Clinical Validation of the Covariates Pharmacokinetic Model for Propofol in an Adult Population

Background And Objective: Pharmacokinetic or pharmacokinetic-pharmacodynamic models have been instrumental in facilitating the clinical use of propofol in target-controlled infusion systems in anaesthetic practice. There has been debate over which model should be recommended for practice. The covariates model is an updated pharmacokinetic model for propofol. The aim of this study was to prospectively validate this model in an adult population.

Methods: Twenty-nine patients were included, with a range of ages to assess model performance in younger and older individuals. Subjects received propofol through a target-controlled infusion device programmed with the covariates model. Subjects were randomised to one of two increasing/decreasing regimes of propofol plasma target concentrations between 2 and 5 μg.mL. After the start of the infusion, arterial and venous blood samples were drawn at pre-specified timepoints between 1.5 and 20 min and between 1.5 and 45 min, respectively. Predictive performance was assessed using established methodology.

Results: The model achieved a bias of 9 (- 45 to 82) and precision of 24 (9-82) for arterial samples and bias of - 8 (- 64 to 70) and precision of 23 (9-70) for venous samples. Predicted concentrations tended to be higher than the measured concentrations in female individuals but lower in male individuals. There was no clear systematic difference in the bias between younger and older patients.

Conclusions: The covariates propofol pharmacokinetic model achieved an acceptable level of predictive performance, as assessed by both arterial and venous sampling, for use in target-controlled infusion in clinical practice.

Clinical Trial Registration: NCT01492712 (15 December, 2011).