Reaction time‐monitored patient‐maintained propofol sedation: a pilot study in oral surgery patients

Abstract

SummaryPrevious volunteer studies of an effect-site controlled patient-maintained sedation system using propofol have demonstrated a risk of oversedation. We have incorporated a reaction time monitor into the handset to add an individualised patient-feedback mechanism. This pilot study assessed if the reaction time-feedback modification would prove safe and effective in 20 healthy patients receiving sedation while undergoing oral surgery. All patients successfully sedated themselves without reaching any unsafe endpoints. All 20 maintained verbal contact throughout. The mean (SD) lowest peripheral blood oxygen saturation was 98.0 (2.1)% breathing room air. No patient required supplementary oxygen. The mean (SD) maximum effect-site propofol concentration reached was 1.6 (0.5) lg.ml À1. The present system was found to be safe and effective, allowing oral surgery treatment under conscious sedation, but preventing oversedation. Effect-site controlled, patient-maintained sedation with propofol allows the patient to control target controlled infusions of propofol, and hence his/her level of sedation, using a hand-held demand button. The system sets a target effect-site concentration [1] at a low level initially, which can be increased incrementally by the patient pressing the handset button twice within 1 s. The system increases the plasma concentration up to 100% greater than 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 time-based lockout, the patient is not able to obtain a further increment until the plasma concentration decreases to within 10% of the target effect-site concentration -an 'effect-site lockout'. As the brain is the site of action of propofol, this allows for equilibration between the blood and brain. This technique was found by our group to be safe and effective in patients having dental surgery [2], but the potential for oversedation was demonstrated in volunteers who were instructed to try deliberately to oversedate themselves [3][4][5].

Patient-maintained propofol sedation for adult patients undergoing surgical or medical procedures: a scoping review of current evidence and technology

“…PMPS has been examined in four healthy volunteer studies (a total of 70 participants), 10,12,18,21 nine observational clinical studies (251 participants), 9,11,13,15,17,19,22,23 and three prospective RCTs (150 participants). 15,17,20 One RCT protocol, published by the authors of this review, comparing PMPS with anaesthetist-controlled propofol sedation in lower limb arthroplasty surgery was identified.…”

“…24 The studies identified have taken place in the setting of general surgery, 17 orthopaedic surgery, 17,23 endoscopic retrograde cholangiopancreatography (ERCP), 11 colonoscopy, 15,20 and oral surgery. 13,14,16,17,19,22 Table 2 Pharmacokinetic models and sedation algorithms used in published studies. Terms are defined as follows: Starting concentration, the concentration of propofol at which participants commence the sedation regime; Increment concentration, the increase applied to the target-site concentration of propofol obtained by each participant handheld trigger activation; Lock-out time, the time after an increment in target-site concentration during which a subsequent handheld trigger activation will not cause a further increment; Maximum obtainable concentration, the 'ceiling' target-site concentration, above which the sedation will not increment regardless of handheld trigger activations; Decrement concentration, the targetsite concentration reduction which is automatically applied in the event of no handheld trigger activations within the decrement time; Decrement time, the time which must expire with no handheld trigger activations before the decrement concentration is automatically applied; Minimum concentration, the target-site concentration below which the sedation will not decrement during the sedation period.…”

“…In the absence of a commercially available infusion device capable of PMPS, researchers report a variety of infusion devices modified by serial-port connection to bespoke software in order to deliver PMPS. The Omheda 9000 device (BOC Healthcare, Manchester, UK), 8 Graseby 3400 (Smiths Medical Ltd, Ashford, UK), 8,9e18 Graseby 3500 (Smiths Medical Ltd, Ashford, UK), 21,22 Asena GH (BD Ltd, Wokingham, UK), 20 Alaris PK (BD Ltd, Wokingham, UK), 23 and the Perfusor fm (B. Braun Medical, Melsungen, Germany) 24 have all been modified in this manner. One study did not specify the technology by which their PMPS algorithm was delivered.…”