Anesthesia Can Be Fatal to These Dogs — Is Your Dog on This List?

Story at-a-glance -

  • Canine stress syndrome (CSS) is a rare genetic disorder that can cause a potentially fatal response to certain triggers
  • Certain breeds are predisposed to carry the gene mutation for CSS
  • Symptoms typically occur when a dog with CSS is under stress or has received certain anesthetic drugs
  • Certain types of anesthesia can be fatal to these dogs, which is why it’s very important to prescreen through DNA testing
  • Dogs with CSS can be given a safer anesthetic, however, procedures should be kept as short as possible to minimize the risk of a CSS episode

By Dr. Becker

Canine stress syndrome (CSS), which is also called canine malignant hyperthermia (CMH), is a relatively rare inherited disorder that can cause a dog to have potentially life-threatening reactions in response to specific triggers.

The disorder is called canine stress syndrome because it tends to show itself when a dog is under stress or overstimulated. Triggers for episodes of CSS include:


Ingestion of food ingredients such as caffeine or hops


Environmental stress

Too much exercise


Intense exercise

Certain anesthesia agents and other specific drugs that affect the neurologic and muscular systems of the body

Certain breeds are predisposed to carry the genetic mutation that causes CSS. The condition has been reported in the Bichon Frise, Border Collie, Golden Retriever, Greyhound, Labrador Retriever, the Pointer, Saint Bernard and the Springer Spaniel.

What Causes Canine Stress Syndrome?

Canine stress syndrome is caused by defective calcium ion channels in the striated muscles that connect the bones in a dog’s legs and spine. These muscles are responsible for voluntary, coordinated movements such as walking and head movements.

Muscle contractions are dependent on calcium levels. In normal muscles, increases and decreases in calcium levels occur very rapidly, allowing precise control of muscle movement.

However, in a dog with CSS, faulty control of calcium levels leads to calcium leakage, which makes muscles more susceptible to physiological stress, as well as certain drugs.

In addition, when the muscles in a CSS dog are activated, it triggers the release of abnormally large amounts of calcium, resulting in muscle rigidity.

CSS Signs to Watch For

Canine stress syndrome causes a range of symptoms, including:

Abnormally high body temperature

Increased breathing rate

Muscle tremors

Bluish tinge to skin and mucous membranes

Muscle rigidity

Unstable blood pressure


Fluid buildup in the lungs

Rapid, irregular heartbeat

Impaired blood coagulation

In a worst-case scenario, kidney failure can also occur.

Diagnosing CSS

Diagnosis of malignant hyperthermia is usually based on observing the symptoms a dog develops while under stress or after being given certain anesthetic drugs. Symptoms can occur gradually or quickly, and include muscle stiffness, twitching and increased heart and respiratory rates.

Dogs under stress, but not anesthetized, may have open-mouthed breathing and an increased breathing rate, along with temporary breaks in breathing. In light-colored dogs, the skin can at first lighten, then turn red and finally take on a bluish hue. The body temperature can increase to as much as 113 degrees F during the episode.

There are several laboratory tests than can help identify dogs susceptible to CSS, but they can’t be used as a diagnostic tool in the middle of a crisis.

If a dog with CSS undergoes anesthesia using halothane gas or other types of inhaled anesthesia, the results can be quickly fatal. This is why it’s very important to identify a dog with this mutation through DNA testing prior to scheduling surgical procedures.

Treating Canine Stress Syndrome

There is no cure for malignant hyperthermia. Since episodes come on suddenly and are typically very severe, sadly, this condition is often fatal. That’s why it’s important to identify dogs with the gene mutation as early as possible, and take steps to prevent CSS symptoms from ever developing.

It is recommended that dogs with this disorder who require anesthesia for any type of veterinary procedure receive a muscle relaxant drug prior to being anesthetized. Certain anesthetic agents like halothane must be avoided, but fortunately, there are other anesthetic drugs that are safe to use with CSS patients.

Veterinary procedures must be kept as short as possible because CSS episodes most often occur after an animal has been anesthetized for more than an hour.

Most CSS treatments focus on managing secondary conditions resulting from defective calcium metabolism. In traditional veterinary medicine, these may include seizure control medications, glucose therapy and the use of tranquilizers during stressful situations.

Feeding frequent, small meals instead of one or two large meals each day may help CSS dogs maintain normal blood glucose levels, which can reduce the frequency of seizures. These dogs should also be protected from stressful situations, intense exercise and food and drugs that can trigger symptoms.

However, since stressful situations are sometimes unavoidable, I recommend using natural substances to help reduce your dog’s apprehensiveness, including homeopathics (Aconite and Belladonna are most commonly prescribed), Bach Rescue Remedy, Bach Rock Rose and calming herbs such as valerian and rhodiola.

While these natural calming agents aren’t a guarantee your dog won’t have an episode, they may enhance his or her stress threshold. While these precautions aren’t foolproof in preventing malignant hyperthermia, they can reduce the chances that a crisis will develop.