SummaryPatient-maintained sedation using propofol has recently been shown to be effective for dental surgery. We compared this new technique to the established technique of operator administered midazolam. The two groups were compared before, during and after sedation. The two primary outcomes were time until discharge and oxygen saturation. Vital signs, anxiety and psychomotor skills were also compared. State anxiety was reduced to a greater extent in the propofol group (mean difference 10 (SD 4) mm; p = 0.010. Propofol patients recovered quicker (mean difference 7 (SD 1.4) min; p = 0.001). Propofol patients had a smaller reduction in arterial oxygen saturation (mean difference 0.8 (SD 0.3)%; p = 0.030), and a reduced increase in heart rate (mean difference 9 (SD 2) beats.min -1 ; p < 0.001). Both techniques were well tolerated and safe. Propofol sedation offered superior anxiolysis, quicker recovery, less amnesia and less depression of simple psychomotor function.

SummaryWe have designed a new effect-site controlled, patient-maintained sedation system for delivering propofol. In the previous systems we developed, the patients retained the use of the handset throughout the procedure and were able to increase the level of sedation. However, it was found that this could potentially lead to oversedation. In the present system, the patients were able to increase their level of sedation until a level was reached that was judged by the patients as being adequate to allow them to tolerate the injection of dental local anaesthetic. The handset was then taken from the patients and the effect site concentration of propofol was maintained at that level for the remainder of the procedure. To assess its safety and efficacy, the system was used to sedate 40 patients presenting for dental procedures under sedation. The system was used successfully and treatment was completed in 39 patients. The system was found to be safe. Both surgeon and patient approval scores were high. Although this study demonstrates the efficacy of effect-site controlled, patient-maintained propofol sedation in this group of patients, further work is required to confirm its safety. At present, patients receiving conscious sedation in the UK for dental procedures usually receive incremental doses of midazolam administered by an operatorsedationist. The safety of this regimen has been questioned in a variety of clinical situations [1][2][3][4], and an alternative propofol-based sedation system has been developed recently [5][6][7][8]. The majority of targetcontrolled propofol infusion systems in clinical use are plasma level controlled. It is known that the clinical effect of propofol lags behind changes in its plasma concentration, which reflects the time taken for propofol to move from the plasma compartment to its site of action for sedation or hypnosis in the brain. It is assumed that when the clinical effect of propofol has reached a plateau, the plasma and brain concentrations have equilibrated. The effect-site concentration is a mathematically derived term that corresponds with the clinical effect of propofol [9]. Patient-maintained sedation (PMS) involves the patient controlling a target-controlled infusion of propofol by operating a patient-controlled handset, and has been assessed in a number of surgical models [5][6][7][8]. This has recently been changed from controlling the target plasma concentration of propofol, to controlling the effect-site concentration (C e ) [10].Ultimately, it is hoped that the system will be safe for use in the absence of an anaesthetist. However, in the previous pilot studies the patients retained the use of the handset throughout the procedure and were able to

SummaryPrevious volunteer studies of an effect-site controlled, patient-maintained sedation system using propofol have demonstrated a risk of over-sedation. We have incorporated a reaction-time monitor into the handset of the patientmaintained sedation system to add an individualised patient-feedback mechanism. This study assessed if such reactiontime feedback modification would reduce the risk of over-sedation in 20 healthy volunteers deliberately attempting to over-administer themselves propofol. All the volunteers successfully sedated themselves without reaching any unsafe endpoints. All volunteers maintained verbal contact throughout, in accordance with the definition of conscious sedation. The mean (SD) lowest S p O 2 was 97 (1.7) % when breathing room air and no volunteer required supplementary oxygen. The mean (SD) maximum effect-site propofol concentration reached was 1.7 (0.4) lg.ml . The present system was found to be safer than its predecessors, allowing conscious sedation, but preventing over-sedation. Accepted: 9 September 2012Effect-site controlled, patient-maintained sedation with propofol allows the patient to control their level of sedation using a hand-held demand button. The system sets a target effect-site concentration [1] at a low level that can then be increased when the patient presses the handset button twice within 1 s. The system increases the plasma concentration to twice that of the target effect-site concentration to 'force' the drug rapidly into the effect-site, and then reduces the plasma concentration as the target effect-site concentration is approached.Instead of a traditional lockout period, the patient cannot initiate a further increment until the plasma concentration decreases to within 10% of the target effect-site concentration. As the brain is the site of action of propofol, this paradigm allows equilibration between the blood and brain to occur. We have found this technique to be safe and effective in patients undergoing dental surgery [2], but before such systems can be used safely in the absence of an anaesthetist, it is necessary to demonstrate that patients are unable to

Single-use equipment, as presently recommended for tonsillectomy surgery by the UK Department of Health, makes laryngoscopy more difficult for anaesthetists.