Wide inter-individual variability of bispectral index and spectral entropy at loss of consciousness during increasing concentrations of dexmedetomidine, propofol, and sevoflurane  K. Kaskinoro, A. Maksimow, J. Långsjö, R. Aantaa, S. Jääskeläinen, K. Kaisti, M. Särkelä, H. Scheinin  British Journal of Anaesthesia  Volume 107, Issue 4, Pages 573-580 (October 2011) DOI: 10.1093/bja/aer196 Copyright © 2011 The Author(s) Terms and Conditions

Fig 1 Study set-up. After recording the baseline values, drug administration was initiated (for details, see the Methods section). Each targeted concentration level was maintained for 10 min. LOC was tested by requesting subjects to open their eyes at 5 min intervals. After LOC, the study drug administration was discontinued and consciousness was tested at 1 min intervals until ROC was detected (first meaningful response to the request). The time points for LOC testing are indicated with vertical arrows (arbitrary): the solid arrows indicate a meaningful response, while the dashed arrows indicate unresponsiveness to the request (the first dashed arrow indicating LOC). The thick solid arrow indicates ROC (the first meaningful response after the study drug discontinuation). British Journal of Anaesthesia 2011 107, 573-580DOI: (10.1093/bja/aer196) Copyright © 2011 The Author(s) Terms and Conditions

Fig 2 Individual BIS and SE values during pre-LOC (i.e. last meaningful response), LOC (i.e. the first testing event when the subject no longer responded), and ROC (i.e. the first meaningful response after discontinuation of the study drug) for all three drugs. Paired t-test statistics (pre-LOC vs LOC and LOC vs ROC) are presented with asterisks (*P<0.05, **P<0.01, ***P<0.001). British Journal of Anaesthesia 2011 107, 573-580DOI: (10.1093/bja/aer196) Copyright © 2011 The Author(s) Terms and Conditions

Fig 3 Characteristic behaviour of BIS and SE during the study session. One subject is included from each group: dexmedetomidine, propofol, and sevoflurane. The time and the time points of consciousness testing are presented on the horizontal (x) axis. The solid arrows indicate a meaningful response, while the dashed arrows indicate unresponsiveness to consciousness testing (the first dashed arrow indicating LOC). BIS and SE values are presented on the vertical (y) axis. With increasing concentrations of dexmedetomidine, BIS and SE decreased, but the reactivity to stimulus (LOC testing) remained evident (the peaking index values at ∼5 min intervals) until LOC is reached. At ROC, all indices return to higher level. However, as the subject was allowed to lie quietly after awakening, the indices tended to decrease again, although the administration of dexmedetomidine had been terminated after LOC. In the propofol group, the indices decreased slowly towards LOC and rose gradually after propofol infusion was terminated. The example from the sevoflurane group demonstrates how clinical LOC is reached even though the indices remain quite high before LOC. In these examples, LOC was reached at the fourth step and second test with dexmedetomidine, with propofol at the third step and first test and for sevoflurane at the second step and first test (LOC testing was performed twice at each level). British Journal of Anaesthesia 2011 107, 573-580DOI: (10.1093/bja/aer196) Copyright © 2011 The Author(s) Terms and Conditions