LA Sx Exam #2: Wound Management Flashcards
What are three synovial structures that can be damaged with distal limb injuries?
1) Joints
2) Tendon sheaths = tarsal, carpal, digital
3) Bursas = calcaneus, navicular
What type of distal limb wound is considered an emergency? What is our goal with these types of wounds?
One involving a synovial structure (joint, tendon sheath, bursa) = commonly infected, synovial membrane is a great bacterial medium
GOAL = eliminate the infection before irreversible damage occurs
*Duration of infection and therapy determine prognosis, survival, etc.
Two main/general methods to eliminate wound/synovial infections
1) Systemic antimicrobial tx
2) Local antimicrobial tx = lavage, topical, intra-articular or intra-thecal, regional limb perfusion, antibiotic impregnanted delivery systems
Route, duration, and types of systemic antibiotics for treatment of systemic infection
- Route = IV first, then oral if necessary
- Duration = until after clinical signs resolve (synovial infections often 2-3 weeks past that point)
- Types = penicilin+gentamicin, penicillin+ceftiofur, enrofloaxacin, oral TMS
Four reasons that provide the rationale for using local over systemic treatment
1) Vascular trauma and inflammation don’t always permit delivery of IV antibiotics to areas = allows bacteria to proliferate
2) Infection and cellular debris = low pH = decreases antibiotic activity = allows bacteria to proliferate
3) High systemic doses can be toxic, don’t often need that high of a dose locally
4) Synovial membrane = great bacterial medium
Purpose and options for local lavage treatment
> Purpose = remove foreign debris, reduce bacterial contamination
- Isotonic saline + 0.1-0.2% povidone iodine = doesn’t always work with lots of cellular debris
- Isotonic saline + 0.05% chlorhex
- Isotonic saline + antibiotics
- Use a drip set and 18-gauge needle to get sufficient but not excessive pressure
- Tap water = causes cell swelling (hypotonic), stop after granulation tissue forms
Things used for local topical treatment (most recommended?) and pros/cons
- Antiseptics
- Antbiotics = based on C&S
- Wound aersol sprays
- Herbal therapies
- Surgeon preference = silver sulfadiazine
- Does it promote resistance
- Need to create a clean wound to work, debride and create a bleeding clean wound (scab = too late)
- Furazone = carcinogenic, decreases wound healing
True or false - with intra-articular or intra-thecal treatments, you want to enter your catheter/CRI into a wound that is different than the original wound
True
Methods and antimicrobials used with local intra-articular/thecal treatments
- Methods = direct, catheter, continuous infusion pump
- Amikacin = 500mg - 1 gram (not in cattle)
- Gentamicin = 200mg - 1 gram
- Cefazolin = 250-500mg (IM only)
- Ceftiofur = 150-500mg
- Penicillin = 2-5 million units
What do you have to remember with aminoglycosides and intra-thecal or intra-articular therapy? (2)
1) Needs to be > 500 mg, otherwise it’s ineffective
2) Subtract out local dose from systemic dose in neonates to avoid nephrotoxicity
Goal of regional limb perfusions
> > Treatment that rapidly reaches high concentration of antibiotics in infected tissues (synovium and subchondral bone)
- Promotes rapid bacterial elimination
- Decrease damage to affected synovial structures
- ADJUNCTIVE TX = use with systemic antimicrobials or surgical tx
Commonly used drugs and doses with regional limb perfusions
- Commonly use 1 gram = don’t see the reaction/inflammation we see going synovially, if we go regionally
- Risk = vasculitis, skin sloughing
a) Gentamicin = 500mg - 1 gram
b) Amikacin = 500mg - 1 gram
c) Penicillin = 10-20 million units
d) Enrofloaxacin = 1.5 mg/kg
Pros and cons of regional IV and IO antibiotic infusions
+ IV = technically easier
+ IV = doesn’t require general anesthesia
+ IV = reaches higher levels in tissue than IO
- IV = can form hematomas
- IO = technically more challenging, drilling into medullary bone
- IO = requires general anesthesia
+ IO = easier if there’s more soft tissue swelling present
+ IO = repeated daily treatments w/ minimal adverse effects (less hematoma risk)
+ IO = easier in younger animals
Regional limb perfusion technique
1) SEDATE and standing horse (don’t always have to block, but always sedate) - detomidine+butorphanol
+/- Local block w/ carbocaine at or below the fetlock (low or high 4-pt, ulnar/median and tibial/peroneal nerves)
2) Apply tourniquet for 20-30 min, proximal to affected area
3a) IV = infuse antibiotic via superficial vein (medial lateral plantar/palmar veins, cephalic/saphenous if more proximal)
3b) IO = directly into medullary cavity with special screw (doesn’t require a tourniquet)
4) Infuse 30 mL for neonates, 60 mL for adults (antibiotics diluted with saline) over 1-30 minutes
5) Remove catheter and wrap site - OR - remove/leave screw
Why do we use local repository treatment (4), what are the two types? (2)
> Biodegradable and non-biodegradable
- Achieves sustained high concentrations in tissue w/o toxic effects
- Reduced labor/time with daily intra-articular infusions
- Useful in difficult to handle patients
- Can use expensive antibiotics that would be cost prohibitive systemically
Types of biodegradable and non-biodegradable repositories
> Biodeg = collagen-based membrane or sponge, beads of plaster or Paris or hydroxyapatite, polylactic or polyglycolic acid (like sutures)
Non-biodeg = PMMA beads
True or false - antibiotics beads work better if tissues can be closed
True - allows you to achieve high enough concentrations in the wound
New wound management strategies (5)
1) Systemic or regional supplemental immunoglobulins = $$, promote bacterial phagocytosis, neutralize toxin, inhibit bacterial attachment
2) Vacuum-assisted closure = increase blood flow, reduce edema, accelerate granulation tissue formation, reduce bacteria
3) Hyperbaric oxygen tissue = high O2 levels in tissue
4) Chelating agents = reduce damage done by gram neg bacteria
5) Biotherapy = maggots, leeches
Main types of wounds and what causes them (5)
1) Laceration = result of tearing = MOST COMMON = extensive damage, necrosis, sloughing
2) Incised wounds = result of sharp edged objects, minimal tearing/bruising of edges
3) Stab or puncture wounds = almost always get infected (poor drainage)
4) Abrasion or contusion = severe blunt trauma, may form large hematomas
5) Burns - thermal, scalding, freezing, sun, rope
True or false - large animals commonly have multiple wounds from an injury
True - always do a thorough PE
General wound treatment
1) History and PE
* Arrest any major hemorrhage w/ direct pressure (leave on for < 1-2 hours to prevent necrosis), direct ligation is preferred (watch out for nerves)
2) Examine wound to determine site, depth, structures involved
3) Restrain horse
4) Clip hair around wound (covered with lube to prevent hair contam)
5) Surgical prep of wound w/ antiseptic
6) Sedation and GA required to lavage and explore the wound
True or false - all wounds in large animals should be considered contaminated?
True
True or false - organic and inorganic particles in soil increase the number of organisms that cause infection
FALSE - REDUCE bacterial counts
What is considered sufficient pressure to irrigate a wound?
10-15 psi
What is the problem with using high PSI’s to lavage wounds?
Risk the potential to drive particles deeper into tissue
Problem with using hosepipe water to lavage wounds
Hypotonic, will cause tissue overlogging = may be worth it if that’s all you have
What do you have to remember when using antiseptics to lavage wounds?
Concentrated solutions = cytotoxic, may lead to increased wound breakdown
- 1% iodine (1 ml per 100 ml diluent)
- 05% chlorhex (2.5 ml per 100 ml diluent)
What is the treatment of choice for wounds with devitalized or contaminated tissue?
Surgical debridement - can be bulk (en block) or layered (more common with limited soft tissue on distal limbs)
Treatment of choice for superficial grazes, abrasions, erosions
Clean wound, topical application of oinment (silver sulfadiazine) = keeps it moist, may reduce pain
Pros and potential cons of primary wound closure
> Primary = sutured
+ Immediate cover of wound
+ Reduces scarring
+ Requires less aftercare
+ Produces a faster return to function
- May not be able to do so on tight distal limbs
- May trap infection if done inappropriately
- Swollen or contaminated tissues may breakdown after suturing
- Can abscess = more expensive to treat, not cosmetic when it heals
What is considered to be the “golden period” for wound healing after it occurs?
6-8 hours - afterwards, bacteria begin to colonize and it becomes infected
What type of lavage system is the most effective for removing adhered particles?
High pressure and pulsatile systems
When does skin retraction occur with wounds?
Begins immediately and continues for the first 15 days of healing
When and what types of drains do we place with wounds?
- Closed suction = involving joints or tendons = necessary to maintain a closed environment
- Passive drains (penrose) = where fluid is expected to pool
- Away from primary wound to prevent dehiscence
- Large enough that drainage can occur
- Wrap to prevent infection or damage to the system
Should you use hydrogen peroxide to lavage wounds?
No - only suitable for anaerobic wounds
Differences between healing with secondary intention on limbs and trunk
- Limbs = minimal wound contraction (little skin or SQ, may appear to ENLARGE), heal by SLOW epithelialization
- Body = contract rapidly = close with less epithelialization and scarring
When does skin contraction stop?
> When skin tension is greater than skin contraction
> When skin edges meet and provide contact inhibition
What do myofibroblasts due in granulation tissue?
Anchor to the wound edges, contract to reduce the size of the wound
True or false - granulation tissue is resistant to infection
TRUE
Things that may help reduce granulation tissue formation
- Control any wound infections
- Local corticosteroid tx
- Restrict movement
- Application of a cast
Is proud flesh common in ponies and small horses?
NO - more common in larger horses
Treatment of exuberant granulation tissue
> Resection - doesn’t require general or regional anesthesia = absence of sensory nerves
Pressure bandage to control hemorrhage
Skin graft for full thickness defects
*Larger masses = done under GA so the mass can be removed to 0.5 cm below skin margin
Does chemical cautery (topicals like Cu sulphate or silver nitrate) help to prevent granulation tissue formation
NO - destroy advancing epithelium and migration across the wound
