Tying up

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Tying Up

Exertional Rhabdomyolysis, Monday-morning Disease, Azoturia, Set Fast, Black Water, Paralytic Myoglobinuria, Exertional Myopathy

Exertional rhabdomyolysis syndrome (ERS), also known as "tying up", is a term used to describe a disease in which horses develop abnormal muscle pain and cramping during or immediately after exercise. ERS can develop as a one-time event, sporadic episodes, or chronic recurring events.
  • Sporadic or One-time episodes: Sporadic or one-off episodes are usually caused by a dietary imbalance (electrolyte imbalance, vitamin E and/or selenium deficiency, excessive grain in diet), overexertion (increase in exercise intensity beyond current level or heat exhaustion which causes a muscle strain), or from a viral infection.
  • Recurring (repeated) episodes: Recurrent tying up episodes are more likely to be related to horses with an underlying myopathy, such as Polysaccharide Storage Myopathy, Immune-Mediated Myositis, and Recurrent exertional rhabdomyolysis. The recurrent form is usually found after the horse reaches a level of fitness, during slower pace exercise, or before an event.
Typing episodes typically occur within 15 to 30 minutes of exercise. All of a sudden, the horse becomes stiff and develops a stilted, short-strided gait and may even refuse to move. Other clinical signs may include muscle fasciculations or trembling, excessive sweating, increased heart rate, firm and painful muscles, lameness, or sudden onset of weakness.

Symptoms

Stiff gait
Lameness
Sudden onset of weakness
Increased respiratory rate
Profusely sweating
Short, choppy stride
Reluctance to move
Decreased performance
Hard, swollen muscles
Trembling
Coffee-colored urine

Diagnosis

  • History
  • Clinical signs
  • Physical exam
  • Laboratory tests (mild to marked elevations in serum CK, LDH and AST at rest)
  • Urinalysis
  • Genetic testing

Treatment


TreatmentDetails
Prevent further exertion
Oral and/or IV fluids if dehydrated or myoglobinuric
Acepromazineto increase blood flow and decrease anxiety (however not if the horse is dehydrated)
Dantrolene sodiumorally at 4 to 6 mg/kg every 8 hours
Rest with hand walking
Intravenous DMSO (< 10% solution)
Analgesialidocaine CRI, butorphanol, detomidine can be used.
Care with NSAIDs especially if myoglobinuria or renal compromise present.
Monitor plasma electrolytes
Diet ManagementMinimize amount of grain in diet.
An additional vitamin and mineral supplement may be beneficial.

Prevention

  • Maximizing the horse's turnout time
  • Providing electrolytes during hot riding conditions
  • A high fiber/low starch diet.

Scientific Research References

Good Overviews

Risk Factors

  • Female horses appear to be predisposed to this disease.
  • Horses with an underlying myopathy (such as Polysaccharide storage myopathy, Recurrent exertional rhabdomyolysis, or Mitochondrial myopathy)
  • Genetics
  • Electrolyte imbalance
  • Endurance horses

Commonly Affected Breeds

Thoroughbred icon