Reevaluation by Clinical Grading Scale for Malignant Hyperthermia Reported in Korean Journal of Anesthesiology

Malignant hyperthermia

Malignant hyperthermia (MH) is an uncommon, life-threatening pharmacogenetic disorder of the skeletal muscle. It presents as a hypermetabolic response in susceptible individuals to potent volatile anesthetics with/without depolarizing muscle relaxants; in rare cases, to stress from exertion or heat stress. Susceptibility to malignant hyperthermia (MHS) is inherited as an autosomally dominant trait with variable expression and incomplete penetrance. It is known that the pathophysiology of MH is related to an uncontrolled rise of myoplasmic calcium, which activates biochemical processes resulting in hypermetabolism of the skeletal muscle. In most cases, defects in the ryanodine receptor are responsible for the functional changes of calcium regulation in MH, and more than 300 mutations have been identified in the RYR1 gene, located on chromosome 19q13.1. The classic signs of MH include increase of end-tidal carbon dioxide, tachycardia, skeletal muscle rigidity, tachycardia, hyperthermia and acidosis. Up to now, muscle contracture test is regarded as the gold standard for the diagnosis of MHS though molecular genetic test is used, on a limited basis so far to diagnose MHS. The mortality of MH is dramatically decreased from 70-80% to less than 5%, due to an introduction of dantrolene sodium for treatment of MH, early detection of MH episode using capnography, and the introduction of diagnostic testing for MHS. This review summarizes the clinically essential and important knowledge of MH, and presents new developments in the field.

Malignant hyperthermia during general anesthesia for a surgery of idiopathic scoliosis: A case report

Malignant hyperthermia is a potentially fatal hypermetabolic syndrome characterized by skeletal muscle rigidity and hyperpyrexia. We had an 11-year-old female presented for a surgery for idiopathic scoliosis of the thoracic vertebra. Generalized muscle rigidity and tachycardia were revealed 1 hour 35 minutes after isoflurane administration. Then the body temperature was risen to 43degrees C within 10 minutes and the arterial blood gas analysis showed a severe respiratory and metabolic acidosis. Under the suspicion of malignant hyperthermia, the patient was treated by discontinuing all anesthetic agents, hyperventilation with 100% oxygen, surface cooling with ice pack and the administration of dantrolene sodium. But, the patient died of renal failure and disseminated intravascular coagulation after 50 days postoperatively.

Anesthetic experience for patients with malignant hyperthermia susceptibility determined by molecular genetic test: A report of 2 cases

Malignant hyperthermia (MH) is a potentially fatal pharmacogenetic disorder manifested as a life threatening hypermetabolic crisis in susceptible individuals following exposure to inhalation anesthetics and to depolarizing muscle relaxants. The preoperative diagnosis of MH susceptibility is difficult. The gold standard for determination of MH susceptibility is the in vitro contracture test. However, it is invasive, requiring skeletal muscle biopsy and is not widely available. Recent advances in genetic testing for mutations that result in MH during anesthesia have helped some genetic test have limitations in clinical application due to the diversity of mutations. In Korea, we found the RYR1 genetic mutation by molecular genetic testing for MH susceptibility in a family for which MH had occurred. Based on the results of genetic testing, we could known MH susceptibility of 2 patients. We believe that the genetic testing for MH can be developed and used with some limitations in clinical settings in Korea.