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BACKGROUND Approximate entropy, a measure of signal complexity and regularity, quantifies electroencephalogram changes during anesthesia. With increasing doses of anesthetics, burst-suppression patterns occur. Because of the high-frequency bursts, spectrally based parameters such as median electroencephalogram frequency and spectral edge frequency 95 do not(More)
BACKGROUND Previous studies have provided evidence that clinical levels of propofol alter the functions of voltage-dependent sodium channels, thereby inhibiting synaptic release of glutamate. However, most of these experiments were conducted in the presence of sodium-channel activators, which alter channel inactivation. This study electrophysiologically(More)
The voltage-dependent action of the intravenous anesthetic pentobarbital on human brain sodium channels activated by batrachotoxin was examined using planar lipid bilayer methods. Fractional open time-data were fitted by Boltzmann functions to yield simple parameters characterizing the voltage-dependence of the fractional open time. Pentobarbital caused a(More)
We investigate several quantifiers of the electroencephalo-gram (EEG) signal with respect to their ability to indicate depth of anesthesia. For 17 patients anesthetized with Sevoflurane, three established measures (two spectral and one based on the bispectrum), as well as a phase space based nonlinear correlation index were computed from consecutive EEG(More)
The voltage- and frequency-dependent interactions of pentobarbital with voltage-gated sodium channels were examined in whole-cell patch-clamp recordings. Using rat brain IIA and rat muscle rSkM1 sodium channels expressed in stably transfected Chinese hamster ovary cell lines, it was found that pentobarbital reduced peak inward sodium currents with IC50(More)
BACKGROUND Although voltage-dependent sodium channels have been proposed as possible molecular sites of anesthetic action, they generally are considered too insensitive to be likely molecular targets. However, most previous molecular studies have used peripheral sodium channels as models. To examine the interactions of volatile anesthetics with mammalian(More)
The molecular mechanisms by which anaesthetics interfere with neuronal function are controversial. We have examined the effects of pentobarbitone on muscle-derived (eel electroplax) sodium channels incorporated into planar bilayers under exactly the same experimental conditions that we used previously to study the anaesthetic modification of human brain(More)
BACKGROUND The spinal H-reflex has been shown to correlate with surgical immobility, i.e., the absence of motor responses to noxious stimulation, during isoflurane anesthesia. Here, the authors established individual concentration-response functions for H-reflex amplitude and tested the predictive power of the H-reflex for movement responses during(More)
BACKGROUND Movement responses are an important indicator of noxious perception in the unconscious state. To allow for a continual monitoring of the responsiveness to noxious stimuli during general anaesthesia, surrogate parameters are needed. Here we compare the performance of the bispectral index (BIS) and the RIII threshold in predicting reactions to(More)
BACKGROUND The predominant target of anesthetics to suppress movement responses to noxious stimuli is located in the spinal cord. Although volatile anesthetics appear to produce immobility by actions on the ventral rather than the dorsal horn, the site of action of propofol remains unclear. METHODS In a crossover design, the authors compared in 13(More)