Accelerated contractures after administration of ryanodine to skeletal muscle of malignant hyperthermia susceptible patients.

A genetic disorder of the calcium releasing ryanodine receptor has recently been postulated in malignant hyperthermia (MH) and ryanodine-induced contractures differ between subjects who are malignant hyperthermia 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 both cumulative (0.4-10.0 mumol litre-1 every 3 min) and bolus (10.0 mumol litre-1) application. Contracture with cumulative ryanodine application started significantly earlier in MHS (9.6 (SEM 0.5) min) than in MHN patients (24.6 (1.3) min). A significant difference in start of contracture between MHS (4.8 (0.6) min) and MHN (14.5 (0.6) min) patients occurred also after bolus application of ryanodine. The ryanodine contracture test seems to be a potentially specific in vitro diagnostic test for MH.