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.

An Association between OXPHOS-Related Gene Expression and Malignant Hyperthermia Susceptibility in Human Skeletal Muscle Biopsies.

Malignant hyperthermia (MH) is a pharmacogenetic condition of skeletal muscle that manifests in hypermetabolic responses upon exposure to volatile anaesthetics. This condition is caused primarily by pathogenic variants in the calcium-release channel RYR1, which disrupts calcium signalling in skeletal muscle. However, our understanding of MH genetics is incomplete, with no variant identified in a significant number of cases and considerable phenotype diversity. In this study, we applied a transcriptomic approach to investigate the genome-wide gene expression in MH-susceptible cases using muscle biopsies taken for diagnostic testing. Baseline comparisons between muscle from MH-susceptible individuals (MHS, n = 8) and non-susceptible controls (MHN, n = 4) identified 822 differentially expressed genes (203 upregulated and 619 downregulated) with significant enrichment in genes associated with oxidative phosphorylation (OXPHOS) and fatty acid metabolism. Investigations of 10 OXPHOS target genes in a larger cohort (MHN: n = 36; MHS: n = 36) validated the reduced expression of ATP5MD and COQ6 in MHS samples, but the remaining 8 selected were not statistically significant. Further analysis also identified evidence of a sex-linked effect in SDHB and UQCC3 expression, and a difference in ATP5MD expression across individuals with MH sub-phenotypes (trigger from in vitro halothane exposure only, MHSh (n = 4); trigger to both in vitro halothane and caffeine exposure, MHShc (n = 4)). Our data support a link between MH-susceptibility and dysregulated gene expression associated with mitochondrial bioenergetics, which we speculate plays a role in the phenotypic variability observed within MH.

Lethal multiple pterygium syndrome, large cystic hygroma, and cleft palate: Rare and severe fetal presentations of RYR1- and NEB-related congenital myopathies.

Congenital myopathies are a genetically heterogeneous group of neuromuscular disorders that commonly present with congenital hypotonia and weakness but can also present broadly. The most severe presentation is neonatal with arthrogryposis and, rarely, fetal akinesia and pterygia, features also seen in lethal multiple pterygium syndrome (LMPS). We describe two fetuses with similar phenotype, including hydrops fetalis, large cystic hygromas, bilateral talipes, and fetal akinesia in the second trimester. Genetic diagnoses were made using exome sequencing. Both fetuses had a severe form of congenital myopathy. In the first fetus, we identified two novel compound heterozygous likely pathogenic variants consistent with autosomal recessive RYR1-related congenital myopathy (congenital myopathy 1B). In the second fetus, we identified two likely pathogenic variants, one of which is novel, likely in trans consistent with a diagnosis of autosomal recessive NEB-related congenital myopathy. Reaching a genetic diagnosis for these fetuses allowed the families to receive accurate genetic counseling for future pregnancies. These fetuses highlight the genetic and phenotypic heterogeneity of LMPS, and support a broad approach to genetic testing.

The novel rapid formulation of intravenous dantrolene (NPJ5008) versus standard dantrolene (Dantrium®): A clinical part-randomised phase 1 study in healthy volunteers.

BACKGROUND: Delays in treating anaesthesia-induced malignant hyperthermia increase risks of complications and death. NPJ5008 is a novel formulation of the indicated treatment, dantrolene sodium, developed to shorten preparation and administration times compared with the reference formulation Dantrium®. The two formulations have been compared preclinically. OBJECTIVES: Assess bioequivalence of overall dantrolene (free acid) exposure of NPJ5008 versus Dantrium® and ascertain similarities in their pharmacokinetics and safety/tolerability profiles. Evaluate preparation/administration time savings for the new formulation. DESIGN: Part 1 of this open-label trial in humans was a 1 : 1 randomised crossover study; part 2 was a single-arm study. Trial pharmacy data and laboratory simulations assessed preparation/administration step timings. SETTING: Single clinical centre in the UK, April to July 2021. PARTICIPANTS: Twenty-one healthy male and female individuals. INTERVENTIONS: Part 1: single intravenous 60 mg dose of NPJ5008 or Dantrium®, sequentially. Part 2: single intravenous 120 mg dose of NPJ5008. Simulation: five vials per formulation using paediatric and adult cannulas. MAIN OUTCOME MEASURES: Overall drug exposure to last measurable concentration (AUC 0 to last ) and extrapolated to infinity (AUC 0 to ∞ ) were primary endpoints. Other pharmacokinetic, clinical and muscle-function parameters, and adverse events, were monitored. RESULTS: Adjusted geometric mean ratios of NPJ5008 versus Dantrium® were 90.24 and 90.44% for AUC 0 to last and AUC 0 to ∞ , respectively, with the 90% confidence intervals (CI) within the 80 to 125% acceptance interval, establishing bioequivalence. No new safety issues emerged: any adverse events were of a similar magnitude across treatments and related to pharmacological properties of dantrolene. Pharmacy and simulation data revealed that every step in preparation and administration was 26 to 69% faster for NPJ5008 than Dantrium®. CONCLUSION: NPJ5008 showed comparable pharmacokinetic and safety profiles to Dantrium®, while reducing dantrolene dose preparation/administration times, potentially reducing patient complications/healthcare resourcing in malignant hyperthermia. TRIAL REGISTRATION: EudraCT Number: 2020-005719-35, MHRA approval.

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.

Evaluation of Malignant Hyperthermia Features in Patients with Pathogenic or Likely Pathogenic RYR1 Variants Disclosed through a Population Genomic Screening Program.

BACKGROUND: Malignant hyperthermia (MH) susceptibility is a heritable musculoskeletal disorder that can present as a potentially fatal hypermetabolic response to triggering anesthesia agents. Genomic screening for variants in MH-associated genes RYR1 and CACNA1S provides an opportunity to prevent morbidity and mortality. There are limited outcomes data from disclosing variants in RYR1, the most common MH susceptibility gene, in unselected populations. The authors sought to identify the rate of MH features or fulminant episodes after triggering agent exposure in an unselected population undergoing genomic screening including actionable RYR1 variants. METHODS: The MyCode Community Health Initiative by Geisinger (USA) is an electronic health record-linked biobank that discloses pathogenic and likely pathogenic variants in clinically actionable genes to patient-participants. Available electronic anesthesia and ambulatory records for participants with actionable RYR1 results returned through December 2020 were evaluated for pertinent findings via double-coded chart reviews and reconciliation. Descriptive statistics for observed phenotypes were calculated. RESULTS: One hundred fifty-two participants had an actionable RYR1 variant disclosed during the study period. None had previous documented genetic testing for MH susceptibility; one had previous contracture testing diagnosing MH susceptibility. Sixty-eight participants (44.7%) had anesthesia records documenting triggering agent exposure during at least one procedure. None received dantrolene treatment or had documented muscle rigidity, myoglobinuria, hyperkalemia, elevated creatine kinase, severe myalgia, or tea-colored urine. Of 120 possibly MH-related findings (postoperative intensive care unit admissions, hyperthermia, arterial blood gas evaluation, hypercapnia, or tachycardia), 112 (93.3%) were deemed unlikely to be MH events; 8 (6.7%) had insufficient records to determine etiology. CONCLUSIONS: Results demonstrate a low frequency of classic intraanesthetic hypermetabolic phenotypes in an unselected population with actionable RYR1 variants. Further research on the actionability of screening for MH susceptibility in unselected populations, including economic impact, predictors of MH episodes, and expanded clinical phenotypes, is necessary.

Anesthetic Management of Coronary Artery Bypass Grafting in a Patient with Charcot-Marie-Tooth Disease and Multivessel Coronary Artery Disease.

BACKGROUND The anesthetic management of patients with Charcot-Marie-Tooth disease (CMT) requires special deliberation. Previous literature has suggested that patients with CMT may have increased sensitivity to non-depolarizing neuromuscular blocking agents, and hyperkalemia associated with the administration of succinylcholine has been reported. The potential risk of malignant hyperthermia and underlying cardiopulmonary abnormalities, such as pre-existing arrhythmias, cardiomyopathy, or respiratory muscle weakness, must also be considered in patients with CMT. CASE REPORT We describe a case of a patient with a history of CMT and multivessel coronary artery disease who underwent coronary artery bypass grafting (CABG). Careful consideration was given to the anesthetic plan, which consisted of thorough pre- and perioperative evaluation of cardiac function, total intravenous anesthesia with propofol and remifentanil infusions, the use of a non-depolarizing neuromuscular blocking agent, and utilization of a malignant hyperthermia protocol with avoidance of volatile anesthetics to decrease the possible risk of malignant hyperthermia. Following a 3-vessel CABG, no anesthetic or surgical complications were noted and the patient was discharged on postoperative day 6 after an uneventful hospital course. CONCLUSIONS Exacerbation of underlying cardiac and pulmonary abnormalities associated with the pathophysiology of CMT, as well as patient response to neuromuscular blocking and volatile agents, should be of concern for the anesthesiologist when anesthetizing a patient with CMT. Therefore, CMT patients undergoing surgery require special consideration of their anesthetic management plan in order to ensure patient safety and optimize perioperative outcomes.

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.

Functional characterization of RYR1 variants identified in malignant hyperthermia susceptible individuals.

Malignant hyperthermia is a pharmacogenetic disorder triggered by halogenated anesthetic agents in genetically predisposed individuals. Approximately 70 % of these individuals carry mutations in RYR1, the gene encoding the ryanodine receptor calcium channel of skeletal muscle. In this study, we performed functional analysis of 5 RYR1 variants identified in members from 8 families who had been diagnosed by the IVCT. Of the 68 individuals enrolled in the study, 43 were diagnosed as MHS, 23 as MHN, and 2 individuals were not tested. Here we demonstrate that the 5 RyR1 variants cause hypersensitivity to RyR1 agonist-mediated calcium release. According to the EMHG scoring matrix these five genetic variants can be classified as follows: c.8638G>A (p.E2880K) and c.11314C>T (p.R3772W) likely pathogenic, c.11416G>A (p.G3806R), c.14627A>G (p.K4876R) and c.14813T>C (p.I4938T), pathogenic (RefSeq NM_000540.3). We propose that the newly functionally characterized RYR1 variants, be included in the panel of variants to be used for the molecular diagnosis of MHS.

Pancreatitis in RYR1-related disorders.

Mutations in RYR1 encoding the ryanodine receptor (RyR) skeletal muscle isoform (RyR1) are a common cause of inherited neuromuscular disorders. Despite its expression in a wide range of tissues, non-skeletal muscle manifestations associated with RYR1 mutations have only been rarely reported. Here, we report three patients with a diagnosis of Central Core Disease (CCD), King-Denborough Syndrome (KDS) and Malignant Hyperthermia Susceptibility (MHS), respectively, who in addition to their (putative) RYR1-related disorder also developed symptoms and signs of acute pancreatitis. In two patients, episodes were recurrent, with severe multisystem involvement and sequelae. RyR1-mediated calcium signalling plays an important role in normal pancreatic function but has also been critically implicated in the pathophysiology of acute pancreatitis, particularly in bile acid- and ethanol-induced forms. Findings from relevant animal models indicate that pancreatic damage in these conditions may be ameliorated through administration of the specific RyR1 antagonist dantrolene and other compounds modifying pancreatic metabolism including calcium signalling. These observations suggest that patients with RYR1 gain-of-function variants may be at increased risk of developing acute pancreatitis, a condition which should therefore be considered in the health surveillance of such individuals.

Congenital Myasthenic Syndrome With Malignant Hyperthermia Susceptibility in a Child Undergoing Adenotonsillectomy for Obstructive Sleep Apnea: A Case Report.

Congenital myasthenic syndromes are rare genetic diseases involving pathologic proteins in the neuromuscular junction. Malignant hyperthermia susceptibility is a genetic disorder involving a hypermetabolic response to volatile anesthetics and depolarizing neuromuscular blocking agents. We present the first reported case of a 3-year-old boy with both congenital myasthenic syndrome and malignant hyperthermia susceptibility, resulting from a mutation in the ryanodine receptor type 1 gene, who underwent an adenotonsillectomy for severe obstructive sleep apnea. We discuss the anesthetic challenges in navigating these 3 comorbidities in the setting of airway surgery.

A WeChat applet-based national remote emergency system for malignant hyperthermia in China: a usability study.

BACKGROUND: Malignant hyperthermia (MH) is a rare anesthetic emergency with a high mortality rate in China. We developed a WeChat applet-based National Remote Emergency System for Malignant Hyperthermia (MH-NRES) to provide a real-time emergency system to help Chinese anesthesiologists deal with MH crises. However, it is imperative that close attention should be paid to the usability of the applet. PURPOSE: The objectives of this study were to (1) evaluate the usability of the applet-based MH-NRES for anesthesiologists; and (2) to test the validity and reliability of a modified mHealth app usability questionnaire. METHODS: A modified User Version of the Mobile Application Rating Scale (uMARS) was designed. Together with System Usability Scale (SUS) and Post-Study System Usability Questionnaire (PSSUQ), another two well-validated questionnaires, uMARS were then used to evaluate the usability of MH-NRES. The Cronbach alpha of the total score and the subscales of uMARS was calculated to evaluate the internal consistency. The correlation coefficients among three questionnaires were calculated. RESULTS: In this study, 118 anesthesiologists provided responses to the questionnaire. The overall mean uMARS score was 4.43 ± 0.61, which ranged from 3 to 5. The mean PSSUQ score were in good to excellent range with mean of 6.02 ± 0.97, which ranged from 3.19 to 7. The overall SUS score was 76.0 ± 17.6, which ranged from 45 to 100. The total uMARS score had excellent internal consistency (Cronbach alpha = 0.984). uMARS and its subscales were strongly correlated with PSSUQ (coefficient 0.758-0.819, P < 0.001) and SUS (coefficient 0.535-0.561, P < 0.001), respectively. CONCLUSIONS: Data obtained from the usability evaluation questionnaires in this study indicated a high quality of the MH-NRES on the ease of use, satisfaction and perceived usefulness, which suggest this system might be a useful tool for anesthesiologists' education and management of MH crises. Future feedback from high-fidelity simulation and clinical scenarios are need for further usability evaluation of this system.

Watchful Eye Prevents Catastrophe in Case of Malignant Hyperthermia: A Case Report.

CASE: A 49-year-old woman presented with a displaced left posterior wall acetabular fracture-dislocation and a left comminuted intra-articular distal radius fracture sustained in a motor vehicle accident. Fifteen minutes after anesthesia induction for operative fixation of the fractures, the patient experienced severe hypertension, increased end-tidal carbon dioxide, and fever. A diagnosis of malignant hyperthermia (MH) was made before incision. The patient was medically stabilized, and her acetabular fracture-dislocation was placed in skeletal traction until she was deemed fit for surgery 4 days later. CONCLUSION: This case report highlights the importance of early recognition of MH and perioperative management.