Suspected Malignant Hyperthermia Reactions in New Zealand

Abstract

Early clinical signs, triggering agents, time to onset of reaction, mortality and methods of treatment were identified in 123 suspected malignant hyperthermia reactions. In vitro contracture test results were compared with clinical signs and the Malignant Hyperthermia Clinical Grading Scale. Increased end-tidal carbon dioxide is the earliest sign when not preceded by masseter spasm. Earlier diagnosis reduces the incidence of rigidity and severe metabolic acidosis. The combination of suxamethonium and a potent volatile anaesthetic agent triggers an earlier reaction compared with a volatile agent alone. There has been zero mortality since 1981, essentially due to a combination of advanced monitoring capability, increased anaesthetist awareness of malignant hyperthermia, and dantrolene availability. DNA analysis has identified nine New Zealand families with ryanodine receptor gene mutations. A positive DNA test indicates malignant hyperthermia susceptibility with "causative" mutations but discordance requires that negative DNA tests are confirmed with in vitro contracture test. This test also demonstrated the shortcomings of the Malignant Hyperthermia Clinical Grading Scale.

The effect of succinylcholine on malignant hyperthermia events in susceptible swine

“…Interestingly, a significant rise of body temperature only occurred after administration of a combination of both pharmacological agents, reflecting the severe metabolic breakdown. Our findings suggest an additive effect of SCh as postulated by previous investigations in which the onset of an MH episode was significantly enhanced and the increase of serum creatine kinase was more pronounced after a combination of SCh and volatile anaesthetics [10,19,20]. …”

Functional and genetic characterization of clinical malignant hyperthermia crises: a multi-centre study

“…Surprisingly we did not observe differences in the CGS of crises triggered by a SCh only versus SCh and volatile anesthetics. However the onset of MH crises was significantly faster when volatile anesthetics were combined with SCh [56]. The fact that we observed a SCh associated clinical crisis in the absence of volatile anesthetics does not prove MH triggering because undetected genetic variations or conditions explaining SCh hypersensitivity cannot be excluded.…”

Analysis of the Clinical Variables Associated with Recrudescence after Malignant Hyperthermia Reactions

“…Dantrolene sodium, the treatment for MH, inhibits calcium release via RyR1 antagonism. 7,8 Although most patients with MH can be treated successfully with dantrolene, 9 recrudescence or return of the signs and symptoms of MH can occur hours after resolution of the initial event. Although recrudescence has been reported in case reports, 10 -14 no formal study of clinical factors associated with recrudescence of MH has been performed.…”