Awareness during anesthesia: how sure can we be that the patient is sleeping indeed?

Awareness during surgery is a very serious problem for the anesthetist and the patient as well. Such incidents are the cause for 2% of the legal claims against anesthetists while patients with intraoperative awareness experience describe it as the worst thing they have ever suffered from. Pain, anxiety and inability to react due to muscle paralysis often lead to the situation called posttraumatic stress disorder which demands psychiatric support. The fact that there are patients who report intraoperative experience, even several days after surgery, raises questions about the way the anesthetic drugs interfere with the mechanisms of memory and consciousness while, in bibliography, there are studies proving that even deeply anesthetized patients can be influenced by auditory stimuli without being able to recall them. Intraoperative monitoring of the anesthesia depth is important for the prevention of this problem. From all the available devices only the Bispectral Index Monitoring (BIS) has been proven to be effective for this purpose but the high cost per person and the low specificity in preventing awareness episodes do not allow its everyday use. The surgeon and especially the anesthesiologist must be aware of the risk factors, the prevention measures and the actions that must be taken after an awareness incident in order to minimize the unfortunate complications for both the patient and the doctors.