ACCELERATED CONTRACTURES AFTER ADMINISTRATION OF RYANODINE TO SKELETAL-MUSCLE OF MALIGNANT HYPERTHERMIA SUSCEPTIBLE PATIENTS

A genetic disorder of the calcium releasing ryanodine receptor has rec ently been postulated in malignant hyperthermia (MH) and ryanodine-ind uced contractures differ between subjects who are malignant hypertherm ia susceptible (MHS) and non-susceptible (MHN). We tested 39 patients from 26 families for MH, using the procedure of the European Malignant Hyperthermia Group. A ryanodine contracture test was performed by bot h cumulative (0.4-10.0 mumol litre-1 every 3 min) and bolus (10.0 mumo l litre-1) application. Contracture with cumulative ryanodine applicat ion started significantly earlier in MHS (9.6 (SEM 0.5) min) than in M HN patients (24.6 (1.3) min). A significant difference in start of con tracture between MHS (4.8 (0.6) min) and MHN (14.5 (0.6) min) patients occurred also after bolus application of ryanodine. The ryanodine con tracture test seems to be a potentially specific in vitro diagnostic t est for MH.