Out of every 1000 patients, two at most wake up during their operation. Unintended awareness in the patient is thus classified as an occasional complication of anesthesia — but being aware of things happening during the operation, and being able to recall them later, can leave a patient with long-term psychological trauma.
How to avoid such awareness events, and what treatment is available for a patient who does experience awareness, is the subject of a report by Petra Bischoff of the Ruhr University in Bochum and Ingrid Rundshagen of the Charité Berlin in the current issue of Deutsches Ärzteblatt International (Dtsch Arztebl Int 2011; 108(1-2): 1-7).
The usual culprit in cases of unintended awareness during an operation is an inadequate depth of anesthesia. In addition, several risk factors exist that promote awareness events. For example, children have eight to ten times the risk of being aware under anesthesia. Long-term use of painkillers or misuse of medication can also make patients more liable to this kind of experience. The nature of the operation and the surrounding circumstances can also play a part: cesarean sections and emergency operations carry a higher risk of awareness than other kinds of surgery, and operations at night a higher risk than those carried out during the day.
For prevention of awareness during anesthesia, the authors recommend taking into account the risk factors that have been mentioned and raising the level of vigilance among medical personnel for awareness phenomena by regular training sessions. Premedication with benzodiazepines and not using muscle relaxants are also worthwhile measures. Additionally, it is important to measure the anesthetic gas concentrations regularly and monitor brain electrical activity by EEG. If possible, the patient should be given hearing protection. If a post-traumatic stress disorder does occur, the prognosis is good if professional treatment is started without delay.