[Malignant hyperthermia in Austria. I. Epidemiology and clinical aspects]

Investigation of malignant hyperthermia (MH) was started in 1975; by March 1986, 79 suspected cases had been reported. In vitro contracture tests were performed in 66 probands or their parents; in 61 of these (92%), MH was confirmed and 5 (8%) proved negative. In 4 lethal crises, the parents refused biopsy, but because of well-documented clinical histories these were also included as confirmed MH reactions. We were able to analyse 65 cases of documented MH, and 9 patients are still to be investigated. About 18% of all Austrian hospitals (29 of 158) had reported 1-14 MH reactions (mean 2.7/hospital); it must therefore be assumed that a high number of crises are either not detected or not reported, and the total incidence of MH cannot be estimated. In our hospital (the University Hospital of Vienna), the incidence was 1:23,600 (including children and adults), whereas in Bludenz (Vorarlberg), the incidence was as low as 1:1,300 (in children only). This might partly be explained by genetic factors (such as inbreeding); we identified 3 families, all from Vorarlberg (which is a small, secluded mountain area), in which both parents were carriers of the MH trait. Fulminant crises (of which three times as many were rigid as were non-rigid) accounted for 58%, and masseter spasm for 26%, of all MH reactions. There was a significant influence of sex (72% males) and age (71% less than 20 years) on incidence. Neuromuscular symptoms or other signs reported to be associated with MH were found in only 5 patients (8%). During crises, cardiac symptoms (81%) and cyanosis (71%) were frequently observed; rigidity (45%) and body temperature above 39 degrees C (27%) showed remarkably low incidences. The overall mortality was 17% (11 of 65); it was significantly increased if the maximum temperature exceeded 39 degrees C, after acute surgery or anaesthesia lasting greater than 60 min, and in patients aged over 20 y. Most crises required no specific therapy; dantrolene was administered to only 10 patients. In the future, earlier detection via better monitoring, improved documentation, and mandatory reporting of suspected MH reactions should allow a more detailed description of MH and could further decrease the mortality associated with this condition.