Myopathic manifestations across the adult lifespan of patients with malignant hyperthermia susceptibility: a narrative review

Malignant hyperthermia susceptibility (MHS) designates individuals at risk of developing a hypermetabolic reaction triggered by halogenated anaesthetics or the depolarising neuromuscular blocking agent suxamethonium. Over the past few decades, beyond the operating theatre, myopathic manifestations impacting daily life are increasingly recognised as a prevalent phenomenon in MHS patients. At the request of the European Malignant Hyperthermia Group, we reviewed the literature and gathered the opinion of experts to define MHS-related myopathy as a distinct phenotype expressed across the adult lifespan of MHS patients unrelated to anaesthetic exposure; this serves to raise awareness about non-anaesthetic manifestations, potential therapies, and management of MHS-related myopathy. We focused on the clinical presentation, biochemical and histopathological findings, and the impact on patient well-being. The spectrum of symptoms of MHS-related myopathy encompasses muscle cramps, stiffness, myalgias, rhabdomyolysis, and weakness, with a wide age range of onset mainly during adulthood. Histopathological analysis can reveal nonspecific abnormalities suggestive of RYR1 involvement, while metabolic profiling reflects altered energy metabolism in MHS muscle. Myopathic manifestations can significantly impact patient quality of life and lead to functional limitations and socio-economic burden. While currently available therapies can provide symptomatic relief, there is a need for further research into targeted treatments addressing the underlying pathophysiology. Counselling early after establishing the MHS diagnosis, followed by multidisciplinary management involving various medical specialties, is crucial to optimise patient care.

Impact of a digital manual for guidance on malignant hyperthermia: patient education

Background

Malignant hyperthermia (MH) is a rare, hereditary disease with a hypermetabolic response to volatile anesthetics/succinylcholine. Susceptible patients face difficulties due to a lack of knowledge about MH. As informational materials could increase knowledge and adherence to prevention/therapy, digital information about rare diseases validated for patients is needed. Our objective was to evaluate the following: (1) the impact of digital manuals on the knowledge/quality of life of MH patients and (2) access to MH services.

Materials and methods

Fifty MH-susceptible patients filled out a virtual questionnaire twice (demographic/economic/clinical data, MH knowledge and impact on daily life, and SF-36 quality of life). Test groups 1 (n = 17) and 2 (n = 16) were evaluated 30 and 180 days after receiving a digital manual, and the control group (n = 17; without manual) was evaluated after 180 days. We collected the MH service data about the number of contacts.

Results

Twenty-four (48%) patients reported problems in personal/professional life, sports, clinical/surgical/dental treatments, and military service, in addition to concerns about emergency care and complaints of sequelae. The percentage of correct answers in the second MH knowledge questionnaire increased for test group 2 (62% vs. 74.1%; unpaired t test, p < 0.01), was significantly greater in test groups 1 (68.1%) and 2 (74.1%) than in the control group (56.5%; Kruskal–Wallis, p < 0.05), and correlated with more time studying the manual and reports of MH-related problems (multiple regression, p < 0.05).

Conclusions

The digital manual improved patients’ MH knowledge. Online contacts with the MH service increased, allowing greater information dissemination. As informational materials could increase knowledge/adherence to prevention/therapy, digital information about MH validated for patients should be implemented.

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.

Malignant Hyperthermia-A Case From Camp Humphreys, South Korea, and Lessons for the Military Health System

Although malignant hyperthermia (MH) is a well-known complication of anesthesia, it presents unique considerations in the military health system. In this case report, the authors present a 26-year-old male active duty service member who experienced an MH crisis during a routine bilateral sagittal split osteotomy. The case presented here, which occurred at Brian D Allgood Army Community Hospital at Camp Humphreys, South Korea, highlights the challenges presented when caring for these patients in minimally staffed environments with frequent turnover of staff. The authors discuss the challenges to the military system such as the importance of adequate documentation of MH-susceptible service members, the benefits of rapidly dissolving dantrolene sodium nanosuspension, and the necessity for frequent training of military medical staff in the recognition and management of MH.

Risk factors and future directions for preventing and diagnosing exertional rhabdomyolysis

Exertional rhabdomyolysis may occur when an individual is subjected to strenuous physical exercise. It is occasionally associated with myoglobinuria (i.e. "cola-colored" urine) alongside muscle pain and weakness. The pathophysiology of exertional rhabdomyolysis involves striated muscle damage and the release of cellular components into extracellular fluid and bloodstream. This can cause acute renal failure, electrolyte abnormalities, arrhythmias and potentially death. Exertional rhabdomyolysis is observed in high-performance athletes who are subjected to intense, repetitive and/or prolonged exercise but is also observed in untrained individuals and highly trained or elite groups of military personnel. Several risk factors have been reported to increase the likelihood of the condition in athletes, including: viral infection, drug and alcohol abuse, exercise in intensely hot and humid environments, genetic polymorphisms (e.g. sickle cell trait and McArdle disease) and epigenetic modifications. This article reviews several of these risk factors and proposes screening protocols to identify individual susceptibility to exertional rhabdomyolysis as well as the relevance of proteomics for the evaluation of potential biomarkers of muscle damage.

Genetic counseling for patients with positive genomic screening results: Considerations for when the genetic test comes first

Emerging genetic testing delivery models have enabled individuals to receive testing without a medical indication. This article will highlight key considerations for patient care in the setting of adult patients with positive results for monogenic disease identified through genomic screening. Suggestions for how to adapt genetic counseling to a genomic screening population will encompass topics such as phenotyping, risk assessments, and the use of existing guidelines and resources. Case examples will demonstrate principles of genotype-first patient care.

Isoflurane Induced Malignant Hyperthermia in a Patient with Glucose 6-Phosphate Dehydrogenase Deficiency and Growth Hormone Abuse

Malignant hyperthermia is a pharmacogenetic disorder in the regulation of calcium in skeletal muscles which is related to an uninhibited muscle hypermetabolic reaction to potent inhalation agents, the depolarizing muscle relaxant succinylcholine, and to stressors such as vigorous exercise and heat. MH is diagnosed by the clinical presentation of the disease and laboratory testing. There are a few previous studies working on if there is an association between the occurrence of malignant hyperthermia and the existence of glucose 6-phosphate dehydrogenase (G6PD) deficiency, and there was no report on growth hormone doping in the literature. So, our main goal was to show this rare case of malignant hyperthermia seen in a G6PD patient with growth hormone abuse who underwent surgery and to find if there is an association between G6PD deficiency, growth hormone abuse, and malignant hyperthermia. Our patient was a 17-year-old boy with right lower quadrant abdominal pain and tenderness who underwent appendectomy. At the end of the operation, the patient developed with an increased heart rate (sinus tachycardia), increased body temperature and end-tidal carbon dioxide (ETCO2) level, masseter muscle rigidity, and then, generalized body rigidity, so the malignant hyperthermia susceptibility was considered. The patient was managed by cooling down the patient and the administration of dantrolene. We could hypothesize that malignant hyperthermia might be associated with G6PD deficiency as a triggering factor, but has no association with recombinant human growth hormone (rhGH) abuse. Another main lesson which this study tells us is to make a careful and proper history taking before going on an operation for preoperative evaluation and identification of patients with any form of suspicious drug abuse in order not to receive volatile inhalational agents and, also, performing some preventive measures including avoidance of heat extremes and restricting athletic activity in a patient with a history of malignant hyperthermia, and if the malignant hyperthermia susceptibility is suspected, urgent management should be carried out. As the association between G6PD deficiency, human growth hormone abuse, and malignant hyperthermia has remained unclear up-to-date, further potent studies are seriously needed in the future.

Pharmacogenetics in Practice: Estimating the Clinical Actionability of Pharmacogenetic Testing in Perioperative and Ambulatory Settings

Most literature describing pharmacogenetic implementations are within academic medical centers and use single-gene tests. Our objective was to describe the results and lessons learned from a multisite pharmacogenetic pilot that utilized panel-based testing in academic and nonacademic settings. This was a retrospective analysis of 667 patients from a pilot in 4 perioperative and 5 outpatient cardiology clinics. Recommendations related to 12 genes and 65 drugs were classified as actionable or not actionable. They were ascertained from Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines and US Food and Drug Administration (FDA) labeling. Patients displayed a high prevalence of actionable results (88%, 99%) and use of medications (28%, 46%) with FDA or CPIC recommendations, respectively. Sixteen percent of patients had an actionable result for a current medication per CPIC compared with 5% per FDA labeling. A systematic approach by a health system may be beneficial given the quantity and diversity of patients affected.

Exertional rhabdomyolysis: Relevance of clinical and laboratory findings, and clues for investigation

Some degree of exertional rhabdomyolysis (ER), striated muscle breakdown associated with strenuous exercise, is a well-known phenomenon associated with endurance sports. However in rare cases, severe and/or recurrent ER is a manifestation of an underlying condition, which puts patients at risk for significant morbidity and mortality. Selecting the patients that need a diagnostic work up of an acute rhabdomyolysis episode is an important task.

Based on the diagnostic work up of three illustrative patients treated in our hospital, retrospectively using the ‘RHABDO’ screening tool, we discuss the clinical and biochemical clues that should trigger further investigation for an underlying condition. Finally, we describe the most common genetic causes of this clinical syndrome.

Return of secondary findings in genomic sequencing: Military implications

Background

Genomic sequencing has become a widely used tool in clinical and research settings in both civilian and military healthcare systems.

Methods

In this paper, we consider potential military‐specific implications of returning genomic sequencing secondary findings to ensure the proper protections, policies, and processes are in place for the use of this information.

Results

We specifically use two examples to highlight potential military implications of the return of secondary findings.

Conclusion

Clinicians and researchers are strongly encouraged to consider the military implications of the return of results for informed consent of service members or their families undergoing clinical or research genomic sequencing.

Management of a Patient With a History of Nonanesthesia-Related Malignant Hyperthermia Undergoing Laparoscopic Cholecystectomy: A Case Report

A 36-year-old African American with a medical history of nonanesthesia-related malignant hyperthermia (MH) who was taking chronic oral dantrolene therapy presented with right upper quadrant pain for a laparoscopic cholecystectomy. A multidisciplinary perioperative plan was implemented with the goal of avoiding triggering an MH episode or rhabdomyolysis. He developed a postoperative left brachial vein thrombus of unclear etiology, possibly related to dantrolene administration or his underlying susceptibility to MH.

Rethinking status dystonicus

Status dystonicus is a movement disorder emergency that has been a source of controversy in terms of terminology, phenomenology, and management since it was first described in 1982. Here we argue that the current use of the term status dystonicus falls well short of the precision needed for either clinical or academic use. We performed a critical review on this topic, describing possible pathophysiological mechanisms and areas of uncertainties. This review also addresses the problems derived by the extreme clinical heterogeneity of this condition, as the lack of an objective criterion useful for the definition, or the fact that status dystonicus may present not only in the context of a known dystonic syndrome. We propose a new possible definition that includes not only dystonia but also other hyperkinetic movements in the wide range of movement disorders that can be seen during an episode. The new definition keeps the term status dystonicus and highlights the fact that this is a medical emergency based on the impairment of bulbar and/or respiratory function requiring hospital admission as the principal feature. Furthermore, the new definition should not consider as necessary unspecific features as patient's condition at baseline, the distribution of dystonia, occurrence of systemic symptoms such as fever or laboratory findings. We hope that this proposal will stimulate the debate on this subject among our peers, further developing a clinical and pathophysiological understanding of status dystonicus. © 2017 International Parkinson and Movement Disorder Society.