Investigation of bispectral index asymmetry in patients with cerebral infarction

Bispectral index (BIS) monitoring is widely used for assessing the depth of anesthesia using a unilateral forehead electroencephalogram. We previously experienced a case of low BIS during general anesthesia in a patient with subacute unilateral cerebral infarction (CI). We hypothesized that patients with unilateral CI sequelae show asymmetric BIS values during propofol-based general anesthesia. Fifty patients with or without CI sequelae (25 patients each) were enrolled in this study. BIS was monitored by symmetrically attaching BIS sensors to the forehead, while anesthesia was induced and maintained with mainly propofol. The primary endpoint was the laterality of BIS and 95% spectral edge frequency (SEF) during surgery in the CI group. The median CI duration was 48 months (interquartile range, 23–96). There was no significant BIS and SEF laterality in the control group (P=0.174 and P=0.417, respectively). In the CI group, BIS and SEF laterality failed to achieve statistical significance (P=0.069 and P=0.381, respectively). In addition, there was no significant difference in BIS and SEF asymmetry between groups (P=0.271 and P=0.238, respectively). Therefore, the findings for patients with chronic CI in this study were not consistent with those of our previous case. Hirosaki Med.J. 65:156―163,2014