Bilateral Bispectral Index (BIS)-Vista as a measure of physiologic sleep in sleep-deprived anesthesiologists

Anesthesiologists who work extended hours exhibit acute and chronic sleep deprivation. The newest bilateral Bispectral Index (BIS)-Vista monitor offers new advantages over earlier models, which include a new algorithm (version 1.4). One possible useful application for BIS monitoring of physiological sleep would be in critically ill patients who almost uniformly suffer from sleep disruption and deprivation because they loose their circadian rhythm due to the harsh noisy environment of critical care units. Previous studies, which used earlier versions of the BIS monitor to depict normal physiologic sleep, produced widely conflicting results. The aim of our study was to assess whether the new BIS-Vista monitor would exhibit a temporal decline that corresponds to natural physiologic sleep stages in healthy sleep-deprived, post-call anesthesiologists.

BIS-Vista sensors were bilaterally mounted, according to the manufacturer guidelines, onto the forehead of 10 healthy sleep-deprived volunteer anesthesiologists. Using the conventional Rechtschaffen and Kales criteria, BIS values during the awake, S1, S2, S3, S4, and rapid eye movement (REM) sleep stages were recorded.

Mean±SD BIS values during the awake, S1, S2, S3, S4, and REM sleep stages significantly declined for the left (96±2, 82±11, 73±10, 53±13, 43±11, 66±9) and right (97±2, 78±11, 69±9, 50±10, 39±13, 61±14) hemispheres respectively. There were no significant interhemispheric differences in BIS values over time (two-way ANOVA). However, in one subject, the left and right BIS values were mostly discordant throughout the recordings.

We demonstrated that although the BIS-Vista monitor was neither designed nor validated for monitoring normal physiologic sleep, it depicted a temporal decline that corresponds to normal physiologic sleep stages in sleep-deprived anesthesiologists.