[The predictability of inspiratory and endexpiratory concentrations of isoflurane and enflurane using pharmacokinetic models and interindividual variability].

Abstract

The predictability of the inspiratory and endexpiratory concentrations of the volatile anaesthetics isoflurane and enflurane by pharmacokinetic models was investigated. 67 patients of ASA-classes 1-2 that underwent minor surgical procedures were studied. The pharmacokinetic model consisted of two parts, a model of the anaesthesia machine and a model of the patient. The mean values of the predicted/measured concentrations of isoflurane had an amount of 1.01 +/- 0.13 (inspiratory) and 0.97 +/- 0.13 (endexpiratory), the mean values of enflurane showed a value of 1.00 +/- 0.11 (inspiratory) and 0.97 +/- 0.13 (endexpiratory). The interindividual variances amounted to between 10% and 40% of the variance of all patients. This corresponded to a standard deviation of about 6% (inspiratory) while the endexpiratory concentrations showed a standard deviation about 8% for the average values of every patient.