Best practice & research. Clinical anaesthesiology
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Since 1997, bispectral index (BIS; Aspect Medical Systems Inc., Natick, MA) has been in clinical practice and a wealth of experimental research has accumulated on its use. Originally, the device was approved only for monitoring hypnosis and has now received an indication for reducing the incidence of intraoperative awareness during anesthesia. Numerous studies have documented the ability of BIS to reduce intermediate outcomes such as hypnotic drug administration, extubation time, postoperative nausea and shortened recovery room discharge. ⋯ Some limitations exist to the use of BIS and it is not useful for some individual hypnotic agents (ketamine, dexmedetomidine, nitrous oxide, xenon, opioids). BIS technology is moving out of the operating room and into diverse environments where conscious and deep sedation are provided. Anesthesiologists need to be actively involved in promoting patient safety and helping transition this technology into broader use.
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The patient state index (PSI) is a clinically validated measure of the effect of anaesthesia and sedation. The PSI is calculated via a proprietary algorithm by a high-resolution 4-channel electroencephalograph (EEG) monitor after advanced artifact rejection. ⋯ The EEG monitor, initially called the PSA4000, is also the SEDLine monitor, the newest generation of the device. The SEDLine system provides the clinician the option of storing and downloading patient data for future use as well as monitoring bilateral brain function and symmetry with a density spectral array (DSA) display.
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Sleep stages are conventionally scored according to recommendations by a committee chaired by Rechtschaffen and Kales in 1968. With these rules normal sleep is divided into rapid eye movement sleep and non-rapid eye movement sleep. Non-rapid eye movement sleep is subdivided into four further stages. ⋯ Furthermore, there is considerable interscorer variability, the scoring is time consuming, tedious and difficult to perform. To overcome these limitations automatic sleep scoring devices using processed EEG technology are developed. These developments are discussed in this chapter.
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Best Pract Res Clin Anaesthesiol · Mar 2006
ReviewConcepts of EEG processing: from power spectrum to bispectrum, fractals, entropies and all that.
Over the past two decades, methods of processing the EEG for monitoring anaesthesia have greatly expanded. Whereas power spectral analysis was once the most important tool for extracting EEG monitoring variables, higher-order spectra, wavelet decomposition and especially methods used in the analysis of complex dynamical systems such as non-linear dissipative systems are nowadays attracting much attention. This chapter reviews some of these methods in brief. However, a comparison of some of the newer approaches with the more traditional ones with respect to clinical end-points by association measures and to the signal-to-noise ratio raises some doubt over whether the newer EEG-processing techniques really do better than the more traditional ones.
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The SNAP electroencephalogram (EEG) monitor, described as an interesting, innovative EEG tool that samples raw EEG signals and uses its own unique algorithm, analyses both high- (80-420 Hz) and low- (0-20 Hz) frequency components of the signal. This is termed the SNAP index, and it ranges from 100 (arbitrarily representing the fully awake state) to 0 to provide functional data points for patient management. ⋯ Compared with other EEG devices, there is no evidence that SNAP is superior to others in generating more specific information about 'depth of sedation'. Moreover, the influence of high-frequency electromyographic activity on the SNAP needs to be clarified.