The Pharmacokinetics of Inhaled Anesthetics During the Induction of Anesthesia is Defined As the Ratio of the End-Tidal Anesthetic Concentration (Fa) to the Inspired Anesthetic Concentration (Fi) Consistent With Their Relative Blood:gas Partition Coefficients, the Fa/Fi of Poorly Soluble Anesthetics (Nitrous Oxide, Desflurane, Sevoflurane) Increases More Rapidly Than that of Anesthetics With Greater Solubility in Blood. A Decrease in the Rate of Change in the Fa/Fi after 5 to 15 Minutes (Three Time Constants) Reflects Decreased Tissue Uptake of the Anesthetic As the Vessel-Rich Group Tissues Become Saturated. (Data are Mean ± Sd.)
(From Yasuda N, Lockhart SH, Eger EI II, et al. Comparison of kinetics of sevoflurane and isoflurane in humans. Anesth Analg. 1991;72:316-324, with permission.)
The pharmacokinetics of inhaled anesthetics during the induction of anesthesia is defined as the ratio of the end-tidal anesthetic concentration (FA) to the inspired anesthetic concentration (FI). Consistent with their relative blood:gas partition coefficients, the FA/FI of poorly soluble anesthetics (nitrous oxide, desflurane, sevoflurane) increases more rapidly than that of anesthetics with greater solubility in blood. A decrease in the rate of change in the FA/FI after 5 to 15 minutes (three time constants) reflects decreased tissue uptake of the anesthetic as the vessel-rich group tissues become saturated. (Data are mean ± SD.)