[Tests of contracture and sensitivity to malignant hyperthermia in 27 patients]

Twenty-seven patients, four of whom had presented with a crisis of malignant hyperthermia and the 23 other being close relatives of such patients, underwent a muscle biopsy so as to determine their susceptibility to malignant hyperthermia. Halothane-caffeine contracture tests, interpreted in accordance with the criteria of the European Group on Malignant Hyperthermia, yielded the following results: 13 positive (MHS), 10 negative (MHN), 4 equivocal (MHE). The history, clinical examination, CPK level, histoenzymatic morphology and electron microscopic study did not provide information sensitive enough to use for the detection of susceptibility to malignant hyperthermia. This confirmed the literature: the halothane-caffeine contracture test remains the only reliable diagnostic test to detect this susceptibility, despite the search for non invasive tests. If the mechanism of triggering a contracture to increasing doses of caffeine is well known in normal muscle, it is the smaller concentrations required which suggests malignant hyperthermia abnormality. The halothane effect is less well understood. A concentration less than or equal to 2 vol % yields a contracture only in MHS muscle. Differences in protocols used by American authors emphasize the importance of standardization as used by the European Group, which is the only way of collecting and comparing results on well over a thousand patients. This confrontation should reduce the number of equivocal diagnoses and allow a correct classification of patients at risk or their relatives as MHS or MHN.