An Alternative Position for the BIS-Vista Montage in Frontal Approach Neurosurgical Cases

Abstract

We determined that the nasal montage produces values that have slightly more variability compared with that ideally desired, but the variability is not clinically significant. In cases where the standard BIS-vista montage would interfere with the operative field, an alternative positioning of the BIS montage across the nasal bridge and under the eye can be used.

Comparison of bispectral index scores from the standard frontal sensor position with those from an alternative mandibular position

“…However, there is variability in 95% CI depending on various anesthetic states. Although a clinically acceptable limit of agreement has not been defined, some authors consider it to be ± 10 BIS units [5,6]. In our case, 95% CI is over 10 BIS units.…”

“…The "limit of agreement" was defined as a bias of ± 1.96 SD, in which 95% of the difference between the 2 placements were expected to lie between the limits, which would suggest that the 2 positions could be used interchangeably. According to previous studies [5,6], we considered a clinically acceptable level of "limit of agreement" to be ± 10 BIS units. We used scatter plots to evaluate BIS score correlations and calculated the R coefficient.…”

“…In one study, occipital placement had a strong relationship (r 2 = 0.961) with standard frontal placement during general anesthesia for neurosurgery [4]. In contrast, other studies found poor agreement between occipital and frontal placement with a discrepancy of over ± 10 BIS units [5,6]. A third study found BIS values with nasal placement had adequate agreement with standard frontal placement [6].…”

“…In contrast, other studies found poor agreement between occipital and frontal placement with a discrepancy of over ± 10 BIS units [5,6]. A third study found BIS values with nasal placement had adequate agreement with standard frontal placement [6]. …”

Could this be another story of montage?

“…Previous versions of the BIS software, however, showed strong correlation between the different placements [5,6]. A recent study comparing the standard BIS montage with an alternate BIS montage across the nasal bridge demonstrated appropriate agreement between the two montage positions [7]. However, a drawback to a nasal montage would be the requirement for increased eye protection and vigilance because of the close proximity to the inferior aspect of the eye.…”