What are Exertional Rhabdomyolysis?
Equine rhabdomyolysis, or exertional rhabdomyolysis, in horses is a condition where the muscles cramp and become painful. Typically, the pain, cramping, and other symptoms of equine rhabdomyolysis are usually associated with physical activity. The muscles actually dissolve after exercising. This condition can also severely inhibit the horse’s performance, and, for some horses, their career. Fortunately, there are several pain management techniques that can be put into place to help minimize the pain and control the symptoms.
Research continues to be conducted on this syndrome, which may have several different causes. This syndrome is diagnosed in two specific types: chronic or recurring exertional rhabdomyolysis (RER) and sporadic exertional rhabdomyolysis. Both have very similar symptoms; however, one episode or period of time with a diagnosis of rhabdomyolysis is considered to be sporadic. Sporadic ER is typically preventable and is the result of various issues with the horse’s lifestyle. Chronic ER, or RER, is due to an inherited condition and typically affects specific breeds.
Equine rhabdomyolysis, or tying up, in horses is characterized by the cramping and tightness of muscles after exercising. This condition is also known as exertional rhabdomyolysis, and may be chronic (recurring) or sporadic in nature.
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Symptoms of Exertional Rhabdomyolysis in Horses
If your horse is having any of the following symptoms, make an appointment with your veterinarian. Symptoms of exertional rhabdomyolysis include:
- Pain occurring after exercising
- Painful muscles in the topline regions
- Shallow breathing
- Rapid breathing
- Muscle contractions
- Renal failure, over time
Recurrent sporadic forms may affect specific breeds of horses, and tend to affect males more so than females. Certain types of horses have a higher chance of getting ER in the chronic form; this may be due to genetics.
- Quarter horses
- Draft breeds
Causes of Exertional Rhabdomyolysis in Horses
There are several causes of ER in horses, and some of the causes of sporadic ER may be prevented. Causes of both sporadic tying up and chronic, or recurrent, tying up can include:
- Muscle strain
- Deficiency of electrolytes
- Deficiency of vitamin E
- Selenium deficiency
- Herpes infections
- Influenza infections
- Inherited conditions
- Abnormal calcium regulation (intramuscular)
- Possible exposure to potassium, halothane, and caffeine may cause muscle sensitivity
- Polysaccharide storage myopathy
- High grain diet
- Research still being conducted
Diagnosis of Exertional Rhabdomyolysis in Horses
If you suspect your horse may be suffering from exertional rhabdomyolysis, make an appointment with your veterinarian. He will begin by performing a complete physical examination of your horse, taking preliminary blood samples, and possibly conducting a biochemistry profile.
Your medical professional will perform a serum blood test and will be using the results of this test to give him much information on his diagnosis. Evaluated will be serum AST (aspartate transaminase, a vital enzyme) and CK (creatine kinase), especially in cases of recurrent exertional rhabdomyolysis. Your veterinarian will take a closer look at the enzyme elevations from the muscles and will generally be conducted when the CK levels peak, which is approximately four hours after physical activity. This laboratory test will be repeated the next day as well, after exercise for accurate results.
Your veterinarian may perform a muscle biopsy to investigate the fibers of the muscle to aid him in a definitive diagnosis. He may also choose to perform genetic testing by sending blood samples or hair samples to a genetic laboratory.
If your horse is experiencing sporadic tying up, your veterinarian will rely on the blood sample which can determine the activity within your horse’s muscles, the serum AST and CT testing to measure the protein levels within your horse. Genetic testing is typically not performed for sporadic tying up, as this condition occurs intermittently and is not inherited.
Treatment of Exertional Rhabdomyolysis in Horses
There are several different options for exertional rhabdomyolysis in terms of treatment. The type of treatment is dependent upon whether your horse is suffering from the sporadic or chronic form. Treatment methods may include:
Medications for Pain
Medications such as acepromazine, xylazine, detomidine, or other tranquilizers help with analgesic therapy and sedation. Medications such as these are given for horses in severe pain from tying up. Often, these medications may be combined with others at a consistent infusion rate. Anti-inflammatory medications and steroids may also be given to ease your horse’s pain and discomfort from his muscle pain.
Your horse may need extra fluids in order to prevent dehydration or to rehydrate your horse, especially after medications are given. IV fluids are essential in restoring electrolytes and giving your horse’s bodily systems and muscles the hydration they need in order to recover. Specific types of fluids may also be given in conjunction with solution to prevent potassium levels from becoming abnormally high or too low.
Methocarbamol is a muscle relaxer that may be effective on your horse, depending on his condition. This also depends on the dosage given. Dantrium sodium may be administered to aid in the reduction of contracting muscles and severe tightening from cramps. Your veterinarian will determine the dosage amount and how often it needs to be repeated, if necessary.
Recovery of Exertional Rhabdomyolysis in Horses
Recovery depends on the condition of your horse after treatment, and how well he responds. Fortunately, there is much research being conducted on this condition, and with recurrent or chronic cases, more genetic tests are being researched.
Your veterinarian may recommend lifestyle changes in order to decrease his bouts of exertional rhabdomyolysis. Your horse may require rest for a specific amount of time recommended by your veterinarian; he will need to begin exercising once this time period is over, as moderate exercise can help horses in the recovery. Your medical professional may also recommend a decrease in the amount of carbohydrates and grains while increasing his amounts of hay and fresh pasture. Your veterinarian may also recommend supplements to add to his diet, such as potassium. Be sure to ask your veterinarian any questions about the addition of supplements in terms of the types and amounts.
If your veterinarian recommends any other decrease in activity or ways to gradually begin increasing his activity, be sure to follow his instructions. If you see any new symptoms develop, contact him with any questions or concerns.