What is malignant hyperthermia (MH)?
Malignant hyperthermia (MH) is an inherited disorder of the muscles, which muscles respond differently to anesthesia gases and certain muscle relaxants. The reaction ultimately gives a temperature rise of the whole body, in which cell injury and even death can result.
General
Another name for Malignant hyperthermia (now used in the text: MH) is malignant hyperpyrexia. The incidence is 1 in 50,000 anesthetics, and 1 in 7,500 anesthetics in children. In some areas, the disease is more common MH: parts of Wisconsin and North Carolina, further certain groups from Austria and French pioneers in Quebec.
Signs And Symptoms Of Malignant Hyperthermia (MH)
First creates muscle rigidity (a contorted state), for example in the jaw muscles and muscle breakdown (rhabdomyolysis). The result is a high metabolism in the whole body from the muscles with production of carbon dioxide (CO2) and acid (acidosis). Often, the body temperature is raised, but this may also occur late in the disease. Eventually with serious arrhythmias such as tachycardia (especially ventricular). Secondary may kidney damage (by muscle decay and deposition of muscle breakdown in the kidney, the urine is therefore discolored). Also, there may be brain damage. In 10% of cases, fails, the therapy and the patient dies. In the blood, one can measure the amount of CK (creatine kinase) in the muscle decay is able to demonstrate, in addition, it is necessary to measure blood gases (with the acidity and the amount of carbon dioxide). The urine can be shown myoglobin (myoglobinuria).
Causes
In all currently used vaporous anesthetics (anesthetic gases) Malignant hyperthermia is described. These are the halogenated hydrocarbons, isoflurane, enflurane, halothane, Desflurane, and Sevoflurane. Older volatile anesthetics such as halothane would form a stronger trigger for triggering MH than the newer Desflurane and Sevoflurane. Nitrous oxide does not give MH.
In addition to the volatile anesthetic agents are also the depolarizing curares (muscle relaxants) such as succinylcholine able to provoke malignant hyperthermia. The historical classic combination of Halothane with Succinylcholine was a very strong trigger to MH-susceptibele persons. Nondepolarising curares lure no malignant hyperthermia out.
For patients with well-known MH, there is the alternative of total intravenous anesthesia with substances such as propofol in combination with opiates.
Associated syndromes
In general, MH is associated with various muscle diseases (neuromuscular diseases). These include Duchenne muscular dystrophy, Becker muscular dystrophy, facioscapulohumeral dystrophy and hyperkaliëmische familial periodic paralysis. Patients with exercise-induced rhabdomyolysis may also be susceptible to MH.
MH / Malignant Hyperthermia Treatment, Therapy
Besides cooling with ice and cold infusions is the cornerstone of treatment Dantrolene, a certain kind of muscle relaxant. This is a muscle relaxant medication that actually works and the only way to break the cascade of increasingly severe temperature rise. Preparing dantrolene for patient use is very laborious and additional manpower in case of MH very necessary. Dantrolene is in about 90% of the cases employed. The dose Dantrolene (Dantrium) is 2 mg / kg bolus repeat every 5 minutes up to 10 mg / kg. Thereafter, this should be repeated every 12 hours. For a good response, it must be given orally for 3 days in a dose of 1-2 mg / kg 4 times a day. Dantrolene is also used in Neurolept Malignant Syndrome Heatstroke and extreme temperature rise with drugs such as cocaine and ecstasy (Ecstasy).
Heredity
Malignant hyperthermia (MH) is an autosomal dominant inherited. This means that there is a probability of 50% that has been done to a child of a person with MH. In 50% of the cases concerned, the ryanodine receptor, with 30 point mutations have been described. There are also involved other receptors.