Bispectral Index Changes during Acute Brainstem TIA/Ischemia

Abstract

We describe a 76-year-old patient who suffered a brainstem TIA just before being anesthetised for cardiac surgery. The TIA was registered on BIS and resulted in a drop in BIS to a value of 60. When consciousness returned spontaneously, the BIS increased to 85. The relative use of the BIS during an operation is discussed. We believe that the lack of input from the brainstem to the frontal cortex resulted in the reduced cortical electrical activity as registered with the BIS.

Bispectral index as a possible early marker of cerebral hypoperfusion

“…Hayashida et al .,[ 6 ] similarly found decreases in BIS values and cerebral hemoglobin saturation during periods of hypotension during pediatric cardiac surgery.Hemmerling et al .,[ 7 ] found BIS to be an indicator of cerebral hypoperfusion during off pump coronary artery bypass graft (CABG). Bleeker and colleagues.,[ 8 ] also found that BIS values dropped in a patient who suffered from a transient ischemic attack (TIA) prior to induction for CABG.…”

“…Apart from this hypoperfusion of brainstem may result in a decrease in BIS values due to multiple afferent projections from brain stem nuclei to the cortex. [ 8 ] Abnormal EEG as in patients with dementia, cerebral palsy, postictal state, and severe brain injury may all result in low BIS values.…”