Epidemiological and clinical features of malignant hyperthermia: A scoping review

Malignant hyperthermia (MH) is a potentially fatal inherited pharmacogenetic disorder related to pathogenic variants in the RYR1, CACNA1S, or STAC3 genes. Early recognition of the occurrence of MH and prompt medical treatment are indispensable to ensure a positive outcome. The purpose of this study was to provide valuable information for the early identification of MH by summarizing epidemiological and clinical features of MH. This scoping review followed the methodological framework recommended by Arksey and O'Malley. PubMed, Embase, and Web of science databases were searched for studies that evaluated the epidemical and clinical characteristics of MH. A total of 37 studies were included in this review, of which 26 were related to epidemiology and 24 were associated with clinical characteristics. The morbidity of MH varied from 0.18 per 100 000 to 3.9 per 100 000. The mortality was within the range of 0%-18.2%. Identified risk factors included sex, age, disorders associated with MH, and others. The most frequent initial clinical signs included hyperthermia, sinus tachycardia, and hypercarbia. The occurrence of certain signs, such as hypercapnia, delayed first temperature measurement, and peak temperature were associated with poor outcomes. The epidemiological and clinical features of MH varied considerably and some risk factors and typical clinical signs were identified. The main limitation of this review is that the treatment and management strategies were not assessed sufficiently due to limited information.

Fatigue, depression, and physical activity in patients with malignant hyperthermia: a cross-sectional observational study

BACKGROUND

Malignant Hyperthermia (MH) is a pharmacogenetic disorder triggered by halogenated anesthesia agents/succinylcholine and characterized by hypermetabolism crisis during anesthesia, but also by day-to-day symptoms, such as exercise intolerance, that may alert the health professional.

OBJECTIVE

The study aimed to analyze the incidence of fatigue in MH susceptible patients and the variables that can impact perception of fatigue, such as the level of routine physical activity and depression.

METHODS

A cross-sectional observational study was carried out with three groups ... 22 patients susceptible to MH (positive in vitro muscle contracture test), 13 non-susceptible to MH (negative in vitro muscle contracture test) and 22 controls (no history of MH). Groups were assessed by a demographic/clinical questionnaire, a fatigue severity scale (intensity, specific situations, psychological consequences, rest/sleep response), and the Beck depression scale. Subgroups were re-assessed with the Baecke habitual physical exercise questionnaire (occupational physical activity, leisure physical exercise, leisure/locomotion physical activity).

RESULTS

There were no significant differences among the three groups regarding fatigue intensity, fatigue related to specific situations, psychological consequences of fatigue, fatigue response to resting/sleeping, depression, number of active/sedentary participants, and the mean time and characteristics of habitual physical activity. Nevertheless, unlike the control sub-group, the physically active MH-susceptible subgroup had a higher fatigue response to resting/sleeping than the sedentary MH susceptible subgroup (respectively, 5.9.ß...ß1.9 vs. 3.9.ß...ß2, t-test unpaired, p.ß<.ß0.05).

CONCLUSION

We did not detect subjective fatigue in MH susceptible patients, although we reported protracted recovery after physical activity, which may alert us to further investigation requirements.

BMI and malignant hyperthermia pathogenic ryanodine receptor type 1 sequence variants in Switzerland: A retrospective cohort analysis

BACKGROUND

Ryanodine receptor type 1 (RYR1) sequence variants are pathogenic for malignant hyperthermia. Variant carriers have a subtle increase in resting myoplasmic calcium concentration compared with nonaffected individuals, but whether this has metabolic effects in daily life is unknown.

OBJECTIVES

We analysed the potential effect of malignant hyperthermia-pathogenic RYR1 sequence variants on BMI as a single factor. Due to the heterogeneity of genetic variants predisposing to malignant hyperthermia, and to incomplete information about their regional distribution, we describe the prevalence of RYR1 variants in our population.

DESIGN

A retrospective cohort study.

SETTING

A single University hospital.

PATIENTS

Patients from malignant hyperthermia families with pathogenic RYR1 sequence variants were selected if BMI was available.

OUTCOME MEASURES

BMI values were compared amongst malignant hyperthermia susceptible (MHS) and malignant hyperthermia-negative individuals using hierarchical multivariable analyses adjusted for age and sex and considering family clustering. Variant prevalence was calculated.

RESULTS

The study included 281 individuals from 42 unrelated malignant hyperthermia families, 109 of whom were MHS and carriers of the familial RYR1 sequence variants. Median [IQR] BMI in MHS individuals with pathogenic RYR1 variants was 22.5 kg m-2 [21.3 to 25.6 kg m-2]. In malignant hyperthermia-negative individuals without variants, median BMI was 23.4 kg m-2 [21.0 to 26.3 kg m-2]. Using multivariable regression adjusted for age and sex, the mean difference was -0.73 (95% CI -1.51 to 0.05). No carrier of a pathogenic RYR1 sequence variant was found to have BMI higher than 30 kg m-2. Only 10 RYR1 variants from the list of the European MH Group were found in our cohort, the most common being p.Val2168Met (39% of families), p.Arg2336His (24%) and p.Arg614Cys (12%).

CONCLUSION

The observed tendency towards lower BMI values in carriers of malignant hyperthermia-pathogenic RYR1 sequence variants points to a possible protective effect on obesity. This study confirms regional differences of the prevalence of malignant hyperthermia-pathogenic RYR1 sequence variants, with just three variants covering 75% of Swiss MHS families.

TRIAL REGISTRATION

This manuscript is based on a retrospective analysis.

Malignant hyperthermia when dantrolene is not readily available

BACKGROUND

Malignant hyperthermia is a rare but life-threatening pharmacogenetic muscle disorder characterized by abnormal hypermetabolic reactions and commonly triggered in susceptible individuals by volatile anesthetics or succinylcholine, or both. Unfortunately, the specific medicine dantrolene is not readily available in many countries including China. The aim of this study was to find the characteristics of malignant hyperthermia under the situation that dantrolene is not readily available.

METHODS

The cases of malignant hyperthermia reported on the most commonly used databases in China from 1985 to 2020 were analyzed. The inclusion criteria were the MH episodes only related to anesthesia. The exclusion criteria were dubious MH episodes only caused by Ketamine administration or MH episodes irrelevant to anesthesia. Independent samples t-test and Pearson's chi-squared test were applied to assess the difference between the survived and death cases.

RESULTS

Ninety-two cases of malignant hyperthermia reported on the most commonly used databases in China from 1985 to 2020 were analyzed. Median (IQR [range]) age was 18.5 (11.8-37.0 [0-70.0]) years. Compared with the survived cases, the death cases had higher maximum end-tidal partial pressure of CO2 (P = 0.033), the maximum arterial partial pressure of CO2 (P = 0.006), temperature first measured when the patient was first discovered abnormal (P = 0.012), and maximum temperature (P < 0.001). Besides, the death cases had less minimum pH (P < 0.001) and higher potassium (P < 0.001) and were more likely to have coagulation disorders (p = 0.018). Concerning treatment, cases used furosemide (P = 0.024), mannitol (P = 0.029), blood purification treatment (P = 0.017) had the advantage on the outcome. Creatine phosphokinase, myoglobin, and MB isoenzyme of creatine phosphokinase differed greatly among cases during the first week. 43 (46.7%) cases had congenital diseases. 12 (13.0%) cases were reported with abnormal laboratory test results or abnormal signs that are possibly relevant before anesthesia.

CONCLUSIONS

In countries that dantrolene is not readily available, early warning, diagnosis, and prompt effective therapies are crucial for MH patients to survive.

Malignant Hyperthermia

Malignant Hyperthermia (MH) is a life-threatening pharmacogenetic disorder which results from exposure to volatile anesthetic agents and depolarizing muscle relaxants. It manifests as a hypermetabolic response resulting in tachycardia, tachypnea, hyperthermia, hypercapnia, acidosis, muscle rigidity and rhabdomyolysis. An increase in the end-tidal carbon dioxide is one of the earliest diagnostic signs. Dantrolene sodium is effective in the management of MH, and should be available whenever general anesthesia is administered. This review also aims to highlight the genetics and pathology of MH, along with its association with various inherited myopathy syndromes like central core disease, multi-mini core disease, Native-American myopathy, and King-Denborough syndrome.

Malignant hyperthermia: a review

Malignant hyperthermia (MH) is a pharmacogenetic disorder of skeletal muscle that presents as a hypermetabolic response to potent volatile anesthetic gases such as halothane, sevoflurane, desflurane, isoflurane and the depolarizing muscle relaxant succinylcholine, and rarely, in humans, to stressors such as vigorous exercise and heat. The incidence of MH reactions ranges from 1:10,000 to 1: 250,000 anesthetics. However, the prevalence of the genetic abnormalities may be as great as one in 400 individuals. MH affects humans, certain pig breeds, dogs and horses. The classic signs of MH include hyperthermia, tachycardia, tachypnea, increased carbon dioxide production, increased oxygen consumption, acidosis, hyperkalaemia, muscle rigidity, and rhabdomyolysis, all related to a hypermetabolic response. The syndrome is likely to be fatal if untreated. An increase in end-tidal carbon dioxide despite increased minute ventilation provides an early diagnostic clue. In humans the syndrome is inherited in an autosomal dominant pattern, while in pigs it is autosomal recessive. Uncontrolled rise of myoplasmic calcium, which activates biochemical processes related to muscle activation leads to the pathophysiologic changes. In most cases, the syndrome is caused by a defect in the ryanodine receptor. Over 400 variants have been identified in the RYR1 gene located on chromosome 19q13.1, and at least 34 are causal for MH. Less than 1 % of variants have been found in CACNA1S but not all of these are causal. Diagnostic testing involves the in vitro contracture response of biopsied muscle to halothane, caffeine, and in some centres ryanodine and 4-chloro-m-cresol. Elucidation of the genetic changes has led to the introduction of DNA testing for susceptibility to MH. Dantrolene sodium is a specific antagonist and should be available wherever general anesthesia is administered. Increased understanding of the clinical manifestation and pathophysiology of the syndrome, has lead to the mortality decreasing from 80 % thirty years ago to <5 % in 2006.

Hypothesis: exertional heat stroke-induced myopathy and genetically inherited malignant hyperthermia represent the same disorder, the human stress syndrome

Exertional heat stroke is usually experienced as a result of a prolonged and intensive exercise. It is a life-threatening condition that is characterized by an increase in core body temperature and rhabdomyolysis. The associated hyperkalemia and metabolic acidosis may lead to an acute renal, cardiac, and hemostatic failure. Exactly, the same symptoms are noticed in case of the anesthesia-induced malignant hyperthermia (MH), an inherited disorder of the skeletal muscle ryanodine receptor. This receptor is a Ca(2+) channel that is activated by the volatile anesthetic agents and depolarizing muscle relaxant. The presence of MH-associated ryanodine receptor variant in the individuals who suffered from EH and improvement of the symptoms with dantrolene has frequently raised the question as to whether the two disorders actually represent one and the same disease. Nevertheless, an exact explanation of the susceptibility of the genetically predisposed MH individuals to ER remains elusive. We have attempted to review the published clinical reports to explore the possibility that ER and EH represent one and the same disorder.

[Anesthetic malignant hyperthermia: what's new in 2012?]

Malignant hyperthermia (MH) is a pharmacogenetic disorder of anesthesia. Recent advances dealing with epidemiology of MH and the safe anesthetic course of MH susceptible patients are shortly presented here with a special insight into the preparation of modern anesthesia workstations, which they will share in operating room.

[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.

Effects of ryanodine on skeletal muscle lactate and pyruvate in malignant hyperthermia-susceptible and normal swine as assessed by microdialysis

BACKGROUND

The caffeine/halothane contracture test in North America and the in vitro contracture test in Europe are currently the only validated bioassays for diagnosing malignant hyperthermia susceptibility and phenotyping families. Both tests are invasive requiring surgical muscle biopsy. Here, we report first use of the selective ryanodine receptor type I agonist ryanodine in a percutaneous microdialysis protocol designed to test whether microdialysis-induced local metabolic responses of skeletal muscle due to ryanodine receptor activation can differentiate between malignant hyperthermia-sensitive and normal pigs.

METHODS

Six microdialysis catheters were implanted percutaneously into the adductor muscles of the right and left thighs of malignant hyperthermia-susceptible (n = 9) and normal (n = 8) anaesthetized (ketamine/propofol) and mechanically ventilated swine. Systemic blood gases, haemodynamic parameters and creatine kinase levels were measured before, during and after microdialysis perfusion of ryanodine. After a post-implantation equilibration period of 30 min, one catheter perfused (2 micro min-1) with 0.9% NaCl (control) and was compared with the remaining five catheters perfused with increasing concentrations of ryanodine (0.2-100 micromol). Lactate and pyruvate levels were measured enzymatically.

RESULTS

Continuous perfusion with ryanodine revealed dose-dependent sigmoidal increases in the dialysate lactate and lactate-pyruvate ratio parameters; these effects were greatly augmented in malignant hyperthermia-susceptible pigs compared to normal pigs (two- to threefold): estimated EC50 greatly decreased (>19-fold) while the maximum effect increased (>twofold) in the malignant hyperthermia-susceptible group.

CONCLUSION

The in vivo percutaneous microdialysis protocol for skeletal muscle, using ryanodine as the ryanodine receptor type I agonist and dialysed lactate-pyruvate parameters as metabolic index, can reproducibly differentiate between malignant hyperthermia-susceptible and normal swine.

Fulminant-type malignant hyperthermia in Japan: cumulative analysis of 383 cases

We investigated the transition of clinical signs of fulminant-type malignant hyperthermia (f-MH) by analyzing a database consisting of 383 cumulative cases of f-MH from 1961 to 2004. The cases were divided by time period into group 1 (1961-1984), group 2 (1985-1994), and group 3 (1995-2004). The variables considered were age, sex, type of agents used (succinylcholine and volatile anesthetics), dantrolene administration, clinical signs, laboratory data, and mortality. The level of statistical significance was considered to be less than 5%. Groups 1, 2, and 3 consisted of 196, 127, and 60 cases, respectively. In groups 1, 2, and 3, the rates of dantrolene administration were 18.4%, 93.6%, and 86.7%; the rates of occurrence of ventricular arrhythmia were: 75.2%, 55.6%, and 35.0%; and the rates of generalized muscle rigidity were 64.7%, 60.9%, and 23.9%, respectively. The mortality rate decreased over time, from 42.3% in group 1, to 15.0% in group 2 and group 3. We considered that this decrease occurred because of the increased use of dantrolene and the early diagnosis of malignant hyperthermia in the latter two groups.

Molecular genetic detection of susceptibility to malignant hyperthermia in Belgian families

Malignant hyperthermia is an autosomal dominant myopathy triggered by volatile anesthetics or succinylcholine in susceptible persons. While in vitro contracture testing (IVCT) is the gold standard to establish malignant hyperthermia (MH) susceptibility, genetic analysis is increasingly used to diagnose this condition. This work aimed to determine the frequency and distribution of ryanodine receptor (RYR1) mutations in the Belgian MH-population as investigated by IVCT in our centre, as well as the discordance rates between the 2 techniques. Sequence analysis of 16 RYRI-exons in 29 selected families resulted in the detection of 10 mutations (4 Gly341Arg, 2 Arg614Leu, and 1 Cys35Arg, Arg614Cys, Arg2163Cys and Arg2435His). Discordance between IVCT and mutation analysis was observed in only 6 out of 96 individuals from 4 different families. No mutation-positive/ IVCT-negative diagnosis was found. Genetic evaluation of RYR1-mutations can secure a diagnosis and aid in genetic counselling of individual family members but only in those families in which significant clinical information is present, as well as phenotyping by IVCT has been realized.

Malignant Hyperthermia in China

Malignant hyperthermia has rarely been reported in China. We report the first case of malignant hyperthermia, verified by caffeine-halothane contracture test and genetic testing, in a Chinese patient.

Malignant hyperthermia—The perioperative nurse's role

Malignant hyperthermia (MH) usually is triggered during or after administration of commonly used general anesthetics, and it can result in death if left untreated. The only definitive diagnostic test for MH is the caffeine halothane contracture test. A new molecular genetic diagnostic blood test may offer a less-invasive alternative for some patients. Hyperthermia, the cardinal sign of MH, is a relatively late symptom. Other clinical signs include tachyarrhythmias, tachypnea, and acidosis. Perioperative nurses should perform MH risk assessments during routine preoperative interviews to identify patients at risk for MH crisis. Perioperative nurses must respond rapidly and ensure the cooperation of the OR team when dealing with MH.

Malignant hyperthermia

Malignant hyperthermia (MH) is a rare genetic condition which may manifest for the first time during anaesthesia associated with a routine surgical procedure. Characterised initially by muscle rigidity, increased body temperature and metabolic acidosis, the syndrome may prove fatal unless prompt, effective treatment is administered. The sudden development of MH constitutes a medical emergency; hence it is essential that theatre practitioners are knowledgeable about the presenting symptoms and management of the condition.

[Malignant hyperthermia]

Malignant hyperthermia is an autosomal dominant disorder of the skeletal muscle that predisposes affected individuals to a life-threatening hypermetabolic reaction in response to volatile anaesthetics and depolarizing muscle relaxants. The underlying heterogeneous genetic defects are mainly point mutations within the ryanodine receptor gene of the sarcoplasmic reticulum. Following the introduction of efficient diagnostic and therapeutic tools--the in vitro contracture test and intravenous treatment with dantrolene--a dramatic decline in mortality rates has been observed. The association of malignant hyperthermia-like reactions with other neuromuscular disorders requires the collaboration of several clinical disciplines to achieve a timely recognition of this still life-threatening disorder.

Malignant hyperthermia: clinical features and management

Malignant hyperthermia is a syndrome that has no symptoms until the individual is given an anaesthetic, although cases have occurred as a result of Ecstasy ingestion. Delays in making the correct diagnosis can prove fatal. Practitioners should be aware of the agents that are known to trigger an MH reaction and the clinical manifestations of the condition. Treatment includes discontinuing the triggering agent, administering dantrolene and cooling the body.

King-Denborough Syndrome: report of two Brazilian cases

We report on two boys aged 2 and 6 years-old respectively with dysmorphic face, ptosis, down-slanting palpebral fissures, hypertelorism, epicanthic folds, low-set ears, malar hypoplasia, micrognathia, high-arched palate, clinodactyly, palmar simian line, pectus excavatum, winging of the scapulae, lumbar lordosis and mild thoracic scoliosis who present congenital hypotonia, slightly delayed motor development, diffuse joint hyperextensibility and mild proximal weakness. The muscle biopsy revealed minimal but identifiable changes represented by size fiber variability, type I fiber predominance and atrophy, perimysial fibrous infiltration and some disarray of the intermyofibrillary network. These cases correspond to the first Brazilian reports of the King-Denborough syndrome and our objective is increasing the awareness of this disorder as these patients are predisposed to developing malignant hyperthermia.

Malignant hyperthermia and myotonic disorders

Advances in physiology and molecular genetics have promoted greater understanding of the various clinical manifestations of muscle disorders. For example, myotonia or profound weakness may be observed in sodium channel disease (e.g., paramyotonia congenita or hyperkalemic periodic paralysis), depending on the specific channel defect or with slight changes in membrane potential. Observed effects of anesthetic techniques have been essential to elucidating the primary muscular nature of myotonia. Commonly used anesthetic medications have potentially lethal (e.g., MH) or serious (e.g., myotonic dystrophy) adverse effects. Conversely, lidocaine or propofol may have therapeutic benefit for patients with skeletal muscle sodium channel disorders. Additional investigation is required to improve our understanding of how age, gender, or other factors determine the phenotypic expression of malignant hyperthermia. Future research holds the promise for more accurate pre-anesthetic identification of persons with heritable myopathies, especially those who are asymptomatic. Enhanced awareness of multiple organ system involvement in myotonic dystrophy is essential for planning perioperative care. Patients with periodic paralysis require that we know factors that incite or inhibit the development of their attacks. Advances in bench research and detailed clinical studies will further improve our ability to provide optimal care for patients with muscle disorders.

RYR1 mutations causing central core disease are associated with more severe malignant hyperthermia in vitro contracture test phenotypes

Malignant hyperthermia (MH) and central core disease (CCD) are autosomal dominant disorders of skeletal muscle. Susceptibility to MH is only apparent after exposure to volatile anesthetics and/or depolarizing muscle relaxants. CCD patients present with diffuse muscular weakness but are also at risk of MH. Mutations in RYR1 (19q13.1), encoding a skeletal muscle calcium release channel (ryanodine receptor), account for the majority of MH and CCD cases. Fifteen RYR1 N-terminal mutations are considered causative of MH susceptibility, five of which are also associated with CCD. In the first extensive UK population survey, eight of 15 mutations were detected in 85 out of 297 (29%) unrelated MH susceptible cases, with G2434R detected in 53 cases (18%). Mutation type was shown to affect significantly MH phenotypes (in vitro contracture test (IVCT) response to caffeine, halothane, and ryanodine). RYR1 mutations associated with both CCD and MH (R163C, R2163H, R2435H) had more severe caffeine and halothane response phenotypes than those associated with MH alone. Mutations near the amino terminal (R163C, G341R) had a relatively greater effect on responses to caffeine than halothane, with a significantly increased caffeine:halothane tension ratio compared to G2434R of the central domain. All phenotypes were more severe in males than females, and were also affected by muscle specimen size and viability. Discordance between RYR1 genotype and IVCT phenotype was observed in seven families (nine individuals), with five false-positives and four false-negatives. This represents the most extensive study of MH patient clinical and genetic data to date and demonstrates that RYR1 mutations involved in CCD are those associated with one end of the spectrum of MH IVCT phenotypes.

Suspected malignant hyperthermia reactions in New Zealand

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.

Identification of the Arg1086His mutation in the alpha subunit of the voltage-dependent calcium channel (CACNA1S) in a North American family with malignant hyperthermia

Individuals from a large North American population were screened for the presence of the mutation in the alpha1 subunit of the voltage-dependent calcium channel (CACNA1S) that has recently been associated with malignant hyperthermia (MH). This Arg1086His mutation was screened for in 154 MH normal (MHN) individuals and 112 MH susceptible (MHS) individuals, who were diagnosed by the North American protocol of the in vitro contracture test. PCR and restriction enzyme analysis was used to test for the mutation. The Arg1086His mutation in the CACNA1S was not found in any of the MHN individuals. In contrast, two related individuals (grandfather and grandson, father and son of the MH proband) among the MHS group exhibited this mutation. However, a third MHS individual in the same family (granddaughter, cousin of the grandson) did not exhibit this mutation. These results indicate that this mutation may be associated with MH in this family. Genetic alterations in the CACNA1S associated with MH are present in approximately 1% of this North American MHS population.

Screening of the ryanodine receptor gene in 105 malignant hyperthermia families: novel mutations and concordance with the in vitro contracture test

Malignant hyperthermia (MH) in man is an autosomal dominant disorder of skeletal muscle Ca(2+)-regulation. During anesthesia in predisposed individuals, it is triggered by volatile anesthetics and depolarizing muscle relaxants. In >50% of the families, MH susceptibility is linked to the gene encoding the skeletal muscle ryanodine receptor (RYR1), the calcium release channel of the sarcoplasmic reticulum, on chromosome 19q12-13.2. To date, 21 RYR1 mutations have been identified in a number of pedigrees. Four of them are also associated with central core disease (CCD), a congenital myopathy. Screening for these 21 mutations in 105 MH families including 10 CCD families phenotyped by the in vitro contracture test (IVCT) according to the European protocol revealed the following approximate distribution: 9% Arg-614-Cys, 1% Arg-614-Leu, 1% Arg-2163-Cys, 1% Val-2168-Met, 3% Thr-2206-Met and 7% Gly-2434-Arg. In one CCD family, the disease was caused by a recently reported MH mutation, Arg-2454-His. Two novel mutations, Thr-2206-Arg and Arg-2454-Cys were detected, each in a single pedigree. In the 109 individuals of the 25 families with RYR1 mutations cosegregation between genetic result and IVCT was almost perfect, only three genotypes were discordant with the IVCT phenotypes, suggesting a true sensitivity of 98.5% and a specificity of minimally 81.8% for this test. Screening of the transmembraneous region of RYR1 did not yield a new mutation confirming the cytosolic portion of the protein to be of main functional importance for disease pathogenesis.

Failure to identify the ryanodine receptor G1021A mutation in a large North American population with malignant hyperthermia

Anesthesia-induced malignant hyperthermia (MH) is a rare inherited disorder of skeletal muscle. Several mutations in the ryanodine receptor (RYR1) have been found to be causative of MH. The G1021A mutation in the RYR1 is one of the most frequently occurring mutations in European populations. MH normal (165) and MH susceptible (114) North American patients were screened for the presence of the G1021A mutation. This mutation was not found in any of the patients tested. These studies support the absence of this mutation in the normal population. Furthermore, these findings emphasize the importance of viewing the distribution of MH mutations as variable gene pools with frequencies dependent on the geographical location of the population examined.

[Incidence of disposition for malignant hyperthermia in patients with neuromuscular diseases]

PURPOSE

It has been suggested that malignant hyperthermia (MH) occurs more frequent in patients with neuromuscular diseases (NMD) than in patients without NMD when they are exposed to volatile anaesthetics and/or succinylcholine. However, whereas central core disease (CCD) and MH susceptibility (MHS) are closely associated, the relationship between MH and other NMD is still uncertain. The purpose of this study was to evaluate the MH status of individuals with specific NMD with the in vitro contracture test (IVCT) and to ascertain the risk for MH in individuals with NMD.

METHODS

After institutional approval and informed consent, 29 patients of 3-59 years of age (27.2 +/- 17.3) with clinical suspicion for NMD and MH were enrolled in this prospective study. After excision of a skeletal muscle sample from M. vastus lateralis, patients were first classified as MHS, MH-equivocal (MHE) and MH-normal (MHN) by the IVCT according to the European MH protocol. Additionally, small muscle samples were excised from each patient for histological, histochemical and morphometric examination.

RESULTS

Fourteen patients were diagnosed by the IVCT as MHS and 9 as MHN. In 6 patients MH status was equivocal. In six patients CCD was diagnosed, in 14 individuals muscular dystrophies and in 5 patients myotonias. Two patients had unspecific myopathies and one patient a carnitine deficiency syndrome. One patient with Friedreich's ataxia was investigated because of a MH crisis and classified as MHE. All CCD patients and two of three individuals with Duchenne's muscular dystrophy were tested as MHS.

CONCLUSION

In this study 69% of the NMD patients were diagnosed as susceptible to MH with the IVCT. These results suggest, that NMD patients bear a high risk for MH. On the other hand, it has been discussed that in vitro contracture testing is not specific in NMD patients because skeletal muscle specimens from these patients have an elevated in vitro sensitivity. However, regarding our results and from a clinical point of view, patients with NMD should be treated like MHS individuals, unless they have undergone IVCT and were classified as MH-normal.

[Regional distribution of predisposition to maligant hyperthermia in Germany: tate in 1997]

Malignant hyperthermia (MH) is a rare autosomally dominantly hereditary and potentially life-threatening disease. The prevalence of the genetic MH predisposition is estimated as 1:10,000 to 1:20,000. In Germany no data on the regional distribution are available. Therefore, the purpose of this investigation is to summarise and present the epidemiological data of all German MH laboratories. Nine German hospitals offer the specific in vitro contracture test to diagnose the MH predisposition. All German MH laboratories carry out the examination in accordance with the standardised protocol of the European Malignant Hyperthermia Group. The laboratories were asked to provide the number of all patients investigated, excluding those suffering from other neuromuscular diseases, separated according to diagnostic groups and their places of residence, the number of the identified MH-families as well as the number of the clinically suspected and investigated MH cases with their places of residence. Eight MH laboratories provided the requested data. Until September 1997 a total of 2620 patients were investigated. In 865 patients (34%) MH suspicion was confirmed (diagnosis: MHS). 1494 patients (56%) were released by investigation from MH-suspicion (diagnosis: MHN). In 261 patients (10%) the MH-predisposition remained unsolved (diagnosis: MHE). 580 MH families were identified. Among 2620 patients 757 were clinically suspected MH cases. 35% of these suspected MH cases were classified as MHS, 10% as MHE and 55% as MHN. The documentation of the patients places of residence classified as MHS and MHE into a map of Germany demonstrates an exhaustive distribution with an increased regional prevalence in the areas of the MH laboratories. This concentration in the area of the MH laboratories becomes even more evident, when the places of residence of the MH suspected cases are demonstrated. In conclusion, the distribution of the MH predisposition is uniform and exhaustive in Germany. The presented regional concentration of clinically suspected MH cases among the MH laboratories is mainly interpreted as an expression of effective regional education and information. Considering the overall incidence of the MH predisposition as described above only 15-20% of the MH patients have so far been identified. The MH laboratories have already released about 10,000 patients from the suspicion of MH predisposition. A preliminary prevalence of at least 1:60,000 to 1:80,000 in Germany can be estimated according to the presented data.

[Evaluation of malignant hyperthermia episodes with the Clinical Grading Scale]

PURPOSE

The Clinical Grading Scale (CGS) was introduced to predict malignant hyperthermia (MH) susceptibility in adverse anaesthetic events. Because many of the clinical symptoms that occur during MH episodes are nonspecific, the CGS was designed as a tool to estimate the qualitative likelihood of MH. The purpose of this study was to compare the results of the CGS with the established in vitro contracture test (IVCT).

METHODS

92 patients with a personal history for MH were tested for MH susceptibility with the IVCT according to the protocol of the European MH Group. All patients were also evaluated with the CGS. Clinical indicators for the CGS are rigidity, muscle breakdown, respiratory acidosis, temperature increase and cardiac involvement. There are additional indicators in case of a family history for MH. For each indicator 3-15 points are added to build a raw score; this raw score corresponds to a MH rank in the CGS that describes the likelihood of MH in the suspected event. The higher the raw score rank, the higher the likelihood of MH and vice versa.

RESULTS

From 92 patients, 32 (35%) were diagnosed as MH-susceptible (MHS) with the IVCT, 47 (51%) were MH-normal (MHN), and 13 (14%) were MH-equivocal (MHE). One patient with MH-rank 1 (MH almost never) in the CGS was diagnosed as MHS; on the other hand no patient with MH-rank 6 (MH almost certain) in the CGS was diagnosed as MHN. However, the majority of patients (72%) were assigned to ranks 3 and 4 (MH somewhat less than likely/MH somewhat greater than likely). The qualitative likelihood of MH could therefore not be clearly estimated.

CONCLUSION

Our study shows that the MH-rank of the CGS corresponds poorly with the results of the IVCT. In any case the evaluation of an MH suspicious event depends on the availability of data of that event. It is often difficult to obtain sufficient data, especially if the event occurred a long while ago. In these cases the MH rank may underestimate the likelihood of MH susceptibility. On the other hand, overestimation is also possible because some of the scoring indicators depend on the anaesthesiologist's judgement only. At present, the use of the CGS is neither validated nor clinically feasible. The CGS cannot replace IVCT.

[A remote access system for inquiry of centrally stored data on patients suspected of malignant hyperthermia . A prototypical development for the Internet]

OBJECTIVES

Malignant hyperthermia (MH) is an inherited, potentially life-threatening syndrome of the skeletal muscles. It is a life-threatening complication of anaesthesia with a high mortality (8-10%). The risk of the patient during anaesthesia due to an overlooked predisposition for MH can be reduced by organisational measures, such as, all data of MH-susceptible patients and their families known in Germany must be brought together in a central register, MH-relevant data of patients must be readily retrievable, optional oral advice for those making an inquiry must be available.

METHODS

To achieve this goal, a client-server system has been implemented: Standard Multimedia personal computers installed at the user's (anaesthetist's) site, linked to the Internet, will act as clients. On a server, relevant data of patients concerning MH-susceptibility are integrated in a central database. The newly developed software of this project ensures the legally prescribed data security on the server and the data routes. At the client's site, standard software together with automatically installed programmes from the server using Java applets ensure easy use and maintenance.

IMPLEMENTATION

The total system was implemented and tested. Its functionality and high availability was demonstrated during this test period. Relevant aspects of data security were successfully examined by the data security officer of the University Hospitals of Baden-Württemberg. The user can optionally call a multifunctional teleconference which secures on-line advice if needed. This system demonstrates a safe and quick retrieval of MH relevant data of patients via Internet while at the same time guaranteeing all aspects of data protection and security.

CONCLUSION

A prototypical database access system is described. It ensures safe access to patient data via Internet, while guaranteeing all aspects of data security.

Clinical reassessment of malignant hyperthermia in Abitibi-Témiscamingue

PURPOSE

In 1992, 1812 individuals (1.2% of the population) were labelled at risk for malignant hyperthermia (MH) in seven families from Abitibi-Témiscamingue. To evaluate the effective risk in this population, a multidisciplinary study was undertaken which included clinical, genealogical and molecular aspects. This paper presents the clinical aspects of the study.

METHOD

For each of the 1546 individuals reached, all anesthetic exposures were screened for elements relevant to MH. Malignant hyperthermia events were analyzed with "the clinical grading scale." All 44 reports of caffeine halothane contracture tests were reappraised. Finally, genealogical study was done to complete each family tree up to the initial French settlers in order to identify links between these seven families through common ancestors.

RESULTS

Following this reassessment, the families were compared and classified into four groups. Two families (1097 individuals) are not considered to be at a higher risk for MH than the population in general. Two families are still considered possibly at risk. Finally, one family (402 individuals) is highly at risk and two other families are probably at risk. Family trees did not show any link up to the colonization of Abitibi-Témiscamingue in the beginning of this Century but common ancestors were found around the 9th generation.

CONCLUSION

This clinical reassessment will help to focus education and prevention on a much smaller group of individuals still considered potentially at risk for MH. By adequate evaluation of phenotypes, combined with the use of a genealogical approach, it will be possible to target families for molecular research.

RYR mutation G1021A (Gly341Arg) is not frequent in Danish and Swedish families with malignant hyperthermia susceptibility

Malignant hyperthermia (MH) is a pharmacogenetic disorder. Susceptibility to MH (MHS) is presumed to be inherited in an autosomal dominant way. MH crises are triggered by halogenated inhalational anaesthetics and suxamethonium, and may be lethal if not treated early and adequately. Until now, eight mutations in the RYR1 gene have been described as causes of MHS phenotype in various MH families. The mutation RYR1 G1021A (Gly341Arg) has been reported to account for approximately 10% of Caucasian MHS cases. However, in our study this mutation was discovered in only 1 out of 89 Scandinavian families, indicating that this mutation may be the cause of MHS in only about 1% of MHS families in those populations. The mutation may have been brought to Scandinavia by an immigrant.

On the nature of the link between malignant hyperthermia and exertional heatstroke

Malignant hyperthermia (MH) is a rare myopathy inducing severe accident when carriers are exposed to triggering agents. MH susceptibility (MHS) is assessed by pharmacological tests performed on muscle strips. Exertional heat stroke (EHS) is a severe accident occurring during long and strenuous exercise. It has been observed that numerous EHS patients are susceptible to MH according to pharmacological tests. Because most of those EHS-MHS subjects were soldiers, we hypothesize that military duty could select subjects with infraclinical myopathy and therefore would increase the MHS:EHS subject ratio.

Incidence of malignant hyperthermia reactions in 2,214 patients undergoing muscle biopsy

To determine the incidence of malignant hyperthermia (MH) reactions after trigger-free anaesthesia in a large population of MH-susceptible (MHS) patients, the charts of 2,214 patients who underwent elective muscle biopsy for malignant hyperthermia were reviewed. Either general or regional anaesthesia with non-triggering drugs was used. For general anaesthesia, the trachea was intubated in the absence of muscle relaxants. The halothane/caffeine contracture test was performed on the biopsied muscle. Suspected MH reactions were identified according to their site of occurrence (in the operating room, recovery room or ward). Ninety-seven percent of patients received a general anaesthetic; 3% received a regional anaesthetic or field block. Of the 2214 patients whose muscles were biopsied, 1082 patients were biopsy-positive for MH. Five patients in whom MH reactions were diagnosed in the recovery room were all subsequently proved to be biopsy-positive for MH. Four of the five received intravenous dantrolene as part of their therapy; the fifth received only symptomatic therapy as parenteral dantrolene was not commercially available. All patients recovered completely from their reactions. We conclude that the incidence of MH reactions in biopsy-positive patients who receive a trigger-free anaesthetic for minor surgery is small (0.46%, (0.15-1.07%, 95% CI)). These reactions occur in the immediate postoperative period.

Anaesthesia for a child with centronuclear myopathy

Centronuclear myopathy (CNM) is an inherited condition involving most muscle fibres in all the body mass, first described in 1966, which has a varying spectrum of presentations. Until recently it had not been associated with an increased risk of malignant hyperpyrexia. A seven-year-old male with CNM was admitted to our hospital for elective surgery. High dose propofol anaesthesia was used, supplemented with N2O/O2 from a new anaesthesia machine. The operation was successful with uncomplicated anaesthesia and recovery.

Ultrasonography: not useful in detecting susceptibility to malignant hyperthermia

MH is a rare, potentially fatal complication of general anesthesia. Halothane-caffeine contracture testing of a muscle biopsy is the only accepted diagnostic test for MH. A previous report indicated that ultrasonography may aid in diagnosis of MH. Using sonographic examination of the thigh and calf, we evaluated eight patients with proved susceptibility to MH and eight control patients. Two radiologists independently evaluated the sonograms for echogenicity and definition of fascial planes. We detected no consistent and reliable differences between control and MH patients. We conclude that, in our hands, ultrasonography is not useful in differentiating patients with MH from normal persons.

[Malignant hyperthermia in Tuscany: a study of a five year period from 1986 to 1990]

The authors report the results of a survey on M. H. in Tuscany during five years from 1986 to 1990, in order to ascertain frequency, to point out the system of evaluation of the reported cases, to pick out risk-subjects, to find out the presence of dantrolene in various hospitals and to contribute to the surveys held all over the nation. That is the reason why all the persons responsible for Anaesthesiology Depts. and their collaborators were interested in this survey, through a questionnaire which, where necessary, was further developed. The great number of participants, who supplied their data, allowed is to establish trustworthy values of the set objectives. The number of MH cases was coincident with national and international data: the necessity emerged of an only collecting center and of a sale system of classification of data in order to record and compare them in an homogenous way. Detection of subjects was made possible, in most cases, by personal and familiar anamnesis, and it allowed the very few suspect cases to be sent to the specific centers. We recommend that dantrolene, even though present in most hospitals, be available more widespreadly.

Malignant hyperthermia

Major advances have occurred in the management of MH since this disorder was first described. Despite the initially high mortality, deaths secondary to MH have dramatically decreased over the past 15 years, which is due in large part to the discovery of efficacious therapy. It is also a result of ever-increasing awareness and appreciation of the syndrome by physicians, other health care providers, and patients. Research has provided many answers to questions about the pathologic mechanisms of this disorder, and an animal model exists for testing new therapies; however, many questions remain. It is hoped that future investigations such as advances in genetic mapping may provide a specific, noninvasive method of predictive testing. It is possible that a complete understanding of MH and its mechanisms could teach us more about the ways anesthetic agents work. For now, identifying individuals at risk, rigorously avoiding exposure to potential anesthetic triggering agents in MH-susceptible patients, and promptly recognizing and treating unexpected MH episodes are the primary means of reducing morbidity and mortality from MH. Interested and informed clinicians and families are the patient's best allies against MH.