Henrik Rueffert

Do Variations in the 5-ht3a and 5-ht3b Serotonin Receptor Genes ( htr3a and htr3b ) Influence the Occurrence of Postoperative Vomiting?

BACKGROUND: Postoperative nausea and vomiting are unpleasant side effects of general anesthesia. Besides known risk factors (female gender, nonsmoker, history, and opioids), a genetic influence of the serotonin receptor system on the development of nausea and vomiting has repeatedly been proposed. In this pilot study, we therefore investigated the genes of the serotonin receptor subunits A and B (HTR3A and HTR3B) for genetic variants. METHODS: We included 95 patients who had suffered from postoperative vomiting (POV) after general anesthesia and 94 control patients. After DNA isolation, the entire HTR3A and HTR3B coding regions, the 5′ flanking regions, and exon/intron boundaries were screened for genetic variants. Correlation of identified genetic variants with POV was determined by logistic regression. RESULTS: We identified 16 different variants in the HTR3A gene and 19 in the HTR3B gene. By using a multivariate logistic regression model that also included classical risk factors, the HTR3A variant c1377A>G was associated with a significantly higher risk (odds ratio [OR] 2.972; 95% confidence interval [CI] 1.466–6.021; P = 0.003) and the HTR3B variants c5+201_+202delCA (OR 0.421; 95% CI 0.257–0.69; P = 0.001) and c6-137C>T (OR 0.034; 95% CI 0.003–0.332; P = 0.004) were associated with a lower risk for POV. However, all significant genetic variants were located in noncoding regions of their gene. CONCLUSIONS: Genetic variations in the HTR3A and HTR3B gene seem to be associated with the individual risk of developing POV. How strong their influence is within the multifactorial genesis of POV needs to be investigated in additional studies with an appropriate sample size.

Functional characterization of malignant hyperthermia-associated RyR1 mutations in exon 44, using the human myotube model

Malignant hyperthermia (MH) is a pharmacogenetic disorder with an autosomal dominant inheritance. During exposure to triggering agents as volatile anaesthetics, affected individuals may develop a potentially fatal hypermetabolic syndrome caused by excessive calcium release from the sarcoplasmic reticulum in skeletal muscle. More than 60 MH associated mutations were found in the gene of skeletal muscle ryanodine receptor (RyR1), but only some of them have been functionally characterized. Primary human myotubes were cultured from carriers of RyR1 mutations in exon 44 (Ala2350Thr, Arg2355Trp, Gly2375Ala) and from MH non-susceptible individuals. Investigation of calcium homeostasis with the calcium sensitive probe Fura 2 showed a higher sensitivity to the ryanodine receptor agonists 4-chloro-m-cresol, caffeine and halothane for the myotubes derived from the mutation carriers as compared to those of the control group. The presence of RyR1 mutations with impact on calcium homeostasis emphasizes the functional significance of exon 44.

The Ile2453Thr mutation in the ryanodine receptor gene 1 is associated with facilitated calcium release from sarcoplasmic reticulum by 4-chloro-m-cresol in human myotubes

Central core disease (CCD) is a congenital disorder of skeletal muscle that is characterised histologically by typical central cores in type 1 skeletal muscle fibres. This disease is associated with malignant hyperthermia susceptibility and has been linked to the gene of skeletal muscle ryanodine receptor RYR1. In this study, we present a family with the spontaneous occurrence of the RYR1 Ile2453Thr mutation. Affected individuals were diagnosed as susceptible to malignant hyperthermia in the in vitro contracture test (IVCT) and showed histological signs of CCD. Myotubes were derived from the index patient. The calcium homeostasis in response to the ryanodine receptor agonist 4-chloro-m-cresol (4CmC) was investigated by calcium imaging using the Ca(2+)-sensitive fluorescent probe FURA 2. In the myotubes derived from the mutation carrier, the EC(50) of 4CmC was reduced to 94 micro as compared to 201 microM in a control group of 16 individuals non-susceptible to malignant hyperthermia. In the myotubes of the non-affected family members, the EC(50) was found within the same range as that of the control group. The reduction of EC(50) indicates a facilitated calcium release from sarcoplasmic reticulum in the myotubes of the index patient suggesting that the RYR1 Ile2453Thr mutation is pathogenic for the malignant hyperthermia susceptibility and CCD of the two affected individuals.

A new mutation in the skeletal ryanodine receptor gene (RYR1) is potentially causative of malignant hyperthermia, central core disease, and severe skeletal malformation

Malignant hyperthermia susceptibility (MHS) and central core disease (CCD) have been shown to result from missense mutations in the ryanodine receptor gene of the skeletal muscle (RYR1). A 15‐year‐old patient who had spondylocostal dysostosis (SCD) developed an MH crisis during general anesthesia. The patient was characterized phenotypically by block vertebrae, vertebral fusion, short neck and thorax, fused ribs, craniofacial abnormalities, spina bifida occulta, and a diaphragmatic defect closed surgically in early infancy. The diagnosis MH susceptible (MHS) was confirmed by the in vitro contracture test (IVCT) on a muscle biopsy. Surprisingly, the histopathological investigation revealed the presence of CCD too. Molecular genetic investigation of the RYR1 gene was performed to search for known MH‐related mutations. Cluster regions of the RYR1 gene, in which mutations have already been found, were examined by direct automated sequencing. In addition to the diagnosis MHS and CCD we were able to identify a novel RYR1 mutation in exon 46: 7358ATC > ACC, resulting in an Ile2453Thr substitution. This mutation was also present in the mother, in whom MH disposition and CCD were determined by muscle investigations. We suggest that the newly identified RYR1 mutation is closely associated with MH and CCD. A probable causative role of the RYR1 gene in SCD patients should be assessed by further genetic investigations.

Blood/Gas partition coefficients for isoflurane, sevoflurane, and desflurane in a clinically relevant patient population.

BACKGROUND:The blood/gas partition coefficient of a certain volatile anesthetic is of clinical importance because it determines its velocity of uptake into and elimination from the body of a patient and thus its pharmacokinetic behavior. To date, the blood/gas partition coefficients of isoflurane, sevoflurane, and desflurane have been measured in small numbers of subjects or in particular study groups, for example, healthy volunteers, patients experiencing a common kind of disease, or mothers immediately after giving birth. The objective of this study was to determine the blood/gas partition coefficients of these volatile anesthetics at 37°C in a larger clinically relevant and adult patient population. Furthermore, we tested whether age, gender, body mass index, hemoglobin concentration, or hematocrit had an influence on the coefficients. METHODS:Blood samples were taken from 120 fasting operative patients with ASA physical status I to III and aged 19 to 86 years. All subjects were randomly enrolled in study groups for the separate determinations of the blood/gas partition coefficients of isoflurane (n = 41), sevoflurane (n = 41), and desflurane (n = 38) by headspace gas chromatography. To check the quality of the measurements, we determined the distilled water/gas partition coefficients of those anesthetics and compared them with previously published values. RESULTS:We found a blood/gas partition coefficient of 1.45 ± 0.12 (mean ± SD) for isoflurane, 0.74 ± 0.06 for sevoflurane, and 0.57 ± 0.04 for desflurane. Values of this study are 5.07%, 12.12%, and 7.55% higher for isoflurane, sevoflurane, and desflurane, respectively, than the previously published mean values (all P ⩽ 0.001). There were only trends for small correlations between the blood/gas partition coefficient of isoflurane and hemoglobin concentration (Pearson r = 0.32; P = 0.041) and hematocrit (r = 0.37; P = 0.016). We found no other potentially significant correlations of the partition coefficients with patient age, body mass index, hemoglobin concentration, or hematocrit (all remaining P > 0.069). Furthermore, the coefficients did not differ significantly between female and male patients. The evaluation of the distilled water/gas partition coefficients of isoflurane (0.59 ± 0.04), sevoflurane (0.37 ± 0.04), and desflurane (0.27 ± 0.03) proved the validity of the gas chromatography method used in this study. CONCLUSIONS:The blood/gas partition coefficients of the modern volatile anesthetics, in particular, those of sevoflurane and desflurane, may be higher than that has been hitherto reported. Therefore, their uptake and elimination may occur more slowly in some patients than has been supposed. The blood/gas partition coefficients of isoflurane, sevoflurane, and desflurane measured in this study appear to be representative because they were determined in a clinically and numerically relevant patient cohort.

Spontaneous Occurrence of the Disposition to Malignant Hyperthermia

ONE characteristic of malignant hyperthermia (MH) is the autosomal-dominant mode of inheritance. This implies that at least one parent of an affected patient should be predisposed to MH. In this report, we describe two families in which MH susceptibility developed spontaneously through a neomutation. These families attracted attention because both parents of an MH-susceptible individual were diagnosed as MH-negative in the in vitro contracture test (IVCT). The IVCT was performed with halothane and caffeine according to the protocol of the European MH Group. This test may provide the following diagnoses: MH-susceptible (MH-positive), MH-negative, or MH-equivocal (possible MH-positive). Cluster regions of the skeletal ryanodine receptor gene (RYR1), in which MH-related mutations have been identified, were amplified by polymerase chain reaction and subsequently analyzed by the direct sequencing technique previously described. Chromosome 19 microsatellite markers were amplified by polymerase chain reaction using labeled fluorescent-tag primers (D19S228, 19S421, RYR.PCR1, D19S422, D19S223, as recommended by the European MH Group, genetic section§) and were checked by fragment gel analysis in the ABI PRISM 377 DNA sequencer (Applied Biosystems, Foster City, CA).

100 telephone conversations about malignant hyperthermia

Results 100 inquiries were analysed: 76 patients and 24 medical doctors called. Out of the 24 medical doctors, 16 were anaesthesiologists. Reason for malignant hyperthermia (MH) inquiry: Positive family anamneses (37%), own anaesthetic accident (29%) or general information about MH (34%). In the group of positive family anamneses, 34 patients with MH or their relatives and three medical doctors sought information. The described anaesthetic accident ranged from reaction to death during an operative procedure. Inquiries based on an anaesthetic accident were addressed by a patient 20 times and by a medical doctor 9 times. Some curious questions were asked: Anaesthetist: “Patient had an anaesthetic incident forty years ago. What should I do?” (anaesthetic management) Patient: “My anaesthetist refused the anaesthesia as long as I m not tested for MH!” (suspicious family history) Intensive care physician: “Our patient on the ICU must immediately be tested for MH because he has a rhabdomyolysis and we don t no why!” (no triggering substances!) Patient: “My uncle had problems during anaesthesia. Now our family should be tested. How do I proceed?” General practitioner: “MH was suspected in a muscular biopsy.”