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. 2005 Jun;94(6):810-20.
doi: 10.1093/bja/aei140. Epub 2005 Apr 15.

Impact of age on both BIS values and EEG bispectrum during anaesthesia with sevoflurane in children

E Wodey  1 , O Tirel, J Y Bansard, A Terrier, C Chanavaz, R Harris, C Ecoffey, L Senhadji
Affiliations

Impact of age on both BIS values and EEG bispectrum during anaesthesia with sevoflurane in children

E Wodey et al. Br J Anaesth. 2005 Jun.

Abstract

Background: The aim of this study was to evaluate the potential relationship between age, BIS (Aspect), and the EEG bispectrum during anaesthesia with sevoflurane.

Methods: BIS and raw EEG were recorded at a steady state of 1 MAC in 100 children, and during a decrease from 2 to 0.5 MAC in a sub-group of 29 children. The bispectrum of the EEG was estimated using MATLAB software. For analysis, the bispectrum was divided into 36 frequencies of coupling (P(i))--the MatBis. A multiple correspondence analysis (MCA) was used to establish an underlying structure of the pattern of each individual's MatBis at 1 MAC. Clustering of children into homogeneous groups was conducted by a hierarchical ascending classification (HAC). The level of statistical significance was set at 0.05.

Results: At 1 MAC, the BIS values for all children ranged from 20 to 74 (median 40). Projection of both age and BIS value recorded at 1 MAC onto the structured model of the MCA showed them to be distributed along the same axis, demonstrating that the different values of BIS obtained in younger or older children are mainly dependent on their MatBis. At 1 MAC, six homogeneous groups of children were obtained through the HAC. Groups 5 (30 months; range 23-49) and 6 (18 months; range 6-180) were the younger children and Group 1 (97 months; range 46-162) the older. Groups 5 and 6 had the highest median values of BIS (54; range 50-59) (55; range 26-74) and Group 1 the lowest values (29; range 22-37).

Conclusion: The EEG bispectrum, as well as the BIS appeared to be strongly related to the age of children at 1 MAC sevoflurane.

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Figures

Figure 1
Figure 1
An example of the representation of the 36 frequencies of coupling (Pi) of the bispectrum calculated every 20 sec for one child’s EEG (MatBis).
Figure 2
Figure 2
Top: Expired sevoflurane concentration in the sub-group of 29 children during recording. Bottom: BIS index recorded during the decrease of sevoflurane concentration in the sub-group of 29 children. TO: at 2 MAC (4 mins after intubation); T10: at the steady state at 1 MAC; T20: at the steady state at 0.5 MAC. Box plot (Range; 10–90th centile; 25–75th centile; Median). * vs T0: p< 0.05; † vs T10 (1 MAC): p< 0.05.
Figure 3
Figure 3
Top: Structured model of the MCA obtained with the pattern of each individual EEG bispectrum, also showing the groups of children obtained through the hierarchical ascending classification. Bottom: Representation of the 36 frequencies of coupling (Pi) of the MatBis used to establish the structured model of the MCA. Arrows represent the contribution of the main Pi to the position of each child in the structured model of MCA. The units of axes F1 and F2 are arbitrary - representing distance between children as a function of the similarity or difference in their EEG bispectra at 1 MAC.
Figure 4
Figure 4
Projection of age, weight and BIS index values (recorded at the steady state at 1 MAC sevoflurane) onto the two dominant axes (F1 and F2) of the structured model of the MCA. The units of axes F1 and F2 are arbitrary - representing distance between children as a function of the similarity or difference in their EEG bispectra at 1 MAC.
Figure 5
Figure 5
Change in position in the structured model of MCA of the sub-group of 29 children during the decrease of sevoflurane. From higher concentration (2 MAC) to 1 MAC (T10; steady state) and from 1 MAC to 0.5 MAC (T20: steady state). Each point represents one minute. The units of axes F1 and F2 are arbitrary.
Figure 6
Figure 6
Position of the sub-group of 29 children on axis F1 (top) and axis F2 (bottom) of the structured model of the MCA during the decrease of sevoflurane concentration over time. T0: 2 MAC; T1 and T5 intermediate time; T10: steady state at 1 MAC; T15 intermediate time; T20: steady state at 0.5 MAC. Box plot (Range; 10–90th centile; 25–75th centile; Median). * vs T0: p< 0.05; †vs T10 (1 MAC): p< 0.05.
Figure A1
Figure A1
Examples of the EEG bispectra of nine children at the steady state of 1 MAC of sevoflurane. The children represented in the first column are all under 2 years old, in the middle column between 6 and 7 years old, and in the third column greater than 10 years old. They are unordered examples of children in these age groups.
Figure A2
Figure A2
Top: Representation of the correlation between clinical variables (age, BIS and end-tidal sevoflurane concentration) and children’s coordinates on the two most dominant axes (F1 and F2) of the MCA model at the steady state 1 MAC sevoflurane (age-corrected) in all children. Bottom: Representation of the correlation between BIS values measured in all children at the steady state of 1 MAC sevoflurane (age-corrected) with age, and end-tidal sevoflurane concentration respectively.
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