SummaryThe bispectral index, a new processed electroencephalographic parameter which may give information on depth of anaesthesia, was used in 58 patients undergoing outpatient gynaecological surgery in order to study if the addition of bispectral index monitoring to standard clinical monitoring could improve the titration of target propofol concentration when using effect-site target-controlled propofol infusion for sedation. In Group 1 (n ¼ 30), the bispectral index was recorded but the anaesthetist was unaware of the readings and therefore only classical signs of depth of anaesthesia were used to guide the anaesthetist in controlling the effect-site concentration. In Group 2 (n ¼ 28), bispectral index readings were available to the anaesthetist and effect-site concentration was adjusted to ensure that bispectral index was maintained between 40 and 60. Similar propofol induction and maintenance doses, blood and effect-site concentrations and mean bispectral index were found in the two groups. A greater percentage of bispectral index readings lying outside the target range (i.e. < 40 or > 60) and more movement at incision and during maintenance were found in Group 1. There was a trend towards more implicit awareness in patients in Group 1. Bispectral index was found to be useful for measuring depth of sedation when using propofol target-controlled infusion. Propofol dosage could not be decreased but a more consistent level of sedation could be maintained due to a more satisfactory titration of target effectsite concentration. For many years, anaesthetists have tried to correlate the pharmacokinetics and pharmacodynamics of propofol in order to achieve the most appropriate dosage schemes for continuous intravenous infusion [1]. Recently, a pharmacokinetically based technique for the administration of propofol (target-controlled infusion, TCI) has proved to have many advantages [2]. The concept underlying TCI techniques is to apply the three-compartmental pharmacokinetic model for propofol [3] and to predict by calculation its concentration in one of the compartments, e.g. the central (blood) compartment or the theoretical effect-site compartment [4]. Target-controlled infusion devices will rapidly achieve and maintain the desired predicted concentration in the chosen compartment [5]. Effect compartment modelling is motivated by the observed dissociation between the measured blood concentrations of the drug and the currently measured indices of drug effect, e.g. the processed electro-encephalogram (EEG). The hysteresis between pharmacokinetics and pharmacodynamics can be quantified by a rate constant, k e1 . The time course of a drug effect is found to parallel the time course of the effect compartment modelling. It therefore becomes appealing to be able to control quantitatively the drug concentration in the effect compartment rather than in the central compartment [6,7]. This method can provide a better prediction of anaesthetic drug effect [8].
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.