Influence of a modified propofol equilibration rate constant (k e0) on the effect-site concentration at loss and recovery of consciousness with the Marsh model

Abstract

Summary This study compared the predicted effect-site concentration of propofol at loss and recovery of consciousness when using target-controlled infusion devices with the same pharmacokinetic model (Marsh) but a different plasma effect-site equilibration rate constant (ke0), the DiprifusorTM (ke0 0.26 min-1) and Base Primea™ (ke0 1.21 min-1). We studied 60 female patients undergoing minor gynaecological surgery under general anaesthesia. Although the total dose of propofol and time until loss of consciousness were comparable, the effect-site concentration at loss of consciousness was significantly lower with the Diprifusor than with the Base Primea (1.2 (0.3) μg.ml-1 vs 4.5 (0.9) μg.ml-1, respectively, p < 0.001). The effect-site concentration at recovery of consciousness was significantly higher with the Diprifusor than with the Base Primea (1.8 (0.4) μg.ml-1 vs 1.5 (0.2) μg.ml-1, respectively, p = 0.01). In conclusion, the effect-site concentration of propofol differs depending on the ke0, despite the use of the same pharmacokinetic model. Therefore, the ke0 should be considered when predicting loss and recovery of consciousness based on the effect-site concentration of propofol. © 2013 The Association of Anaesthetists of Great Britain and Ireland.