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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)
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 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)
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(More)
1. Voltage-dependent sodium channels are important for neuronal signal propagation and integration. 2. Non-mammalian preparations, such as squid giant axon, have sodium channels which have been found to be insensitive to clinical anesthetic concentrations. 3. On the other hand, sodium channels from mammalian neurons are much more sensitive to block by(More)
BACKGROUND AND OBJECTIVES Target-controlled infusion, via the calculated effect compartment concentrations, may help anaesthesiologists to titrate anaesthetic depth and to shorten recovery from anaesthesia. METHODS In this prospective, randomized clinical study, we compared the performance of six inexperienced anaesthesiologists with <1 yr of training(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)
BACKGROUND The most common measure to compare potencies of volatile anesthetics is minimum alveolar concentration (MAC), although this value describes only a single point on a quantal concentration-response curve and most likely reflects more the effects on the spinal cord rather than on the brain. To obtain more complete concentration-response curves for(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)