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

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

Abstract

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.

Keywords: Awareness; Bispectral index monitor; Consciência; Depth of anesthesia; Monitor do índice bispectral; Profundidade da anestesia; Tempo de atraso; Time delay.

Copyright © 2019 Sociedade Brasileira de Anestesiologia. Publicado por Elsevier Editora Ltda. All rights reserved.

Figures

Figure 1
Figure 1
Anesthesia setup.
Figure 2
Figure 2
Block diagram of BIS modulation.
Figure 3
Figure 3
Data results from all 45 patients: (A) Effect-site concentration of propofol and remifentanil for each patient during the first 15 min of anesthesia induction; (B) Real versus modeled BIS values.
Figure 4
Figure 4
Time delay (Δt) between the real and the modeled BIS for: (A) Patient no. 5; (B) Patient no. 19; (C) Patient no. 22 and (D) Patient no. 27.
Figure 5
Figure 5
Time delay (Δt) between the real and the modeled BIS for all patients.

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