Theoretical basis of target controlled anaesthesia: history, concept and clinical perspectives

The technique of target controlled infusion (TCI) has influenced the development of intravenous anaesthesia substantially and opened the possibility of many new and exciting applications in peri-operative anaesthetic care. The launch of ‘Diprifusor™’ as the first commercially available TCI system for propofol in 1996 was the cornerstone of a successful research period within the last decade, which evaluated the pharmacokinetic foundations of computer assisted intravenous drug delivery. We are now in a period where TCI technology is becoming a part of the routine anaesthetic techniques for the practitioner rather than a research tool for specialists and enthusiasts. This review gives an overview of the history of target controlled anaesthesia, the rational pharmacokinetic basis of TCI development, the preliminary clinical experience with the new technique, the performance and accuracy of available TCI devices and the potential technical pitfalls in clinical routine. Although these developments were predominantly made with intravenous anaesthetic drugs, the knowledge of target controlled anaesthesia can principally be transferred to the administration of inhalational drugs, especially in the advent of new quantitative anaesthesia machines. As well as the clinical application of TCI with propofol and, in the near future, with remifentanil, target controlled systems are expected to play a significant role as research tools in the evaluation of drug interactions in anaesthesia, in the development of novel control techniques for the administration of sedative and analgesic drugs in the peri-operative period, and in optimizing the accuracy of feedback control systems.