Asymmetry of the bispectral index in lateral decubitus position during one-lung ventilation: A prospective-observational study
Abstract Background Use of the bispectral index (BIS) reduces cases of intraoperative awareness and deep sedation. Although non-invasive, the BIS values are often misunderstood. This study evaluated the effects of BIS readings during intra-operative positioning and ventilation. Methods Forty-four patients undergoing esophageal cancer surgery were enrolled. BIS sensors were applied on right and left sides. A > 10% difference in BIS reading between the two sides was defined as ‘asymmetry.’ Results Intraoperative BIS asymmetry was observed in 14 (32.6%) patients in the supine position, but 43 (100%) patients in the left lateral decubitus position. The maximum differences between BIS values were observed 15 minutes after one-lung ventilation in the left lateral decubitus position (mean 6.8 ± 4.6, range [1-27]). Conclusion During one-lung ventilation in the lateral decubitus position, care should be taken when placing a BIS sensor and interpreting BIS values.