A case of awareness despite an "adequate depth of anesthesia" as indicated by a Bispectral Index monitor.

We report a case of awareness that occurred despite the presence of an "adequate" depth of anesthesia as measured by Bispectral Index. Our patient was at high risk for this complication. Hypotension limited the use of sevoflurane, and neuromuscular, sympathetic, and beta-adrenergic blockade prevented the patient from responding to his awareness. Preoperative use of opioids and gabapentin for chronic pain may have modified his response to anesthesia or affected his Bispectral Index reading. Our attempt to measure depth of anesthesia may have resulted in false reassurance concerning adequacy of anesthesia and contributed to awareness.