Abstract
Background: There is some evidence that electroencephalography guidance of general anesthesia can decrease postoperative delirium after non-cardiac surgery. There is limited evidence in this regard for cardiac surgery. A suppressed electroencephalogram pattern, occurring with deep anesthesia, is associated with increased incidence of postoperative delirium (POD) and death. However, it is not yet clear whether this electroencephalographic pattern reflects an underlying vulnerability associated with increased incidence of delirium and mortality, or whether it is a modifiable risk factor for these adverse outcomes. Methods: The Electroe ncephalography Guidance of Anesthesia to Alleviate Geriatric Syndromes ( ENGAGES-Canada) is an ongoing pragmatic 1200 patient trial at four Canadian sites. The study compares the effect of two anesthetic management approaches on the incidence of POD after cardiac surgery. One approach is based on current standard anesthetic practice and the other on electroencephalography guidance to reduce POD. In the guided arm, clinicians are encouraged to decrease anesthetic administration, primarily if there is electroencephalogram suppression and secondarily if the EEG index is lower than the manufacturers recommended value (bispectral index (BIS) or WAVcns below 40 or Patient State Index below 25). The aim in the guided group is to administer the minimum concentration of anesthetic considered safe for individual patients. The primary outcome of the study is the incidence of POD, detected using the confusion assessment method or the confusion assessment method for the intensive care unit; coupled with structured delirium chart review. Secondary outcomes include unexpected intraoperative movement, awareness, length of intensive care unit and hospital stay, delirium severity and duration, quality of life, falls, and predictors and outcomes of perioperative distress and dissociation. Discussion: The ENGAGES-Canada trial will help to clarify whether or not using the electroencephalogram to guide anesthetic administration during cardiac surgery decreases the incidence, severity, and duration of POD. Registration: ClinicalTrials.gov ( NCT02692300) 26/02/2016.