Bispectral index decreased to "0" in propofol anesthesia after a cross-clamping of descending thoracic aorta.

THE Bispectral Index (BIS) monitor (BIS® monitor; Aspect Medical System, Inc., Newton, MA) integrates electroencephalographic data via a proprietary algorithm based on empirical data into a nominal 100 to 0 scale, in which 100 represents the awake state and 0 represents the isoelectric electroencephalogram. The BIS® monitor is highly capable of correctly predicting both the loss and recovery of consciousness and has been reported to be more reliable in assessing the level of sedation and hypnosis during surgery than other available processed electroencephalogram algorithms. It also has been used clinically to guide anesthetic drug administration and to quantify the pharmacokinetic and pharmacodynamic action of anesthetic drugs in the laboratory setting. We report a case of a rapid decrease in the BIS score during total intravenous anesthesia using propofol after cross-clamping the descending thoracic aorta for elective thoracic aortic aneurysm repair and suggest that the BIS® monitor provides useful information on altered propofol pharmacokinetics after aortic cross-clamping.