Risk of malignant hyperthermia among patients with neuroleptic malignant syndrome and their families.

The occurrence of malignant hyperthermia in 20 patients who had had neuroleptic malignant syndrome and in their 108 first-degree relatives was retrospectively studied. The patients had experienced a total of 20 courses of ECT and 12 surgical operations in which drugs that can cause malignant hyperthermia were used, but no cases of malignant hyperthermia had occurred, and no cases had occurred in the 37 relatives who had undergone surgery or ECT. The authors conclude that patients who have had malignant neuroleptic syndrome are not at considerably greater risk than others for developing malignant hyperthermia during surgery or ECT; the clinical data suggest that the two disorders are not related.