Malignant hyperthermia 2020: Guideline from the Association of Anaesthetists.

Malignant hyperthermia is defined in the International Classification of Diseases as a progressive life-threatening hyperthermic reaction occurring during general anaesthesia. Malignant hyperthermia has an underlying genetic basis, and genetically susceptible individuals are at risk of developing malignant hyperthermia if they are exposed to any of the potent inhalational anaesthetics or suxamethonium. It can also be described as a malignant hypermetabolic syndrome. There are no specific clinical features of malignant hyperthermia and the condition may prove fatal unless it is recognised in its early stages and treatment is promptly and aggressively implemented. The Association of Anaesthetists has previously produced crisis management guidelines intended to be displayed in all anaesthetic rooms as an aide memoire should a malignant hyperthermia reaction occur. The last iteration was produced in 2011 and since then there have been some developments requiring an update. In these guidelines we will provide background information that has been used in updating the crisis management recommendations but will also provide more detailed guidance on the clinical diagnosis of malignant hyperthermia. The scope of these guidelines is extended to include practical guidance for anaesthetists dealing with a case of suspected malignant hyperthermia once the acute reaction has been reversed. This includes information on care and monitoring during and after the event; appropriate equipment and resuscitative measures within the operating theatre and ICU; the importance of communication and teamwork; guidance on counselling of the patient and their family; and how to make a referral of the patient for confirmation of the diagnosis. We also review which patients presenting for surgery may be at increased risk of developing malignant hyperthermia under anaesthesia and what precautions should be taken during the peri-operative management of the patients.

Penicillin allergy de-labelling ahead of elective surgery: feasibility and barriers.

BACKGROUND: Around 10-15% of the in-patient population carry unsubstantiated 'penicillin allergy' labels, the majority incorrect when tested. These labels are associated with harm from use of broad-spectrum non-penicillin antibiotics. Current testing guidelines incorporate both skin and challenge tests; this is prohibitively expensive and time-consuming to deliver on a large scale. We aimed to establish the feasibility of a rapid access de-labelling pathway for surgical patients, using direct oral challenge. METHODS: 'Penicillin allergic' patients, recruited from a surgical pre-assessment clinic, were risk-stratified using a screening questionnaire. Patients at low risk of true, immunoglobulin E (IgE)-mediated allergy were offered direct oral challenge using incremental amoxicillin to a total dose of 500 mg. A 3-day course was completed at home. De-labelled patients were followed up to determine antibiotic use in surgery, and attitudes towards de-labelling were explored. RESULTS: Of 219 patients screened, 74 were eligible for inclusion and offered testing. We subsequently tested 56 patients; 55 were de-labelled. None had a serious reaction to the supervised challenge, or thereafter. On follow-up, 17 of 19 patients received appropriate antimicrobial prophylaxis during surgery. Only three of 33 de-labelled patients would have been happy for the label to be removed without prior specialist testing. CONCLUSION: Rapid access de-labelling, using direct oral challenge in appropriately risk-stratified patients, can be incorporated into the existing surgical care pathway. This provides immediate and potential long-term benefit for patients. Interest in testing is high among patients, and clinicians appear to follow clinic recommendations. Patients are unlikely to accept removal of their allergy label on the basis of history alone. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov: AN17/92982.

Management of a surgical patient with a label of penicillin allergy: narrative review and consensus recommendations.

Unsubstantiated penicillin-allergy labels are common in surgical patients, and can lead to significant harm through avoidance of best first-line prophylaxis of surgical site infections and increased infection with resistant bacterial strains. Up to 98% of penicillin-allergy labels are incorrect when tested. Because of the scarcity of trained allergists in all healthcare systems, only a minority of surgical patients have the opportunity to undergo testing and de-labelling before surgery. Testing pathways can be modified and shortened in selected patients. A variety of healthcare professionals can, with appropriate training and in collaboration with allergists, provide testing for selected patients. We review how patients might be assessed, the appropriate testing strategies that can be used, and the minimum standards of safe testing.

Consensus clinical scoring for suspected perioperative immediate hypersensitivity reactions.

BACKGROUND: Grading schemes for severity of suspected allergic reactions have been applied to the perioperative setting, but there is no scoring system that estimates the likelihood that the reaction is an immediate hypersensitivity reaction. Such a score would be useful in evaluating current and proposed tests for the diagnosis of suspected perioperative immediate hypersensitivity reactions and culprit agents. METHODS: We conducted a Delphi consensus process involving a panel of 25 international multidisciplinary experts in suspected perioperative allergy. Items were ranked according to appropriateness (on a scale of 1-9) and consensus, which informed development of a clinical scoring system. The scoring system was assessed by comparing scores generated for a series of clinical scenarios against ratings of panel members. Supplementary scores for mast cell tryptase were generated. RESULTS: Two rounds of the Delphi process achieved stopping criteria for all statements. From an initial 60 statements, 43 were rated appropriate (median score 7 or more) and met agreement criteria (disagreement index <0.5); these were used in the clinical scoring system. The rating of clinical scenarios supported the validity of the scoring system. Although there was variability in the interpretation of changes in mast cell tryptase by the panel, we were able to include supplementary scores for mast cell tryptase. CONCLUSION: We used a robust consensus development process to devise a clinical scoring system for suspected perioperative immediate hypersensitivity reactions. This will enable objectivity and uniformity in the assessment of the sensitivity of diagnostic tests.

Malignant hyperthermia, environmental heat stress, and intracellular calcium dysregulation in a mouse model expressing the p.G2435R variant of RYR1.

BACKGROUND: The human p.G2434R variant of the RYR1 gene is most frequently associated with malignant hyperthermia (MH) in the UK. We report the phenotype of a knock-in mouse that expresses the RYR1 variant p.G2435R, which is isogenetic with the human variant. METHODS: We observed the general phenotype; determined the sensitivity of myotubes to caffeine-, KCl, and halothane-induced Ca2+ release; determined the in vivo response to halothane or increased ambient temperature; and determined the in vivo myoplasmic intracellular Ca2+ concentration in skeletal muscle before and during exposure to volatile anaesthetics. RESULTS: RYR1 pG2435R/MH normal (MHS-Heterozygous[Het]) or RYR1 pG2435R/pG2435R (MHS-Homozygous[Hom]) mice were fully viable under typical rearing conditions, although some male MHS-Hom mice died spontaneously. The normalised half-maximal effective concentration (95% confidence interval) for intracellular Ca2+ release in myotubes in response to KCl [MH normal, MHN, 21.4 (19.8-23.1) mM; MHS-Het 16.2 (15.2-17.2) mM; MHS-Hom 11.2 (10.2-12.2) mM] and caffeine (MHN, 5.7 (5-6.3) mM; MHS-Het 4.5 (3.9-5.0) mM; MHS-Hom 1.77 (1.5-2.1) mM] exhibited a gene dose-dependent decrease, and there was a gene dose-dependent increase in halothane sensitivity. Intact animals show a gene dose-dependent susceptibility to MH with volatile anaesthetics or to heat stroke. RYR1 p.G2435R mice had elevated skeletal muscle intracellular resting [Ca2+]i, (values are expressed as mean (SD)) (MHN 123 (3) nM; MHS-Het 156 (16) nM; MHS-Hom 265 (32) nM; P<0.001) and [Na+]i (MHN 8 (0.1) mM; MHS-Het 10 (1) mM; MHS-Hom 14 (0.7) mM; P<0.001) that was further increased by exposure to volatile anaesthetics. CONCLUSIONS: RYR1 pG2435R mice demonstrated gene dose-dependent in vitro and in vivo responses to pharmacological and environmental stressors that parallel those seen in patients with the human RYR1 variant p.G2434R.

Genetic epidemiology of malignant hyperthermia in the UK.

BACKGROUND: Gaps in our understanding of genetic susceptibility to malignant hyperthermia (MH) limit the application and interpretation of genetic diagnosis of the condition. Our aim was to define the prevalence and role of variants in the three genes implicated in MH susceptibility in the largest comprehensively phenotyped MH cohort worldwide. METHODS: We initially included one individual from each positive family tested in the UK MH Unit since 1971 to detect variants in RYR1, CACNA1S, or STAC3. Screening for genetic variants has been ongoing since 1991 and has involved a range of techniques, most recently next generation sequencing. We assessed the pathogenicity of variants using standard guidelines, including family segregation studies. The prevalence of recurrent variants of unknown significance was compared with the prevalence reported in a large database of sequence variants in low-risk populations. RESULTS: We have confirmed MH susceptibility in 795 independent families, for 722 of which we have a DNA sample. Potentially pathogenic variants were found in 555 families, with 25 RYR1 and one CACNA1S variants previously unclassified recurrent variants significantly over-represented (P<1×10-7) in our cohort compared with the Exome Aggregation Consortium database. There was genotype-phenotype discordance in 86 of 328 families suitable for segregation analysis. We estimate non-RYR1/CACNA1S/STAC3 susceptibility occurs in 14-23% of MH families. CONCLUSIONS: Our data provide current estimates of the role of variants in RYR1, CACNA1S, and STAC3 in susceptibility to MH in a predominantly white European population.

Mesenchymal Stromal Cells are Readily Recoverable from Lung Tissue, but not the Alveolar Space, in Healthy Humans.

Stromal support is critical for lung homeostasis and the maintenance of an effective epithelial barrier. Despite this, previous studies have found a positive association between the number of mesenchymal stromal cells (MSCs) isolated from the alveolar compartment and human lung diseases associated with epithelial dysfunction. We hypothesised that bronchoalveolar lavage derived MSCs (BAL-MSCs) are dysfunctional and distinct from resident lung tissue MSCs (LT-MSCs). In this study, we comprehensively interrogated the phenotype and transcriptome of human BAL-MSCs and LT-MSCs. We found that MSCs were rarely recoverable from the alveolar space in healthy humans, but could be readily isolated from lung transplant recipients by bronchoalveolar lavage. BAL-MSCs exhibited a CD90Hi , CD73Hi , CD45Neg , CD105Lo immunophenotype and were bipotent, lacking adipogenic potential. In contrast, MSCs were readily recoverable from healthy human lung tissue and were CD90Hi or Lo , CD73Hi , CD45Neg , CD105Int and had full tri-lineage potential. Transcriptional profiling of the two populations confirmed their status as bona fide MSCs and revealed a high degree of similarity between each other and the archetypal bone-marrow MSC. 105 genes were differentially expressed; 76 of which were increased in BAL-MSCs including genes involved in fibroblast activation, extracellular matrix deposition and tissue remodelling. Finally, we found the fibroblast markers collagen 1A1 and α-smooth muscle actin were increased in BAL-MSCs. Our data suggests that in healthy humans, lung MSCs reside within the tissue, but in disease can differentiate to acquire a profibrotic phenotype and migrate from their in-tissue niche into the alveolar space. Stem Cells 2016;34:2548-2558.

Assessing the pathogenicity of RYR1 variants in malignant hyperthermia.

BACKGROUND: . Missense variants in the ryanodine receptor 1 gene ( RYR1 ) are associated with malignant hyperthermia but only a minority of these have met the criteria for use in predictive DNA diagnosis. We examined the utility of a simplified method of segregation analysis and a functional assay for determining the pathogenicity of recurrent RYR1 variants associated with malignant hyperthermia. METHODS: . We identified previously uncharacterised RYR1 variants found in four or more malignant hyperthermia families and conducted simplified segregation analyses. An efficient cloning and mutagenesis strategy was used to express ryanodine receptor protein containing one of six RYR1 variants in HEK293 cells. Caffeine-induced calcium release, measured using a fluorescent calcium indicator, was compared in cells expressing each variant to that in cells expressing wild type ryanodine receptor protein. RESULTS.: We identified 43 malignant hyperthermia families carrying one of the six RYR1 variants. There was segregation of genotype with the malignant hyperthermia susceptibility phenotype in families carrying the p.E3104K and p.D3986E variants, but the number of informative meioses limited the statistical significance of the associations. HEK293 functional assays demonstrated an increased sensitivity of RyR1 channels containing the p.R2336H, p.R2355W, p.E3104K, p.G3990V and p.V4849I compared with wild type, but cells expressing p.D3986E had a similar caffeine sensitivity to cells expressing wild type RyR1. CONCLUSIONS: . Segregation analysis is of limited value in assessing pathogenicity of RYR1 variants in malignant hyperthermia. Functional analyses in HEK293 cells provided evidence to support the use of p.R2336H, p.R2355W, p.E3104K, p.G3990V and p.V4849I for diagnostic purposes but not p.D3986E.

Does regional anaesthesia improve outcome?

This review examines the recent evidence of an impact of regional anaesthesia on important clinical outcomes. Evidence was obtained from a variety of studies, with increasing numbers of analyses of large databases being prominent. The benefits and limitations of these approaches are considered in order to provide a context for interpretation of the data they generate. There should be little argument that correctly performed and appropriately used regional anaesthetic techniques can provide the most effective postoperative analgesia for the duration of the block, but the majority of studies suggest that this does not translate into improved longer-term surgical outcomes. The evidence for reduced incidence of major complications when regional anaesthesia is compared with, or added to, general anaesthesia is mixed. There appears to be a small effect in reducing blood loss during major joint arthroplasty. Some, but not all, studies demonstrate a reduced incidence of respiratory and infective complications with regional anaesthesia, but the effect on cardiovascular complications is variable. There are even some data consistent with a hypothesis that general anaesthesia may be protective against postoperative cognitive dysfunction. In conclusion, there is probably no generally applicable benefit in long-term outcomes with regional anaesthesia. More likely is an interaction between patient factors, the surgical procedure, and the relative capability of the anaesthetist to manage different types of anaesthesia.

Peripheral regional anaesthesia and outcome: lessons learned from the last 10 years.

BACKGROUND: Our aim was to review the recent evidence for the efficacy of peripheral regional anaesthesia. METHODS: Following a systematic literature search and selection of publications based on prospectively agreed upon criteria, we produced a narrative review of the most commonly performed peripheral regional anaesthetic blocks for surgery on the upper limb, the lower limb, and the trunk. We considered short-term and longer-term benefits and complications among the outcomes of interest. RESULTS: Where good quality evidence exists, the great majority of the blocks reviewed were associated with one or any combination of reduced postoperative pain, reduced opioid consumption, or increased patient satisfaction. For selected surgical procedures, the use of blocks avoided general anaesthesia and was associated with increased efficiency of the surgical pathway. The exceptions were supraclavicular block, where there was insufficient evidence, and transversus abdominis plane block, where the evidence for efficacy was conflicting. The evidence for the impact of the blocks on longer-term outcomes was, in general, inadequate to inform clinical decision making. Permanent complications are rare. CONCLUSIONS: The majority of peripheral regional anaesthetic techniques have been shown to produce benefits for patients and hospital efficiency. Further interventional trials are required to clarify such benefits for supraclavicular block and transversus abdominis plane block and to ascertain any longer-term benefits for almost all of the blocks reviewed. Permanent complications of peripheral regional anaesthetic blocks are rare but accurate estimates of their incidence are yet to be determined.

Teicoplanin allergy - an emerging problem in the anaesthetic allergy clinic.

BACKGROUND: Anaphylaxis to teicoplanin appears to be extremely rare, with only one confirmed case report worldwide. Two anaesthetic allergy clinics in the UK have received a number of suspected cases referred for investigation, and we present here the first case series of teicoplanin allergy. METHODS: We investigated 20 cases of suspected teicoplanin allergy, identified from the two clinics over a period of two years. We devised a set of five criteria to categorize the certainty of their diagnosis. These included: (1) reaction within 15 min of administration of teicoplanin, (2) ≥2 features of anaphylaxis present, (3) positive skin testing or challenge testing, (4) raised serum mast cell tryptase (MCT), (5) alternative diagnosis excluded. Based on these criteria we defined the likelihood of IgE-mediated allergy to teicoplanin as: definite-met all criteria; probable-met criteria 1.2 and 5, plus 3 or 4; uncertain-met criteria 1.2 and 5; excluded- any others. RESULTS: We identified 7 'definite', 7 'probable' and 2 'uncertain' cases of teicoplanin allergy. Four cases were excluded. CONCLUSIONS: IgE-mediated anaphylaxis to teicoplanin appears to be more common than previously thought. This is true even if only definitive cases are considered. Investigation of teicoplanin allergy is hampered by the lack of standardized skin test concentrations. In some cases, there was a severe clinical reaction, but without any skin test evidence of histamine release. The mechanism of reaction in these cases is not known and requires further study.

European Malignant Hyperthermia Group guidelines for investigation of malignant hyperthermia susceptibility.

It is 30 yr since the British Journal of Anaesthesia published the first consensus protocol for the laboratory diagnosis of malignant hyperthermia susceptibility from the European Malignant Hyperthermia Group. This has subsequently been used in more than 10 000 individuals worldwide to inform use of anaesthetic drugs in these patients with increased risk of developing malignant hyperthermia during general anaesthesia, representing an early and successful example of stratified medicine. In 2001, our group also published a guideline for the use of DNA-based screening of malignant hyperthermia susceptibility. We now present an updated and complete guideline for the diagnostic pathway for patients potentially at increased risk of developing malignant hyperthermia. We introduce the new guideline with a narrative commentary that describes its development, the changes to previously published protocols and guidelines, and new sections, including recommendations for patient referral criteria and clinical interpretation of laboratory findings.

Effect of concentration of local anaesthetic solution on the ED50 of bupivacaine for supraclavicular brachial plexus block.

BACKGROUND: The aim of this trial was to compare the effect of concentration of bupivacaine solution on the ED50 dose required for supraclavicular brachial plexus block. METHODS: Nineteen ASA I, II, or III patients of either sex undergoing elective upper limb surgery under ultrasound-guided supraclavicular brachial block were recruited in this double-blind, randomized trial which followed an up-and-down sequential allocation design. The patients were randomly allocated to three groups who then received 0.25%, 0.375%, or 0.5% bupivacaine. The study design and analysis followed Dixon's small sample model using a 'nominal' sample size of six in each group. The data from previous research were used to guide the dose levels and dose intervals for the three groups. RESULTS: The median effective volume [95% confidence interval (CI)] for 0.25%, 0.375%, and 0.5% bupivacaine for supraclavicular block was 26.8 (18.6-38.4), 18.1 (12.1-26.0), and 12.0 (8.4-17.3) ml, respectively. The ED50 dose (95% CI) for 0.25%, 0.375%, and 0.5% bupivacaine was 66.9 (46.6-96.0), 68.0 (47.4-97.6), and 60.1 (41.8-86.3) mg, respectively. The difference in the ED50 dose between the three concentrations was not statistically significant. CONCLUSIONS: Our study demonstrates that the ED50 dose of bupivacaine for supraclavicular block is not dependent on the concentration. Lowering the concentration or the strength of the local anaesthetic leads to an increase in the volume required for successful block.