Brazilian Journal of Anesthesiology
Brazilian Journal of Anesthesiology
Scientific Article

Evaluation of Bispectral Index time delay in response to anesthesia induction: an observational study

Avaliação do tempo de atraso do índice bispectral na resposta à indução da anestesia: estudo observacional

Ana Leitão Ferreira, Joaquim Gabriel Mendes, Catarina Sofia Nunes, Pedro Amorim

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Background and objectives: According to the manufacturer, the Bispectral Index (BIS) has a processing time delay of 5---10 s. Studies addressing this have suggested longer delays. We evaluated the time delay in the Bispectral Index response. Methods: Based on clinical data from 45 patients, using the difference between the predicted and the real BIS, calculated during a fixed 3 minutes period after the moment the Bispectral Index dropped below 80 during the induction of general anesthesia with propofol and remifentanil. Results: The difference between the predicted and the real BIS was in average 30.09 ± 18.73 s. Conclusion: Our results may be another indication that the delay in BIS processing may be much longer than stated by the manufacture, a fact with clinical implications


Bispectral index monitor; Depth of anesthesia; Awareness; Time delay


Justificativa e objetivos: De acordo com o fabricante, o índice bispectral (BIS) tem um tempo de processamento de cinco a dez segundos. Estudos que avaliaram esse tempo de processamento sugeriram atrasos mais longos. Nós avaliamos o tempo de atraso na resposta do BIS. Métodos: Com base em dados clínicos de 45 pacientes, calculamos a diferenc¸a entre o tempo de atraso previsto e real do índice bispectral durante um período fixo de três minutos após o momento em que o BIS caiu abaixo de 80 durante a induc¸ão da anestesia geral com propofol e remifentanil. Resultados: A diferenc¸a entre o BIS previsto e real foi em média 30,09 ± 18,73 segundos. Conclusão: Nossos resultados sugerem que o atraso no processamento do índice bispectral pode ser muito maior que o declarado pelo fabricante, um fato com implicac¸ões clínicas.


Monitor do índice bispectral; Profundidade da anestesia; Consciência; Tempo de atraso


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