Study Evaluating Ways of Preventing Patients From Being Awake During High-Risk Surgery and Anesthesia

The overall purpose of this study is to see if a Bispectral Index (BIS) monitor, a Food and Drug Administration (FDA) approved brain monitoring device, will help to reduce the risk of patients remembering being awake during surgery. The BIS monitor may be able measure how asleep a patient is during surgery. Using the BIS monitor to guide anesthesia will be compared with using the concentration of anesthetic gas to guide anesthesia.