Canine Stress Syndrome in Dogs

Seen most often in heavily muscled dogs, canine stress syndrome can be triggered by exercise, stress, certain foods, and specific drugs. It is not clear whether it only takes one triggering event or multiple exposures, since many signs of a stress syndrome episode are not recognized.

Anesthesia has been implicated as a trigger, and can result in an elevated carbon dioxide level in the blood within the first ten minutes of administration. The condition can be fatal if anesthesia is not discontinued immediately.

Canine stress syndrome, also called malignant hyperthermia, is a rare genetic disorder that creates a metabolic disease in the skeletal muscles. This dysfunction can cause life-threatening reactions to certain triggers. Symptoms tend to appear in an affected dog who is overstimulated or experiencing a highly stressful situation.

Episodes generally begin with an elevated body temperature and muscle spasms, and if not treated quickly, can escalate to a cardiac arrest or organ failure.

If under anesthesia, your dog would be monitored for signs of an episode by the attending veterinarians. At home, symptoms can be so small that they go unnoticed, or they can appear as a full-fledged episode. Signs your dog is having a reaction from stress syndrome include:

• Abnormally elevated body temperature
• Muscle spasms
• Increased breathing rate
• Increased heart rate
• Muscle rigidity
• Open-mouthed breathing
• Blood pressure fluctuations
• Bluish color to mucous membranes and skin
• Fluid in the lungs
• Dehydration
• Weight loss
• Loss of appetite
• Weakness 
• Seizures
• Kidney failure 
• Cardiac arrest
• Death

Canine stress syndrome is caused by an inherited mutation in the autosomal dominant gene RYR1. This results in defective calcium ion channels in the muscles that connect bones in the spine and legs. In normal dogs, calcium levels increase and decrease rapidly to produce muscle contractions that create movements. A dog affected by canine stress syndrome has faulty control of those calcium channels, which results in calcium leakage. This in turn leads to muscle rigidity, muscle contraction, and an increased metabolism which leads to an excess of carbon dioxide in the blood and an elevated temperature.  

The serious symptoms of canine stress syndrome appear after exposure to certain triggers. These triggers include:

• Inhaled anesthetic drugs, such as halothane, isoflurane, sevoflurane, or desflurane
• Depolarizing neuromuscular blocking drugs, or muscle relaxants such as succinylcholin
• Stress, including psychological and environmental
• Too much exercise
• Overstimulation
• Excitement
• Apprehension 
• Foods containing caffeine or hops
• Vaccines

There are breeds who seem to be predisposed to carry the defective gene. These include:

• Bichon Frise
• Border Collie
• Golden Retriever
• Greyhound
• Labrador Retriever
• Pointer
• Saint Bernard 
• Springer Spaniel

A diagnosis of canine stress syndrome is often based on observed symptoms in an anesthetized dog, or one who is under stress. Due to the progressive and life-threatening nature of the symptoms, treatment may be administered before any definitive testing to confirm the diagnosis has taken place. As such, many vets may wish to test dogs suspected of stress syndrome before any surgical procedures take place. 

One such test is called the In Vitro Contracture Test (IVCT). This involves taking a muscle biopsy to test its contracture response to triggering agents, such as caffeine or halothane. This specialized test is not available at all clinics, and can be risky as anesthesia will need to be administered for the procedure. 

More often, a DNA test that requires only a blood sample can detect the RYR1 genetic mutation. Other tests that can help a diagnosis can include observation under halothane exposure, an erythrocyte fragility test, urine and blood testing, and an electrocardiogram.

There is no cure for canine stress syndrome, but there are ways that you and your veterinarian can manage the condition in your dog. 

If your dog requires anesthesia, your vet may administer a muscle relaxant beforehand. Drugs other than halothane can be used, and procedures should be kept short, as symptoms of the syndrome generally appear after an hour of being under anesthesia. Stress before any procedures should be minimized.

As soon as your dog shows any symptoms, treatment should begin immediately. Any inhalant anesthesia should be discontinued, and symptomatic treatment follows as needed. The muscle relaxant Dantrolene is often given. Other treatments can include using ice packs, ventilation and oxygen therapy, fluid and electrolyte therapy, glucose and insulin therapy, seizure control medications, tranquilizers, corticosteroids, or sodium bicarbonate. 

Help your dog at home by keeping him away from stressful situations, intense exercise, and any other possible triggers, such as caffeine or certain drugs. There are natural remedies to reduce your dog’s stress levels, including valerian, rhodiola, and certain homeopathics. Feeding smaller, more frequent meals can help to maintain healthy blood glucose levels.

The prognosis for canine stress syndrome is fair to poor, as often, once the symptoms are recognized, the condition can be fatal. Seek medical treatment as soon as any symptoms are noticed for the best chance of survival. With quick and proper care, your dog can recover, but the condition will need to be managed for the rest of his life. Careful monitoring before, during, and after any procedures that require anesthesia can alert you and your vet to a possible episode. Manage the condition at home by removing your dog from stressful situations and monitoring for any signs of symptoms.

While you cannot prevent this condition from occurring in your dog, you can determine if your dog is affected. This can be done through DNA or IVCT testing with your veterinarian. To prevent future generations from being affected, do not breed dogs diagnosed with canine stress syndrome.