Korean J Anesthesiol.  2008 Oct;55(4):404-411. 10.4097/kjae.2008.55.4.404.

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

• Choi BM
• Yang CS
• Woo DH
• Koo MS
• Kim SH
• Lee MA
• Kwak HS
• Noh GJ

• KMID: 2237399
• DOI: http://doi.org/10.4097/kjae.2008.55.4.404

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.

Keyword

approximate entropy; electroencephalogram; pharmacodynamics; sevoflurane

MeSH Terms

Anesthesia
Anesthetics
Colon, Sigmoid
Electroencephalography
Entropy
Humans
Methyl Ethers
Anesthetics
Methyl Ethers