Entropia espectral: um novo método para adequação anestésica

Rogean Rodrigues Nunes; Murilo Pereira de Almeida; James Wallace Sleigh

doi:10.1590/S0034-70942004000300013

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Entropia espectral: um novo método para adequação anestésica

Spectral entropy: a new method for anesthetic adequacy

Rogean Rodrigues Nunes; Murilo Pereira de Almeida; James Wallace Sleigh

http://dx.doi.org/10.1590/S0034-70942004000300013 Braz J Anesthesiol, vol.54, n3, p.404-422, 2004

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Resumo

JUSTIFICATIVA E OBJETIVOS: O uso de sinais clínicos para avaliar a adequação da anestesia, embora empregado universalmente, não são confiáveis. Vários equipamentos surgiram objetivando o melhor manuseio intra-operatório das drogas anestésicas, alguns deles mensurando diretamente a atividade cortical cerebral (hipnose). Entretanto, nenhum deles apresenta características diretas de avaliação da atividade sub-cortical (resposta motora). CONTEÚDO: A entropia espectral mensura a irregularidade, complexidade ou a quantidade de desordem do eletroencefalograma e tem sido sugerida como um indicador do estado anestésico. O sinal é coletado na região fronto-temporal e tratado através da equação de Shannon (H = - Sp k log p k, onde p k são as probabilidades de um evento discreto k), resultando em dois tipos de análises: 1. Entropia de estado (SE), que consiste na avaliação da atividade elétrica cortical cerebral (0,8-32Hz) e 2. Entropia de resposta (RE), que analisa as freqüências de 0,8 - 47Hz (contêm componentes eletroencefalográficos-cortical e eletromiográficos-sub-cortical). CONCLUSÕES: A ativação da musculatura frontal pode indicar inadequação do componente sub-cortical (nocicepção). Esta ativação é observada como um "gap" entre SE e RE. Deste modo, é possível avaliar diretamente tanto o componente cortical (SE), como o sub-cortical (RE), possibilitando melhor adequação dos componentes anestésicos.

Palavras-chave

MONITORIZAÇÃO, MONITORIZAÇÃO, MONITORIZAÇÃO

Abstract

BACKGROUND AND OBJECTIVES: Though universally employed, clinical signs to evaluate anesthetic adequacy are not reliable. Over the past years several pieces of equipment have been devised to improve intraoperative handling of anesthetic drugs, some of them directly measuring cerebral cortical activity (hypnosis). None of them, however, has offered the possibility of directly evaluating sub-cortical activity (motor response). CONTENTS: Spectral entropy measures irregularity, complexity or amount of EEG disorders and has been proposed as indicator of anesthetic depth. Signal is collected from the fronto-temporal region and processed according to Shannon's equation (H = - Sp k log p k, where p k represents the probability of a discrete k event), resulting in two types of analyses: 1) state entropy (SE), which evaluates cerebral cortex electrical activity (0.8 - 32Hz) and 2) response entropy (RE), containing both subcortical electromyographic and cortical electroence- phalographic components and analyzes frequencies in the range 0.8 - 47Hz. CONCLUSIONS: Frontal muscles activation may indicate inadequacy of the subcortical component (nociception). Such activation appears as a gap between SE and RE. This, it is possible to directly evaluate both cortical (SE) and subcortical (RE) components providing better anesthetic adequacy.

Keywords

MONITORING, MONITORING, MONITORING

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Entropia espectral: um novo método para adequação anestésica

Spectral entropy: a new method for anesthetic adequacy

Rogean Rodrigues Nunes; Murilo Pereira de Almeida; James Wallace Sleigh

Resumo

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Abstract

Keywords

Referencias

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