[Deep anesthesia, poorly tolerated anesthesia?]

Besides very low depth of anesthesia (DOA) index values, special intraoperative electroencephalography (EEG) patterns, such as burst suppression patterns and the correlation with postoperative delirium and mortality have been examined. Over the last decade the 13 studies described in this article yielded information that documented low DOA indices or burst suppression patterns increased the risk of either postoperative cognitive dysfunction or mortality; however, these were mainly secondary data analyses or retrospective observational studies. The first prospective interventional study regarding triple low could not confirm this correlation. Meanwhile, the first prospective interventional studies on avoidance of excessive EEG suppression are currently in progress. The results would not only enable the formulation of evidence-based recommendations but should also provide indicatíons and references as to whether the above mentioned observations can be explained by a causal association or an epiphenomenon.