Heat Production and the Importance of Temperature Management in Malignant Hyperthermia

Abstract

Malignant hyperthermia (MH) is a rare pharmacogenetic, subclinical disorder of the striated skeletal muscle. Acute episodes are usually triggered by exposure to halogenated volatile anesthetics and/or succinylcholine. During an MH episode, the patient's muscles go into a hypermetabolic state, which in turn causes variable clinical signs and symptoms: i.e., muscle rigidity, respiratory and metabolic acidosis, muscle breakdown, cardiac responses (tachycardia) and ultimately elevation of body temperature. At the cellular level, MH is the consequence of abnormally sustained high myoplasmic calcium concentrations, which causes dramatically elevated turnover of energy rich compounds (e.g., adenosine triphosphate (ATP)). Although often a late sign of MH, the production of heat can play an important role in the treatment and clinical consequences of an elicited episode. In other words, the production of heat thereby is not merely a simple consequence of MH, but a substrate of high relevance during an ongoing MH event: it has been suggested that heat itself may trigger MH in some genetic mutations. Since the introduction of dantrolene, which has provided a specific MH therapy by normalizing myoplasmic calcium levels, mortality of MH has decreased from 70% to 4%. Nevertheless, strong consideration for proper temperature management of the known or suspected MH patient, in all clinical areas (pre-, intra- and post-operative), is critical: as hyperthermia can cause multisystemic involvements, including the brain, the heart and the hemostatic system.