Impact of bispectral index monitoring on dose requirement of dexmedetomidine during total parotidectomy under general anesthesia without muscle relaxants.

BACKGROUND AND AIMS: For facial nerve monitoring during parotidectomy, neuromuscular blockers should be avoided. Assessment of depth of anesthesia based on clinical signs or end-tidal anesthetic gas concentration is unreliable. We compared intraoperative dexmedetomidine requirement with and without bispectral index (BIS) monitoring in patients undergoing total parotidectomy under general anesthesia (GA) without muscle relaxants.

MATERIAL AND

METHODS

This was a prospective, randomized study conducted in 60 patients undergoing total parotidectomy under GA with nerve conduction studies. Following induction and intubation, all patients received dexmedetomidine 1 µg/kg bolus. In Group A, BIS values were continuously monitored. Following initial bolus, only when the BIS value was >50, dexmedetomidine infusion was restarted at 0.5 µg/kg/h and adjusted to maintain BIS between 40 and 50. In Group B, dexmedetomidine 1 µg/kg bolus was given, followed by 0.5 µg/kg/h initially and infusion. Infusion rate was titrated based on hemodynamic variables and patient immobility. If patients in any group moved intraoperatively, propofol 0.5 mg/kg, not >30 mg, was given, and dose of dexmedetomidine infusion was increased by 0.1 µg/kg/h increments to a maximum dose of 0.7 µg/kg/h.

RESULTS

Rate of dexmedetomidine infusion was significantly lower in Group A compared to Group B (0.058 ± 0.011 vs. 0.547 ± 0.133 µg/kg/h). Extubation time was significantly lower in Group A (14.40 ± 8.845 vs. 30.27 ± 9.903 min). Hemodynamic responses, sevoflurane and propofol consumption, incidence of intraoperative patient immobility, hypotension, and use of vasopressors were comparable in both groups.

CONCLUSIONS

Use of BIS monitoring in patients undergoing total parotidectomy under GA without muscle relaxants resulted in significant reduction in intraoperative dexmedetomidine consumption with significantly shorter extubation time.