Bispectral index monitoring correlates with the level of consciousness in brain injured patients

BACKGROUND In general, measuring the level of consciousness in neurological patients is important. To assess the patient's mental status, the Glasgow Coma Scale (GCS) and the level of consciousness (drowsiness, stupor, and coma) have been used in clinical situations. The aim of the present study was to identify the correlation between bispectral index (BIS) and level of consciousness in brain injured patients. METHODS Eighty-nine adult patients of both sexes were included in the study. A blinded observer evaluated the mental status (GCS and level of consciousness) of a patient who is admitted in intensive care unit with brain injury, while an investigator noted the patient's BIS. The BIS was measured using a BIS monitor, Model A-3000 vista™ with Sensor Bis quatro™ (Aspect Medical Systems, Norwood, USA). A Spearman's rank correlation coefficient was used to determine if the level of consciousness correlated with the BIS. RESULTS In 89 patients, the BIS was found to be significantly correlated with the level of consciousness (r = 0.723, P < 0.01) and GCS (r = 0.646, P < 0.01). The BIS values increased with an increasing level of consciousness. Mean BIS values of coma, semicoma, stupor and drowsiness were 0.14 ± 0.23, 38.9 ± 18.0, 60.3 ± 14.5, and 73.6 ± 16.5, respectively. CONCLUSIONS In the present study, a significant correlation existed between level of consciousness and BIS. These findings suggest that BIS may be used for assessing the level of consciousness in brain injured patients. However, the scatter of BIS values for any level of consciousness limited the worth of BIS in predicting mentality except in coma patients.