At the University of Michigan, a parallel study will be conducted - Michigan Awareness Control Study, MACS (NCT00689091) - enrolling 30,000 patients to assess whether the BIS monitor decreases the likelihood of anesthesia awareness among all patients undergoing general anesthesia, regardless of their risk profile. The investigators of this study and the BAG-RECALL study have collaborated in designing these studies and are pre-specifying that common outcome measures will be examined collaboratively including data from both studies.