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Flashcards in Muscle Deck (42)
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1
Q

What do all muscle diseases result in?

A
  1. Changes in conductivity
  2. Damage to muscle tissue
  3. Muscle atrophy
2
Q

What do we use to measure rhabdomyolysis severity?

A

CK values

Short half life so only useful soon after muscle damage has occurred or to track muscle damage effects

3
Q

What are the two types of muscle atrophy?

A

Neurogenic or myogenic

Aka no longer innervated or no longer paying attention to innervation

4
Q

What is rhabdomyolysis?

A

Disintegration or dissolution of muscle tissues

aka muscle necrosis

5
Q

What is myositis?

A

Inflammation of voluntary muscle tissues

6
Q

What is HYPP?

A

Aka Impressive Disease

Homozygous recessive genetic disease causing bigger muscles that are closer to firing potential at rest which predisposes to random firing

7
Q

What kind of horses typically have HYPP?

A

Quarter horse and quarter horse mixes

Theorized descendants of Impressive who is thought to have started the disease with a heritable point mutation

8
Q

What are the clinical signs of HYPP?

A

Odd behavior, fasiculations, recumbency, acute death associated with hyperkalemia

9
Q

What can HYPP episodes be triggered by?

A
  • Stress
  • Sudden cold exposure
  • Transportation
  • Sudden dietary changes
  • Recovery from anesthesia/surgery
10
Q

What are HYPP episodes typically NOT triggered by?

A

Exercise- if signs are seen only post exercise look for other causes

May be associated with increased sympathetic tone which protects from episodes

11
Q

How do you diagnose HYPP?

A

Genetic testing- UCLA
Potassium challenge test- used more in research

NOT CK levels- no muscle damage in minor episodes

12
Q

How do you treat HYPP?

A

Breeding management for prevention best strategy

During episodes- IV Ca gluconate (brings up firing threshold), Insulin or dextrose (drives potassium intracellularly)

Acetazolamine- potassium wasting diuretic to minimize episodes

13
Q

T/F: Some horses will “out-grow” HYPP episodes and clinical signs will diminish.

A

True- still should not be used for breeding

14
Q

How do you control HYPP?

A
  • Avoid high potassium feeds (alfalfa), feed in smaller frequent meals, avoid fasting
  • Regular episodes
  • Avoid stress
15
Q

What is the hallmark of exertional myopathies?

A

Rhabdomyolysis

16
Q

What are other names for exertional myopathies?

A

Monday Morning Disease, Tying-Up, Set-Fast, Chronic intermittent Rhabdomyolysis, paralytic myoglobinuria, exercise-associated myositis

17
Q

What are some specific conditions associated with exertional myopathies?

A
  • Polysaccharide storage myopathy (quarter and draft horses)

- Recurrent exertional rhabdomyolysis (thoroughbreds)

18
Q

What are some causes of exertional myopathies?

A

Dietary, overexertion, genetic/inherited conditions, circulatory issues

19
Q

What is monday morning disease?

A

Horse that was fed grain all week while it was working and then fed grain on it’s off day and then had issues on the next day

Mostly seen in Draft horses

20
Q

What are some genetic/inherited errors in metabolism resulting in exertional myopathies?

A

PSSM and RER in belgians, quarter horses, thoroughbreds

21
Q

What are some circulatory disorders resulting in exertional myopathies?

A

Post anesthetic myopathies and compartmental syndrome

22
Q

What are some metabolic/endocrine issues that can lead to exertional myopathy?

A
  • Electrolyte imbalances
  • Abnormal thyroid function
  • Hormonal imbalances
23
Q

What is the simplest cause of exertional myopathy?

A

Exertion…. they’re being trained too hard

24
Q

What kind of circulatory issues do we see with exertional myopathies?

A
 Compromised perfusion of the muscles 
 Increasingly acidic environment
 Muscle necrosis, breakdown
 Hypoxia
 Swelling which further contributes to reduced perfusion and ongoing hypoxemic state of muscles
25
Q

What is type I exertional myopathy present with?

A

Associated with limited exercise- not overworked
 2-4 year old “nervous” or “high-strung” filly (most end up being RER horses)
 Weekend rider – used of unfit horse for exercise out of their ability
 Wont develop really bad CS

26
Q

What is type II exertional myopathy present with?

A

Associated with protracted exercise
 Endurance horse in high competition
• In generally very fit but can be overworked
• If it “ties up” it does not mean the horse will do it again in the future—just don’t overwork it
 Electrolyte and circulatory causes

27
Q

What are some clinical sighs of exertional myopathy?

A

Fasciulations, sweating, muscle swelling, tachycardia and tachypnea, hardened painful muscles

Variable degrees of pigmenturia and myogolbinuria depending on severity of episode

28
Q

What is the difference in muscle presentation between exertional myopathies and HYPP episodes?

A

HYPP will not have hardened painful muscles

29
Q

What are the CK values that are useful for determining cause of increase?

A

CK – 150-400 IU/L = normal tells about acute, on-going damage
980 IU/L: Not tying up – more compatible with blood draws that you are “fishing” in
2000 IU/L: Colic-y horses moving around/throwing themselves
20,000 IU/L: Rhabdomyolysis occurs at 10,000 but you still need to look at timing

30
Q

What are common PE/lab findings with an acute episode of exertional myopathy?

A

PE: hard, swollen, painful muscles
Chem: May see electrolyte imbalances and acidosis

31
Q

What is important to look at in mild or recurrent episodes of exertional myopathy?

A

Urinary fractional excretion of electrolytes
Exercise challenge test
Vit E/Sel evaluation
Muscle biopsies

32
Q

What is the goal with an exercise challenge test?

A

Produce CK elevation without clinical signs to show damage to muscle with little work- indicates a genetic issue

33
Q

When are muscle biopsies most helpful in diagnosing?

A

Genetic inherited disorders with recurrent episodes

34
Q

What is the goal of long term management of exertional myopathies?

A

Prevent whatever set off the episode to begin with

35
Q

How do you treat an episode of exertional myopathy?

A

Limit the muscle damage nby limiting movement
Restore normal electolyte balance
Relieve pain and inflammation (phenylbutazone)
Improve renal perfusion

36
Q

T/F: Excessive/prolonged myoglobinuria can cause acute renal failure.

A

True- one of the only causes of renal failure in the horse and typically cause of death in horses with exertional myopathies

37
Q

How can you change the diet of a horse with exertional myopathies to help prevent episodes?

A

High fat diet- rice bran and high oil content (18-22%)

38
Q

How does dietary management help horses with PSSM and RER?

A

PSSM- decrease in muscle cell glycogen accumulation

RER- calmer animals and reduces CK elevation with exercise, lower resting HR and lower PCV

39
Q

What is the most important aspect of post-anesthetic myopathies?

A

Muscle mass and length of surgery

Draft horses most prone to it

40
Q

What can be done during surgery to help prevent post-anesthetic myopathies?

A

Maintaining MAP >60

41
Q

What is RER?

A

o Autosomal dominant Inherited disorder of Thoroughbreds – 65% are fillies
o Frequency 2 years

42
Q

What is PSSM?

A

o Autosomal dominant: Glycogen synthase 1 gene point mutation
o Increased clearance of glucose in circulation
o Accumulation of glycogen and abnormal polysaccharides in muscle cells
o Identified: QTR and Drafts but also seen in American paint horses, appaloosas, and warmbloods