The utility of bispectral index monitoring in flexible bronchoscopy: A single-center, retrospective observational study

Background The desired depth of sedation during flexible bronchoscopy is one in which verbal contact is possible whenever necessary. Although it is common that the depth of sedation is assessed by validated instruments such as the modified observer's assessment of alertness and sedation (MOAA/S) score, the repeated stimulation associated with the assessment can affect the sedation. The bispectral index (BIS) has been widely used for general anesthesia due to its objective and noninvasive nature. However, the utility of BIS monitoring and a target BIS value for use during bronchoscopy have not been fully elucidated. Methods We performed a retrospective observational study to assess the utility of the BIS value for monitoring conscious sedation during bronchoscopy at Kobe University Hospital from August 2020 to April 2021. Results Eighteen patients underwent bronchoscopy with BIS monitoring. The BIS value significantly correlated with the MOAA/S score (r = 0.2, p < 0.01), and the correlation was stronger in sufficiently sedated patients (r = 0.486, p < 0.01). The lowest MOAA/S score during the procedure was highly correlated with the BIS value (r = 0.625, p < 0.01). The BIS monitoring seemed to be more sensitive to changes in the sedation level than the MOAA/S score, heart rate and mean arterial pressure. The median BIS value at an MOAA/S score of 3-4, the desired depth of sedation, was 82.0. Conclusions BIS value is useful for monitoring sedation during bronchoscopy. This study suggests that a BIS value of 82 reflects an adequate level of sedation.