Abnormal uptake and release of Ca 2+ ions from human malignant hyperthermia-susceptible sarcoplasmic reticulum 1 1Abbreviations: CICR, Ca2+-induced Ca2+ release; HEK-293, human embryonic kidney; HSR, heavy sarcoplasmic reticulum; IVCT, in vitro caffeine halothane contracture test; MH, malignant hyperthermia; MHS, malignant hyperthermia-susceptible; MHN, malignant hyperthermia normal; MOPS, 3-[N-Morpholino]propanesulphonic acid; RYR1, ryanodine receptor skeletal muscle gene; and TFP, trifluoperazine

A Case Report of an Incidental Ultrasound Finding in a Suspected Malignant Hyperthermia Patient

Malignant hyperthermia (MH) is a rare but life-threatening genetic disorder of the skeletal muscles triggered by inhalation anesthetics or succinylcholine. A 49-year-old female developed symptoms of MH shortly after a lumbar surgery. Despite being insidious, MH was diagnosed based on the clinical grading scale. We incidentally discovered fine fasciculations in extremities while inserting an ultrasound-guided arterial catheter. On receiving dantrolene, her symptoms improved within 20 minutes; a subsequent ultrasound revealed no fasciculations. Although halothane contracture testing was not available, the fasciculations that resolved with dantrolene administration in a MH suspected patient opens up a new potential avenue of diagnostics.

Management of Common Postoperative Complications

Postoperative complications are common. Major guidelines have been published on stratifying and managing adverse cardiovascular events and thromboembolic events, but there is often less literature supporting management of other, more common, postoperative complications, including acute kidney injury, gastrointestinal complications, postoperative anemia, fever, and delirium. These common conditions are frequently seen in hospital and can contribute to longer lengths of stay and rising health care costs. These complications are often due to the interplay between both patient-specific and surgery-specific risk factors. Identifying these risk factors, while addressing and optimizing modifiable risks, can mitigate the likelihood of developing these postoperative complications. Often, a multidisciplinary approach, including care team members through all phases of the surgical encounter, is needed. Cardiovascular and thrombotic complications have been addressed in prior articles in this perioperative series. We aim to cover other common postoperative complications, such as acute renal failure, postoperative gastrointestinal complications, anemia, fever, and delirium that often contribute to longer lengths of stay, rising health care costs, and increased morbidity and mortality for patients.

Heat stroke

Heat stroke is a life-threatening condition clinically diagnosed as a severe elevation in body temperature with central nervous system dysfunction that often includes combativeness, delirium, seizures, and coma. Classic heat stroke primarily occurs in immunocompromised individuals during annual heat waves. Exertional heat stroke is observed in young fit individuals performing strenuous physical activity in hot or temperature environments. Long-term consequences of heat stroke are thought to be due to a systemic inflammatory response syndrome. This article provides a comprehensive review of recent advances in the identification of risk factors that predispose to heat stroke, the role of endotoxin and cytokines in mediation of multi-organ damage, the incidence of hypothermia and fever during heat stroke recovery, clinical biomarkers of organ damage severity, and protective cooling strategies. Risk factors include environmental factors, medications, drug use, compromised health status, and genetic conditions. The role of endotoxin and cytokines is discussed in the framework of research conducted over 30 years ago that requires reassessment to more clearly identify the role of these factors in the systemic inflammatory response syndrome. We challenge the notion that hypothalamic damage is responsible for thermoregulatory disturbances during heat stroke recovery and highlight recent advances in our understanding of the regulated nature of these responses. The need for more sensitive clinical biomarkers of organ damage is examined. Conventional and emerging cooling methods are discussed with reference to protection against peripheral organ damage and selective brain cooling.

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

BACKGROUND

Malignant hyperthermia (MH) is a rare pharmacogenetic disorder which is characterized by life-threatening metabolic crises during general anesthesia. Classical triggering substances are volatile anesthetics and succinylcholine (SCh). The molecular basis of MH is excessive release of Ca2+ in skeletal muscle principally by a mutated ryanodine receptor type 1 (RyR1). To identify factors explaining the variable phenotypic presentation and complex pathomechanism, we analyzed proven MH events in terms of clinical course, muscle contracture, genetic factors and pharmocological triggers.

METHODS

In a multi-centre study including seven European MH units, patients with a history of a clinical MH episode confirmed by susceptible (MHS) or equivocal (MHE) in vitro contracture tests (IVCT) were investigated. A test result is considered to be MHE if the muscle specimens develop pathological contractures in response to only one of the two test substances, halothane or caffeine. Crises were evaluated using a clinical grading scale (CGS), results of IVCT and genetic screening. The effects of SCh and volatile anesthetics on Ca2+ release from sarcoplasmic reticulum (SR) were studied in vitro.

RESULTS

A total of 200 patients met the inclusion criteria. Two MH crises (1%) were triggered by SCh (1 MHS, 1 MHE), 18% by volatile anesthetics and 81% by a combination of both. Patients were 70% male and 50% were younger than 12 years old. Overall, CGS was in accord with IVCT results. Crises triggered by enflurane had a significantly higher CGS compared to halothane, isoflurane and sevoflurane. Of the 200 patients, 103 carried RyR1 variants, of which 14 were novel. CGS varied depending on the location of the mutation within the RyR1 gene. In contrast to volatile anesthetics, SCh did not evoke Ca2+ release from isolated rat SR vesicles.

CONCLUSIONS

An MH event could depend on patient-related risk factors such as male gender, young age and causative RyR1 mutations as well as on the use of drugs lowering the threshold of myoplasmic Ca2+ release. SCh might act as an accelerant by promoting unspecific Ca2+ influx via the sarcolemma and indirect RyR1 activation. Most MH crises develop in response to the combined administration of SCh and volatile anesthetics.

Minimally invasive metabolic testing for malignant hyperthermia susceptibility: a systematic review of the methodology and results

IMPORTANCE OF THE FIELD

Malignant hyperthermia (MH) is a potentially lethal hypermetabolic syndrome that develops in susceptible individuals exposed to volatile anesthetics or depolarizing neuromuscular blocking agents. Because genetic screening is successful only in 30 - 50% of all suspected cases, contracture testing following an open muscle biopsy is performed to diagnose MH susceptibility. Two different protocols exist, the in vitro contracture test (IVCT) for Europe and the caffine halothane contracture test for the US. As replacement for the IVCT, an in vivo metabolic test might allow an equal discrimination of MH susceptible individuals. In this systematic review, all available metabolic testing methods are analyzed.

WHAT THE READER WILL GAIN

The reader will gain insight in methods and results of alternative approaches to diagnose MH.

AREAS COVERED IN THIS REVIEW

Relevant studies involving in vivo metabolic testing were systematically searched (Medline) and reviewed. Their ability to discriminate MH susceptible individuals was analyzed and compared. Any systemic or local side effects were documented and evaluated in order to allow more robust conclusions based on larger sample sizes than the single trials.

TAKE HOME MESSAGE

All discussed study protocols allowed an adequate discrimination of MH susceptible individuals. The latest study protocol reaches a specificity of 79% with a sensitivity of 100%. No severe systemic or local adverse effects could be seen in the pooled analysis. Minimally invasive metabolic testing is a promising novel approach to diagnose MH. Further multi-center studies have to be conducted to optimize the results in order to replace the IVCT.

Malignant hyperthermia: a pharmacogenetic disorder

Malignant hyperthermia (MH) is a pharmacogenetic disorder triggered by volatile anesthetics or depolarizing muscle relaxants in predisposed individuals. Exercise or stress-induced MH episodes, in the absence of any obvious pharmacological trigger, have been reported, but these are rare. A considerable effort has taken place over the last two decades to identify mutations associated with MH and characterize their functional effects. A number of different, but complementary systems, have been developed and implemented to this end. The results of such studies have identified commonalities in functional affects of mutations, and also uncovered unexpected complexities in both the structure and function of the skeletal muscle calcium-release channel. The following review is an attempt to provide a summary of the background to current MH research, and highlight some recent advances in our knowledge of the molecular basis of the phenotypic expression of this disorder.

[Anesthesia in malignant hyperthermia]

Malignant hyperthermia is a condition for which the anesthesiologist must be prepared to take specific measures. Associated mortality is high despite correct diagnosis and, occasionally, the right treatment. Malignant hyperthermia is rare in Spain, however, and perhaps for this reason the Spanish public health authorities have not made an effort to respond to persistent calls for a national reference center for study and diagnosis, such as can be found in other European countries. The problem of malignant hyperthermia may become worse in the near future due to changes in the population brought about by immigration. It is therefore necessary to establish appropriately revised protocols and action plans to cope with this possibility. A reference center cannot be created by individuals, but we can become more aware of the need to establish up-to-date protocols in our departments in order to be prepared for this situation.

Analysis of the global RNA expression profiles of skeletal muscle cells treated with statins

The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) are the most effective drugs for hypercholesteloremia. However, a significant side effect of statin treatment is rhabdomyolysis. In order to study the effect of statins in skeletal muscle cells, we used a DNA microarray analysis to investigate the changes in gene expression profiles brought about by statins in two skeletal muscle cell lines, namely, differentiated rat L6 myotubes and a human skeletal muscle cell line (hSkMC). In both cell lines, the statins (atorvastatin, cerivastatin and pitavastatin) induced the expression of four genes, which relate to cholesterol metabolism, namely, HMG-CoA synthase 1, HMG-CoA reductase, farnesyl diphosphate synthase and isopentenyl-diphosphate delta isomerase. Statin inhibited the synthesis of cholesterol at least five times more effectively in hSkMCs than in the hepatocytes. In addition, unlike in osteoblasts or coronary artery smooth muscle cells, statins upregulated the mRNA expression of cholesterol-associated enzymes in hSkMCs. These results provide basic information on skeletal muscle cells treated with statins and indicate that the cells are sensitive to the inhibition of HMG-CoA reductase, which may be related to the pathogenesis of muscle damage in statin therapy.

3,4-Methylenedioxymethamphetamine (Ecstasy) Activates Skeletal Muscle Nicotinic Acetylcholine Receptors

Adverse 3,4-methylenedioxymethamphetamine (MDMA; ecstasy) effects are usually ascribed to neurotransmitter release in the central nervous system. Since clinical features such as fasciculations, muscle cramps, rapidly progressing hyperthermia, hyperkalemia, and rhabdomyolysis point to the skeletal muscle as additional target, we studied the effects of MDMA on native and cultured skeletal muscle. We addressed the question whether malignant hyperthermia (MH)-susceptible (MHS) muscle is predisposed to adverse MDMA reactions. Force measurements on muscle strips showed that 100 microM MDMA, a concentration close to that determined in some MDMA users, regularly enhanced the sensitivity of skeletal muscle to caffeine-induced contractures but did not cause contractures on its own. The left-shift of the dose-response curve induced by MDMA was greater in normal than in MHS muscle. Furthermore, MDMA did not release Ca(2+) from isolated sarcoplasmic reticulum vesicles. These findings do not support the view of an MH-triggering effect on muscle. However, MDMA induced Ca(2+) transients in myotubes and increased their acidification rate. Surprisingly, alpha-bungarotoxin, a specific antagonist of the nicotinic acetylcholine receptor (nAChR), abolished these MDMA effects. The nAChR agonistic action of MDMA was confirmed by patch-clamp measurements of ion currents on human embryonic kidney cells expressing nAChR. We conclude that the neuromuscular junction is a target of MDMA and that an activation of nAChR contributes to the muscle-related symptoms of MDMA users. The drug may be of particular risk in individuals with abundant extrajunctional nAChR such as in generalized denervation or muscle regeneration processes and may act on central nAChR.

Enhanced response to caffeine and 4-chloro-m-cresol in malignant hyperthermia-susceptible muscle is related in part to chronically elevated resting [Ca2+]i

Malignant hyperthermia (MH) is a potentially fatal pharmacogenetic syndrome caused by exposure to halogenated volatile anesthetics and/or depolarizing muscle relaxants. We have measured intracellular Ca(2+) concentration ([Ca(2+)](i)) using double-barreled, Ca(2+)-selective microelectrodes in myoballs prepared from skeletal muscle of MH-susceptible (MHS) and MH-nonsusceptible (MHN) swine. Resting [Ca(2+)](i) was approximately twofold in MHS compared with MHN quiescent myoballs (232 +/- 35 vs. 112 +/- 11 nM). Treatment of myoballs with caffeine or 4-chloro-m-cresol (4-CmC) produced an elevation in [Ca(2+)](i) in both groups; however, the concentration required to cause a rise in [Ca(2+)](i) elevation was four times lower in MHS than in MHN skeletal muscle cells. Incubation of MHS cells with the fast-complexing Ca(2+) buffer BAPTA reduced [Ca(2+)](i), raised the concentration of caffeine and 4-CmC required to cause an elevation of [Ca(2+)](i), and reduced the amount of Ca(2+) release associated with exposure to any given concentration of caffeine or 4-CmC to MHN levels. These results suggest that the differences in the response of MHS skeletal myoballs to caffeine and 4-CmC may be mediated at least in part by the chronic high resting [Ca(2+)](i) levels in these cells.

Calcium release from sarcoplasmic reticulum is facilitated in human myotubes derived from carriers of the ryanodine receptor type 1 mutations Ile2182Phe and Gly2375Ala

Malignant hyperthermia (MH) is caused by increased calcium release from sarcoplasmic reticulum, triggered by volatile anesthetics or depolarizing muscle relaxants. Numerous mutations associated with MH have been detected in the skeletal muscle type ryanodine receptor gene (RyR1), but so far facilitated calcium release has only been demonstrated for a few of them. This is a prerequisite for confirming the causative role of an RyR1 mutation for MH. Calcium release from sarcoplasmic reticulum induced by 4-chloro-m-cresol (4CmC), caffeine, and halothane was determined in human myotubes by calcium imaging. The RyR1 Ile2182Phe mutation and the RyR1 Gly2375Ala mutation have been identified in individuals susceptible to MH. In myotubes of individuals carrying the RyR1 Ile2182Phe or the RyR1 Gly2375Ala mutation, the EC(50) for caffeine and halothane was reduced; in the Ile2182Phe myotubes, the EC(50) for 4CmC was also reduced, all consistent with facilitated calcium release from the sarcoplasmic reticulum. From these data we conclude that both mutations are pathogenic for MH.

Increased sensitivity of the ryanodine receptor to halothane-induced oligomerization in malignant hyperthermia-susceptible human skeletal muscle

Mutations in the skeletal muscle RyR1 isoform of the ryanodine receptor (RyR) Ca2+-release channel confer susceptibility to malignant hyperthermia, which may be triggered by inhalational anesthetics such as halothane. Using immunoblotting, we show here that the ryanodine receptor, calmodulin, junctin, calsequestrin, sarcalumenin, calreticulin, annexin-VI, sarco(endo)plasmic reticulum Ca2+-ATPase, and the dihydropyridine receptor exhibit no major changes in their expression level between normal human skeletal muscle and biopsies from individuals susceptible to malignant hyperthermia. In contrast, protein gel-shift studies with halothane-treated sarcoplasmic reticulum vesicles from normal and susceptible specimens showed a clear difference. Although the alpha2-dihydropyridine receptor and calsequestrin were not affected, clustering of the Ca2+-ATPase was induced at comparable halothane concentrations. In the concentration range of 0.014-0.35 mM halothane, anesthetic-induced oligomerization of the RyR1 complex was observed at a lower threshold concentration in the sarcoplasmic reticulum from patients with malignant hyperthermia. Thus the previously described decreased Ca2+-loading ability of the sarcoplasmic reticulum from susceptible muscle fibers is probably not due to a modified expression of Ca2+-handling elements, but more likely a feature of altered quaternary receptor structure or modified functional dynamics within the Ca2+-regulatory apparatus. Possibly increased RyR1 complex formation, in conjunction with decreased Ca2+ uptake, is of central importance to the development of a metabolic crisis in malignant hyperthermia.

Malignant hyperthermia

Malignant hyperthermia (MH) is an uncommon, life-threatening, acute pharmacogenetic disorder of the skeletal muscle cell. It manifests in susceptible individuals as a hypermetabolic response on exposure to halogenated volatile anaesthetics and depolarizing muscle relaxants. There may also be a relationship between susceptibility to MH, heat stroke and exercise-induced rhabdomyolysis. The pathophysiology of the crisis involves an uncontrolled release of cytoplasmic free calcium from the sarcoplasmic reticulum leading to activation of energy-producing biochemical pathways. Organ system failure and rhabdomyolysis may occur as a result of high fever, hyperkalaemia and acidosis. The ryanodine receptor, the calcium-release channel of the sarcoplasmic reticulum, is the primary locus for malignant hypothermia susceptibility. Multiple mutations in the gene for the ryanodine receptor protein are causative. Other genes may also be involved. A classical fulminant crisis presents with a rising end-tidal carbon dioxide, skeletal muscle rigidity, tachycardia, hyperthermia and acidosis. Mortality may be as high as 70% if the syndrome is not recognized and treated. Immediate discontinuation of triggering agents, oxygenation, and correction of acidosis and electrolyte abnormalities, cooling and dantrolene are essential for treatment of the syndrome. Thanks to clinical and research investigations, widespread education and the introduction of dantrolene sodium, the mortality from MH is less than 5%. This chapter provides an overview and an update of MH.

The Ile2453Thr mutation in the ryanodine receptor gene 1 is associated with facilitated calcium release from sarcoplasmic reticulum by 4-chloro-m-cresol in human myotubes

Central core disease (CCD) is a congenital disorder of skeletal muscle that is characterised histologically by typical central cores in type 1 skeletal muscle fibres. This disease is associated with malignant hyperthermia susceptibility and has been linked to the gene of skeletal muscle ryanodine receptor RYR1. In this study, we present a family with the spontaneous occurrence of the RYR1 Ile2453Thr mutation. Affected individuals were diagnosed as susceptible to malignant hyperthermia in the in vitro contracture test (IVCT) and showed histological signs of CCD. Myotubes were derived from the index patient. The calcium homeostasis in response to the ryanodine receptor agonist 4-chloro-m-cresol (4CmC) was investigated by calcium imaging using the Ca(2+)-sensitive fluorescent probe FURA 2. In the myotubes derived from the mutation carrier, the EC(50) of 4CmC was reduced to 94 micro as compared to 201 microM in a control group of 16 individuals non-susceptible to malignant hyperthermia. In the myotubes of the non-affected family members, the EC(50) was found within the same range as that of the control group. The reduction of EC(50) indicates a facilitated calcium release from sarcoplasmic reticulum in the myotubes of the index patient suggesting that the RYR1 Ile2453Thr mutation is pathogenic for the malignant hyperthermia susceptibility and CCD of the two affected individuals.

Current concepts in malignant hyperthermia

Malignant hyperthermia (MH) is a rare, potentially lethal, clinically and genetically heterogeneous pharmacogenic myopathy, which during or after general anesthesia manifests as MH crisis (MHC) in genetically predisposed, but otherwise mostly normal, individuals (MH susceptibles) in response to anesthetic-triggering agents. MHC can also occur in patients with central core disease. MCH-like crises have been reported in those with Duchenne/Becker muscular dystrophy, myotonic dystrophy, mitochondriopathy, and various other conditions. MH susceptibility is diagnosed if there is an MHC in the individual or family history or by the in vitro caffeine-halothane contracture test. Although screening for mutations in the ryanodine-receptor-1 gene and the dihydropyridine-receptor gene, respectively, could further substantiate the diagnosis, the caffeine-halothane-contracture test still remains the gold standard for diagnosing MH susceptibility. The most well-known triggers of an MHC are depolarizing muscle relaxants and volatile anesthetics. Therapy of an MHC comprises discontinuation of triggering agents, oxygenation, and correction of the acidosis and electrolyte disturbances, treatment of arrhythmias, cooling, and dantrolene. If MH susceptibility is not known preoperatively and an MHC unexpectedly interrupts anesthesia, consultation by a specialist in MH susceptibility after anesthesia is essential to investigate the patient for MH susceptibility or subclinical myopathy, guide laboratory investigations, manage therapy, and counsel the family on further risk. To further reduce morbidity and mortality of those with MHC, anesthesiologists and neurologists should be well educated and should strengthen their clinical vigilance. Research should be intensified and extended with regard to the development of new in vitro tests to further elucidate the heterogeneous genetic background of MH susceptibility.

The differential effect of halothane and 1,2-dichlorohexafluorocyclobutane on in vitro muscle contractures of patients susceptible to malignant hyperthermia

Malignant hyperthermia (MH) is an autosomal dominant, potentially fatal pharmacogenetic disorder of skeletal muscle. Approximately half of all known MH families show a linkage to the ryanodine receptor type 1 (RY1) gene. Although our knowledge of the diagnosis, genetics, and therapy of MH has improved, the exact pathogenesis and the role of volatile anesthetics as trigger substances for an MH crisis remain unknown. Compounds that do not obey the Meyer-Overton hypothesis (i.e., nonimmobilizers) are today an important part of research on anesthetic mechanisms. We designed this study to test the hypothesis that the nonimmobilizer 1,2-dichlorohexafluorocyclobutane (2N) compared with halothane has different effects on in vitro muscle contractures of muscle bundles from MH-susceptible (MHS) individuals. In vitro muscle contracture tests were performed with either halothane (approximately 660 microM, equivalent to approximately 4 minimum alveolar anesthetic concentration [MAC]) or 2N ( approximately 100 microM, equivalent to approximately 5 times predicted MAC). MAC is defined as the anesthetic concentration that prevents nocifensive movements after a surgical stimulus in 50% of subjects. In contrast to halothane, 2N caused only minimal muscle contractures in muscle bundles from six MHS patients (0.13 g [0.04-0.31 g] vs 1.95 g [1.60-4.70 g], median values and ranges; P = 0.004). Halothane and 2N differ in their effects on muscle contractures of MHS individuals, possibly because of a differing action on MH RY1.

IMPLICATIONS

Using in vitro contracture tests, we showed that halothane and the nonimmobilizer 1,2-dichlorohexafluorocyclobutane differ in their effects on contractures of muscle bundles from individuals susceptible to malignant hyperthermia (MH) as a result of their differing action on MH ryanodine receptors. These findings render this receptor a possible molecular target for volatile anesthetic action.

Involvement of the cardiac ryanodine receptor/calcium release channel in catecholaminergic polymorphic ventricular tachycardia

The cardiac ryanodine receptor (RyR2), the major calcium release channel on the sarcoplasmic reticulum (SR) in cardiomyocytes, has recently been shown to be involved in at least two forms of sudden cardiac death (SCD): (1) Catecholaminergic polymorphic ventricular tachycardia (CPVT) or familial polymorphic VT (FPVT); and (2) Arrhythmogenic right ventricular dysplasia type 2 (ARVD2). Eleven RyR2 missense mutations have been linked to these diseases. All eleven RyR2 mutations cluster into 3 regions of RyR2 that are homologous to the three malignant hyperthermia (MH)/central core disease (CCD) mutation regions of the skeletal muscle ryanodine receptor/calcium release channel RyR1. MH/CCD RyR1 mutations have been shown to alter calcium-induced calcium release. Sympathetic nervous system stimulation leads to phosphorylation of RyR2 by protein kinase A (PKA). PKA phosphorylation of RyR2 activates the channel. In conditions associated with high rates of SCD such as heart failure RyR2 is PKA hyperphosphorylated resulting in "leaky" channels. SR calcium leak during diastole can generate "delayed after depolarizations" that can trigger fatal cardiac arrhythmias (e.g., VT). We propose that RyR2 mutations linked to genetic forms of catecholaminergic-induced SCD may alter the regulation of the channel resulting in increased SR calcium leak during sympathetic stimulation.