Effect of Operation Room Background Noise on Bispectral Index during Propofol Sedation

Dae Woo Kim, MD, PhD,* Ho Yeong Kil, MD, PhD,^† Paul F. White, PhD, MD, FANZCA^‡

* Department of Anesthesiology, The Catholic University of Korea; ^† Hallym University, Seoul, Korea; ^‡ University of Texas Southwestern Medical Center at Dallas

Background and Goal of Study: In a noisy hospital setting, it is not easy to induce hypnosis or sedation calmly. Although the noise stress has been neglected, it seems to disturb a patient's sleep or induction of sedation. Therefore, we tried to evaluate the effects of loud operating room (OR) background noise on bispectral index (BIS) during monitored anesthesia care (MAC) by using an audiometer and BIS monitor.

Materials and Methods: Thirty unpremedicated patients were scheduled two times for nasal or dental procedures at an interval of two or three days. In a randomized, cross-over study design, we prospectively compared the BIS values according to the loudness of OR noise in two different depths of sedation during MAC. Propofol target controlled infusion (TCI) was started at a propofol target concentration (C_T) 2.0 mg/ml using a DiprifusorÔ with flash mode until a BIS 80 and/or a Observer's Assessment of Alertness/Sedation (OAAS) score of 4 (group 1), and BIS 75 and/or a OAAS score 3 (group 2) was obtained. We evaluated the effect site concentrations and the elapsed time and checked the BIS at 50, 80, 110, and 120 dB of sound pressure level (SPL) in both groups.

Results: In contrast to the group 2, the BIS values at 80, 110 and 120 dB in the group 1 were significantly increased compared to the value at 50 dB in the same group (P < 0.05)(Fig.1).

Fig. 1: Effect of background noise on bispectral (BIS) values in the two propofol sedation groups: ■ = Group 1 and ■ = Group 2. * = P<0.05 compared to BIS at 50 dB and †= P<0.05 compared to BIS at 80 dB.

Conclusions: The loud OR background noise might interfere with induction of sedation to a degree, which was more noticeable on light to moderate sedation than for deep sedation.