Bispectral Index monitoring correlates with sedation scales in brain-injured patients

Abstract

Objective: Monitoring critically ill, brain-injured patients with a decreased level of consciousness is challenging. Our goal is to determine in this population the correlation between the Bispectral Index (BIS) and three commonly used sedation agitation scales: the Richmond Agitation-Sedation Scale (RASS), the Sedation-Agitation Scale (SAS) and the Glasgow Coma Scale (GCS) scores.

Design: Prospective, single-blinded observational study.

Setting: Eight-bed neurology-neurosurgery intensive care unit at the Cleveland Clinic Foundation.

Patients: Thirty critically ill patients admitted to the neurointensive care unit with primary brain injury and a decreased level of consciousness.

Measurements and main results: Patients were prospectively evaluated for level of consciousness using the RASS, SAS, and GCS every hour and simultaneously were monitored continuously with a BIS monitor for 6 hrs. A Spearman's correlation coefficient was used to correlate the BIS scores with clinical scales. In 15 patients monitored with the newer BIS XP version, the BIS values correlated significantly with the RASS (R2 = .810; p < .0001), SAS (R2 = .725; p < .0001), and GCS (R2 = .655; p < .0001). In 15 patients monitored with the older BIS 2.1.1 software, the correlation was as follows: for RASS, R2 = .30 (p < .008), for SAS: R2 = .376 (p < .001), and for GCS: R2 = .274 (p < .015). This correlation was maintained in patients who received sedative medications.

Conclusions: A statistically significant correlation existed between BIS values and the RASS, SAS, and GCS scores in critically ill brain-injured patients, with and without sedation. The newer BIS XP software package may be a useful adjunctive tool in objective assessment of level of consciousness in brain-injured patients.