PubMed Health⌕ Search

Biomedical subjects

T W Bouillon

Publications and source records attributed to T W Bouillon.

5 recordsLinked to original sources
PubMed2005

[Effect compartment equilibration and time-to-peak effect. Importance of a pharmacokinetic-pharmacodynamic principle for the daily clinical practice].

Contrary to the situation in "classical" clinical pharmacology, non-steady state phenomena play a fundamental role for clinical pharmacology in anesthesia. Their understanding is of tantamount importance for the safe and efficient application of drugs relevant to anesthesia. Concepts like optimised target-controlled infusion (TCI), effect compartment targeting and the small margin of error tolerable during maintained spontaneous ventilation, force the anesthesiologist to acquire a firm understanding of the difference between the concentration time course at the effect side vs. time course of the plasma concentration. The underlying concepts, their application for the rational use of muscle relaxants, propofol with TCI systems, volatile anaesthetics and opioids will be discussed.

Algorithms↗
PubMed2001

Onset of propofol-induced burst suppression may be correctly detected as deepening of anaesthesia by approximate entropy but not by bispectral index.

The bispectral index (BIS) is a complex EEG variable that combines several disparate descriptors of the EEG into a single value. Approximate entropy is a novel EEG measure that quantifies the regularity of a data time series such as EEG. We report two patients in which the EEG effect of propofol was quantified very similarly by BIS and approximate entropy. However, at the beginning of burst suppression of the EEG, BIS did not indicate an increased anaesthetic drug effect, while approximate entropy did.

Adult↗
PubMed2001

Shannon entropy applied to the measurement of the electroencephalographic effects of desflurane.

BACKGROUND: The Shannon entropy is a standard measure for the order state of sequences. It quantifies the degree of skew of the distribution of values. Increasing hypnotic drug concentrations increase electroencephalographic amplitude. The probability density function of the amplitude values broadens and flattens, thereby changing from a skew distribution towards equal distribution. We investigated the dose-response relation of the Shannon entropy of the electroencephalographic amplitude values during desflurane monoanesthesia in comparison with previously used electroencephalographic parameters. METHODS: Electroencephalographic records previously obtained in 12 female patients during gynecologic laparotomies were reanalyzed. Between opening and closure of the peritoneum, desflurane vapor settings were varied between 0.5 and 1.6 minimum alveolar concentration. Electroencephalographic Shannon entropy, approximate entropy, median electroencephalographic frequency, SEF 95, total power, log total power, and Bispectral Index were determined, and their correlations with the desflurane effect compartment concentration, obtained by simultaneous pharmacokinetic-pharmacodynamic modeling, were compared. RESULTS: The electroencephalographic Shannon entropy increased continuously over the observed concentration range of desflurane. The correlation of the Shannon entropy (R2 = 0.84+/-0.08, mean +/- SD) with the desflurane effect compartment concentrations is similar to approximate entropy (R2 = 0.85+/-0.12), SEF 95 (R2 = 0.85+/-0.10), and Bispectral Index (R2 = 0.82+/-0.13) and is more statistically significant than median frequency (R2 = 0.72+/-0.17), total power (R2 = 0.67+/-0.18), and log total power (R2 = 0.80+/-0.09). CONCLUSIONS: The Shannon entropy seems to be a useful electroencephalographic measure of anesthetic drug effect.

Adult↗
PubMed2000

Bispectral index (BIS) and burst suppression: revealing a part of the BIS algorithm.

OBJECTIVE: The bispectral index (BIS) is a complex EEG parameter which integrates several disparate descriptors of the EEG into a single variable. One of the subparameters incorporated in the BIS is the suppression ratio, quantifying the percentage of suppression during burst suppression pattern. The exact algorithm used to synthetize the information to the BIS value is unpublished and still unknown. This study provides insight into the integration of the suppression ratio into the BIS algorithm. METHODS: EEG data of 10 healthy volunteers during propofol infusion were analyzed. Propofol concentrations were ramped up to 4 predetermined concentrations (1, 2, 3, 4, 6, 8, 9, or 12 microg/ml) using a computer controlled infusion pump (STANPUMP). EEG recordings were performed with an Aspect A-1000 EEG monitor (Version 3.22). The relationship of the processed EEG variables bispectral index and suppression ratio, calculated by the Aspect A-1000 monitor, was analyzed. RESULTS: Up to 40% suppression ratio the average BIS values remained constant regardless of suppression ratios (r = 0.13). Beyond a suppression ratio of 40%, BIS and suppression ratio were invariably linearly correlated (r = -1). At a suppression ratio > or = 40% the BIS value could be calculated as BIS = 50 - suppression ratio/2. CONCLUSIONS: Suppression ratio values > 40% are linearly correlated with BIS values from 30 to 0. An increasing anesthetic drug effect resulting in an increase of the duration of suppression to a suppression ratio up to 40% is not adequately reflected by the BIS value.

Adult↗