Inappropriate elevation of bispectral index values in robot assisted thyroidectomy with electromyographic endotracheal tube -A case report-

Abstract

We report a case of an erroneously elevated bispectral index (BIS) during robot assisted thyroidectomy using an electromyographic endotracheal tube (EMG tube), which is safe and useful for laryngeal electromyographic monitoring. Ten minutes after start of the operation, a sudden increase of BIS value up to 98 was noticed. The BIS values were not decreased to < 65 with supplemental anesthetics. The anesthetic method was changed from total intravenous anesthesia to balanced anesthesia. The BIS sensor and monitor were changed and other models were used. These interventions did not alter BIS values. BIS levels remained between 60 and 70 throughout the main procedure and intermittently increased to the mid-90s without any trace of poor signal quality. At the end of the surgery, the BIS values returned to normal range. The patient did not complain of intraoperative recall. Knowledge of potential interference from the use of an EMG tube must be considered when interpreting BIS.

Data Driven Investigation of Bispectral Index Algorithm

“…It is notable that increase of EMG power was a classifier of the BIS ranges. Previous reports of an erroneous increase in BIS were related with an unexpected EMG pattern for conventional general anaesthesia, such as muscle relaxation in an awake patient 3,5 , or reversal of muscle relaxation in anaesthetized patients 26–28 ; and high frequency band electrical noise 4,6–8,10 . Our results and previous reports suggest that the original BIS algorithm needs to be more improved to properly measure anaesthetic depth without being affected by high frequency signals including EMG 29 .…”

Comparative Analysis of Phase Lag Entropy and Bispectral Index as Anesthetic Depth Indicators in Patients Undergoing Thyroid Surgery with Nerve Integrity Monitoring

“…During anesthesia, many artifacts can influence EEG-based DOA monitors, which can lead to inappropriate titration of anesthetics. Although BIS monitors reject artifactual signals from epochs and rejected data can be estimated by interpolation, case reports have described artifactual signals producing BIS values that did not correlate with DOA 1226. Other case reports noted that NIM using EMG ETT influenced the quality of EEG signals, falsely increased BIS values 2627.…”

“…Although BIS monitors reject artifactual signals from epochs and rejected data can be estimated by interpolation, case reports have described artifactual signals producing BIS values that did not correlate with DOA 1226. Other case reports noted that NIM using EMG ETT influenced the quality of EEG signals, falsely increased BIS values 2627. EMG ETT is an endotracheal tube containing paired wire electrodes, which contact the vocal cords at the glottic level and allow surgeons to confirm the site of the recurrent laryngeal nerve with a stimulating probe.…”

Influence of electrocautery-induced electromagnetic interference on quantitative electroencephalographic monitoring of hypnosis during general anesthesia: comparison between the ADMS® and the BIS VISTATM

“…Based on the original artifact sites, they are classified into three major categories: (1) artifacts from outside the head; (2) artifacts from within the head but outside the brain, EMG; and (3) artifacts from within the brain, atypical or pathologic EEGs [ 14 ]. Artifacts from outside the head have been reported to result from atrial pacers [ 15 ], warming blanket/convective air-warming systems [ 16 – 18 ], endoscopic shavers [ 19 ], electromagnetic systems [ 11 ], and laryngeal electromyography monitoring with an EMG endotracheal tube [ 20 ]. Most of these papers reported increased BIS during or after ECT and are clinical case reports of one or two patients’ findings.…”