Awareness without explicit recall. Features and research perspective

Intraoperative awareness (IA) is the postoperative recollection of an unexpected and unwanted experience occurred during general anesthesia. It is a serious and rare anesthesia complication, with a complex physiopathology, and clinical features often poorly understood. Anesthesiologists are led to believe that all the patients who suffered from an IA event can report their experience through a process of explicit memory retrieving. The axiom that explains the correlation between IA occurrence and conscious recollection (If I do not remember it, I have not experienced it') is only in part true, and applicable to the anesthesia awareness with explicit recall (AAWR) phenomenon, which represents the best-known IA subtype. It is underestimated that anesthesia practice may interfere with the hidden subconscious world. Indeed, an intraoperative unexpected sensory experience can more often shift the explicit memorization way and, in turn, configures the awareness without explicit recall (AWER) picture (the other IA subtype). It is debated if these episodes may be defined as conscious experiences without subsequent recollection on recovery, or they really represent the expression of unconscious experiences. Probably, both hypotheses could be accepted. Many dark sides should be better explored, but it is certain that this underestimated complication is strictly closed to the development of postoperative psychological/psychiatric sequelae. The present work is aimed to give an overview on the AWER phenomenon, suggesting strategies for studying these potentially deleterious 'experiences'.