Pharmacogenomic profile of actionable molecular variants related to drugs commonly used in anesthesia: WES analysis reveals new mutations

Background: Genetic interindividual variability is associated with adverse drug reactions (ADRs) and affects the response to common drugs used in anesthesia. Despite their importance, these variants remain largely underexplored in Latin-American countries. This study describes rare and common variants found in genes related to metabolism of analgesic and anaesthetic drug in the Colombian population. Methods: We conducted a study that included 625 Colombian healthy individuals. We generated a subset of 14 genes implicated in metabolic pathways of common medications used in anesthesia and assessed them by whole-exome sequencing (WES). Variants were filtered using two pipelines: A) novel or rare (minor allele frequency-MAF <1%) variants including missense, loss-of-function (LoF, e.g., frameshift, nonsense), and splice site variants with potential deleterious effect and B) clinically validated variants described in the PharmGKB (categories 1, 2 and 3) and/or ClinVar databases. For rare and novel missense variants, we applied an optimized prediction framework (OPF) to assess the functional impact of pharmacogenetic variants. Allelic, genotypic frequencies and Hardy-Weinberg equilibrium were calculated. We compare our allelic frequencies with these from populations described in the gnomAD database. Results: Our study identified 148 molecular variants potentially related to variability in the therapeutic response to 14 drugs commonly used in anesthesiology. 83.1% of them correspond to rare and novel missense variants classified as pathogenic according to the pharmacogenetic optimized prediction framework, 5.4% were loss-of-function (LoF), 2.7% led to potential splicing alterations and 8.8% were assigned as actionable or informative pharmacogenetic variants. Novel variants were confirmed by Sanger sequencing. Allelic frequency comparison showed that the Colombian population has a unique pharmacogenomic profile for anesthesia drugs with some allele frequencies different from other populations. Conclusion: Our results demonstrated high allelic heterogeneity among the analyzed sampled, enriched by rare (91.2%) variants in pharmacogenes related to common drugs used in anesthesia. The clinical implications of these results highlight the importance of implementation of next-generation sequencing data into pharmacogenomic approaches and personalized medicine.

Low-dose Succinylcholine to Facilitate Laryngeal Mask Airway Insertion: A Comparison of Two Doses

Background and Aims:

Around the world, the use of the laryngeal mask airway (LMA) is becoming more common for different surgeries accounting for it being the dominant choice of airway in numerous surgeries. Although propofol is known to blunt the laryngeal reflexes often patient movement, coughing, and gagging occur on insertion. This study aims to identify the optimum dose of succinylcholine required to facilitate LMA insertion comparing placebo, 0.1 mg/kg and 0.25 mg/kg of succinylcholine. Further objectives were to compare (a) the overall insertion conditions of the LMA, (b) the number of insertion attempts, (c) the amount of propofol consumption, and (d) the hemodynamics in the three groups.

Setting and Design:

This is a prospective, double-blinded, randomized control trial of 283 patients randomized into three groups-placebo, 0.1 mg/kg and 0.25 mg/kg of succinylcholine. It was done in the day case theatres of a tertiary hospital in Southern India.

Subjects and Methods:

Patients were induced with 2 mg/kg of propofol, after 2 μg/kg of fentanyl. The study drug was given after loss of consciousness. After 60 s, a classic LMA was inserted by the standard method by a single investigator. Jaw relaxation, coughing, gagging, movement, laryngospasm, ease of insertion, number of attempts, propofol usage, and hemodynamics were assessed.

Statistical Analysis:

Statistical methods used were analysis of variance with Bonferroni's t-test, Chi-square test, and Fisher's test. P < 0.05 was considered statistically significant.

Results:

Jaw relaxation was significantly better in the 0.25 mg/kg succinylcholine group. There was no significant difference in coughing and gagging in the groups, but patient movement was more in the placebo group. Two patients in the placebo group experienced partial laryngospasm. Overall insertion conditions were significantly better in the 0.25 mg/kg group compared to the other two groups. Propofol consumption was significantly more in the placebo group.

Conclusions:

The study concludes that 0.25 mg/kg succinylcholine facilitates insertion of the LMA.

Aggregate penetrance of genomic variants for actionable disorders in European and African Americans

In populations that have not been selected for family history of disease, it is unclear how commonly pathogenic variants (PVs) in disease-associated genes for rare Mendelian conditions are found and how often they are associated with clinical features of these conditions. We conducted independent, prospective analyses of participants in two community-based epidemiological studies to test the hypothesis that persons carrying PVs in any of 56 genes that lead to 24 dominantly inherited, actionable conditions are more likely to exhibit the clinical features of the corresponding diseases than those without PVs. Among 462 European American Framingham Heart Study (FHS) and 3223 African-American Jackson Heart Study (JHS) participants who were exome-sequenced, we identified and classified 642 and 4429 unique variants, respectively, in these 56 genes while blinded to clinical data. In the same participants, we ascertained related clinical features from the participants' clinical history of cancer and most recent echocardiograms, electrocardiograms, and lipid measurements, without knowledge of variant classification. PVs were found in 5 FHS (1.1%) and 31 JHS (1.0%) participants. Carriers of PVs were more likely than expected, on the basis of incidence in noncarriers, to have related clinical features in both FHS (80.0% versus 12.4%) and JHS (26.9% versus 5.4%), yielding standardized incidence ratios of 6.4 [95% confidence interval (CI), 1.7 to 16.5; P = 7 × 10^-4) in FHS and 4.7 (95% CI, 1.9 to 9.7; P = 3 × 10^-4) in JHS. Individuals unselected for family history who carry PVs in 56 genes for actionable conditions have an increased aggregated risk of developing clinical features associated with the corresponding diseases.

[Malignant hyperthermia: multifactorial events leading to a crisis]

This case-report focused on the occurrence of a crisis of malignant hyperthermia on a young biker (21 y.o.) victim of a severe traffic accident. This observation gives some key points: the delayed occurrence of the crisis after 4 hours of surgery, the multi-factorial events that triggered the crisis; the choice to perform a quick diagnosis through gene analysis in comparison to the standard tests of caffeine on a muscular biopsy. These different points are discussed with a proposal of algorithm in the situation.

Gene dose influences cellular and calcium channel dysregulation in heterozygous and homozygous T4826I-RYR1 malignant hyperthermia-susceptible muscle

Malignant hyperthermia susceptibility (MHS) is primarily conferred by mutations within ryanodine receptor type 1 (RYR1). Here we address how the MHS mutation T4826I within the S4-S5 linker influences excitation-contraction coupling and resting myoplasmic Ca(2+) concentration ([Ca(2+)](rest)) in flexor digitorum brevis (FDB) and vastus lateralis prepared from heterozygous (Het) and homozygous (Hom) T4826I-RYR1 knock-in mice (Yuen, B. T., Boncompagni, S., Feng, W., Yang, T., Lopez, J. R., Matthaei, K. I., Goth, S. R., Protasi, F., Franzini-Armstrong, C., Allen, P. D., and Pessah, I. N. (2011) FASEB J. doi:22131268). FDB responses to electrical stimuli and acute halothane (0.1%, v/v) exposure showed a rank order of Hom ≫ Het ≫ WT. Release of Ca(2+) from the sarcoplasmic reticulum and Ca(2+) entry contributed to halothane-triggered increases in [Ca(2+)](rest) in Hom FDBs and elicited pronounced Ca(2+) oscillations in ∼30% of FDBs tested. Genotype contributed significantly elevated [Ca(2+)](rest) (Hom > Het > WT) measured in vivo using ion-selective microelectrodes. Het and Hom oxygen consumption rates measured in intact myotubes using the Seahorse Bioscience (Billerica, MA) flux analyzer and mitochondrial content measured with MitoTracker were lower than WT, whereas total cellular calpain activity was higher than WT. Muscle membranes did not differ in RYR1 expression nor in Ser(2844) phosphorylation among the genotypes. Single channel analysis showed highly divergent gating behavior with Hom and WT favoring open and closed states, respectively, whereas Het exhibited heterogeneous gating behaviors. [(3)H]Ryanodine binding analysis revealed a gene dose influence on binding density and regulation by Ca(2+), Mg(2+), and temperature. Pronounced abnormalities inherent in T4826I-RYR1 channels confer MHS and promote basal disturbances of excitation-contraction coupling, [Ca(2+)](rest), and oxygen consumption rates. Considering that both Het and Hom T4826I-RYR1 mice are viable, the remarkable isolated single channel dysfunction mediated through this mutation in S4-S5 cytoplasmic linker must be highly regulated in vivo.