Diagnosis and rescue of malignant hyperthermia induced by anesthesia during radical surgery in a cervical cancer patient using the National Remote Emergency System: A case report

RATIONALE

Malignant hyperthermia (MH) is a rare yet serious medical complication that typically arises following general anesthesia or the administration of specific anesthetics. Due to the infrequency of MH, anesthesiologists often lack sufficient expertise in identifying and managing it, leading to misdiagnosis and inappropriate treatment. There is an urgent need to enhance the diagnosis and management of MH through the utilization of relevant tools.

PATIENT CONCERNS

In this case, a 52-year-old woman underwent radical cervical cancer surgery under general anesthesia, with no family or significant medical history. She experienced a gradual increase in end-tidal carbon dioxide (ETCO2) to a maximum of 75 mm Hg and a rise in body temperature from 36.5 to 37.5 °C in a very short period, as well as a blood gas analysis showing a pH of 7.217.

DIAGNOSIS

The anesthesiologist immediately used The WeChat applet-based National Remote Emergency System for Malignant Hyperthermia (MH-NRES), and the score was 40, which indicated that the patient was very likely to have MH.

INTERVENTIONS

We immediately discontinued sevoflurane and switched total intravenous anesthesia to maintain general anesthesia, with a rapid intravenous infusion of dantrolene sodium.

OUTCOMES

The ETCO2 and the temperature quickly dropped to normal, followed by successful completion of the surgery, and the patient was discharged 8 days after surgery.

LESSONS

The experience can provide a basis use of MH-NRES and improve the ability of anesthesiologists to deal with intraoperative MH as well as increase the survival probability of patients.

Malignant hyperthermia safety - A nationwide survey of publicly funded Swedish healthcare

BACKGROUND

Malignant hyperthermia (MH) is a rare pharmacogenetic disorder that can lead to a life-threatening reaction during general anaesthesia with triggering agents. Prompt life-saving treatment includes the immediate administration of the antidote dantrolene. This study investigated Swedish healthcare providers' awareness and adherence to guidelines and recommendations with respect to MH and whether adherence to safe MH-praxis varies with hospital care-complexity level and private versus public management form.

METHOD

Agreements and procurement specifications between all 21 Swedish County Councils and privately run surgical care providers were reviewed alongside with questionnaire-aided collection of information from 62 publicly funded health care providers (both privately and publicly run).

RESULTS

No procurement requirement specification or contract contained requirements on anaesthesia or aspects of MH. All publicly run hospitals stocked dantrolene and 28 out of 52 (54%) stocked the recommended amount. Seven out of nine (78%) of the privately run institutions stocked dantrolene, and one stocked the recommended amount. Publicly run hospitals adhered to recommendations to a greater extent than privately run institutions, both with respect to stocking of dantrolene (p = .02) and to stocking the recommended amount (p = .03).

CONCLUSIONS

Contracts between Swedish county councils and private surgical care subcontractors rarely outline expectations of standards for the safe practice of anaesthesia such as preparedness to handle a life-threatening MH reaction. Among Swedish publicly funded anaesthesia providers there is room for improvement in adherence to the EMHG guideline on dantrolene availability. Publicly run hospitals seem to have better compliance with these recommendations than privately run institutions. Raising awareness about current guidelines is important to improve safety for known and unknown MH-susceptible individuals.

Climate Change, Emerging Vector-Borne Illnesses, and Anesthetic Considerations

As a result of the widespread prevalence of anesthetic usage, anesthesia-related complications are well studied, ranging from benign postoperative nausea and vomiting to potentially fatal complications, such as paralysis, malignant hyperthermia, and death. However, one intersection that still needs further analysis is the relationship between vector-borne illnesses (VBIs) and anesthetic complications. With the advent of climate change and global warming, what were previously endemic vectors have spread far beyond their typical regions, resulting in the spread of VBI. As the incidence of VBIs rapidly increases in the United States, operations for diagnostic testing, and thus the identification and treatments of these VBIs, have significantly diminished. A literature review was conducted to analyze case reports of patients with VBIs and anesthetic concerns with sources from PubMed and Google Scholar databases, and a wide range of complications were found.

The Anesthesiologists' Perception of Malignant Hyperthermia and Availability of Dantrolene in China: A Cross-Sectional Survey

Background

Malignant hyperthermia (MH) is a hypermetabolic syndrome with high mortality rates. Early detection and prompt intravenous administration of dantrolene are crucial for effective management of MH. However, there is currently a lack of comprehensive nationwide surveys on the availability of dantrolene and anesthesiologists' understanding of MH in China.

Methods

A nationwide survey was conducted between January 2022 and June 2022. Online questionnaires on the cognition of MH among anesthesiologists in China were sent through social platforms to anesthesiologists in mainland China. Data regarding participants' perception of MH-related knowledge, availability of domestic dantrolene, and reported MH cases were collected in this study.

Results

Responses were collected from a total of 11,354 anesthesiologists representing 31 provinces across the Chinese mainland. Among the 11 scoring questions, the highest accuracy rates were observed for the question regarding therapeutic drugs for MH (99.3%) and the characteristics of MH (98.0%). Conversely, the question pertaining to the earliest clinical signs of MH had the lowest accuracy rate (23.5%). Significant variations were observed in the scores among different professional titles (P=0.003), academic degree (P<0.001), hospital classification (P<0.001), and urban hierarchy (P<0.001). Of the respondents, 919 (8.1%) anesthesiologists reported dantrolene availability in their hospitals, and 631 (5.6%) indicated unclear. A total of 136 hospitals in this survey reported at least one previous case of MH.

Conclusion

Mainland China faces challenges such as insufficient experience in diagnosing and treating MH, as well as difficulty in obtaining dantrolene. To improve the public awareness of MH, it is imperative to establish and promote a refined MH training system. Additionally, a streamlined and rapid dantrolene linkage emergency system should be implemented to ensure prompt access to the drug.

Muscle fibre mitochondrial [Ca2+ ] dynamics during Ca2+ waves in RYR1 gain-of-function mouse

AIM

A fraction of the Ca2+ released from the sarcoplasmic reticulum (SR) enters mitochondria to transiently increase its [Ca2+ ] ([Ca2+ ]mito ). This transient [Ca2+ ]mito increase may be important in the resynthesis of ATP and other processes. The resynthesis of ATP in the mitochondria generates heat that can lead to hypermetabolic reactions in muscle with ryanodine receptor 1 (RyR1) variants during the cyclic releasing of SR Ca2+ in the presence of a RyR1 agonist. We aimed to analyse whether the mitochondria of RYR1 variant muscle handles Ca2+ differently from healthy muscle.

METHODS

We used confocal microscopy to track mitochondrial and cytoplasmic Ca2+ with fluorescent dyes simultaneously during caffeine-induced Ca2+ waves in extensor digitorum longus muscle fibres from healthy mice and mice heterozygous (HET) for a malignant hyperthermia-causative RYR1 variant.

RESULTS

Mitochondrial Ca2+ -transient peaks trailed the peak of cytoplasmic Ca2+ transients by many seconds with [Ca2+ ]mito not increasing by more than 250 nM. A strong linear relationship between cytoplasmic Ca2+ and [Ca2+ ]mito amplitudes was observed in HET RYR1 KI fibres but not wild type (WT).

CONCLUSION

Our results indicate that [Ca2+ ]mito change within the nM range during SR Ca2+ release. HET fibre mitochondria are more sensitive to SR Ca2+ release flux than WT. This may indicate post-translation modification differences of the mitochondrial Ca2+ uniporter between the genotypes.

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.

Perioperative Management of Paraneoplastic Necrotizing Myopathy in Thyroidectomy: A Case Report

Perioperative management of patients with myopathies can be challenging due to the increased risk of malignant hyperthermia (MH) and anesthesia-induced rhabdomyolysis (AIR). However, currently, there is no evidence regarding the optimal anesthetic management for paraneoplastic necrotizing myopathy (PNM) (total intravenous anesthetic vs. volatile anesthetics). Here, I report a case where anesthesia was administered safely using volatile anesthetics. A 63-year-old female presented with PNM associated with papillary thyroid carcinoma, necessitating urgent thyroidectomy. The patient, previously diagnosed with anti-3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) antibody-associated myopathy, exhibited progressive weakness and dysphagia, prompting suspicion of PNM. The patient's compromised respiratory status, attributed to tracheal compression by a large goiter, necessitated an urgent thyroidectomy. Anesthetic management considerations included the potential effect of HMGCR-M on respiratory muscles and the need for careful planning to mitigate postoperative complications. The patient underwent total thyroidectomy, left central compartment clearance, and tracheostomy. The surgery proceeded uneventfully, with meticulous monitoring and adjustment of anesthetic agents to maintain hemodynamic stability. Postoperatively, the patient recovered well, demonstrating complete resolution of neurological symptoms during a three-month follow-up. The case underscores the importance of recognizing paraneoplastic syndromes in the context of thyroid surgery and highlights potential challenges faced by anesthesiologists. Despite the lack of established safety data for anesthetic drugs in HMGCR-M necrotizing myopathy, the case demonstrates the successful use of sevoflurane and rocuronium.

Anesthetic Management of a Patient With Central Core Disease Undergoing Thoracoscopic Lung Resection: The Importance of Neuromuscular Monitoring at the Masseter Muscle

Central core disease is a rare muscular disorder in which anesthetic considerations for the prevention of malignant hyperthermia and for avoidance of residual neuromuscular block are required. A 63-year-old woman with central core disease underwent thoracoscopic sublobar lung resection under total IV anesthesia with a prepared anesthetic workstation. The rocuronium-induced neuromuscular block was monitored by using acceleromyography at the left adductor pollicis muscle and the right masseter muscle. The recovery of neuromuscular block at the masseter was slower than that at the adductor pollicis. The patient showed no symptoms of malignant hyperthermia and residual neuromuscular block and had an uneventful postoperative course. In the present case, malignant hyperthermia was successfully prevented with general anesthesia that is free of triggering agents using a prepared anesthetic machine. The authors speculate that the masseter may be an auxiliary site for neuromuscular monitoring to ensure recovery from neuromuscular block in patients with central core disease.

The Structural-Functional Crosstalk of the Calsequestrin System: Insights and Pathological Implications

Calsequestrin (CASQ) is a key intra-sarcoplasmic reticulum Ca2+-handling protein that plays a pivotal role in the contraction of cardiac and skeletal muscles. Its Ca2+-dependent polymerization dynamics shape the translation of electric excitation signals to the Ca2+-induced contraction of the actin-myosin architecture. Mutations in CASQ are linked to life-threatening pathological conditions, including tubular aggregate myopathy, malignant hyperthermia, and Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT). The variability in the penetrance of these phenotypes and the lack of a clear understanding of the disease mechanisms associated with CASQ mutations pose a major challenge to the development of effective therapeutic strategies. In vitro studies have mainly focused on the polymerization and Ca2+-buffering properties of CASQ but have provided little insight into the complex interplay of structural and functional changes that underlie disease. In this review, the biochemical and structural natures of CASQ are explored in-depth, while emphasizing their direct and indirect consequences for muscle Ca2+ physiology. We propose a novel functional classification of CASQ pathological missense mutations based on the structural stability of the monomer, dimer, or linear polymer conformation. We also highlight emerging similarities between polymeric CASQ and polyelectrolyte systems, emphasizing the potential for the use of this paradigm to guide further research.

Comparison of Transcriptomic Changes in Survivors of Exertional Heat Illness with Malignant Hyperthermia Susceptible Patients

Exertional heat illness (EHI) is an occupational health hazard for athletes and military personnel-characterised by the inability to thermoregulate during exercise. The ability to thermoregulate can be studied using a standardised heat tolerance test (HTT) developed by The Institute of Naval Medicine. In this study, we investigated whole blood gene expression (at baseline, 2 h post-HTT and 24 h post-HTT) in male subjects with either a history of EHI or known susceptibility to malignant hyperthermia (MHS): a pharmacogenetic condition with similar clinical phenotype. Compared to healthy controls at baseline, 291 genes were differentially expressed in the EHI cohort, with functional enrichment in inflammatory response genes (up to a four-fold increase). In contrast, the MHS cohort featured 1019 differentially expressed genes with significant down-regulation of genes associated with oxidative phosphorylation (OXPHOS). A number of differentially expressed genes in the inflammation and OXPHOS pathways overlapped between the EHI and MHS subjects, indicating a common underlying pathophysiology. Transcriptome profiles between subjects who passed and failed the HTT (based on whether they achieved a plateau in core temperature or not, respectively) were not discernable at baseline, and HTT was shown to elevate inflammatory response gene expression across all clinical phenotypes.

Effects of Remimazolam on Intracellular Calcium Dynamics in Myotubes Derived from Patients with Malignant Hyperthermia and Functional Analysis of Type 1 Ryanodine Receptor Gene Variants

Remimazolam is a novel general anesthetic and its safety in patients with malignant hyperthermia (MH) is unknown. We used myotubes derived from the skeletal muscle of patients with MH to examine the response to ryanodine receptor 1 (RYR1) agonist and remimazolam in MH-susceptible patients. Patients underwent muscle biopsy for the Ca2+-induced Ca2+ release (CICR) rate test, a diagnostic tool for MH in Japan. Ten patients had myotubes obtained from skeletal muscle cultures, and the genes associated with malignant hyperthermia in these patients were analyzed. The EC50 of caffeine, cresol, and remimazolam to induce intracellular calcium concentration change were compared between myotubes from CICR-negative genetic test patients and myotubes from other patients. Eight of the ten were CICR-positive, five of whom had RYR1 causative gene mutations or variants. Two patients had CICR-negative genetic tests, and as expected had the highest EC50 (the concentration of a drug that gives a half-maximal response) in response to caffeine, 4CmC and remimazolam. Three patients had a positive CICR but no known variants in RYR1 or CACNA1S (voltage-gated calcium channel subunit alpha1S). Myotubes in these patients had significantly lower EC50s for all agents than myotubes in CICR-negative patients. When myotubes from a patient who was CICR-negative and had no gene variant were used as a control, myotubes from CICR-positive patients were more hyper-responsive than controls to all stimulants used. The EC50 for remimazolam was lowest for myotubes from CICR-positive, RYR1-mutant patients, at 206 µM (corresponding to 123 µg/mL). The concentration was more than 80-times higher than the clinical concentration. RYR1 gene variants in R4645Q and W5020G were shown to be causative gene mutations for MH. Intracellular calcium in myotubes from MH patients are elevated at high concentrations of remimazolam but not at clinically used concentrations of remimazolam. Remimazolam appears to be safe to use in patients with MH.

Malignant hyperthermia: Report on a successful rescue of a case with the highest temperature of 44.2°C

Malignant hyperthermia (MH) is an inherited skeletal muscle disorder caused primarily by a genetic mutation, usually in the calcium channel gene of the muscle. This mutation can lead to muscle hypersensitivity to volatile anesthetics (such as sevoflurane) and the depolarizing muscle relaxant succinylcholine, resulting in hyperthermia, muscle stiffness, metabolic disturbances, and other severe physiological reactions. This condition may prove fatal unless it is recognized in its early stages and treatment is administered promptly and aggressively. We report a 13-year-old adolescent who underwent laparoscopic appendectomy and developed MH after the use of inhalational anesthetics, manifested by unremitting hyperthermia with a maximum temperature of 44.2°C, muscle rigidity, tachycardia, hypercapnia; and malignant arrhythmias, cardiogenic shock, hyperkalemia, metabolic, and respiratory acidosis. After early and timely recognition, multidisciplinary management and administration of dantrolene, the case was successfully treated. Exome sequencing revealed a point mutation (amino acid change) on the RYR1 gene: c.12700G>C(p.Val4234Leu). Due to the lack of ready-made dantrolene in our hospital, the patient in this case received dantrolene treatment only 6 h after the first observation of high body temperature. We review the development of the disease and summarize the success of treatment and what can be done to improve the chances of saving the patient's life if dantrolene is not available in time.

Isoflurane Alters Presynaptic Endoplasmic Reticulum Calcium Dynamics in Wild-Type and Malignant Hyperthermia-Susceptible Rodent Hippocampal Neurons

Volatile anesthetics reduce excitatory synaptic transmission by both presynaptic and postsynaptic mechanisms which include inhibition of depolarization-evoked increases in presynaptic Ca2+ concentration and blockade of postsynaptic excitatory glutamate receptors. The presynaptic sites of action leading to reduced electrically evoked increases in presynaptic Ca2+ concentration and Ca2+-dependent exocytosis are unknown. Endoplasmic reticulum (ER) of Ca2+ release via ryanodine receptor 1 (RyR1) and uptake by SERCA are essential for regulation intracellular Ca2+ and are potential targets for anesthetic action. Mutations in sarcoplasmic reticulum (SR) release channels mediate volatile anesthetic-induced malignant hyperthermia (MH), a potentially fatal pharmacogenetic condition characterized by unregulated Ca2+ release and muscle hypermetabolism. However, the impact of MH mutations on neuronal function are unknown. We used primary cultures of postnatal hippocampal neurons to analyze volatile anesthetic-induced changes in ER Ca2+ dynamics using a genetically encoded ER-targeted fluorescent Ca2+ sensor in both rat and mouse wild-type (WT) neurons and in mouse mutant neurons harboring the RYR1 T4826I MH-susceptibility mutation. The volatile anesthetic isoflurane reduced both baseline and electrical stimulation-evoked increases in ER Ca2+ concentration in neurons independent of its depression of presynaptic cytoplasmic Ca2+ concentrations. Isoflurane and sevoflurane, but not propofol, depressed depolarization-evoked increases in ER Ca2+ concentration significantly more in mouse RYR1 T4826I mutant neurons than in wild-type neurons. The RYR1 T4826I mutant neurons also showed markedly greater isoflurane-induced reductions in presynaptic cytosolic Ca2+ concentration and synaptic vesicle (SV) exocytosis. These findings implicate RyR1 as a molecular target for the effects of isoflurane on presynaptic Ca2+ handling.

A case report of Andersen-Tawil syndrome misdiagnosed with myodystrophy

Andersen-Tawil syndrome (ATS) is a rare periodic paralysis caused by the KCNJ2 gene mutation. Here, we report on an ATS patient misdiagnosed with myodystrophy. A 66-year-old man presented with a 60-year history of episodic weakness in the proximal muscles of the upper and lower limbs. The man has been diagnosed with muscle pathology and has undergone genetic examinations in many hospitals since childhood. We conducted a correct diagnosis in combination with the patient's history, electrical physiology, and genetic analysis and identified a heterozygous KCNJ2 gene variant (c.220A > G; p.T74A). Patients with ATS can develop permanent myasthenia characterized by chronic progressive myopathy. ATS patients should also pay special attention to the risks of anesthesia in surgery, including malignant hyperthermia (MH), muscle spasms affecting tracheal intubation or ventilation, and ventilator weakness. Early diagnosis and therapy could help delay the onset of myasthenia and prevent risks associated with anesthesia accidents.

Rhabdomyosarcoma Associated with Core Myopathy/Malignant Hyperthermia: Combined Effect of Germline Variants in RYR1 and ASPSCR1 May Play a Role

Rhabdomyosarcomas have been described in association with thyroid disease, dermatomyositis, Duchenne muscular dystrophy, and in muscular dystrophy models but not in patients with ryanodine receptor-1 gene (RYR1) pathogenic variants. We described here an 18-year-old male who reported a cervical nodule. Magnetic resonance images revealed a mass in the ethmoidal sinus corresponding to rhabdomyosarcoma. As his father died from malignant hyperthermia (MH), an in vitro contracture test was conducted and was positive for MH susceptibility. Muscle histopathological analysis in the biopsy showed the presence of cores. Molecular analysis using NGS sequencing identified germline variants in the RYR1 and ASPSCR1 (alveolar soft part sarcoma) genes. This report expands the spectrum of diseases associated with rhabdomyosarcomas and a possible differential diagnosis of soft tissue tumors in patients with RYR1 variants.

Real Evidence and Misconceptions about Malignant Hyperthermia in Children: A Narrative Review

Malignant hyperthermia is a rare but life-threatening pharmacogenetic disorder triggered by exposure to specific anesthetic agents. Although this occurrence could affect virtually any patient during the perioperative time, the pediatric population is particularly vulnerable, and it has a five-fold higher incidence in children compared to adults. In the last few decades, synergistic efforts among leading anesthesiology, pediatrics, and neurology associations have produced new evidence concerning the diagnostic pathway, avoiding unnecessary testing and limiting false diagnoses. However, a personalized approach and an effective prevention policy focused on clearly recognizing the high-risk population, defining perioperative trigger-free hospitalization, and rapid activation of supportive therapy should be improved. Based on epidemiological data, many national scientific societies have produced consistent guidelines, but many misconceptions are common among physicians and healthcare workers. This review shall consider all these aspects and summarize the most recent updates.

Anesthetic Management of a Patient With McArdle Disease: A Case Report and Review of the Literature

McArdle disease (glycogen storage disorder type V) is a rare inherited condition resulting in impaired energy metabolism. Challenges in anesthetized patients with McArdle disease include hypoglycemia, rhabdomyolysis, myoglobinuria, acute renal failure, and postoperative fatigue. We review the literature and discuss a successful anesthetic that had no perioperative complications for a patient with McArdle disease undergoing robotic-assisted lung wedge resection. Preoperatively, we obtained a complete blood count, chemistry panel, and creatine kinase level. Intraoperatively, we proceeded with general endotracheal anesthesia and monitored point-of-care electrolytes, hemoglobin, and blood glucose. The patient had an uneventful postoperative recovery and was discharged home on postoperative Day 3. Patients with McArdle disease can undergo safe surgery with appropriate perioperative planning and a well-managed anesthetic. Efforts should focus on mitigating the risks of hypoglycemia, rhabdomyolysis, myoglobinuria, acute renal failure, and postoperative fatigue.

What is malignant hyperthermia susceptibility?

The molecular mechanisms of susceptibility to malignant hyperthermia are complex. The malignant hyperthermia susceptibility phenotype should be reserved for patients who have a personal or family history consistent with malignant hyperthermia under anaesthesia and are subsequently demonstrated through diagnostic testing to be at risk.

Muscle Ultrasound Abnormalities in Individuals with RYR1-Related Malignant Hyperthermia Susceptibility

BACKGROUND

Variants in RYR1, the gene encoding the ryanodine receptor-1, can give rise to a wide spectrum of neuromuscular conditions. Muscle imaging abnormalities have been demonstrated in isolated cases of patients with a history of RYR1-related malignant hyperthermia (MH) susceptibility.

OBJECTIVE

To provide insights into the type and prevalence of muscle ultrasound abnormalities and muscle hypertrophy in patients carrying gain-of-function RYR1 variants associated with MH susceptibility and to contribute to delineating the wider phenotype, optimizing the diagnostic work-up and care for of MH susceptible patients.

METHODS

We performed a prospective cross-sectional observational muscle ultrasound study in patients with a history of RYR1-related MH susceptibility (n = 40). Study procedures included a standardized history of neuromuscular symptoms and a muscle ultrasound assessment. Muscle ultrasound images were analyzed using a quantitative and qualitative approach and compared to reference values and subsequently subjected to a screening protocol for neuromuscular disorders.

RESULTS

A total of 15 (38%) patients had an abnormal muscle ultrasound result, 4 (10%) had a borderline muscle ultrasound screening result, and 21 (53%) had a normal muscle ultrasound screening result. The proportion of symptomatic patients with an abnormal result (11 of 24; 46%) was not significantly higher compared to the proportion of asymptomatic patients with an abnormal ultrasound result (4 of 16; 25%) (P = 0.182). The mean z-scores of the biceps brachii (z = 1.45; P <  0.001), biceps femoris (z = 0.43; P = 0.002), deltoid (z = 0.31; P = 0.009), trapezius (z = 0.38; P = 0.010) and the sum of all muscles (z = 0.40; P <  0.001) were significantly higher compared to 0, indicating hypertrophy.

CONCLUSIONS

Patients with RYR1 variants resulting in MH susceptibility often have muscle ultrasound abnormalities. Frequently observed muscle ultrasound abnormalities include muscle hypertrophy and increased echogenicity.

A novel RYR1 variant in an infant with a unique fetal presentation of central core disease

Ryanodine receptor type 1-related disorder (RYR1-RD) is the most common subgroup of congenital myopathies with a wide phenotypic spectrum ranging from mild hypotonia to lethal fetal akinesia. Genetic testing for myopathies is imperative as the diagnosis informs counseling regarding prognosis and recurrence risk, treatment options, monitoring, and clinical management. However, diagnostic challenges exist as current options are limited to clinical suspicion prompting testing including: single gene sequencing or familial variant testing, multi-gene panels, exome, genome sequencing, and invasive testing including muscle biopsy. The timing of diagnosis is of great importance due to the association of RYR1-RD with malignant hyperthermia (MH). MH is a hypermetabolic crisis that occurs secondary to excessive calcium release in muscles, leading to systemic effects that can progress to shock and death if unrecognized. Given the association of MH with pathogenic variants in RYR1, a diagnosis of RYR1-RD necessitates an awareness of medical team to avoid potentially triggering agents. We describe a case of a unique fetal presentation with bilateral diaphragmatic eventrations who had respiratory failure, dysmorphic facial features, and profound global hypotonia in the neonatal period. The diagnosis was made at several months of age, had direct implications on her clinical care related to anticipated need to long-term ventilator support, and ultimately death secondary an arrhythmia as a result of suspected MH. Our report reinforces the importance of having high suspicion for a genetic syndrome and pursuing early, rapid exome or genome sequencing as first line testing in critically ill neonatal intensive care unit patients and further evaluating the pathogenicity of a variant of uncertain significance in the setting of a myopathic phenotype.

Malignant hyperthermia in Poland: A survey study

Malignant hyperthermia (MH) is a life-threatening syndrome caused by sudden, uncontrolled skeletal muscle hypermetabolism in response to inhalation anesthetics and depolarizing relaxants. The estimated incidence of MH is between 1:10,000 and 1:250,000 anesthetic procedures. In Poland, due to lack of reporting, the incidence of MH is unknown. Dantrolene is imported as a life-saving drug (target import) and temporally authorized for sale. The aim of the study was to evaluate the prevalence of malignant hyperthermia in Poland and to assess the accessibility to dantrolene in Poland. A questionnaire was conducted among the chiefs of anesthesia and intensive care units in Poland. During the years 2014 to 2019, 10 episodes of MH have been reported in 238 surveyed polish anesthesia departments. The estimated prevalence is 1:350,000. Eight patients survived the MH crisis. Dantrolene is stocked in 48 (20%) anesthesiology departments. Among the surveyed hospitals, only in 38 (16%) it is possible to administer dantrolene within 5 minutes of suspecting a MH reaction. Less than half units (44%) have an algorithm for the management of MH episode in the operating theaters. The results of the study revealed, that the prevalence of MH in Poland is lower than the prevalence reported in other countries. Access to dantrolene in Poland is limited.

Distinct pathophysiological characteristics in developing muscle from patients susceptible to malignant hyperthermia

BACKGROUND

Most patients with malignant hyperthermia susceptibility diagnosed by the in vitro caffeine-halothane contracture test (CHCT) develop excessive force in response to halothane but not caffeine (halothane-hypersensitive). Hallmarks of halothane-hypersensitive patients include high incidence of musculoskeletal symptoms at rest and abnormal calcium events in muscle. By measuring sensitivity to halothane of myotubes and extending clinical observations and cell-level studies to a large group of patients, we reach new insights into the pathological mechanism of malignant hyperthermia susceptibility.

METHODS

Patients with malignant hyperthermia susceptibility were classified into subgroups HH and HS (positive to halothane only and positive to both caffeine and halothane). The effects on [Ca²⁺]_cyto of halothane concentrations between 0.5 and 3 % were measured in myotubes and compared with CHCT responses of muscle. A clinical index that summarises patient symptoms was determined for 67 patients, together with a calcium index summarising resting [Ca²⁺]_cyto and spontaneous and electrically evoked Ca²⁺ events in their primary myotubes.

RESULTS

Halothane-hypersensitive myotubes showed a higher response to halothane 0.5% than the caffeine-halothane hypersensitive myotubes (P<0.001), but a lower response to higher concentrations, comparable with that used in the CHCT (P=0.055). The HH group had a higher calcium index (P<0.001), but their clinical index was not significantly elevated vs the HS. Principal component analysis identified electrically evoked Ca²⁺ spikes and resting [Ca²⁺]_cyto as the strongest variables for separation of subgroups.

CONCLUSIONS

Enhanced sensitivity to depolarisation and to halothane appear to be the primary, mutually reinforcing and phenotype-defining defects of halothane-hypersensitive patients with malignant hyperthermia susceptibility.

The Knowledge Profile, Competence and Pending Problems of Chinese Anesthesiologists in Dealing with Malignant Hyperthermia: A Cross-Sectional Survey

Purpose

The National Remote Emergency System for Malignant Hyperthermia (MH-NRES) is an applet in China, designed to help anesthesiologists manage MH crisis. However, there is limited information about encountered difficulties in dealing with MH among Chinese anesthesiologists. The purpose of the study was to explore the current competency and encountered difficulties in the management of MH, as a key first step for assessing the potential user needs to develop the MH-NRES.

Methods

The hospitals of different levels in different provinces across China were invited to participate in an online survey from November to December 2021. Anesthesiologists completed the online questionnaire containing four sections including demographic information, knowledge, competency, and continuing education about MH.

Results

A total of 1357 valid questionnaires were completed from anesthesiologists, most respondents (66.7%, n = 905) correctly answered the MH trigger drugs included volatile anesthetics and succinylcholine. However, most respondents (77.0%, n = 1045) did not know that the recommended initial dose of domestic dantrolene. Up to 83.9% (n = 1138) stated that their hospitals did not store dantrolene for MH emergency. More than half of respondents thought that it would take more than one hour to obtain dantrolene in emergency. Less work experiences, lower levels of hospital and educations and professional titles were associated with lower competency scores in managing MH. Only 31.0% (n = 936) reported that their hospital had ever conducted MH continuing education curricula. Scenario simulation is the training method that most interests the participants (79.0%, n = 1072) but a whopping 46.9% (n = 637) never received simulation.

Conclusion

The study indicated that difficulty in obtaining dantrolene, lack of competency in management of MH, difficulty in obtaining professional help, and poor teamwork were the main problems of most anesthesiologists in face of MH.

An Unusual Combination of Arthrogryposis, Gastroschisis, Cecal Volvulus, and Malignant Hyperthermia in a Young Woman: A Case Report

BACKGROUND The purpose of this study is to discuss a patient with a history of conditions, including arthrogryposis, gastroschisis, and malignant hyperthermia, who presented with cecal volvulus requiring urgent surgical intervention. CASE REPORT A 29-year-old woman with a history of arthrogryposis, gastroschisis, malignant hyperthermia, and multiple childhood abdominal surgeries presents to the Emergency Department (ED) with 2 days of abdominal pain and bloody diarrhea. A CT abdomen/pelvis revealed findings concerning for a cecal volvulus. The patient was premedicated and monitored closely by the anesthesia team due to her history of malignant hyperthermia. She underwent an exploratory laparotomy, where a dilated cecum and proximal ascending colon were found to be completely volvulized around the mesentery. Manual bowel detorsion was performed, which resulted in reperfusion of the ischemic-appearing bowel, which then appeared viable. She recovered well after the procedure and was discharged on postoperative day 5. CONCLUSIONS This case highlights a patient who presented with a combination of 4 findings: arthrogryposis, gastroschisis, malignant hyperthermia, and cecal volvulus. With arthrogryposis reported to be associated with gastroschisis and malignant hyperthermia, this report not only corroborates this association, but also aims to draw attention to the fact that these conditions have potential to occur jointly with cecal volvulus. Given the patient's history of gastroschisis requiring extensive abdominal surgeries that contribute as risk factors for cecal volvulus, it is possible there may be other arthrogryposis patients who present with cecal volvulus similar to that seen in this patient.

Malignant hyperthermia in maxillofacial surgery: Literature review supported by case presentation

OBJECTIVE

Malignant hyperthermia (MH) is characterized by a state of hypermetabolism after exposure to halogenated inhalational anesthetics or succinylcholine. The aims of this study were to carry out an updated review on the subject and report an illustrative case of MH in urgent maxillofacial surgery.

MATERIAL AND METHODS

A search of the PubMed/MEDLINE database using the keyword "malignant hyperthermia" was performed including articles published over the last 11 years in English, Spanish or Portuguese. Exclusion criteria were similar presentations but not associated with MH and cases not related to the use of anesthetic drugs as a trigger of the condition.

CASE REPORT

A 45-year-old man (75 kg, ASA status IE) with a negative family history for neuromuscular diseases, victim of a car accident with a facial fracture, underwent surgery under balanced general anesthesia and developed signs of MH 4 h after anesthesia induction. In our patient, the causative agent was sevoflurane and the diagnosis of MH was confirmed, subsequently, by muscle biopsy.

RESULTS/DISCUSSION

Overall, 44 cases of MH were found. According to the recent literature, MH shows a male predilection (3:1) and the mean age of patients is 32.2 ± 22.2 years. The most frequently cited causative agents were sevoflurane (30.5%), isoflurane (22.2%), and sevoflurane + succinylcholine (13.8%). The most common clinical indicators included hypercarbia (88.8%), hyperthermia (86.1%), and tachycardia (63.8%). Dantrolene was administered in 24 cases. The outcome was favorable in 31 cases (86.1%). The in vitro muscle contracture test (IVCT) was performed in only 15 patients and all of them tested positive. In our patient, the causative agent was sevoflurane and the diagnosis of MH was confirmed by muscle biopsy.

CONCLUSION

The mortality from MH is still high and an early clinical diagnosis and specific treatment with dantrolene are necessary for a favorable outcome. A complete understanding will allow better management of patients with MH. At present, the best management is to identify susceptible patients and to avoid triggering agents, combined with vigilant monitoring.

Clinical Features of Suspected Malignant Hyperthermia in China from 2015 to 2020: A Retrospective Study from China Malignant Hyperthermia Emergency Assistance Group

Purpose

Malignant hyperthermia (MH) is a rare but fatal pharmacogenetic disorder, triggered by inhalational anesthetics or succinylcholine. Since the first nonprofit academic organization China Malignant Hyperthermia Emergency Assistance WeChat-based Group (CMHEA Group) was established in 2015, they have actively participated in the diagnosis and treatment of MH patients. Based on the CMHEA Group, the aim of the study was to retrospectively analyze the characteristics of suspected MH in China from 2015 to 2020.

Methods

We conducted a retrospective analysis of the suspected MH patients from 2015 to 2020, for analyzing the current clinical diagnosis, treatment and prognosis of MH in China.

Results

A total of 58 suspected MH cases occurred from 2015 to 2020, of these, 36 cases were collected with detailed data. The MH clinical grading score of 36 patients ranged from 33 to 73, with a median of 55. Abnormal hyperthermia and hypercarbia were the most common early signs of MH. Four patients were confirmed carrying six different potential MH-causative mutations. Of the total 58 cases, 14 patients (24.1%) received dantrolene and the whole mortality rate was 53.4%. Compared to the patients not receiving dantrolene treatment, the survival rate of patients receiving dantrolene treatment was significantly higher than that of patients not receiving dantrolene (78.6% vs 36.4%, p = 0.007).

Conclusion

The current main diagnostic methods of suspected MH in China are still clinical diagnosis. Hence, it is critical to keep dantrolene for immediate accessibility with the introduction of domestic dantrolene to China. The WeChat group model has played an important but limited role in quick diagnosis and treatment of MH.

European Neuromuscular Centre consensus statement on anaesthesia in patients with neuromuscular disorders

BACKGROUND AND PURPOSE

Patients with neuromuscular conditions are at increased risk of suffering perioperative complications related to anaesthesia. There is currently little specific anaesthetic guidance concerning these patients. Here, we present the European Neuromuscular Centre (ENMC) consensus statement on anaesthesia in patients with neuromuscular disorders as formulated during the 259th ENMC Workshop on Anaesthesia in Neuromuscular Disorders.

METHODS

International experts in the field of (paediatric) anaesthesia, neurology, and genetics were invited to participate in the ENMC workshop. A literature search was conducted in PubMed and Embase, the main findings of which were disseminated to the participants and presented during the workshop. Depending on specific expertise, participants presented the existing evidence and their expert opinion concerning anaesthetic management in six specific groups of myopathies and neuromuscular junction disorders. The consensus statement was prepared according to the AGREE II (Appraisal of Guidelines for Research &amp; Evaluation) reporting checklist. The level of evidence has been adapted according to the SIGN (Scottish Intercollegiate Guidelines Network) grading system. The final consensus statement was subjected to a modified Delphi process.

RESULTS

A set of general recommendations valid for the anaesthetic management of patients with neuromuscular disorders in general have been formulated. Specific recommendations were formulated for (i) neuromuscular junction disorders, (ii) muscle channelopathies (nondystrophic myotonia and periodic paralysis), (iii) myotonic dystrophy (types 1 and 2), (iv) muscular dystrophies, (v) congenital myopathies and congenital dystrophies, and (vi) mitochondrial and metabolic myopathies.

CONCLUSIONS

This ENMC consensus statement summarizes the most important considerations for planning and performing anaesthesia in patients with neuromuscular disorders.

Neuromuscular symptoms in patients with RYR1-related malignant hyperthermia and rhabdomyolysis

Malignant hyperthermia and exertional rhabdomyolysis have conventionally been considered episodic phenotypes that occur in otherwise healthy individuals in response to an external trigger. However, recent studies have demonstrated a clinical and histopathological continuum between patients with a history of malignant hyperthermia susceptibility and/or exertional rhabdomyolysis and RYR1-related congenital myopathies. We hypothesize that patients with a history of RYR1-related exertional rhabdomyolysis or malignant hyperthermia susceptibility do have permanent neuromuscular symptoms between malignant hyperthermia or exertional rhabdomyolysis episodes. We performed a prospective cross-sectional observational clinical study of neuromuscular features in patients with a history of RYR1-related exertional rhabdomyolysis and/or malignant hyperthermia susceptibility (n = 40) compared with healthy controls (n = 80). Patients with an RYR1-related congenital myopathy, manifesting as muscle weakness preceding other symptoms as well as other (neuromuscular) diseases resulting in muscle weakness were excluded. Study procedures included a standardized history of neuromuscular symptoms, a review of all relevant ancillary diagnostic tests performed up to the point of inclusion and a comprehensive, standardized neuromuscular assessment. Results of the standardized neuromuscular history were compared with healthy controls. Results of the neuromuscular assessment were compared with validated reference values. The proportion of patients suffering from cramps (P < 0.001), myalgia (P < 0.001) and exertional myalgia (P < 0.001) was higher compared with healthy controls. Healthcare professionals were consulted because of apparent neuromuscular symptoms by 17/40 (42.5%) patients and 7/80 (8.8%) healthy controls (P < 0.001). Apart from elevated creatine kinase levels in 19/40 (47.5%) patients and mild abnormalities on muscle biopsies identified in 13/16 (81.3%), ancillary investigations were normal in most patients. The Medical Research Council sum score, spirometry and results of functional measurements were also mostly normal. Three of 40 patients (7.5%) suffered from late-onset muscle weakness, most prominent in the proximal lower extremity muscles. Patients with RYR1 variants resulting in malignant hyperthermia susceptibility and/or exertional rhabdomyolysis frequently report additional neuromuscular symptoms such as myalgia and muscle cramps compared with healthy controls. These symptoms result in frequent consultation of healthcare professionals and sometimes in unnecessary invasive diagnostic procedures. Most patients do have normal strength at a younger age but may develop muscle weakness later in life.

Defective ryanodine receptor N-terminus inter-subunit interaction is a common mechanism in neuromuscular and cardiac disorders

The ryanodine receptor (RyR) is a homotetrameric channel mediating sarcoplasmic reticulum Ca2+ release required for skeletal and cardiac muscle contraction. Mutations in RyR1 and RyR2 lead to life-threatening malignant hyperthermia episodes and ventricular tachycardia, respectively. In this brief report, we use chemical cross-linking to demonstrate that pathogenic RyR1 R163C and RyR2 R169Q mutations reduce N-terminus domain (NTD) tetramerization. Introduction of positively-charged residues (Q168R, M399R) in the NTD-NTD inter-subunit interface normalizes RyR2-R169Q NTD tetramerization. These results indicate that perturbation of NTD-NTD inter-subunit interactions is an underlying molecular mechanism in both RyR1 and RyR2 pathophysiology. Importantly, our data provide proof of concept that stabilization of this critical RyR1/2 structure-function parameter offers clear therapeutic potential.

Perioperative management of malignant hyperthermia during general anesthesia: A report of two cases

Malignant hyperthermia (MH) is a lethal complication associated with general anesthesia characterized by sudden onset, rapid progression, and high mortality. We present two seemingly typical cases of intraoperative MH development, with details on perioperative assessment and rescue. Postoperative genetic test showed mutations in the ryanodine receptor type 1 gene.

Gene Panel Sequencing Identifies a Novel RYR1 p.Ser2300Pro Variant as Candidate for Malignant Hyperthermia with Multi-Minicore Myopathy

Malignant hyperthermia (MH), a rare autosomal dominant pharmacogenetic disorder of skeletal muscle calcium regulation, is triggered by sevoflurane in susceptible individuals. We report a Korean having MH with multi-minicore myopathy functionally supported by RYR1-mediated intracellular Ca2+ release testing in B lymphocytes. A 14-year-old boy was admitted for the evaluation of progressive torticollis accompanied by cervicothoracic scoliosis. During the preoperative drape of the patient for the release of the sternocleidomastoid muscle under general anesthesia, his wrist and ankle were observed to have severe flexion contracture. The body temperature was 37.1 °C. To treat MH, the patient was administered a bolus of dantrolene intravenously (1.5 mg/kg) and sodium bicarbonate. After a few minutes, muscle rigidity, tachycardia, and EtCO2 all resolved. Next-generation panel sequencing for hereditary myopathy identified a novel RYR1 heterozygous missense variant (NM_000540.2: c.6898T > C; p.Ser2300Pro), which mapped to the MH2 domain of the protein, a hot spot for MH mutations. Ex vivo RYR1-mediated intracellular Ca2+ release testing in B lymphocytes showed hypersensitive Ca2+ responses to isoflurane and caffeine, resulting in an abnormal Ca2+ release only in the proband, not in his family members. Our findings expand the clinical and pathological spectra of information associated with MH with multi-minicore myopathy.

Heat-hypersensitive mutants of ryanodine receptor type 1 revealed by microscopic heating

Malignant hyperthermia (MH) is a life-threatening disorder caused largely by mutations in ryanodine receptor type 1 (RyR1) Ca²⁺-release channels. Enhanced Ca²⁺ release through the mutant channels induces excessive heat development upon exposure to volatile anesthetics. However, the mechanism by which Ca²⁺ release is accelerated at an elevated temperature is yet to be identified. Fluorescence Ca²⁺ imaging with rapid heating by an infrared laser beam provides direct evidence that heat induces Ca²⁺ release through the RyR1 channel. And the mutant channels are more heat sensitive than the wild-type channels, thereby causing an increase in the cytosolic Ca²⁺ concentration in mutant cells. It is likely that the heat-induced Ca²⁺ release participates as an enhancer in the cellular mechanism of MH.

Thermoregulation is an important aspect of human homeostasis, and high temperatures pose serious stresses for the body. Malignant hyperthermia (MH) is a life-threatening disorder in which body temperature can rise to a lethal level. Here we employ an optically controlled local heat-pulse method to manipulate the temperature in cells with a precision of less than 1 °C and find that the mutants of ryanodine receptor type 1 (RyR1), a key Ca²⁺ release channel underlying MH, are heat hypersensitive compared with the wild type (WT). We show that the local heat pulses induce an intracellular Ca²⁺ burst in human embryonic kidney 293 cells overexpressing WT RyR1 and some RyR1 mutants related to MH. Fluorescence Ca²⁺ imaging using the endoplasmic reticulum–targeted fluorescent probes demonstrates that the Ca²⁺ burst originates from heat-induced Ca²⁺ release (HICR) through RyR1-mutant channels because of the channels’ heat hypersensitivity. Furthermore, the variation in the heat hypersensitivity of four RyR1 mutants highlights the complexity of MH. HICR likewise occurs in skeletal muscles of MH model mice. We propose that HICR contributes an additional positive feedback to accelerate thermogenesis in patients with MH.

Donating Dantrolene: Development and Implementation of a Malignant Hyperthermia Program in a Scarce Resource Setting

Intravenous dantrolene is the first-line treatment of malignant hyperthermia (MH), however, it is not always accessible in lower-middle income countries (LMICs). Facilities in the United States are in a transition period where dantrolene is being replaced with Ryanodex, therefore, there is an opportunity for excess dantrolene to be utilized in LMICs where neither dantrolene nor Ryanodex exist. Thirty-six vials of recently expired, unused dantrolene were obtained for a hospital in a LMIC and an MH program was developed in conjunction with the Lao Friends Hospital for Children (LFHC) anesthesia providers, LFHC liaison, LFHC leadership team, and an expert in the field of MH. Components of the MH program included developing a facility-specific protocol, treatment guidelines, supply list, and educational tools. A designated MH drawer was also created in preparation for an MH event. By procuring dantrolene and implementing an MH program in a facility where no MH protocol, treatment guidelines, supply list, or educational tools existed, LFHC is better equipped to handle a potentially lethal scenario.

Molecular mechanism of the severe MH/CCD mutation Y522S in skeletal ryanodine receptor (RyR1) by cryo-EM

Ryanodine receptors (RyRs) are main regulators of intracellular Ca²⁺ release and muscle contraction. The Y522S mutation of RyR1 causes central core disease, a weakening myopathy, and malignant hyperthermia, a sudden and potentially fatal response to anesthetics or heat. Y522 is in the core of the N-terminal subdomain C of RyR1 and the mechanism of how this mutation orchestrates malfunction is unpredictable for this 2-MDa ion channel, which has four identical subunits composed of 15 distinct cytoplasmic domains each. We expressed and purified the RyR1 rabbit homolog, Y523S, from HEK293 cells and reconstituted it in nanodiscs under closed and open states. The high-resolution cryogenic electron microscopic (cryo-EM) three-dimensional (3D) structures show that the phenyl ring of Tyr functions in a manner analogous to a "spacer" within an α-helical bundle. Mutation to the much smaller Ser alters the hydrophobic network within the bundle, triggering rearrangement of its α-helices with repercussions in the orientation of most cytoplasmic domains. Examining the mutation-induced readjustments exposed a series of connected α-helices acting as an ∼100 Å-long lever: One end protrudes toward the dihydropyridine receptor, its molecular activator (akin to an antenna), while the other end reaches the Ca²⁺ activation site. The Y523S mutation elicits channel preactivation in the absence of any activator and full opening at 1.5 µM free Ca²⁺, increasing by ∼20-fold the potency of Ca²⁺ to activate the channel compared with RyR1 wild type (WT). This study identified a preactivated pathological state of RyR1 and a long-range lever that may work as a molecular switch to open the channel.

Mapping the current evidence on the anesthetic management of adult patients with neuromuscular disorders-a scoping review

PURPOSE

Patients with neuromuscular disorders (NMDs) are at increased risk of perioperative complications. The objective of this scoping review was to examine emerging evidence from published studies, case reports, and review articles on anesthetic management of patients with NMDs, following the methodological frame for scoping reviews.

SOURCES

We searched PubMed and EMBASE for articles published between 1 January 2000 and 14 July 2021.

PRINCIPAL FINDINGS

Three prospective and 21 retrospective studies on altered pharmacokinetics and pharmacodynamics of neuromuscular blocking agents (NMBA) in NMD patients were included. Furthermore, 168 case reports/series reporting 212 anesthetics in 197 patients were included. These studies showed that preanesthetic neuromuscular monitoring can be used for precise NMBA dosing in myasthenia gravis patients. Sugammadex was associated with fewer postoperative myasthenic crises. Perioperative complications were not associated with specific anesthetic agents. Case reports/series showed that in 32% (67/212) of anesthetics, at least one complication was reported. Unexpected intensive care unit admission was a frequently reported complication. Patients with a complicated disease course may have had a higher use of succinylcholine (unadjusted relative risk, 0.13; 95% confidence interval [CI], 0.20 to 0.86) and volatile anesthetics (adjusted odds ratio [OR], 0.38; 95% CI, 0.20 to 0.73; P = 0.004).

CONCLUSION

Evidence on the anesthetic management and perioperative complications of patients with NMDs is mainly based on small retrospective studies and case reports. Further clinical trials or large retrospective studies are required to investigate the choice of safe anesthetic agents. Main areas of interest are the potential benefits of neuromuscular monitoring and sugammadex and the risks possibly associated with volatile anesthetics and succinylcholine.

The effects of dantrolene in the presence or absence of ryanodine receptor type 1 variants in individuals predisposed to malignant hyperthermia

Dantrolene is currently the only drug known to specifically treat malignant hyperthermia (MH) crises. Although dantrolene attenuates Ca²⁺ disorders by acting mainly on the ryanodine receptor type 1 (RYR1), some patients who manifest MH without RYR1 variants have also been successfully treated with dantrolene. Thus, dantrolene appears to have an inhibitory effect on patients with and without RYR1 variants. This study aimed to investigate whether the effects of dantrolene differed depending on the presence or absence of RYR1 variants using muscle cells from MH-predisposed individuals. The study participants were individuals diagnosed with MH predisposition by the Ca²⁺-induced Ca²⁺ release rate test. They were genetically tested and divided into two groups: with and without RYR1 variants. We investigated whether these two groups showed differences in the changes in the half-maximal effective concentration (EC₅₀) for caffeine and the resting intracellular Ca²⁺ concentration ([Ca²⁺]_i) before and after dantrolene administration. Dantrolene administration significantly increased the EC₅₀ (P < 0.0001) and decreased the resting [Ca²⁺]_i (P < 0.0001). The inhibitory effects of dantrolene and the presence of RYR1 variants showed no statistically significant interactions related to the EC₅₀ (P = 0.59) and resting [Ca²⁺]_i (P = 0.21). In conclusion, the presence or absence of RYR1 variants does not appear to influence the effect of dantrolene.

In vitro contractile studies within isolated tissue baths: Translational research from Visible Heart® Laboratories

The isolated tissue bath research methodology was first developed in 1904. Since then, it has been recognized as an important tool in pharmacology and physiology research, including investigations into neuromuscular disorders. The tissue bath is still used routinely as the instrument for performing the "gold standard" test for clinical diagnosis of malignant hyperthermia susceptibility - the caffeine-halothane contracture test. Our research group has utilized this tool for several decades for a range of research studies, and we are currently one of four North American diagnostic centers for determining susceptibility for malignant hyperthermia. This review provides a brief summary of some of the historical uses of the tissue bath. Important experimental considerations for the operation of the tissue bath are further described. Finally, we discuss the different studies our group has performed using isolated tissue baths to highlight the broad potential applications.

Simultaneous malignant hyperthermia reactions in two siblings during living donor liver transplantation

We report a case of simultaneous malignant hyperthermia reactions occurring in two siblings during living donor liver transplantation. This report highlights the conflicting goals in the clinical management of liver transplantation and malignant hyperthermia, including the use of total intravenous anaesthesia and dantrolene in the face of the potential for drug-induced hepatotoxicity in the remnant liver or transplanted liver graft, as well as cautious fluid management needed for liver transplantation balanced against the liberal fluid therapy required to prevent acute kidney injury associated with malignant hyperthermia. The logistical challenges of managing this emergency in two closely related patients are discussed, including rapid preparation of two vapour-free anaesthesia machines, the need for availability of additional dantrolene and the requirement for additional personnel. Prompt recognition, immediate removal of the triggering agents and conversion to total intravenous anaesthesia helped to curtail the malignant hyperthermic reactions in our patients, both of whom made a full recovery.

A case of blepharophimosis: Freeman Sheldon syndrome

PURPOSE

Important implications exist for ophthalmologists when considering possible early surgical intervention for potential amblyogenic anatomical abnormalities. The authors discuss the risks and benefits from an ophthalmological perspective of different interventions and review the genetic testing that confirmed the diagnosis.

OBSERVATIONS

The authors describe the findings and management of an infant with Freeman Sheldon syndrome presenting with blepharophimosis of both eyelids resulting in inability to open both eyes during the first several days of life. Although the mode of inheritance for Freeman Sheldon syndrome (formerly known as Whistling Face Syndrome) is often autosomal dominant, our patient had no known family history of congenital abnormalities or consanguinity. However, genetic testing confirmed a heterozygous variant in MYH3, consistent with autosomal dominant Freeman Sheldon Syndrome. When our patient required gastrostomy (G-tube_placement, we performed an exam under anesthesia (EUA)). As is typical for Freeman Sheldon syndrome patients, intubation was difficult and complicated by pneumothorax. Eye-opening improved slightly after several weeks of life; however, the decision was made to proceed with eyelid surgery to prevent deprivation amblyopia. Surgery is scheduled for a future date. Additionally, the patient had congenital nasolacrimal duct obstruction of the left eye; however, a probing and irrigation failed because of obstruction from the abnormal facial anatomy.

CONCLUSIONS AND IMPORTANCE

Patients with Freeman Sheldon syndrome are at increased risk for complications from anesthesia and surgery. Risks and benefits should be strongly considered and discussed with parent(s)/guardian(s) prior to any surgical intervention. Genetic testing of the MYH3 gene can confirm the diagnosis.

Spinal cord injury-related thermoregulatory impairment masks a fatal malignant hyperthermia crisis: a case report

PURPOSE

Malignant hyperthermia (MH) is a hypermetabolic disorder that can occur in genetically susceptible individuals exposed to halogenated anesthetics and succinylcholine. Spinal cord injury (SCI) above the sixth thoracic vertebra is associated with dysfunction of the sympathetic/parasympathetic nervous pathways, including thermoregulatory dysfunction, presenting as hypothermia in cold environments because of vasodilation and heat loss. This effect could mitigate or obscure an MH episode. Here, we describe development of a fatal MH crisis in a patient with SCI.

CLINICAL FEATURES

A 27-yr-old male patient with an SCI after fracture of the sixth cervical vertebra was admitted for spinal arthrodesis. Anesthetic medications included remifentanil, propofol, succinylcholine, rocuronium, and isoflurane. After the start of the surgery, muscular contractures resembling myoclonus were noted, which resolved with pancuronium administration. Four hours after the start of anesthesia, the patient presented with hyperthermia, hypercarbia, hypotension, muscle rigidity, arrhythmia, and cardiogenic shock, with metabolic/respiratory acidosis. Malignant hyperthermia was suspected and the treatment was started, but he developed cardiopulmonary arrest and died an hour and a half after the first cardiac arrest. Both parents were investigated and were found to have normal creatine kinase levels and positive in vitro contracture tests. His mother carried a variant in the ryanodine receptor type 1 (RYR1) gene (c.14918C>T), which is associated with MH.

CONCLUSION

Spinal cord injury-induced thermoregulatory dysfunction may obscure the early diagnosis of MH and lead to fatal outcome.

Inhalational Anesthesia for Near-fatal Pediatric Asthma Complicated by Malignant Hyperthermia

Acute severe asthma is a commonly encountered condition in the pediatric emergency room and the pediatric intensive care unit (PICU). Its treatment involves the use of bronchodilatory agents acting on different receptors, steroids to reduce ongoing inflammation, and non-invasive or invasive mechanical ventilation to offload the increased work of breathing from the respiratory muscles. Patients refractory to these therapies may require the use of inhaled anesthetic agents and extracorporeal gas exchange (ECMO) for life-threatening asthma exacerbations. Depending on institutional protocols, the use of these therapies may vary. The use of inhaled anesthetic agents for asthma management in the PICU is infrequent and is limited to centers with specialized equipment. Commonly encountered side effects include hypotension, arrhythmias, and delirium. Malignant hyperthermia (MH) is a well-known but infrequent side effect of inhaled anesthetic use, depolarizing muscle agents, and has not been described in the PICU following the use of anesthetics for pediatric asthma.

Malignant Hyperthermia Preparedness Training: Using Cognitive Aids and Emergency Checklists in the Perioperative Setting

PURPOSE

The purpose of this project was to prepare perioperative staff at a military ambulatory surgical center to respond to a malignant hyperthermia crisis effectively with the assistance the Stanford emergency manual cognitive aid.

DESIGN

This is an evidence-based practice improvement project.

METHODS

Multidisciplinary perioperative staff at a military ambulatory surgical center participated in an in-service about the Stanford emergency manual cognitive aid tool, and a simulation exercise was conducted to practice using the tool during a malignant hyperthermia crisis. Preproject and postproject implementation surveys were to used to measure staff perceptions of and willingness to use cognitive aids/emergency checklists during perioperative emergencies.

FINDINGS

Staff positive perception of and willingness to use the Stanford emergency manual cognitive aid improved after implementation of an education session and simulation exercise with the checklist tool.

CONCLUSIONS

Introduction of the Stanford emergency manual cognitive aid to multidisciplinary perioperative staff with an in-service and simulated malignant hyperthermia scenario improved staff perception of cognitive aid use during emergencies. Use of cognitive aid checklists during simulated perioperative emergencies was shown to reduce missed critical treatment steps.

The neuromuscular and multisystem features of RYR1-related malignant hyperthermia and rhabdomyolysis: A study protocol

INTRODUCTION

Malignant hyperthermia (MH) and exertional rhabdomyolysis (ERM) have long been considered episodic phenotypes occurring in response to external triggers in otherwise healthy individuals with variants in RYR1. However, recent studies have demonstrated a clinical and histopathological continuum between patients with RYR1-related congenital myopathies and those with ERM or MH susceptibility. Furthermore, animal studies have shown non-neuromuscular features such as a mild bleeding disorder and an immunological gain-of-function associated with MH/ERM related RYR1 variants raising important questions for further research. Awareness of the neuromuscular disease spectrum and potential multisystem involvement in RYR1-related MH and ERM is essential to optimize the diagnostic work-up, improve counselling and and future treatment strategies for patients affected by these conditions. This study will examine in detail the nature and severity of continuous disease manifestations and their effect on daily life in patients with RYR1-related MH and ERM.

METHODS

The study protocol consists of four parts; an online questionnaire study, a clinical observational study, muscle imaging, and specific immunological studies. Patients with RYR1-related MH susceptibility and ERM will be included. The imaging, immunological and clinical studies will have a cross-sectional design, while the questionnaire study will be performed three times during a year to assess disease impact, daily living activities, fatigue and pain. The imaging study consists of muscle ultrasound and whole-body magnetic resonance imaging studies. For the immunological studies, peripheral mononuclear blood cells will be isolated for in vitro stimulation with toll-like receptor ligands, to examine the role of the immune system in the pathophysiology of RYR1-related MH and ERM.

DISCUSSION

This study will increase knowledge of the full spectrum of neuromuscular and multisystem features of RYR1-related MH and ERM and will establish a well-characterized baseline cohort for future studies on RYR1-related disorders. The results of this study are expected to improve recognition of RYR1-related symptoms, counselling and a more personalized approach to patients affected by these conditions. Furthermore, results will create new insights in the role of the immune system in the pathophysiology of MH and ERM.

TRIAL REGISTRATION

This study was pre-registered at ClinicalTrials.gov (ID: NCT04610619).

The effect of statins on RyR and RyR-associated disease

We sought to review the effects of statins on the ryanodine receptor (RyR) and on RyR-associated diseases, with an emphasis on catecholaminergic polymorphic ventricular tachycardia (CPVT). Statins can affect skeletal muscle and produce statin-associated muscle symptoms (SAMS) but have no adverse effects on cardiac muscle. These contrasting effects may be due to differences in how statins affect the skeletal (RyR1) and cardiac (RyR2) RyR. We searched PubMed to identify English language articles reporting the pathophysiology of the RyR, the effect of statins on RyR function, and on RyR-associated genetic diseases. We selected 150 articles for abstract review, 96 of which provided sufficient information to be included and were reviewed in detail. Fifteen articles highlighted the interaction of statins with the RyR. Nine identified the interaction of statins with RyR1, six addressed the interaction of statins with RyR2, 13 suggested that statins reduce ventricular arrhythmias (VA), and seven suggested that statins increase the risk of malignant hyperthermia (MH). In general, statins increase RyR1 and decrease RyR2 activity. We identified no articles examining the effect of statins on CPVT, a condition often caused by defects in RyR2. Statins appear to increase the risk of MH and decrease the risk of ventricular arrhythmia. The effect of statins on CPVT has not been directly examined, but statins' reduction in RyR2 function and their apparent reduction in VA suggest that they may be beneficial in this condition.

Functional Calsequestrin-1 Is Expressed in the Heart and Its Deficiency Is Causally Related to Malignant Hyperthermia-Like Arrhythmia

Background: Calsequestrins (Casqs), comprising the Casq1 and Casq2 isoforms, buffer Ca²⁺ and regulate its release in the sarcoplasmic reticulum (SR) of skeletal and cardiac muscle, respectively. Human inherited diseases associated with mutations in CASQ1 or CASQ2 include malignant hyperthermia/environmental heat stroke (MH/EHS) and catecholaminergic polymorphic ventricular tachycardia. However, patients with an MH/EHS event often suffer from arrhythmia for which the underlying mechanism remains unknown. Methods: Working hearts from conventional (Casq1-KO) and cardiac-specific (Casq1-CKO) Casq1 knockout mice were monitored in vivo and ex vivo by electrocardiogram and electrical mapping, respectively. MH was induced by 2% isoflurane and treated intraperitoneally with dantrolene. Time-lapse imaging was used to monitor intracellular Ca²⁺ activity in isolated mouse cardiomyocytes or neonatal rat ventricular myocytes (NRVMs) with knockdown, over-expression or truncation of the Casq1 gene. Conformational change in both Casqs was determined by crosslinking Western blot analysis. Results: Like MH/EHS patients, Casq1-KO and Casq1-CKO mice had faster basal heart rate, and ventricular tachycardia upon exposure to 2% isoflurane, which could be relieved by dantrolene. Basal sinus tachycardia and ventricular ectopic electrical triggering also occurred in Casq1-KO hearts ex vivo. Accordingly, the ventricular cardiomyocytes from Casq1-CKO mice displayed dantrolene-sensitive increased Ca²⁺ waves and diastole premature Ca²⁺ transients/oscillations upon isoflurane. NRVMs with Casq1-knockdown had enhanced spontaneous Ca2+ sparks/transients upon isoflurane, while cells over-expressing Casq1 exhibited decreased Ca2+ sparks/transients that were absent in cells with truncation of 9 amino acids at the C-terminus of Casq1. Structural evaluation showed that most of the Casq1 protein was present as a polymer and physically interacted with RyR2 in the ventricular SR. The Casq1 isoform was also expressed in human myocardium. Mechanistically, exposure to 2% isoflurane or heating at 41ºC induced Casq1 oligomerization in mouse ventricular and skeletal muscle tissues, leading to a reduced Casq1/RyR2 interaction and increased RyR2 activity in the ventricle. Conclusions: Casq1 is expressed in the heart, where it regulates SR Ca²⁺ release and heart rate. Casq1 deficiency independently causes MH/EHS-like ventricular arrhythmia by trigger-induced Casq1 oligomerization and a relief of its inhibitory effect on RyR2-mediated Ca²⁺ release, thus revealing a new inherited arrhythmia and a novel mechanism for MH/EHS arrhythmogenesis.