Decrease in bispectral index preceding intraoperative hemodynamic crisis: evidence of acute alteration of propofol pharmacokinetics.

THE bispectral index (BIS, Aspect Medical Systems Inc., Newton, MA) is a processed electroencephalographic variable which correlates with depth of hypnosis in adult patients during general anesthesia. It has also been used clinically to guide anesthetic drug administration, and to quantify the pharmacodynamic action of anesthetic drugs in the laboratory setting. BIS has previously been shown to decrease following hypovolemic cardiac arrest, lagging behind the decrease in blood pressure by approximately 2 min. We report a case of unrecognized venous hemorrhage with a fatal outcome during total intravenous anesthesia (TIVA) for elective abdominal aortic aneurysm repair, where the BIS score began to decrease well before other monitored variables suggested clinical deterioration, and we propose that BISderived data may provide early insights into altered drug pharmacokinetics due to hemorrhage.