Approximate entropy as the measurement of the electroencephalographic effect during sevoflurane induction.

Choi,  Byung Moon; Yang,  Cheol Sueng; Woo,  Dong Hee; Koo,  Min Seok; Kim,  Sang Ho; Lee,  Myung Ae; Kwak,  Ho Sung; Noh,  Gyu Jeong

doi:2008.55.4.404

Original Article

Korean Journal of Anesthesiology 2008;55(4):404-411.
DOI: https://doi.org/10.4097/kjae.2008.55.4.404

Approximate entropy as the measurement of the electroencephalographic effect during sevoflurane induction.

Byung Moon Choi, Cheol Sueng Yang, Dong Hee Woo, Min Seok Koo, Sang Ho Kim, Myung Ae Lee, Ho Sung Kwak, Gyu Jeong Noh

¹Department of Anesthesiology and Pain Medicine, National Medical Center, Seoul, Korea. rios76@nate.com
²Department of Anesthesiology and Pain Medicine, Soonchunhyang University Hospital, Soonchunhyang University College of Medicine, Seoul, Korea.
³Department of Clinical Pharmacology and Therapeutics, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
⁴Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.

Abstract

BACKGROUND
The processed electroencephalograms are useful surrogate measures of quantification of volatile anesthetics effect. We hypothesized that there is a certain relationship between the end-tidal concentration of sevoflurane and approximate entropy (ApEn). The aim of this study was to investigate the effect of sevoflurane on ApEn during induction.
METHODS
Fourteen patients were enrolled. With recording of the electroencephalogram at the F3, F4, P3, and P4 montages, anesthesia was induced by increasing the vapor setting of sevoflurane by 1 vol% up to 8 vol% via a facemask. When the end-tidal concentration of sevoflurane did not show any further change, we increased vapor setting of sevoflurane by 1 vol%. When the end-tidal concentration of sevoflurane did not show any further change with 8 vol% of sevoflurane vapor setting, measurement of electroencephalogram was finished. The relation between end-tidal sevoflurane concentration and ApEn was tested by Spearman correlation.
RESULTS
ApEn showed a significant correlation (R = -0.7551, P < 0.0001) with end-tidal sevoflurane concentration. The final pharmacodynamic parameters estimated by a sigmoid E(max) model were described as follows: E(0) = 0.91, E(max) = 0.28, C(e50) = 1.36 vol%, gamma = 1.27, kappa(e0) = 0.67 min(-1).
CONCLUSIONS
Sevoflurane induction with gradual increase of end-tidal sevoflurane concentration increases the amount of regularity in approximate entropy.

Key Words: approximate entropy; electroencephalogram; pharmacodynamics; sevoflurane