The BAG-RECALL trial received a lot of press in 2011. If you recall, this was a prospective, randomized trial at 3 medical centers of patients who underwent elective surgery. The study found that that the incidence of anesthesia-related awareness was indistinguishable between BIS and standardized end-tidal anesthetic agent monitoring.
Dr. Elizabeth L. Whitlock, Department of Anesthesia and Perioperative Care, University of California, San Francisco, CA and colleagues from the Department of Anesthesiology, Washington University School of Medicine, the Department of Mathematics, Washington University in Saint Louis, Saint Louis, Missouri, and the Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, Michigan, used data from that trial to reexamine the relationship between postoperative delirium, and the use of BIS monitoring compared to standard end-tidal anesthetic agent monitoring. The results of their study will be published in an upcoming issue of Anesthesia & Analgesia in the article titled “Postoperative Delirium in a Substudy of Cardiothoracic Surgical Patients in the BAG-RECALL Clinical Trial.”
The BAG-RECALL trial enrolled 6100 patients and for this study, 310 patients in the trial who received care in the cardiothoracic ICU at Barnes-Jewish Hospital in St. Louis from August 20, 2009, through April 19, 2010, who had documented delirium screens, who underwent cardiac or thoracic surgery, and who had a complete intraoperative record were included. 73 patients were postoperatively delirious. A delirium diagnosis was associated with increased ICU and hospital length of stay and increased rates of mortality. ICU discharge occurred at a median of 2 days for those patients who did not have delirium and at 8 days for patients who had delirium; similarly, hospital discharge occurred at a median of 7 days compared to 17 days for those patients respectively without and with delirium. Of those patients who did not die in hospital, patients without delirium were most likely to be alive at last follow-up. Four independent predictors of postoperative delirium that were identified in this study included the number of units of pRBCs administered intraoperatively, ASA physical status, EuroSCORE, an objective measure of comorbidities and surgical risk, and average end-tidal anesthetic concentration.
Comparing BIS to use of end-tidal anesthesia monitoring, ICU stay was lower by 1 day if BIS monitoring was used. Patients for whom BIS-guided anesthesia was used had a 9.2% nonsignificant reduction in postoperative delirium.
This was not a study of cause and effect. With a larger study, would use of a monitor or type of anesthetic, e.g., propofol and/or dexmedetomidine, result in a lower incidence of postoperative delirium? Alternatively, is postoperative delirium due to known preexisting factors, e.g., EuroSCORE, ASA status, or factors that are as of yet unknown? This is an interesting study, though it’s unclear what we can do to help prevent postoperative delirium.