The Dynamic Relationship between End-tidal Sevoflurane and Isoflurane Concentrations and Bispectral Index and Spectral Edge Frequency of the Electroencephalogram 

1999 ◽  
Vol 90 (5) ◽  
pp. 1345-1353 ◽  
Author(s):  
Erik Olofsen ◽  
Albert Dahan
Keyword(s):  
Bispectral Index ◽  
Effect Compartment ◽  
Spectral Edge Frequency ◽  
Spectral Edge ◽  
Emax Model ◽  
Dynamic Relationship ◽  
Ic50 Values ◽  
American Society ◽  
End Tidal ◽  
Speed Of Onset

Background Inhalational anesthetics produce dose-dependent effects on electroencephalogram-derived parameters, such as 95% spectral edge frequency (SEF) and bispectral index (BIS). The authors analyzed the relationship between end-tidal sevoflurane and isoflurane concentrations (FET) and BIS and SEF and determined the speed of onset and offset of effect (t1/2k(e0)). Methods Twenty-four patients with American Society of Anesthesiologists physical status I or II were randomly assigned to receive anesthesia with sevoflurane or isoflurane. Several transitions between 0.5 and 1.5 minimum alveolar concentration were performed. BIS and SEF data were analyzed with a combination of an effect compartment and an inhibitory sigmoid Emax model, characterized by t1/2k(e0), the concentration at which 50% depression of the electroencephalogram parameters occurred (IC50), and shape parameters. Parameter values estimated are mean +/- SD. Results The model adequately described the FET-BIS relationship. Values for t1/2k(e0), derived from the BIS data, were 3.5 +/- 2.0 and 3.2 +/- 0.7 min for sevoflurane and isoflurane, respectively (NS). Equivalent values derived from SEF were 3.1 +/- 2.4 min (sevoflurane) and 2.3 +/- 1.2 min (isoflurane; NS). Values of t1/2k(e0) derived from the SEF were smaller than those from BIS (P < 0.05). IC50 values derived from the BIS were 1.14 +/- 0.31% (sevoflurane) and 0.60 +/- 0.11% (isoflurane; P < 0.05). Conclusions The speed of onset and offset of anesthetic effect did not differ between isoflurane and sevoflurane; isoflurane was approximately twice as potent as sevoflurane. The greater values of t1/2k(e0) derived from the BIS data compared with those derived from the SEF data may be related to computational and physiologic delays.

The Influence of Remifentanil on the Dynamic Relationship between Sevoflurane and Surrogate Anesthetic Effect Measures Derived from the EEG

2002 ◽  
Vol 96 (3) ◽  
pp. 555-564 ◽  
Author(s):  
Erik Olofsen ◽  
James W. Sleigh ◽  
Albert Dahan
Keyword(s):  
Population Data ◽  
Effect Compartment ◽  
Model Parameters ◽  
Data Set ◽  
Spectral Edge Frequency ◽  
Dynamic Relationship ◽  
Dose Dependent Decrease ◽  
C 50 ◽  
End Tidal ◽  
Dose Dependent

Background The authors modeled the influence of remifentanil on the dynamics of sevoflurane using three parameters derived from the electroencephalogram: 95% spectral edge frequency (SEF), canonical univariate parameter (CUP), and Bispectral Index (BIS). Methods Thirty-six patients with American Society of Anesthesiologists physical status class I or II were recruited, of which 12 received a target remifentanil concentration of 0 ng/ml, eight 2 ng/ml, eight 4 ng/ml, and another eight 8 ng/ml. Next (before surgery), several step-wise changes in the end-tidal sevoflurane concentration (F(ET,sevo)) were performed. A data acquisition system simultaneously recorded F(ET,sevo), the raw electroencephalogram, BIS, and SEF. The authors used a combination of an effect compartment and an inhibitory sigmoid E(MAX) model to describe the relation between F(ET,sevo) and BIS, SEF, and CUP. Model parameters (t(1/2)k(e0), E(MAX), E(MIN), C(50), gamma, CUP weight factors) were estimated using the population data analysis program NONMEM. Significant remifentanil model parameter dependencies (P < 0.01) were determined. Results Determined from SEF, remifentanil had no effect on t(1/2)k(e0) (1.91 +/- 0.26 min [mean +/- standard error]) but caused an increase in C(50) (baseline = 1.48 +/- 0.12%; 80% increase at 8 ng/ml) and decrease in E(MIN) (baseline = 10.8 +/- 0.6 Hz; 80% reduction at 8 ng/ml). Determined from CUP, remifentanil caused a dose-dependent decrease in t(1/2)k(e0) (baseline = 4.31 +/- 1.00 min; 60% decrease at 8 ng/ml), with no effect on C(50) (baseline = 0.88 +/- 0.13%). Determined from BIS, remifentanil caused a dose-dependent decrease in t(1/2)k(e0) (baseline value = 3.11 +/- 0.32 min; 40% decrease at 8 ng/ml), without affecting C(50) (baseline = 1.12 +/- 0.05%). Median R(2) values of the pooled data set were 0.815 for SEF, 0.933 for CUP (P < 0.01 vs. SEF), and 0.952 for BIS (P < 0.01 vs. SEF and CUP). Addition of remifentanil increased the R(2) values for CUP only. Conclusions Remifentanil accelerates sevoflurane blood-brain equilibration without affecting its hypnotic potency as determined from BIS and CUP. In terms of R(2), the authors' pharmacodynamic model describes the anesthetic-BIS relation best.

Influence of Age on Hypnotic Requirement, Bispectral Index, and 95% Spectral Edge Frequency Associated with Sedation Induced by Sevoflurane

2000 ◽  
Vol 92 (1) ◽  
pp. 55-55 ◽  
Author(s):  
Takasumi Katoh ◽  
Hiromichi Bito ◽  
Shigehito Sato
Keyword(s):  
Confidence Interval ◽  
Bispectral Index ◽  
Age Groups ◽  
Verbal Command ◽  
Spectral Edge Frequency ◽  
Sevoflurane Concentration ◽  
Spectral Edge ◽  
End Point ◽  
End Tidal ◽  
Age Range

Background Aging is associated with a reduction in anesthetic requirements. The effects of age on the electroencephalographic response to inhalational anesthesia have not been well documented. The objective of the present study was to determine the influence of age on hypnotic requirement and electroencephalographic derivatives such as bispectral index and 95% spectral edge frequency associated with sedation induced by sevoflurane. Methods Ninety-six patients were randomly allocated into one of three age groups A, B, and C, ranging in age from 18-39 yr, 40-64 yr, and 65-85 yr, respectively. Patients in each group were sedated with sevoflurane at two predetermined concentrations ranging between 0.45% and 0.85%. The relationship between sevoflurane concentration and response to a verbal command, as well as the relationships between response and bispectral index and 95% spectral edge frequency, was determined. Results Multiple regression analysis showed that end-tidal sevoflurane concentration and age significantly affected both bispectral index and 95% spectral edge frequency. ED50 values of sevoflurane concentration for loss of consciousness, defined as no response to verbal command, were different between groups A and C: 0.72 (95% confidence interval: 0.68-0.75) versus 0.59 (95% confidence interval: 0.56-0.62). However, the same effective values of bispectral index and 95% spectral edge frequency at this same clinical end point did not differ. Conclusions Increasing age reduced sevoflurane requirements to suppress responses to a verbal command but did not change bispectral index and 95% spectral edge frequency associated with this end point, and in a population with a wide age range, bispectral index would predict depth of sedation better than end-tidal sevoflurane concentration.

scholarly journals Pregnancy Does Not Enhance Volatile Anesthetic Sensitivity on the Brain

2010 ◽  
Vol 113 (3) ◽  
pp. 577-584 ◽  
Author(s):  
Hiroshi Ueyama ◽  
Satoshi Hagihira ◽  
Masaki Takashina ◽  
Aya Nakae ◽  
Takashi Mashimo
Keyword(s):  
Bispectral Index ◽  
Minimum Alveolar Concentration ◽  
Volatile Anesthetic ◽  
Spectral Edge Frequency ◽  
Hypnotic Effect ◽  
Spectral Edge ◽  
Anesthetic Effect ◽  
Electroencephalographic Study ◽  
End Tidal ◽  
The Brain

Backgrounds Parturients are thought to be more sensitive to inhalational anesthetics because their minimum alveolar concentration is decreased. However, this conventional theory may be wrong, because, according to recent animal studies, minimum alveolar concentration indicates anesthetic effect on the spinal cord but not on the brain. The aim of this electroencephalographic study was to investigate the differences in the hypnotic effect of sevoflurane on parturients and nonpregnant patients. Methods Fifteen parturients undergoing cesarean section and 15 patients undergoing elective gynecologic surgery were enrolled. Anesthesia was induced with 4 mg/kg thiopental, 2 microg/kg fentanyl, and 2 mg/kg suxamethonium or 0.15 mg/kg vecuronium. Anesthesia was maintained with sevoflurane and fentanyl. The electroencephalographic signals, obtained from the bispectral index monitor, were recorded on a computer. We calculated 95% spectral edge frequency, amplitude, and bicoherence using custom software (Bispectrum Analyzer for bispectral index). After confirming that end-tidal sevoflurane had reached equilibrium, we measured electroencephalographic parameters of sevoflurane at 2.0 and 1.5% during surgery and at 1.0 and 0.5% after surgery. Results With the decrease of end-tidal sevoflurane concentration from 2.0 to 0.5%, 95% spectral edge frequency, amplitude, bispectral index, and bicoherence values changed dose-dependently in pregnant and nonpregnant women (P<0.0001). However, there were no significant differences in those electroencephalographic parameters in pregnant and nonpregnant women. Conclusions This electroencephalographic study has shown that pregnancy does not enhance hypnotic effect of sevoflurane. These results suggested that the decrease in minimum alveolar concentration during pregnancy does not mean an enhanced volatile anesthetic effect on the brain.

Fentanyl-mediated reduction in the bispectral index and 95% spectral edge frequency is age-dependent

2003 ◽  
Vol 20 (2) ◽  
pp. 167-169
Author(s):  
N. Anzawa ◽  
K. Hirota ◽  
M. Kitayama ◽  
T. Kushikata ◽  
A. Matsuki
Keyword(s):  
Bispectral Index ◽  
Spectral Edge Frequency ◽  
Spectral Edge ◽  
Age Dependent ◽  
Mediated Reduction

Bispectral index, spectral edge frequency 95%, and median frequency recorded for various concentrations of isoflurane and sevoflurane in pigs

2003 ◽  
Vol 64 (7) ◽  
pp. 866-873 ◽  
Author(s):  
Maria F. Martin-Cancho ◽  
Juan R. Lima ◽  
Laura Luis ◽  
Veronica Crisostomo ◽  
Luis J. Ezquerra ◽  
...  
Keyword(s):  
Bispectral Index ◽  
Median Frequency ◽  
Spectral Edge Frequency ◽  
Spectral Edge

Surgical Stimulation Shifts EEG Concentration–Response Relationship of Desflurane

2001 ◽  
Vol 94 (3) ◽  
pp. 390-399 ◽  
Author(s):  
Heiko Röpcke ◽  
Benno Rehberg ◽  
Michael Koenen-Bergmann ◽  
Thomas Bouillon ◽  
Jörgen Bruhn ◽  
...  
Keyword(s):  
Bispectral Index ◽  
Volatile Anesthetic ◽  
Pharmacodynamic Modeling ◽  
Control Group ◽  
Spectral Edge Frequency ◽  
Spectral Edge ◽  
Desflurane Concentration ◽  
Power Frequency ◽  
Median Power Frequency ◽  
Surgical Stimulation

Background Anesthesiologists routinely increase the delivered anesthetic concentration before surgical stimulation in anticipation of increased anesthetic requirement to achieve certain goals (e.g., amnesia, unconsciousness, and immobility). Electroencephalographic monitoring is one method of determining indirectly anesthetic effect on the brain. The present study investigated the effect of surgical stimuli on the concentration-response relation of desflurane-induced electroencephalographic changes. Methods The electroencephalographic activity was recorded from 24 female patients who received only desflurane after a single induction dose of propofol. Twelve patients served as a control group before surgical stimulation. The other 12 patients, all undergoing lower abdominal surgery, were investigated between opening and closure of the peritoneum. Desflurane vaporizer settings were randomly increased and decreased between 0.5 and 1.6 minimum alveolar concentration as long as anesthesia was considered adequate. Spectral edge frequency 95, median power frequency, and Bispectral Index were calculated. Desflurane effect-site concentrations and the concentration-effect curves for spectral edge frequency 95, median power frequency, and Bispectral Index were determined by simultaneous pharmacokinetic and pharmacodynamic modeling. Results Surgical stimulation shifted the desflurane concentration-electroencephalographic effect curves for spectral edge frequency 95, median power frequency, and Bispectral Index toward higher desflurane concentrations. In the unstimulated group, 2.2 +/- 0.74 vol% desflurane were necessary to achieve a Bispectral Index of 50, whereas during surgery, 6.8 +/- 0.98 vol% (mean +/- SE) were required. Conclusions During surgery, higher concentrations of the volatile anesthetic are required to achieve a desired level of cortical electrical activity and, presumably, anesthesia.

scholarly journals Comparison of Anesthetic Depth Indexes Based on Thalamocortical Local Field Potentials in Rats

2010 ◽  
Vol 112 (2) ◽  
pp. 355-363 ◽  
Author(s):  
Aura Silva ◽  
Hélder Cardoso-Cruz ◽  
Francisco Silva ◽  
Vasco Galhardo ◽  
Luís Antunes
Keyword(s):  
Local Field ◽  
Local Field Potentials ◽  
Burst Suppression ◽  
Permutation Entropy ◽  
Field Potentials ◽  
Anesthetic Depth ◽  
Spectral Edge Frequency ◽  
Spectral Edge ◽  
End Tidal ◽  
High Coherence

Background Local field potentials may allow a more precise analysis of the brain electrical activity than the electroencephalogram. In this study, local field potentials were recorded in the thalamocortical axis of rats to (i) compare the performance of several indexes of anesthetic depth and (ii) investigate the existence of thalamocortical correlated or disrupted activity during isoflurane steady-state anesthesia. Methods Five rats chronically implanted with microelectrodes were used to record local field potentials in the primary somatosensory cortex and ventroposterolateral thalamic nuclei at six periods: before induction of anesthesia; in the last 5 min of randomized 20-min steady-state end-tidal 0.8, 1.1, 1.4, and 1.7% isoflurane concentrations; and after recovery. The approximate entropy, the index of consciousness, the spectral edge frequency, and the permutation entropy were estimated using epochs of 8 s. A correction factor for burst suppression was applied to the spectral edge frequency and to the permutation entropy. The correlation between the derived indexes and the end-tidal isoflurane was calculated and compared for the two studied brain regions indexes. Coherence analysis was also performed. Results The burst suppression-corrected permutation entropy showed the highest correlation with the end-tidal isoflurane concentration, and a high coherence was obtained between the two studied areas. Conclusions The permutation entropy corrected with the classic burst suppression ratio is a promising alternative to other indexes of anesthetic depth. Furthermore, high coherence level of activity exists between the somatosensory cortical and thalamic regions, even at deep isoflurane stages.

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