[Registration of peranesthetic cases of malignant hyperthermia in France. An update]

[Anesthesia in myotonia]

Myotonia is defined as a persistent contraction of skeletal muscles after their stimulation. This contracture is not prevented or relieved by regional anaesthesia or muscle relaxants. The sensitivity to non-depolarizing muscle relaxants is usually normal. Suxamethonium, neostigmine, hypothermia, a rise in kalaemia should be avoided. There have been case reports of malignant hyperthermia in patients with myotonia congenita. Dystrophia myotonica is the second most frequent of the inherited muscle diseases, after Duchenne's dystrophy. The severity of the disease is due more to the muscular atrophy and the multiple organ involvement than to the abnormal contraction. Atrioventricular heart block and dysrhythmias are more common than heart failure. Prolonged apnoea and pneumonia are the main risks of anaesthesia. In severe cases, exists a restrictive respiratory insufficiency which is preceded by a fall in the maximum expiratory pressure. Dysphagias and inefficient coughing may occur early. An increased susceptibility to hypnotic drugs and opiates is a common feature. Spontaneous sleep apnoeas should be sought before anaesthesia, especially by using pulse oximetry. The anaesthetic implications are reemphasized.

[Clinical features of malignant hyperthermia crisis]

Malignant hyperthermia (MH) is a pharmacogenetic disorder. It is classically described as a hypermetabolic state triggered by halogenated anaesthetics and/or depolarizing muscle relaxants. In fact, since Denborough and Lovel's case, it has been shown that MH has a great number of clinical forms. The overwhelming picture of muscular hypercatabolism with fulminating hyperthermia and generalized rigidity is becoming rare. A better knowledge of the first symptoms explains in part the better prognosis: masseter spasm after suxamethonium, an increase in expired CO2 concentration, unexplained tachycardia, ventricular arrhythmias. The use of dantrolene reduced the mortality of MH. The different types of clinical manifestations are due to genetic differences, the concentration of the anaesthetic agent, and the length of time of exposure to the drug. The severity of the episode is linked to environmental factors such as stress, physical exercise, ambient temperature, concomitant use of other drugs. Masseter spasm after suxamethonium is specific for MH, but not pathognomonic. It occurs in 1% of cases in children when using halothane with suxamethonium. However, in those patients who displayed such a spasm, more than 50% had a positive contracture test. Masseter spasm is often associated with severe rhabdomyolysis in patients with muscle dystrophy, especially Duchenne's dystrophy. In the latter case, major cardiac problems may occur at the time of anaesthetic induction. Even if there are no other signs of MH, all patients who have had a masseter spasm must be considered as open to doubt, and should be further explored. MH is often difficult to diagnose in medium severity types.(ABSTRACT TRUNCATED AT 250 WORDS)