitis; may have delayed onset)

foals:
1. bone involvement
2. number of joints involved (hematogenous)
3. acute versus chronic
4. other effects on limb (flexural deformities, angular limb deformities)

Question 14

what are the 3 goals of wound debridement? what classifies a wound infection?

Answer 14

1. decrease bacterial load
2. remove environmental contaminants: feces, soil, other foreign material
3. remove devitalized tissue

wound infection: >10^6 bacteria/gram tissue

Question 15

what are 5 methods of debridement

Answer 15

1. sharp: most common! scalpel blade
2. mechanical: 4x4 gauze, lavage, scraping out stuff in wound
3. enzymatic
4. biologic: sterile maggots
5. chemical

Question 16

what do you do if a wound is very contaminated?

Answer 16

additional debridement!
1. wet-to-dry bandages with hypertonic saline
2. other methods of debridement

Question 17

describe wound closure

Answer 17

1. primary versus secondary intention healing: based on
   -degree of contamination, can choose either
   -delayed primary closure or
   -close part of wound
2. use tension relieving suture patterns!
3. stents:
4. skin creep: towel clamps: skin will stretch under a little bit of tension

Question 18

describe synovial structure treatment

Answer 18

1. dilution is solution!! regular antibiotics alone won’t do it!
2. lavage!
   -multiple large gauge needles
   -front and back of joint
   -standing versus gen anesthesia
   -arthroscopy
3. acute versus chronic
   -more chronic = more aggressive; arthroscopy
   -more acute = needle lavage may suffice

Question 19

what are other treatments fr synovial and nonsynovial wounds?

Answer 19

1. treat pain and inflammation
   -systemic NSAIDs
   -local anesthesia
2. antimicrobials:
   -broad spectrum against environment and skin flora
   -topical/regional methods: IA, IV regional limb perfusion, antimicrobial impregnated gauze
3. wound protection/coaptation