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Revista Brasileira de Anestesiologia
Print version ISSN 0034-7094
VIANNA, Pedro Thadeu Galvão. Monitoring the adequacy of hipnosis by bispectral index. Rev. Bras. Anestesiol. [online]. 2001, vol.51, n.5, pp. 418-425. ISSN 0034-7094. http://dx.doi.org/10.1590/S0034-70942001000500008.
BACKGROUND AND OBJECTIVES: Monitoring the "depth" of anesthesia is a complex process. Most approaches to monitoring anesthetic adequacy involve EEG waves or, more recently, some EEG processed form. Bispectral analysis is a method which allows for EEG analysis in different frequency phases. CONTENTS: Processed EEG starts with the digitalization of the EEG signal. The digitized EEG can then be mathematically transformed by a process known as Fourier analysis, which divides the complex EEG signal in a number of sine wave components, that is, in each portion of different amplitude, but whose sum corresponds to the original EEG waveform. Many parameters are derived from this method. Bispectral index, or simply BIS (100 = awaken to 0= EEG isoelectric) is derived from the best parameters (e.g. spectral edge frequency, median frequency and burst suppression) which are evaluated by statistical analysis. CONCLUSIONS: Clinical experience has shown that BIS may predict a response to skin incision during anesthesia. However, BIS is not independent of the anesthetic technique. There are different responses depending on which hypnotics or analgesics are used.
Keywords : MONITORING [depth of anesthesia]; MONITORING [bispectral index].