Abstract
The existence of a barrier between anesthetic behavioral state transitions has been observed across phyla, but demonstrating that such a barrier exists and is not a pharmacokinetic artifact has not yet been possible in humans. Such an investigation requires temporally precise information regarding the brain concentration of anesthetic in order to demonstrate the specific pharmacokinetic-pharmacodynamic mismatch that is hysteresis. We propose a method to noninvasively determine brain tissue anesthetic concentration using computerized tomography and the radiopaque gaseous anesthetic xenon. Such a technique can be used to investigate pharmacokinetic-pharmacodynamic mismatches in humans.