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.

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.