Lower Bispectral index values in psychiatric patients: A prospective, observational study

Abstract

Background: Bispectral index score (BIS) is a processed electroencephalographic parameter used to measure level of sedation in anaesthetised patients. In few studies of psychiatric patients undergoing electroconvulsive therapy (ECT), it was observed that the BIS values were lower at baseline. It is not clear from those studies whether the BIS values are really low. Also, it is not clear whether the lower values are related to the primary psychiatric illness or the due to the effect of ECT. Therefore, we studied the BIS values in psychiatric illnesses and compared them with the normal controls. Materials and Methods: BIS index was recorded in 237 patients with various psychiatric illness (Group P) and 40 control patients without any psychiatric illness undergoing spinal surgery (Group C). BIS values were recorded in supine position before breakfast and before the morning doses of antipsychotic/benzodiazepine medications. It was recorded during resting state in all the subjects. Results: BIS values were lower in group P compared to control group (a mean of 89.8 ± 7.8 vs 95.7 ± 2.4, P < 0.0001). In the group P, the patients with psychosis and bipolar disorder had significantly lower BIS values than the patients with depression ( P= 0.04). Conclusions: BIS values in psychiatric patients are lower than those in the control group. Psychotic and bipolar disorders are associated with significantly lower BIS values than the depression.

Keywords

• bipolar disorder
• bispectral index
• depression
• diazepam
• monitoring
• psychiatric illness