Variation of bispectral index under TIVA with propofol in a paediatric population

Background. In this prospective observational study, we aim to explore the relationship between age and bispectral index (BIS) values at different plasma concentrations of propofol. Methods. Fifty children aged from 3 to 15 yr were included. Anaesthesia was induced using a target-controlled infusion of propofol with the Kataria pharmacokinetic model together with a bolus of remifentanil followed by a continuous infusion rate at 0.2 mu g kg(-1) min(-1). Target plasma propofol concentration was initially stabilized to 6 mu g ml(-1) and continued for 6 min. The target was then decreased and stabilized to 4 mu g ml(-1) and then to 2 mu g ml(-1). BIS values, plasma propofol concentration, and EEG were continuously recorded. In order to explore the relationship between variations in propofol concentration and the EEG bispectrum, we used a multiple correspondence analysis (MCA). Results are shown in median (range). Results. We found no statistical difference between BIS values with propofol 6 mu g ml(-1) [23 (12-40)] and 4 mu g ml(-1) [28 (9-67)]. At 2 mu g ml(-1), BIS was significantly different [52 (24-71)], but a significant correlation between the age of children and BIS values was found (r(2)=0.66; P < 0.01). There was little change in children's position between 6 and 4 mu g ml(-1) in the structure model of the MCA. From 4 to 2 mu g ml(-1), the position of children moved only on axis 2. Conclusions. These results showed the difficulty to interpret BIS values because of the absence of significant change for higher plasma propofol concentration variation or because of the link with age for the lower plasma concentration.