Malignant hyperthermia

From Dog

Malignant hyperthermia is a rare autosomal-dominant genetic syndrome of dogs characterized by hyperthermia.

Complications of this syndrome may be fatal in some cases due to extensive rhabdomyolysis, generalized skeletal muscle contracture, cardiac dysrhythmia and acute renal injury, often triggered by exposure to fermented hops[1], succinylcholine or volatile anesthetic agents[2], particularly halothane[3].

Clinically affected dogs usually present with hyperthermia (> 40.00C), restlessness, panting, vomiting, signs of abdominal pain, seizures, tachycardia, tachypnea, increased carbon dioxide production, increased oxygen consumption, acidosis, muscle rigidity and rhabdomyolysis. Symptoms are all related to a hypermetabolic response[4].

Blood tests often show hyperkalemia, hyperphosphatemia and elevated levels of AST, creatinine kinase and alkaline phosphatase[5].

A differential diagnosis would include other causes of hyperthermia including sepsis, exercise-induced collapse, polyneuropathy[6], myokymia, ivermectin toxicity, tetanus, lasalocid poisoning, hyperthyroidism and pyrexia.

Treatment in anesthetic patients include cold ice-packs, ethanol rubs on the distal extremities, and use of drugs such as acetylpromazine and dantrolene[7].

In anesthetic risk patients with this condition, anesthetic drugs such as etomidate may be a practical alternative[8].

References

  1. Duncan KL et al (1997) Malignant hyperthermia-like reaction secondary to ingestion of hops in five dogs. J Am Vet Med Assoc 210(1):51-54
  2. Roberts MC et al (2001) Autosomal dominant canine malignant hyperthermia is caused by a mutation in the gene encoding the skeletal muscle calcium release channel (RYR1). Anesthesiology 95(3):716-725
  3. Gleed R (1992) Precautions when using halothane. Vet Clin North Am Small Anim Pract 22(2):323-325
  4. Rosenberg H et al (2007) Malignant hyperthermia. Orphanet J Rare Dis 2:21
  5. Otto K (1992) Malignant hyperthermia as a complication of anesthesia in the dog. Tierarztl Prax 20(5):519-522
  6. Adami C et al (2012) Unusual perianesthetic malignant hyperthermia in a dog. J Am Vet Med Assoc 240(4):450-453
  7. Kobayashi S et al (2009) Dantrolene, a therapeutic agent for malignant hyperthermia, markedly improves the function of failing cardiomyocytes by stabilizing interdomain interactions within the ryanodine receptor. J Am Coll Cardiol 53(21):1993-2005
  8. Robertson S (1992) Advantages of etomidate use as an anesthetic agent. Vet Clin North Am Small Anim Pract 22(2):277-280