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Mahon, P, Greene, BR, Greene, C, Boylan, GB, Shorten, GD;
British Journal of Anaesthesia
Behaviour of Spectral Entropy, Spectral Edge Frequency 90%, and Alpha and Beta Power Parameters During Low-Dose Propofol Infusion
Optional Fields
Background. In this study we analyse the behaviour, potential clinical application and optimal cortical sampling location of the spectral parameters: (i) relative alpha and beta power; (ii) spectral edge frequency 90%; and (iii) spectral entropy as monitors of moderate propofol-induced sedation.. Methods. Multi-channel EEG recorded from 12 ASA 1 (American Society of Anesthesiologists physical status 1) patients during low-dose, target effect-site controlled propofol infusion was used for this analysis. The initial target effect-site concentration was 0.5 mu g ml(-1) and increased at 4 min intervals in increments of 0.5 to 2 mu g ml(-1). EEG parameters were calculated for 2 s epochs in the frequency ranges 0.5-32 and 0.5-47 Hz. All parameters were calculated in the channels: P4-O2, P3-O1, F4-C4, F3-C3, F3-F4, and Fp1-Fp2. Sedation was assessed clinically using the OAA/S (observer's assessment of alertness/sedation) scale.. Results. Relative beta power and spectral entropy increased with increasing propofol effect-site concentration in both the 0.5-47 Hz [F(18, 90) = 3.455, P < 0.05 and F(18, 90) = 3.33, P < 0.05, respectively] and 0.5-32 Hz frequency range. This effect was significant in each individual channel (P < 0.05). No effect was seen of increasing effect-site concentration on relative power in the alpha band. Averaged across all channels, spectral entropy did not outperform relative beta power in either the 0.5-32 Hz [Pk=0.79 vs 0.814 (P > 0.05)] or 0.5-47 Hz range [Pk=0.81 vs 0.82 (P > 0.05)]. The best performing indicator in any single channel was spectral entropy in the frequency range 0.5-47 Hz in the frontal channel F3-F4 (Pk=0.85).. Conclusions. Relative beta power and spectral entropy when considered over the propofol effect-site range studied here increase in value, and correlate well with clinical assessment of sedation..
DOI 10.1093/bja/aen161
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