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.
BackgroundMalignant hyperthermia (MH) is a rare pharmacogenetic disorder which is characterized by life-threatening metabolic crises during general anesthesia. Classical triggering substances are volatile anesthetics and succinylcholine (SCh). The molecular basis of MH is excessive release of Ca2+ in skeletal muscle principally by a mutated ryanodine receptor type 1 (RyR1). To identify factors explaining the variable phenotypic presentation and complex pathomechanism, we analyzed proven MH events in terms of clinical course, muscle contracture, genetic factors and pharmocological triggers.MethodsIn a multi-centre study including seven European MH units, patients with a history of a clinical MH episode confirmed by susceptible (MHS) or equivocal (MHE) in vitro contracture tests (IVCT) were investigated. A test result is considered to be MHE if the muscle specimens develop pathological contractures in response to only one of the two test substances, halothane or caffeine. Crises were evaluated using a clinical grading scale (CGS), results of IVCT and genetic screening. The effects of SCh and volatile anesthetics on Ca2+ release from sarcoplasmic reticulum (SR) were studied in vitro.ResultsA total of 200 patients met the inclusion criteria. Two MH crises (1%) were triggered by SCh (1 MHS, 1 MHE), 18% by volatile anesthetics and 81% by a combination of both. Patients were 70% male and 50% were younger than 12 years old. Overall, CGS was in accord with IVCT results. Crises triggered by enflurane had a significantly higher CGS compared to halothane, isoflurane and sevoflurane. Of the 200 patients, 103 carried RyR1 variants, of which 14 were novel. CGS varied depending on the location of the mutation within the RyR1 gene. In contrast to volatile anesthetics, SCh did not evoke Ca2+ release from isolated rat SR vesicles.ConclusionsAn MH event could depend on patient-related risk factors such as male gender, young age and causative RyR1 mutations as well as on the use of drugs lowering the threshold of myoplasmic Ca2+ release. SCh might act as an accelerant by promoting unspecific Ca2+ influx via the sarcolemma and indirect RyR1 activation. Most MH crises develop in response to the combined administration of SCh and volatile anesthetics.
Context:Sleep deprivation is a common problem on intensive care units (ICUs) influencing not only cognition, but also cellular functions. An appropriate sleep-wake cycle should therefore be maintained to improve patients’ outcome. Multiple disruptive factors on ICUs necessitate the administration of sedating and sleep-promoting drugs for patients who are not analgo-sedated.Aims:The objective of the present study was to evaluate sleep quantity and sleep quality in ICU patients receiving either propofol or flunitrazepam.Settings and Design:Monocentric, randomized, double-blinded trial.Materials and Methods:A total of 66 ICU patients were enrolled in the study (flunitrazepam n = 32, propofol n = 34). Propofol was injected continuously (2 mg/kg/h), flunitrazepam as a bolus dose (0.015 mg/kg). Differences between groups were evaluated using a standardized sleep diary and the bispectral index (BIS).Statistical Analysis Used:Group comparisons were performed by Mann-Whitney U-Test. P < 0.05 was considered to be statistically significant.Results:Sleep quality and the frequency of awakenings were significantly better in the propofol group (Pg). In the same group lower BIS values were recorded (median BIS propofol 74.05, flunitrazepam 78.7 [P = 0.016]). BIS values had to be classified predominantly to slow-wave sleep under propofol and light sleep after administration of flunitrazepam. Sleep quality improved in the Pg with decreasing frequency of awakenings and in the flunitrazepam group with increasing sleep duration.Conclusions:Continuous low-dose injection of propofol for promoting and maintaining night sleep in ICU patients who are not analgo-sedated was superior to flunitrazepam regarding sleep quality and sleep structure.
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