Effects of Position and Sensory Deprivation on BiSpectral Index Data

Many have demonstrated that pre-operative bispectral index (BIS) values may have a link to incidence of post-operative outcomes such as delirium and cognitive decline. To better understand how pre-operative BIS values vary, we investigated the effects of age, position, and sensory deprivation on BIS values among healthy participants (n=24). In this study, participants were recorded in these positions: supine with headphones/blindfold, supine with blindfold, upright with headphones/blindfold, upright with blindfold, upright with headphones, upright without restrictions. These participants were divided by age into three categories: 18-39, 40-64, >65 years old. BIS readings were not significantly different between age groups, including parameters for median frequency, spectral edge frequency, and signal quality index. However, BIS readings varied significantly between all 6 positions. Compared to the first position (emulation of surgical environment) other positions showed significant differences in median frequency, spectral edge frequency, and signal quality index. Along with this, all 6 positions demonstrated an acclimation period of 30 seconds. This indicates that while age may not be an important consideration in using BIS pre-operatively, standardizing the position in which data is collected, along with allowing for an acclimation period, is critical to obtaining consistent BIS readings in future extra-operative usage of BIS.