Facial Nerve Electromyographic Monitoring to Predict Movement in Patients Titrated to a Standard Anesthetic Depth


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Abstract

BACKGROUND:Facial nerve (FN) monitoring has been accepted as a standard of care in craniofacial, middle ear, and skull-based surgeries as a means of reducing iatrogenic injury, localizing the FN, and predicting postoperative neurologic function. Past studies have also shown that FN electromyographic monitoring (FNEMG) may have some clinical utility as a monitor of anesthetic depth and predicting patient movement. In this study, we evaluated Bispectral Index (BIS) and FNEMG using two different anesthetic techniques to determine whether these monitors can be used to predict movement in patients undergoing skull-based surgical procedures.METHODS:Using a single-blinded, randomized, controlled clinical trial, the relationship between FNEMG monitoring and BIS to predict movement during specific craniofacial and skull-based surgeries performed under general anesthesia was evaluated. In addition, a total IV anesthetic (TIVA) technique, using propofol and remifentanil, was compared with an inhaled anesthetic technique, using desflurane (DES), to determine which regimen provides the best conditions of adequate anesthesia and prevents movement in nonparalyzed patients undergoing a surgical procedure requiring FNEMG monitoring.RESULTS:The TIVA technique produced better hemodynamic conditions compared with DES. No significant differences were noted in BIS values between the two groups. However, FNEMG activity was lower in the TIVA group during emergence from the effects of anesthesia. More patients moved during anesthesia with DES compared with TIVA, and of the 10 patients who moved, eight had significant FNEMG activity. The positive predictive value of the FNEMG for movement was found to be 38%, and the negative predictive value was 95%. There was no significant change from baseline values in hemodynamics or BIS value for patients who experienced movement compared with those who did not move with FNEMG activity.CONCLUSION:This study shows that FNEMG may be an effective monitor for predicting patient movement when undergoing craniofacial and skull-based surgeries. BIS monitoring, however, was not an adequate monitor to predict movement in this patient population. The DES group had more hemodynamic variability and FNEMG activity, whereas TIVA proved to be a more effective anesthetic in preventing patient movement when clinically titrated to produce stable operation conditions. FNEMG was a useful clinical tool to help predict and prevent movement in these patients.

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