• The incidence of explicit recall of events during the surgical and anesthetic periods. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  

• Meta-analysis for anesthesia awareness incorporating higher risk patients from the completed B-Unaware Trial (NCT00281489), the BAG-RECALL Trial, and the Michigan Awareness Control Study (MACS)(NCT00689091). [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• Incidence of post-traumatic stress disorder (PTSD). [ Time Frame: Five years ] [ Designated as safety issue: No ]
  
• Association between type of awareness event and PTSD, and whether the PTSD is associated with late reporting (30 days) of awareness. [ Time Frame: 5 years ] [ Designated as safety issue: No ]
  
• Types of dreams and their relationship to BIS and ETAG. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• The relationship between deep hypnotic time, anesthetic dose (MAC), mean arterial pressure, and end tidal carbon dioxide, and early (one-month) and late (one-year) mortality. [ Time Frame: Four years ] [ Designated as safety issue: No ]
  
• Relationship between BIS, heart rate and blood pressure. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• Relationship between BIS and anesthesia dose and concentration. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• Association between baseline BIS values, patient health and early (one-month) and late (one-year) mortality. [ Time Frame: Four years ] [ Designated as safety issue: No ]
  
• Interaction between hemispheric dominance and BIS. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• Effect of red hair phenotypes on the relationship between ETAG and BIS. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• Refinement of risk factors for anesthesia awareness. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• Relationship between rising BIS in the PACU and first memory after surgery. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• Effect of BIS and ETAG protocols on anesthetic dose administration and on BIS readings. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• BIS and mixed venous saturation. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• Induction of anesthesia and hypotension. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• Incidence of postoperative nausea and vomiting. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• Incidence of and severity of postoperative pain. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• Effect of BIS and ETAG protocols on time to open eyes, time to extubation, and time spent in the postoperative recovery unit. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• Effect of a defasciculating dose of a non-depolarizing muscle relaxant on BIS. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• The effect of patient temperature on BIS. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• Incidence of recall of traveling to the OR among patients who receive midazolam in the holding area and whose initial BIS reading in the OR is > 60. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• Relationship between BIS, ETAG and EEG parameters. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• Annual assessment of practitioners' abilities to interpret BIS tracings and to identify artefacts. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• Differences in anesthesia practice among four institutions in the USA and Canada as judged by anesthetic doses and BIS readings. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  
• Postoperative delirium. [ Time Frame: Three years ] [ Designated as safety issue: No ]
  

The incidence of anesthesia awareness (AA) is 0.1-0.2% and may result in post traumatic stress disorders. For some patients, owing to illness, medications, substance misuse or surgery, the risk approaches 1%. The B-AWARE Study by Myles et al. suggested that the bispectral index (BIS) monitor, which reportedly reflects anesthetic depth, may decrease the incidence of AA in higher risk patients by 82%. The American Society of Anesthesiologists has published a practice advisory on AA, which does not recommend the routine use of cerebral function monitors. We propose to test the hypothesis that an anesthetic protocol based on BIS decreases the incidence of AA among higher risk patients compared with an anesthetic protocol based on the end-tidal anesthetic gas (ETAG) concentration. We have completed a randomized, single-blinded prospective feasibility study (The B-Unaware Trial) which enrolled 2000 patients at higher risk for AA. Four patients (0.21%; 95% CI=0.06% to 0.57%) had definite AA, of whom two were in the BIS-guided group and two in the ETAG-guided group. Nine patients (0.46%; 95% CI=0.22% to 0.91%) had definite or possible AA, of whom six were in the BIS-guided group and three in the ETAG-guided group. The BAG RECALL study will be a multi-center, prospective, single-blinded, randomized study enrolling 6000 patients at higher risk for AA. The BAG RECALL study is adequately powered and rigorously designed to answer with a reasonable degree of scientific probability whether BIS guidance results in clinically relevant reduction in anesthesia awareness among higher risk patients undergoing general anesthesia.

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.