Patient-maintained propofol sedation. Assessment of a target-controlled infusion system

We have developed a system which allows patients to operate a target-controlled infusion of propofol to provide sedation and we have studied its use in 36 unpremedicated patients undergoing local and regional anaesthetic procedures lasting 10-280 min. An intravenous propofol infusion was started at a target plasma level of 1 microgram.ml-1. The patient was able to increase the target propofol concentration in 0.2- microgram.ml-1 increments by pressing a demand button. There was a lockout interval of 2 min and a maximum permissible target concentration of 3 micrograms.ml-1. There was considerable interindividual variability in propofol consumption (mean 39.3 micrograms.kg-1.min-1, range 3-131 micrograms.kg-1.min-1), no cardiovascular instability and little oversedation. Eight patients required supplementary oxygen. Optimal sedation was provided at median target concentrations of 0.8-0.9 microgram.ml-1. The target-controlled infusion system bias was-47% and the inaccuracy was 48%. Patient satisfaction was high and 89% said that they would definitely use the technique again. This technique combines the benefits of target-controlled infusion with patient-controlled feedback and produces safe intra-operative sedation.