Approximately a quarter of a billion people undergo surgery every year hoping that the operation will alleviate symptoms, cure diseases, and improve quality-of-life. A concern has arisen that, despite the benefits of surgery, elderly patients might suffer neurological injury from surgery and general anaesthesia leading to persistent cognitive decline. However, many studies of postoperative cognition have had methodological weaknesses, including lack of suitable control groups, dissociation of cognitive outcomes from surgical outcomes, sub-optimal statistical techniques, and absence of longitudinal preoperative cognitive assessments. Emerging evidence suggests that after early cognitive decline, most patients return to their preoperative cognitive trajectories within 3 months of surgery; some even experience subsequent cognitive improvement. In this review, we summarize the scientific literature on perioperative cognition. We propose that the most important determinants of the postoperative cognitive trajectory are the preoperative cognitive trajectory, the success of the surgery, and events in the perioperative period. Postoperative complications, ongoing inflammation, and chronic pain are probably modifiable risk factors for persistent postoperative cognitive decline. When surgery is successful with minimal perioperative physiological perturbations, elderly patients can expect cognition to follow its preoperative course. Furthermore, when surgery alleviates symptoms and enhances quality-of-life, postoperative cognitive improvement is a possible and desirable outcome.

Background Postoperative delirium in the intensive care unit (ICU) is a frequent complication after cardiac or thoracic surgery and is associated with increased morbidity and mortality. Methods In this single-center substudy of the BAG-RECALL trial (NCT00682825) we screened patients after cardiac or thoracic surgery in the ICU twice daily for delirium using the Confusion Assessment Method for the ICU. The primary outcome was the incidence of delirium in patients who had been randomized to intraoperative Bispectral Index (BIS)-guided and end-tidal anesthetic concentration-guided depth of anesthesia protocols. As a secondary analysis, a Bayesian stochastic search variable selection strategy was used to rank a field of candidate risk factors for delirium, followed by binary logistic regression. Results Of 310 patients assessed, 28/149 (18.8%) in the BIS group and 45/161 (28.0%) in the end-tidal anesthetic concentration group developed postoperative delirium in the ICU (odds ratio 0.60, 95% confidence interval 0.35-1.02, p=0.058). Low average volatile anesthetic dose, intraoperative transfusion, ASA physical status, and EuroSCORE were identified as independent predictors of delirium. Discussion A larger randomized study should determine whether brain monitoring with BIS or an alternative method decreases delirium after cardiac or thoracic surgery. The association between low anesthetic concentration and delirium is a surprising finding and could reflect that patients with poor health are both more sensitive to the effects of volatile anesthetic drugs and are also more likely to develop postoperative delirium. Investigation of candidate methods to prevent delirium should be prioritized in view of the established association between postoperative delirium and adverse patient outcomes.

Background-Postoperative delirium in the intensive care unit (ICU) is a frequent complication after cardiac or thoracic surgery and is associated with increased morbidity and mortality.

Summary Although the brain is the target organ of general anaesthesia, the utility of intra‐operative brain monitoring remains controversial. Ideally, the incorporation of brain monitoring into routine practice would promote the maintenance of an optimal depth of anaesthesia, with an ultimate goal of avoiding the negative outcomes that have been associated with inadequate or excessive anaesthesia. A variety of processed electroencephalogram devices exist, of which the bispectral index is the most widely used, particularly in the research setting. Whether such devices prove to be useful will depend not only on their ability to influence anaesthetic management but also on whether the changes they promote can actually affect clinically important outcomes. This review highlights the evidence for the role of bispectral index monitoring, in particular, in guiding anaesthetic management and influencing clinical outcomes, specifically intra‐operative awareness, measures of early recovery, mortality and neurocognitive outcomes.