Malignant hyperthermia

The malignant hyperthermia is a pharmacogenetic disease of the Muscle striated with dominant autosomic Transmission appearing in the form of crisis, in which the principal demonstration is a rise in the body Température putting quickly concerned the vital prognosis.

The malignant crisis of hyperthermia is started by certain drugs with muscular tropism, in particular the halogenous anesthetic . Extremely rare complication of the General anesthesia, it is quickly fatal in the absence of fast diagnosis and of adequate treatment.

Diagnosis

Starting factors

Malignant hyperthermia occurs exclusively at the subjects carrying the genetic anomaly. To date, two Gène S are individualized and four others are localized. The individualized genes are RYR 1 and the CACNA1S. RYR1 is generally in question. The research of the changes responsible for susceptibility to malignant hyperthermia is available only in Europe.

Malignant hyperthermia always makes following the use of a halogenous anesthetic (Halothane, Sévoflurane, Desflurane, Enflurane, Isoflurane). The use of Suxaméthonium (or succinylcholine) is a recognized supporting factor. The responsible products involve a release of Calcium starting from the Réticulum sarcoplasmic responsible for an intense muscular answer with appearance of a Glycogénolyse and production of Lactate, hyperkaliemy, ventricular arrhythmia and myoglobinurie.

Clinical demonstrations

The malignant crisis of hyperthermia appears initially in the form of a Tachycardie with Polypnée (increase in the respiratory frequency, although this demonstration is not obvious because of the use of assisted ventilation), then appears a ventricular arrhythmia by stimulation of the Nervous system sympathetic nerve with intense release of Catécholamine S and Hyperkaliémie. A muscular Hypertonie appears quickly with in particular a spasm of the masséter S, while the body temperature increases by 1 to 2 °C every five minutes by muscular hypercatabolism.

Biological diagnosis

It is retrospective. The standard test rests on the muscular Biopsie with study of the contractility of the muscular cell in the presence of Caféine and of Halothane.

Assumption of responsibility

Treatment

Malignant hyperthermia is a vital urgency. It imposes the dead halt of the administration of halogenous gases and curares, the suspension of the surgical act and implementation the fast of well codified therapeutic measurements which comprise:

a curative treatment: the Dantrolène by intravenous way
of symptomatic measurements: ventilation in pure oxygen, body cooling after monitoring of the temperature (cutaneous cooling, washing of all the body cavities accessible to the frozen physiological salt solution, except for the thorax), dealt with of the disorders of the rate/rhythm, empirical treatment of the hyperkaliemy and the metabolic disorders by intravenous hydration and alkalization.
once the stabilized state, a hospitalization in Réanimation for monitoring continues

Forecast

Even if the reanimation is well led, malignant hyperthermia is fatal in 5 to 10% of the cases.

Prevention

The survivors must imperatively carry on them a chart specifying the diagnosis and comprising a list of prohibited drugs: the halogenous anesthetic and the Suxaméthonium are proscribed with life. The Kétamine, the Atropine, the Vérapamil, the Diltiazem, the Digitalique S, the Theophylline, the Cafeine and the Calcium (by intravenous way) must be avoided.

The related subjects (parents, children, brothers and sisters), in the absence of family tracking, are them also subjected to the malignant risk of hyperthermia. Any patient having had in his entourage a malignant case of hyperthermia must announce it to the doctor anesthetist during the consultation of anesthesia.

References

orpha.net - malignant Hyperthermia of the anesthesia
sfar.org - Procedure of assumption of responsibility
Henry Rosenberg, Nyamkhishig Sambuughin, Malignant Hyperthermia Susceptibility In GeneTests: Medical Genetics Information Resource (database online). Copyright, University off Washington, Seattle. 1993-2005]

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