Pharmacodynamic modelling of changes in arterial blood pressure during propofol anesthesia in volunteers: comparison between invasive and continuous noninvasive measurements

Abstract

The current work compares modelled changes in arterial blood pressure (BP) measured by a continuous noninvasive technique and an established invasive method in response to propofol anesthesia. After approval by the local Ethics Committee, 9 healthy volunteers received anesthesia with propofol by target controlled infusion (TCI). The targeted plasma concentrations were incremented by 0.5 μg·ml− 1 steps. Each infusion step was maintained constant for 15 min. Clinical endpoints of the propofol infusion were burst suppression patterns longer than 2 s in the spontaneous EEG, flattening of spontaneous breathing or drop in mean blood pressure by more than 45% of baseline values. Invasive and noninvasive pressure measurements were performed with a transducer (xtrans) connected to an intra-arterial catheter and a noninvasive blood pressure monitor (Task Force Monitor®), respectively. The relationship between propofol infusion and time course of systolic and mean blood pressure (SBP and MBP, respectively) was modeled using a common sigmoid model. The pharmacodynamic parameters EC50, ke0, and γ were fitted to the data by least-squares regression. The continuous noninvasive method was considered as suitable for indicating propofol induced changes in blood pressure if the estimated pharmacodynamic parameters showed no significant differences to those estimated with established invasive BP measurements (sign test for zero median, α=0.05). The median values for SBP were ke0=0.12 min− 1, EC50=3.4 μg·ml− 1, γ=1.6 and ke0=0.12 min− 1, EC50=2.5 μg·ml− 1, γ=1.2 with the invasive and the noninvasive method (p>0.05), respectively, whereas the median values for MBP were ke0=0.10 min− 1, EC50=2.2 μg·ml− 1, ..=1.9 and ke0=0.11 min− 1, EC50=2.1 μg·ml− 1, γ=1.4 (p>0.05), respectively. The pharmacodynamic parameters estimated with noninvasive BP measurements were not significantly different to those estimated with the established invasive BP measurements. Therefore, the continuous noninvasive BP monitoring method may be useful for pharmacodynamic studies on drug induced BP changes and may monitor acute BP changes during anesthesia.