Muscle Disease Flashcards
How do we diagnose muscle dz?
- CS
- enzymes
- EMG
- muscle biopsy
- exercise challenge test
Describe AST enzyme and it’s use:
- is it muscle specific?
- how long does it take to see/leave?
- NOT muscle specific
- increases slowly (12-24h)
- stays elevated longer (2+ weeks)
Describe CK enzyme:
- is it muscle specific?
- how long does it take to see/leave?
- YES, muscle specific
- very sensitive
- reflects muscle damage
- peak around 6-8h
- decreases within 3 days
What will the CK value look like with:
- Recumbency with colic
- Venipuncture
- Rhabdomyolysis
- 500-1,000
- 300-1,000
- Tens/hundreds of thousands!
Describe the method of obtaining muscle biopsy:
Include unaffected + affected muscle
6mm biopsy
Exercise challenge test:
- method
- normal values
- increases
- 15-30min of light exercise
- normally won’t see any CK elevations
- 5x increase or more = rhabdomyolysis
What is the signalment for Hyperkalemic Periodic Paralysis
Quarter horses
Impressive-line horses
CS for HyPP:
- variable!
- intermittent signs by 2-3yo and normal btwn episodes
HyPP episode triggers:
Stress Sudden cold Transportation Sudden diet changes Surgery/anesthetic recovery
What are the CS associated with HyPP?
Prolapse of 3rd eyelid
Sweating
Muscle fasiculations
Cramping
- episodes can last min-hrs*
- some young horses that are HOMOZYGOUS can get upper resp muscle paralysis and resp stridor*
T/F: HyPP is autosomal recessive inheritance
False!
Autosomal DOMINANT
What [in terms of electrolytes] is abnormal in HyPP?
Abnormal Na channels
Hyperkalemia
Why are the Na channels abnormal? What is wrong with them?
Resting potential is closer to firing
Na channels remain open
T/F: Hyperkalemia in HyPP is only seen during an attack
True!
During attacks, high efflux of K occurs
Risk factors for HyPP
- fasting
- general anesthesia
- concurrent illness
- exercise restriction
How do we diagnose HyPP?
Gene testing
CS
HyperK in an episode
How do you tell patients in renal failure apart from HyPP patients?
Horses in renal failure don’t demonstrate any muscular dysfunctions
otherwise, they both have very high HyperK
T/F: As horses age, episode #s increase
False, the episode #s decrease with age
DDx for HyPP:
Colic
Seizures
How do we treat acute, mild episodes of HyPP?
- light exercise [walking]
- feed some carbs
- feed often
How do we treat acute episodes of HyPP with severe hyperkalemia?
- IV Ca Gluconate [cardioprotection]
2. IV dextrose/insulin to help drive K intracellularly
What are some management changes we can try in treating HyPP?
- Diet: avoid high K feed, feed several times a day
- Minimize stress
- Regular exercise
T/F: we can feed HyPP horses with alfalfa hay, brome hay, canola oil, soybean oil, sugar, beet molasses
False!! These are all foods high in K.
Instead, we should be feeding them foods low in K: grass hay, grains, sugar beet pulp
What is acetazolmide and what does it do for the HyPP horse?
K wasting diuretic BUT since we give lower dose it doesn’t have that diuretic effect.
It stabilizes blood glucose and stimulates insulin secretion
What are some possible etiologies for rhabdo?
- inadequate training [pushing them too hard]
- alteration of blood supply [post-anesthetic hypotensive episodes]
- genetics
- underlying muscle abnormalities
What does a Type I rhabdo horse look like?
Associated with limited exercise 2-4yo nervous filly Weekend rider RER PSSM High grain intake, not exercised regularly
What does a Type II rhabdomyolysis horse look like?
Endurance horses
Overexertion
Electrolyte/perfusion disturbances
T/F: Mild cases of rhabdo occur AFTER race, poor performance, normal urine color, no muscle pathology, painful/firm hindquarters
True
What are some CS of a severely affected rhabdo horse?
- happens DURING exercise
- don’t want to move; colic; recumbent
- pigmenturia
- acute renal failure
How do we diagnose rhabdo?
- elevated enzymes [CK over 10k]
- muscle biopsy
Standard exercise test [shows increase in CK with minimal exertion]
How can we treat rhabdo?
- limit exercise [and further muscle damage]
- NSAIDs [phenylbutazone]
- Muscle relaxant [dantrolene]
- fluids [LRS]
- vasodilators if normal hydration and not hypotensive [ace]
- supportive care
T/F: To reduce rhabdo recurrence we can feed them a high carb, low fat, low protein diet
False!
- we feed them LOW carb, MOD fat, HIGH protein diet
- increase exercise and avoid inactivity periods
- dantrolene as prophylactic
- acepromazine 30min before exercise
What is the signalment for RER horses?
RER = recurrent exertional rhabdomyolysis
- young, nervous fillies
- autosomal dominant
Pathophysiology of RER:
Autosomal dominant, heritable stress-related defect in intracellular Ca regulation
T/F: The most reliable diagnostic measure for RER is muscle biopsy.
True.
Look for centralized nuclei [vs normal peripheral fiber location]
What are some management changes we can make in RER horses? [pretty much same as rhabdo question from before]
- maintain stress-free
- dantrolene
- exercise them [avoid stall rest]
- low carb diet
What is PSSM? What is the signalment here?
PSSM = polysaccharide storage myopathy
Seen in calm draft horses
T/F: Definitive diagnosis of PSSM = glycogen accumulation in cardiac muscle.
False!
The glycogen accumulation is in skeletal muscle
What can we increase in the diets of PSSM horses to help them?
Increase the fat
What is the signalment for anesthetic-related rhabdo?
Muscle mass and hypotension!!!
How do we treat anesthetic rhabdo?
Just like exertional rhabdo!
- NSAIDs
- fluids
- dantrolene
- low carbs, mod fat, high protein
- exercise but only once CK is normal
T/F: one major CS of anesthetic rhabdo is prolonged/difficult anesthetic recovery
True!
