Muscle - Meadows Flashcards
Post anesthetic myopathies risk factors
- Prolonged anesthesia times
- hypotension < 70 mmHg MAP
- Hypoxemia
- Lateral recumbency, inadequate padding, poor positioning
- Well muscled/large horses
- Male horses
Post anesthetic myopathy etiology
- inc intracompartmental pressure of muscle from weight of horse ->
- External pressure exceeds perfusion of capillary beds and they collapse ->
- Decreased perfusion leads to
- tissue hypoxia
- myopathy
- neuropathy
* hypoxia and hypotension from anesthesia exacerbate
Post anesthetic myopathy CS
- Hard, swollen, painful muscles
- Lameness, unwillingness/inability to stand
- Increased sweating, incr HR, m. fasciculations
- Myoglobinuria
Post anesthetic myopathy may be difficult to differentiate
myopathy vs neuropathy, may have components of both
Post anesthetic myopathy TX
- Assist to stand
- IV fluid therapy
- NSAIDS +/- corticosteroids
- Analgesics, +/- anxiolytics
- Physiotherapy
- Other
- dantrolene
- methocarbamol
- furosemide
- nasal O2
Post anesthetic myopathy prognosis
Most horses respond w/in 12-24 hours w/appropriate tx
Post anesthetic myopathy Prevention
- Proper padding and positioning on table
- Minimize anesthetic times
- Maintenance BP, PaO2 under anesthesia
Padding dorsal recumbency
Tuber ischii away from edges of bad
Padding lateral recumbency
Pull bottom leg forward
-off-weights dependent triceps and extensor carpi radialis
Positioning for sx avoid
extreme flexion/extension of limbs
Post anesthetic myopathy draft horses
Pre clip, scrub, OR set up ahead of time
Post anesthetic myopathy DDX
Spinal cord necrosis (draft horses)
Malignant hyperthermia
Fibrotic myopathy etiology
- M. trauma resulting in adhesions b/w semitendinosus and adjacent semimembranosus and biceps femoris
Fibrotic myopathy common in
western performance horses
Fibrotic myopathy CS
- Mechanical lameness (not painful)
- Short cranial phase and rapid caudal movement during caudal movement-foot slaps ground
- More obvious at walk than trot
Fibrotic myopathy TX
Semitendinosus tenotomy
- cut tendonous insertion on tibia medially
- +/- calcaneal tuberosity
Fibrotic myopathy prognosis
- May not see improvement for a few weeks
- Fibrous scar tissue can reform
- post-op rehab and physiotherapy important - SX more successful if only semitendinosus involved
Stringhalt (Equine Reflex Hypertonia)
Two clinical presentations
- Idiopathic (sporadic)
- Unilateral, hindlimb
- Progressive over years, doesn’t spontaneously recover
- etiology unknown - Acquired (Australian)
- Bilateral, hindlimbs
- Outbreaks assoc with european/australian dandelion
- May recover spontaneously
Stringhalt CS
- Mechanical lameness
- Horses may walk out of it
- With Australian form 60% may have RLN
Stringhalt TX
Idiopathic form
-severe cases tenectomy of lateral digital extensor (not all respond)
Acquired form
-Remove from pasture (3/4 horses respond)
-May take 18 mos
Tenectomy of lateral digital extensor
- 2 incisions
- Distal site of tendon insertion transected and pulled through proximal incision
Stringhalt Prognosis
Idiopathic
-guarded to fair (results unpredictable)
Acquired
-fair prognosis
Aortic-iliac Thrombosis etiology
Insufficient perfusion => ischemia in hindlimbs
Aortic-iliac Thrombosis CS
- Gradual onset exercise induced lameness
- late stage -> signs apparent at rest - Absence sweating on affected side
- Hypothermia of distal extremity
- Absence digital pulse
Aortic-iliac Thrombosis DX
- CS
- Rectal palpation/US
- Doppler US (femoral artery)
- PvO2 before and after exercise
Femoral triangle
- Caudal border - pectineus
2. Cranial border - sartorius
Aortic-iliac Thrombosis TX
- Medical TX unsuccessful
2. Surgery - Thrombectomy
Aortic-iliac Thrombosis
Thrombectomy
- Fogarty catheter
- Approach through transverse femoral artery arteriotomy
- High post-surgical complication rate
Aortic-iliac Thrombosis Prognosis
- 65% return to athletic fxn
- 53% return to previous level activity
Clostridial myositis
Clostridium perfingens
-IM injections
-wounds
Give Flunixin PO, not IM
Clostridial myositis CS
- Acute, painful swelling of affected muscles
- soft, warm to cool, then firm - SC crepitus
- Skin sloughing
- pressure necrosis to skin from swelling - If neck affected reluctance to lift/lower head
Clostridial myositis DX
- CS, HX
- U/S
- heterogenous echogenicity with loss normal fiber pattern - Tissue aspirate - c/s
Clostridial myositis TX
- ABX
- Penicillin
- Oxytetracycline
- Metronidazole - Fasciotomy (sooner rather than later)
- NSAIDS
- Tetanus prophylaxis
- Hydrotx, fluids, analgesics, hyperbaric O2
Clostridial myositis prognosis
Overall 73% survival rate
