It is important to assess the level of consciousness in patients with brain injuries to determine modes of treatment and prognosis. We evaluated the Bispectral Index (BIS) to determine if it could be used as an objective tool for evaluation of the level of consciousness in brain-injured patients. We also compared the BIS values to clinical sedation scales such as the Glasgow Coma Scale (GCS), Richmond Agitation-Sedation Scale (RASS), and the Reaction Level Scale (RLS).

Thirty eight patients with brain injuries that were admitted to the neurosurgery intensive care unit (NSICU) were enrolled in this study. An investigator evaluated the clinical sedation scales (GCS, RASS, RLS), while a blind observer noted the BIS in the same patient. The BIS score was obtained three times at an interval of 5 hours. The BISs were measured for 1 minute at 5 min prior to the nursing assessment, during the nursing assessment, and at 5 min after the nursing assessment. The BISs used in the data analysis were the maximal, minimal, and mean values obtained during 1 min, which were defined as BISmax, BISmin, and BISmean. A Spearman's rank correlation coefficient was used to determine if the clinical sedation scales were correlated with the BIS scores.

In 38 patients, the BISmax, BISmin, and BISmean were found to be significantly correlated with the GCS, RASS, and RLS. The BISmean had the highest correlation with GCS ( r = 0.445, P < 0.01), while the BIS min had the lowest correlation with RLS ( r = -0.278, P < 0.01).

The results of BIS monitoring were found to be significantly correlated with sedation scales in patients with brain injuries. These findings suggest that BIS can be used as an objective and continuous method for assessment of the level of consciousness in patients with brain injury.