Muscle - Meadows

Question 1

Post anesthetic myopathies risk factors

Answer 1

1. Prolonged anesthesia times
2. hypotension < 70 mmHg MAP
3. Hypoxemia
4. Lateral recumbency, inadequate padding, poor positioning
5. Well muscled/large horses
6. Male horses

Question 2

Post anesthetic myopathy etiology

Answer 2

1. inc intracompartmental pressure of muscle from weight of horse ->
2. External pressure exceeds perfusion of capillary beds and they collapse ->
3. Decreased perfusion leads to
   - tissue hypoxia
   - myopathy
   - neuropathy
   * hypoxia and hypotension from anesthesia exacerbate

Question 3

Post anesthetic myopathy CS

Answer 3

1. Hard, swollen, painful muscles
2. Lameness, unwillingness/inability to stand
3. Increased sweating, incr HR, m. fasciculations
4. Myoglobinuria

Question 4

Post anesthetic myopathy may be difficult to differentiate

Answer 4

myopathy vs neuropathy, may have components of both

Question 5

Post anesthetic myopathy TX

Answer 5

1. Assist to stand
2. IV fluid therapy
3. NSAIDS +/- corticosteroids
4. Analgesics, +/- anxiolytics
5. Physiotherapy
6. Other
   - dantrolene
   - methocarbamol
   - furosemide
   - nasal O2

Question 6

Post anesthetic myopathy prognosis

Answer 6

Most horses respond w/in 12-24 hours w/appropriate tx

Question 7

Post anesthetic myopathy Prevention

Answer 7

1. Proper padding and positioning on table
2. Minimize anesthetic times
3. Maintenance BP, PaO2 under anesthesia

Question 8

Padding dorsal recumbency

Answer 8

Tuber ischii away from edges of bad

Question 9

Padding lateral recumbency

Answer 9

Pull bottom leg forward

-off-weights dependent triceps and extensor carpi radialis

Question 10

Positioning for sx avoid

Answer 10

extreme flexion/extension of limbs

Question 11

Post anesthetic myopathy draft horses

Answer 11

Pre clip, scrub, OR set up ahead of time

Question 12

Post anesthetic myopathy DDX

Answer 12

Spinal cord necrosis (draft horses)

Malignant hyperthermia

Question 13

Fibrotic myopathy etiology

Answer 13

1. M. trauma resulting in adhesions b/w semitendinosus and adjacent semimembranosus and biceps femoris

Question 14

Fibrotic myopathy common in

Answer 14

western performance horses

Question 15

Fibrotic myopathy CS

Answer 15

1. Mechanical lameness (not painful)
2. Short cranial phase and rapid caudal movement during caudal movement-foot slaps ground
3. More obvious at walk than trot

Question 16

Fibrotic myopathy TX

Answer 16

Semitendinosus tenotomy

• cut tendonous insertion on tibia medially
• +/- calcaneal tuberosity

Question 17

Fibrotic myopathy prognosis

Answer 17

1. May not see improvement for a few weeks
2. Fibrous scar tissue can reform
   - post-op rehab and physiotherapy important
3. SX more successful if only semitendinosus involved

Question 18

Stringhalt (Equine Reflex Hypertonia)

Answer 18

Two clinical presentations

1. Idiopathic (sporadic)
   - Unilateral, hindlimb
   - Progressive over years, doesn’t spontaneously recover
   - etiology unknown
2. Acquired (Australian)
   - Bilateral, hindlimbs
   - Outbreaks assoc with european/australian dandelion
   - May recover spontaneously

Question 19

Stringhalt CS

Answer 19

1. Mechanical lameness
2. Horses may walk out of it
3. With Australian form 60% may have RLN

Question 20

Stringhalt TX

Answer 20

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

Question 21

Tenectomy of lateral digital extensor

Answer 21

• 2 incisions

- Distal site of tendon insertion transected and pulled through proximal incision

Question 22

Stringhalt Prognosis

Answer 22

Idiopathic
-guarded to fair (results unpredictable)
Acquired
-fair prognosis

Question 23

Aortic-iliac Thrombosis etiology

Answer 23

Insufficient perfusion => ischemia in hindlimbs

Question 24

Aortic-iliac Thrombosis CS

Answer 24

1. Gradual onset exercise induced lameness
   - late stage -> signs apparent at rest
2. Absence sweating on affected side
3. Hypothermia of distal extremity
4. Absence digital pulse

Question 25

Aortic-iliac Thrombosis DX

Answer 25

1. CS 2. Rectal palpation/US 3. Doppler US (femoral artery) 4. PvO2 before and after exercise

Question 26

Femoral triangle

Answer 26

1. Caudal border - pectineus | 2. Cranial border - sartorius

Question 27

Aortic-iliac Thrombosis TX

Answer 27

1. Medical TX unsuccessful | 2. Surgery - Thrombectomy

Question 28

Aortic-iliac Thrombosis | Thrombectomy

Answer 28

1. Fogarty catheter 2. Approach through transverse femoral artery arteriotomy 3. High post-surgical complication rate

Question 29

Aortic-iliac Thrombosis Prognosis

Answer 29

- 65% return to athletic fxn | - 53% return to previous level activity

Question 30

Clostridial myositis

Answer 30

Clostridium perfingens -IM injections -wounds Give Flunixin PO, not IM

Question 31

Clostridial myositis CS

Answer 31

1. Acute, painful swelling of affected muscles - soft, warm to cool, then firm 2. SC crepitus 3. Skin sloughing - pressure necrosis to skin from swelling 4. If neck affected reluctance to lift/lower head

Question 32

Clostridial myositis DX

Answer 32

1. CS, HX 2. U/S - heterogenous echogenicity with loss normal fiber pattern 3. Tissue aspirate - c/s

Question 33

Clostridial myositis TX

Answer 33

1. ABX - Penicillin - Oxytetracycline - Metronidazole 2. Fasciotomy (sooner rather than later) 3. NSAIDS 4. Tetanus prophylaxis 5. Hydrotx, fluids, analgesics, hyperbaric O2

Question 34

Clostridial myositis prognosis

Answer 34

Overall 73% survival rate