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Malignant Hyperthermia in Dogs

From the Merck Veterinary Manual

Because greyhounds are very muscular, they have a higher risk of Malignant Hyperthermia. The risk of it happening is low but it does happen.
Please make sure your vet is familiar with Malignant Hyperthermia, especially before anesthesia. Always do bloodwork. If you trust your vet, there should be no reason you can’t put your greyhound under anesthesia. Just make sure your vet is experienced with greyhounds and their quirks.

Malignant hyperthermia is seen mostly in swine, but it has also been reported in dogs (especially Greyhounds), cats, and horses. This syndrome is characterized by abnormally high body temperature, muscle rigidity, a very rapid and irregular heartbeat, increased breathing rate, bluish tinge to skin and mucous membranes, unstable blood pressure, fluid buildup in the lungs, impaired blood coagulation, kidney failure, and death.

Malignant hyperthermia is consistently triggered in susceptible animals by excitement, apprehension, exercise, or environmental stress. Giving certain anesthetics or specific drugs that affect the neurologic and muscular systems also consistently triggers malignant hyperthermia in susceptible animals.

Diagnosis is based on development of clinical signs in an animal that has been given an anesthetic agent or is participating in a stressful event. Signs can develop slowly or rapidly and include muscle stiffness, twitching, a rapid heartbeat, and an increased breathing rate. Animals that are not under anesthesia may show open-mouthed breathing and an increased breathing rate, followed by a temporary break in breathing. Blanching and redness of the skin followed by blotchy blue tinges can be seen in light-colored animals. Body temperature increases rapidly and can reach 113°F (45°C).

Many laboratory tests have been developed to help identify animals susceptible to malignant hyperthermia, but they are not useful for diagnosis of malignant hyperthermia in a sudden crisis.

Treatment and Prevention

Usually, malignant hyperthermia episodes come on suddenly and are very severe. If the condition is recognized early in an animal under anesthesia, supportive measures may be able to save the animal. Unfortunately, regardless of treatment, malignant hyperthermia is usually fatal.

Stress must be minimized to prevent malignant hyperthermia episodes in individual animals. If an animal that is suspected to be susceptible to malignant hyperthermia (or that has survived a previous episode) needs anesthesia and surgery, certain precautions should be taken. These include administering a drug called dantrolene 1 to 2 days before anesthesia and avoiding certain anesthetic agents. Certain local anesthetics are also safe to use. All procedures must be kept as short as possible because malignant hyperthermia happens most often when the animal has been under anesthesia for longer than 1 hour. Although these precautions cannot prevent malignant hyperthermia, they can reduce the chances of a crisis developing.

Whenever a case of malignant hyperthermia is suspected, owners of siblings and breeders should be notified if possible. However, malignant hyperthermia is not always linked to a pedigree line.


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To view the recent ABC Channel 13 news story about Bentley click here.


Bentley with his doctor, Dr. Au, before he was released from O.S.U. on 11/12/2011

Excerpts taken from North Coast Greyhound Connection website.


Bentley, a 6 month old greyhound, arrived to NCGC several weeks ago from a training farm in West Virginia.  Prior to his arrival, NCGC were notified that he sustained serious injuries during a turnout and would never be able to race.  When NCGC representatives traveled to W.V. to pick him up, it was apparent from initial observation that his injuries were more serious than were led to believe.  In addition, he was severely underweight, under 40 lbs.


NCGC veterinarian, Dr. Roger Grothaus, felt that Bentley had been in pain for several months due to improper care of the injuries he sustained and further recommended that he be seen by OSU for a course of treatment due to the seriousness of his injuries.


On November 8th, Bentley was taken to OSU where Dr. Jennifer Au confirmed what Dr. Grothaus suspected.  An infection had developed in his left foreleg to the degree that the cartilage at his elbow joint had dissolved completely.  The infection had now spread internally through bone and tissue and had caused him tremendous pain from his paw up to and including his shoulder.

Dr. Au recommended that it was best to perform a “four point” amputation.  This involves taking the foreleg, shoulder and clavicle.  The amputation was performed on November 9th and was successful.  Bentley is now recovering in his foster home with lots of love and attention to help him with his healing process.

He’s experiencing “phantom pains” which we were told by Dr. Jennifer can result from post-amputation surgeries and will diminish with time.  We are happy to report that he is gaining weight, loves treats and gives plenty of kisses to those that come in contact with him.
In spite of the pain Bentley has endured, his will to live is unending and his happy, positive spirit is addicting to all those that have a chance to meet this little guy in person. Many life lessons can be learned from the positive energy that he emits.


As you can imagine, NCGC is facing an enormous medical bill for Bentley’s surgery and we will do whatever it takes for him. Please consider donating to Bentley’s fund, even just the smallest amount will be greatly appreciated.

There are several ways to donate to Bentley’s fund:

  • Donation jars will be set-up at various NCGC events
  • Facebook Page also has a donation link located on the left-hand side (below our logo),
  • Mail a check (payable to “NCGC”) and mail it to:   NCGC/Treasurer , 116 Canterbury Drive,  Fremont, Ohio 43420.







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