Pharmacodynamic Modeling of Thiopental Depth of Anesthesia

Abstract

Quantitation of the degree of a central nervous depression in man necessary for surgical procedures can be achieved by measuring the anesthetic drug effect and using a pharmacodynamic modeling approach to relate drug concentration to drug effect. Using the intravenous anesthetic drug thiopental, EEG waveform analysis has been used to measure the CNS drug effect. The changes of EEG spectral edge or number of waves per second can be used to estimate CNS sensitivity Using computer-controlled infusion pumps, constant thiopental plasma concentrations can be achieved and clinical responses (movement) observed from relevant noxious stimuli to define clinical anesthetic depth. Finally, it is also possible to relate the EEG measure of anesthetic drug effect to the clinically-observed measures of anesthetic depth.