The effect of noise on the Bispectral index during propofol sedation

Because noise in the operating room has been alleged to interfere with the ability to sedate patients before surgery, we evaluated the effect of noise on the Bispectral index (BIS) value during propofol sedation. Thirty unpre medicated patients were studied before the start of surgery while receiving propofol sedation on two separate occasions according to a randomized, cro ssover protocol design. After achieving a stable baseline BIS value of eith er 75 or 80 with a target-controlled infusion of propofol, an external soun d source administered noise at 50, 80, 110, and 120 dB. The changes in the BIS value were recorded over a 1-min interval at each noise level. In the B IS 75 group, increasing levels of noise did not significantly alter the BIS value. However, in the BIS 80 group, the BIS values at 80, 110, and 120 dB were significantly higher compared to the value at 50 dB. In conclusion, e xperimental noise increases the BIS and appears to have a greater effect on the BIS value at "lighter" levels of propofol sedation.