Effect of Change of Position (Supine vs. Steep Trendelenburg) on Bispectral Index Value During Robotic Surgery

Background: Bispectral Index (BIS) is used to monitor anesthetic depth and is a useful instrument to keep a check on intraoperative awareness. But there are various situations in which it shows false readings. Our aim of the study was to observe the changes in BIS value with steep Trendelenburg position, which is usually done, in robotic pelvic surgeries. Methods: We included 100 patients in our study who underwent robotic prostatectomies and hysterectomies. After anesthetizing the patient, the patient's heart rate, systolic blood pressure, mean arterial pressure, end-tidal desflurane, end-tidal CO(2), and BISwere recorded at three min. intervals, for 15 minutes before and 15 minutes after the Trendelenburg position without surgical stimulus. Results: We found a significant increase in BIS values (p <0.05) after the change of position from supine to steep Trendelenburg. Heart rate, systolic blood pressure, and mean arterial pressure were almost constant. Conclusion: Our study concluded that the BIS value increases when patients were shifted from the supine to Trendelenburg position, which might raise the concern of a decrease in anesthetic depth.