[Clinical implications of enhanced caffeine contracture in malignant hyperthermia (MH) and Duchenne muscular...

The caffeine contracture response was studied on the skinned muscle fiber in patients with MH episodes or with DMD. An abnormally enhanced caffeine contracture was observed in 12 out of 14 subjects with MH episodes and 11 out of 13 patients with DMD. The extent of abnormality was almost the same in both group of patients. Ca-induced Ca release (CICR) of the sarcoplasmic reticulum was also analyzed on the same specimens. CICR was increased in 3 out of 4 cases with MH episodes, but it was decreased or unchanged in 4 patients with DMD. It was suggested that the mechanism of abnormal caffeine contracture might not be the same between MH and DMD. Thus, adverse anesthetic reactions, which are occasionally reported in DMD, could be different from genuine MH in its pathophysiology. However, before concluding this issue, further studies seem necessary concerning the molecular mechanism of abnormal Ca release. In the meantime, studies of caffeine contracture on the skinned fiber are helpful as one of predictive tests of MH and related disorders.