Malignant Hyperthermia in Dogs

Malignant hyperthermia is a disorder that's genetically predisposed in certain dogs. Labrador retrievers in particular may exhibit symptoms of malignant hyperthermia during times of stress. Due to this reason malignant hyperthermia is also termed as "canine stress syndrome." Since this disorder can be potentially fatal, pet owners should understand the causes of malignant hyperthermia and symptoms related to it.

Malignant Hyperthermia

This condition occurs when dogs are genetically predisposed due to mutation in the ryanodine receptor calcium release channel (Ry1) gene. This is turn causes abnormal release of calcium (Ca++), or inadequate Ca++ metabolism. Pets predisposed to malignant hyperthermia are sensitive to certain ingredients present in drugs and food such as caffeine and halothane. The condition also develops if susceptible dogs are exposed to volatile anesthetics. In addition, dogs often exhibit the symptoms of malignant hyperthermia due to exercise induced stress. Clinical studies have revealed the changes that occur in susceptible pets that are administered halothane. Most dogs enter a hyper-metabolic state and exhibit high increase in CO2 production. Rectal temperature readings are also high.

Symptoms of Malignant Hyperthermia Include:

  • Stiffness of the muscles
  • Tachypnea
  • High body temperature
  • Tachycardia
  • Dilation of pupils
  • Seizures

Diagnosis of Malignant Hyperthermia

The symptoms of malignant hyperthermia may occur due to various stimuli that trigger muscle response. The vet will perform a thorough physical examination of the pet and check muscle contraction by using various stimuli to determine the response. Commonly used clinical stimuli include caffeine, ryanodine and halothane. Since malignant hyperthermia is predisposed due to a genetic mutation, ongoing research is trying to identify canine stress syndrome through genetic testing and breeding studies. Other diagnostic tests include DNA assay tests that accurately determine heterozygous and homozygous forms of the gene responsible for malignant hyperthermia.

Treatment Options

Most treatment options used for pets suffering from the condition work effectively to control the disorder. The aim of treatment is to regularize secondary bodily changes that develop due to malignant hyperthermia. Blood glucose levels are maintained, dietary modification is initiated and medications to control seizures are generally prescribed. Although calcium channel blockers are used to treat canine stress syndrome, the response varies in individual pets and side effects of medication like drantolene is a factor to be considered. Drantolene is mostly administered when the disease is in the early stage. Other supportive procedures used to save pets suffering from malignant hyperthermia include oxygen enrichment, IV fluid administration and control of acidosis.

Home Care

Pets genetically predisposed to malignant hyperthermia should be kept in a stress free environment. Dogs that become nervous or excited easily require tranquilizers to calm them during periods of severe stress. Since hypoglycemia is associated with malignant hyperthermia, pets should be given small meals at regular intervals to maintain blood glucose levels. In addition, anti-convulsion drugs prescribed to control seizures should be administered on time according to vet instructions. Any prescribed medication shouldn't be discontinued unless otherwise directed by the vet.

Complete protection from malignant hyperthermia can be attained if carriers of the gene are identified before breeding or through clinical advances that alter abnormal genes. This best preventive procedure is to protect susceptible pets from known stimuli that trigger a hyper-metabolic state.