A Novel Method for Determining the Blood/Gas Partition Coefficients of Inhalation Anesthetics to Calculate the Percentage of Loss at Different Temperatures

The loss by blood/gas λ partition of inhalation anesthetics can be estimated by an equation for the percentage of loss. However, because λs of inhalation anesthetics at different temperatures have not been fully determined so far, the percentage of loss at varying temperature in various headspace volumes cannot be estimated. Therefore, a novel method was developed for the determination of inhalation anesthetic λ, in this study. The method was precise, with a relative standard deviation of less than 5%. The average of λ from seven distinct blood samples at 4°C, 25°C, and 37°C were determined as 6.68, 2.04, and 1.32 of isoflurane; 3.47, 1.10, and 0.65 of sevoflurane; and 2.31, 0.75, and 0.46 of desflurane, respectively. In addition, increasing temperature was found to decrease λ profoundly by a secondary order mechanism. Using the obtained value of λ, the percentage of loss of isoflurane, sevoflurane, and desflurane were then predicted using a 5-mL vacuum tube as a collecting container for an example. In conclusion, a novel method was developed here for λ determination, and λs of isoflurane, sevoflurane, and desflurane at various temperatures were given for estimating the loss resulting from liquid/gas partitioning.