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Functional imaging of the visual cortex during wakefulness and during intravenous anaesthesia: A-6

Rieck, A.; Dueck, M.; Gerbershagen, H. J.; Petzke, F.; Giesecke, T.; Paul, M.; Heelmann, V.ß; Krug, B.; Lehrke, R.; Sturm, V.

European Journal of Anaesthesiology: May 2005 - Volume 22 - Issue - p 2
ESA Best Abstract Prize Competition (BAPC)

Department of Anaesthesiology, University of Cologne, Cologne, Germany

Background and Goal of Study: Previous studies in primates and humans found a strong and reproducible visually induced functional magnetic resonance imaging (fMRI) signal in the visual cortex during mild isoflurane anaesthesia. Accordingly, we hypothesized that visual stimulation might also activate the human visual cortex during intravenous anaesthesia. The aim of this study was to assess the effect of propofol/remifentanil anaesthesia on visual-evoked activation of the visual cortex using fMRI-technique.

Materials and Methods: We studied four volunteers during wakefulness and eight patients during deep surgical anaesthesia maintained with propofol/remifentanil. For visual stimulation a binocular flash stimulus (1.7 Hz) was presented as a block design composed of 8 stimulation periods alternating with resting periods defined by the absence of the experimental stimulus with both periods lasting 25s. Visual processing was analysed using cross-correlation analysis (r > 0.4; P < 0.0001, uncorrected). For data analysis the fMRI software tool BrainVoyager 2000 was used.

Results and Discussions: Mean propofol plasma target concentration was 4.21 ± 0.64 μg/ml and mean rate of remifentanil infusion was 0.31 ± 0.09μg/kg/min during fMRI data acquisition. Binocular visual stimulation during wakefulness as well as during propofol/remifentanil anaesthesia produced a significant activation in the visual cortex including the striate (Brodmann's area (BA) 17) and the extrastriate visual cortex (BA 18, 19). The finding of activated areas in the anaesthetised brain indicates that the underlying mechanism of the fMRI signal is preserved during surgical concentrations of propofol and remifentanil.

Conclusions: (1) This study demonstrates that early visual information processing is preserved during general anaesthesia induced by the intravenous anaesthetics propofol and remifentanil. (2) The fMRI method may be appropriate for further investigating the effect of different anaesthetics on various neuronal networks.

Acknowledgements: This study was funded by KOLN FORTUNE, 66/2001.

© 2005 European Society of Anaesthesiology