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

Abstract

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 microg kg(-1) min(-1). Target plasma propofol concentration was initially stabilized to 6 microg ml(-1) and continued for 6 min. The target was then decreased and stabilized to 4 microg ml(-1) and then to 2 microg 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 microg ml(-1) [23 (12-40)] and 4 microg ml(-1) [28 (9-67)]. At 2 microg ml(-1), BIS was significantly different [52 (24-71)], but a significant correlation between the age of children and BIS values was found (r2=0.66; P<0.01). There was little change in children's position between 6 and 4 microg ml(-1) in the structure model of the MCA. From 4 to 2 microg 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.

Fig 1

An example of the representation of the 36 frequencies of coupling (Pi) of the bispectrum calculated every 20 s for one child’s EEG (MatBis).

Fig 2

BIS values at different plasma propofol concentrations.

Fig 3

BIS values according to age of children at plasma propofol concentration of 6 mcg·ml⁻¹ on the top, of 4 mcg·ml⁻¹ in the middle and of 2 mcg·ml⁻¹ on the lower graph.

Fig 4

Change in children’s position in the structured model of the multiple correspondence analysis during decrease in plasma propofol concentration. The structure model is the same used for sevoflurane (SEVO) and desflurane (DES) in previous studies (1,4). Larger dots represent steady state. The units of axes F1 and F2 are arbitrary.