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.

A multi-dimensional analysis of genotype-phenotype discordance in malignant hyperthermia susceptibility

BACKGROUND

Malignant hyperthermia (MH) susceptibility is an inherited condition, diagnosed either by the presence of a pathogenic genetic variant or by in vitro caffeine-halothane contracture testing. Through a multi-dimensional approach, we describe the implications of discordance between genetic and in vitro test results in a patient with a family history of possible MH.

METHODS

The patient, whose brother had a possible MH reaction, underwent the caffeine-halothane contracture test (CHCT) according to the North American MH Group protocol. Screening of the complete RYR1 and CACNA1S transcripts was done using Sanger sequencing. Additional functional analyses included skinned myofibre calcium-induced calcium release sensitivity, calcium signalling assays in cultured myotubes, and in silico evaluation of the effect of any genetic variants on their chemical environment.

RESULTS

The patient's CHCT result was negative but she carried an RYR1 variant c.1209C>G, p.Ile403Met, that is listed as pathogenic by the European Malignant Hyperthermia Group. Functional tests indicated a gain-of-function effect with a weak impact, and the variant was predicted to affect the folding stability of the 3D structure of the RyR1 protein. Based on American College of Medical Genetics and Genomics/Association of Molecular Pathology guidelines, this variant would be characterised as a variant of uncertain significance.

CONCLUSIONS

Available data do not confirm or exclude an increased risk of MH for this patient. Further research is needed to correlate RyR1 functional assays, including the current gold standard testing for MH susceptibility, with clinical phenotypes. The pathogenicity of genetic variants associated with MH susceptibility should be re-evaluated.

Anesthesia for muscle biopsy to test susceptibility to malignant hyperthermia

Introduction

Malignant hyperthermia is an autosomal dominant pharmacogenetic disorder, characterized by hypermetabolic crisis triggered by halogenated anesthetics and/or succinylcholine. The standard method for diagnosing malignant hyperthermia susceptibility is the in vitro muscle contracture test in response to halothane-caffeine, which requires muscle biopsy under anesthesia. We describe a series of anesthetic procedures without triggering agents in malignant hyperthermia, comparing peripheral nerve block and subarachnoid anesthesia.

Method

We assessed the anesthetic record charts of 69 patients suspected of malignant hyperthermia susceptibility who underwent muscle biopsy for in vitro muscle contracture in the period of 7 years. Demographic data, indication for malignant hyperthermia investigation, in vitro muscle contracture test results, and surgery/anesthesia/recovery data were analyzed.

Results

Sample with 34 ± 13.7 years, 60.9% women, 65.2% of in vitro muscle contracture test positive. Techniques used: peripheral nerve blocks — lateral femoral and femoral cutaneous, latency 65 ± 41 min — (47.8%); subarachnoid anesthesia (49.3%), and total venous anesthesia (1.4%). There was 39.4% failure of peripheral nerve block and 11.8% of subarachnoid anesthesia. Adverse events (8.7%) occurred only with subarachnoid blockade (bradycardia, nausea, and transient neurological syndrome). All patients remained in the post-anesthesia care unit until discharge. Age and weight were significantly higher in patients with blockade failure (ROC cut-off point of 23.5 years and 59.5 kg) and blockade failure was more frequent in the presence of increased idiopathic creatine kinase.

Conclusion

Anesthesia with non-triggering agents has been shown to be safe in patients with malignant hyperthermia susceptibility. Variables such as age, weight, and history of increased idiopathic creatine kinase may be useful in selecting the anesthetic technique for this group of patients.

[Anesthesia for muscle biopsy to test susceptibility to malignant hyperthermia]

INTRODUCTION

Malignant hyperthermia is an autosomal dominant pharmacogenetic disorder, characterized by hypermetabolic crisis triggered by halogenated anesthetics and/or succinylcholine. The standard method for diagnosing malignant hyperthermia susceptibility is the in vitro muscle contracture test in response to halothane-caffeine, which requires muscle biopsy under anesthesia. We describe a series of anesthetic procedures without triggering agents in malignant hyperthermia, comparing peripheral nerve block and subarachnoid anesthesia.

METHOD

We assessed the anesthetic record charts of 69 patients suspected of malignant hyperthermia susceptibility who underwent muscle biopsy for in vitro muscle contracture in the period of 7 years. Demographic data, indication for malignant hyperthermia investigation, in vitro muscle contracture test results, and surgery/anesthesia/recovery data were analyzed.

RESULTS

Sample with 34±13.7 years, 60.9% women, 65.2% of in vitro muscle contracture test positive. Techniques used: peripheral nerve blocks - lateral femoral and femoral cutaneous, latency 65±41minutes - (47.8%); subarachnoid anesthesia (49.3%), and total venous anesthesia (1.4%). There was 39.4% failure of peripheral nerve block and 11.8% of subarachnoid anesthesia. Adverse events (8.7%) occurred only with subarachnoid blockade (bradycardia, nausea, and transient neurological syndrome). All patients remained in the post-anesthesia care unit until discharge. Age and weight were significantly higher in patients with blockade failure (ROC cut-off point of 23.5 years and 59.5kg) and blockade failure was more frequent in the presence of increased idiopathic creatine kinase.

CONCLUSION

Anesthesia with non-triggering agents has been shown to be safe in patients with malignant hyperthermia susceptibility. Variables such as age, weight, and history of increased idiopathic creatine kinase may be useful in selecting the anesthetic technique for this group of patients.

Masseter muscle rigidity and the role of DNA analysis to confirm malignant hyperthermia susceptibility

Malignant hyperthermia (MH) is an uncommon, autosomal dominant disorder of skeletal muscle, triggered by inhalational anaesthetics or depolarizing muscle relaxants. Masseter muscle rigidity (MMR) can be regarded as potentially a preceding sign for an MH reaction. Susceptibility to MH can be determined by the in vitro contracture test (IVCT) or DNA analysis where a familial variant is known. Our aims were to review patients with MMR, where IVCT and DNA analysis had been undertaken, to determine if DNA analysis could be used as an initial screening tool for MH susceptibility, and, by reviewing standard monitored variables (SMVs), to determine if any clinical characteristics could be used to differentiate between MMR patients who are MH susceptible (MHS) and those who are not. Patients with MMR were identified from the Palmerston North Hospital MH Reactions Database. IVCT and DNA analysis results were documented. DNA testing was performed retrospectively in the majority of patients as many patients had presented before DNA analysis was available. Forty-one patients were analysed. Fourteen were DNA positive/IVCT positive and six DNA positive only (48% in total), seven were IVCT positive/DNA negative and 14 were IVCT normal. Increased creatine kinase (>18,000 units/L) was consistent with MH susceptibility. Severity of MMR was not linked to MH susceptibility. This study confirmed that DNA analysis can be used as a first-line test for MH susceptibility in patients presenting with MMR (consistent with European MH Group recommendations). Creatine kinase was the only SMV that was significantly different between MHS and MH normal individuals.