Malignant Hyperthermia in Dogs

A condition called malignant hyperthermia, characterized by the elevation of the body temperature above the normal range may occur in dogs. This disorder commonly occurs in pigs, but it occasionally occurs in horses, dogs, and cats too. Among dogs, Greyhounds are particularly susceptible.

Malignant hyperthermia in dogs is a syndrome that has several associated symptoms such as increased heart rate and breathing rate, irregular heartbeat and blood pressure, fluid accumulation in lungs and problems with coagulation of blood. The affected animal may develop muscle rigidity and a bluish discoloration of the mucus membranes as well as the skin. It may also lead to kidney failure and eventually death.

Stress of all types, particularly due to apprehension, fear, excessive physical exercise or even too much excitement may trigger malignant hyperthermia in dogs. Environmental stress may also play a part. This syndrome may be triggered by some of the medications used for anesthesia and those affecting the neuromuscular system of dogs.

Malignant hyperthermia is diagnosed from the typical symptoms which may appear when the dog is administered anesthesia or when it takes part in an event that causes severe stress. The symptoms such as muscle twitching, sudden muscle stiffness, and an increase in the heartbeat and the rate of breathing may appear suddenly or, in some cases, gradually. The dog may breathe with its mouth open, and at a high rate, interspersed with breaks in the breathing. The skin may turn red initially, which then changes to blue blotches that are usually apparent in dogs with light-colored coats. A sudden elevation of the body temperature above the normal range also occurs along with these symptoms. It can be as high as 1130F or 450C.

Susceptibility to malignant hyperthermia in a dog can be identified by certain diagnostic tests, but they may not help in diagnosing the condition when it suddenly appears in an otherwise healthy animal.

Treatment and Prevention

Malignant hyperthermia may appear suddenly without any indication prior to its occurrence, and can be extremely severe in some cases. Unless it is diagnosed early in an anesthetized dog, and if immediate measures are not taken to reverse the condition, it may lead to death. Often it is fatal even with the best of treatment and care.

Malignant hyperthermia may be prevented to some extent by reducing stress, particularly in the case of dogs that are known to be susceptible. If dogs that have had previous incidences of malignant hyperthermia, and those suspected to be prone to it, require any surgical intervention, special precautions are necessary while giving anesthesia. Some anesthetic drugs should be avoided. The drug dantrolene, when administered one or two days prior to administering anesthesia, may also help. Whenever possible, minor surgical procedures are done under local anesthesia. Since malignant hyperthermia usually develops when the dogs are anesthetized for more than one hour, care is taken to complete the surgery within an hour of administering anesthesia. These measures may reduce the risk of developing malignant hyperthermia, even though they may not necessarily prevent it.

If a dog is suspected of having malignant hyperthermia, it is advisable to notify its breeder or the owners of its siblings as they could be affected by the same syndrome. But it may not always have a genetic link.

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