Malignant hyperthermia is a potentially lethal inherited disorder characterized by disturbance of calcium homeostasis in skeletal muscle. Volatile anesthetics and/or the depolarizing muscle relaxant succinylcholine may induce this hypermetabolic muscular syndrome due to uncontrolled sarcoplasmic calcium release via functionally altered calcium release receptors, resulting in hypoxemia, hypercapnia, tachycardia, muscular rigidity, acidosis, hyperkalemia, and hyperthermia in susceptible individuals. Since the clinical presentation of malignant hyperthermia is highly variable, survival of affected patients depends largely on early recognition of the symptoms characteristic of malignant hyperthermia, and immediate action on the part of the attending anesthesiologist. Clinical symptoms of malignant hyperthermia, diagnostic criteria, and current therapeutic guidelines, as well as adequate management of anesthesia in patients susceptible to malignant hyperthermia, are discussed in this review.
BackgroundMalignant hyperthermia (MH), a metabolic myopathy triggered by volatile anesthetics and depolarizing muscle relaxants, is a potentially lethal complication of general anesthesia in susceptible patients. The implementation of modern inhalation anesthetics that research indicates as less potent trigger substances and the recommended limitations of succinylcholine use, suggests there may be considerable decline of fulminant MH cases. In the presented study, the authors analyzed suspected MH episodes during general anesthesia of patients that were referred to the Wuerzburg MH unit between 2007 and 2011, assuming that MH is still a relevant anesthetic problem in our days.MethodsWith approval of the local ethics committee data of patients that underwent muscle biopsy and in vitro contracture test (IVCT) between 2007 and 2011 were analyzed. Only patients with a history of suspected MH crisis were included in the study. The incidents were evaluated retrospectively using anesthetic documentation and medical records.ResultsBetween 2007 and 2011 a total of 124 patients were tested. 19 of them were referred because of suspected MH events; 7 patients were diagnosed MH-susceptible, 4 MH-equivocal and 8 MH-non-susceptible by IVCT. In a majority of cases masseter spasm after succinylcholine had been the primary symptom. Cardiac arrhythmias and hypercapnia frequently occurred early in the course of events. Interestingly, dantrolene treatment was initiated in a few cases only.ConclusionsMH is still an important anesthetic complication. Every anesthetist must be aware of this life-threatening syndrome at any time. The rapid onset of adequate therapy is crucial to avoid major harm and possibly lethal outcome. Dantrolene must be readily available wherever MH triggering agents are used for anesthesia.
Sevoflurane-induced contractures do not reliably detect MH susceptibility on an individual level. Therefore, sevoflurane is no suitable alternative for diagnostic use. Mutation-specific effects regarding contracture sizes after incubation with sevoflurane, halothane, or caffeine were not found.
In a 59-year-old woman with a perforating eyeball injury to the right eye, the emergency physician induced a preclinical general anesthesia with propofol, fentanyl and the depolarizing muscle relaxant succinylcholine. Anesthesia was maintained using propofol and remifentanil infusion throughout the preoperative period and the subsequent surgical procedure. Postoperatively, isolated rhabdomyolysis with an increase in serum creatine kinase to >20,000 U/l was observed. The diagnosis of malignant hyperthermia (MH) susceptibility could be confirmed in the patient 4 months after the acute event by the in vitro contracture test and detection of the MH causative mutation p.Val4849Ile in exon 101 of the ryanodine receptor gene. Due to the variable expression, for a long time MH often remained unrecognized. Warning symptoms, such as unspecific tachycardia or masseter spasm following succinylcholine injection, should alert emergency physicians to include MH susceptibility in the differential diagnostics. With an estimated genetic MH prevalence of 1:2000-3000, individuals with known or so far unrecognized MH disposition are likely to be among patients treated in the preclinical setting. If a person develops MH symptoms after exposure to triggering agents, immediate hospital admission is essential in order to initiate guideline-conform treatment without further delay because preclinically the life-saving causal measures are not possible due to the lack of supply of dantrolene.
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