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.
From the From the Department of Anesthesiology and Intensive Care Medicine, University Hospital of Leipzig, Leipzig, Saxony, Germany.
Tobias
T
Esper
Markus
M
Wehner
Claus-Dieter
CD
Meinecke
Henrik
H
Rueffert
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D018685:Anesthetics, Inhalation / Q000097:blood*; D001784:Blood Gas Analysis / Q000706:statistics & numerical data*; D015992:Body Mass Index; D000077335:Desflurane; D005260:Female; D006400:Hematocrit; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007530:Isoflurane / Q000031:analogs & derivatives* / Q000097:blood; D008297:Male; D008738:Methyl Ethers / Q000097:blood*; D008875:Middle Aged; D015203:Reproducibility of Results; D000077149:Sevoflurane; D012737:Sex Factors; D055815:Young Adult
D018685:Anesthetics, Inhalation; D006454:Hemoglobins; D008738:Methyl Ethers; D000077149:Sevoflurane; D000077335:Desflurane; D007530:Isoflurane