BOCHUM, Germany, Jan. 21 (UPI) -- For every 1,000 patients under anesthesia, two at most wake up during their operation, which can leave a patient traumatized, German researchers say.

Petra Bischoff of the Ruhr University in Bochum and Ingrid Rundshagen of the Charite Berlin say being aware of things happening during surgery -- unintended awareness -- and being able to recall them later is classified as an occasional complication of anesthesia.


However, unintended awareness can leave a patient with long-term psychological trauma, the researchers say.

Bischoff and Rundshagen say the usual culprit in cases of unintended awareness during an operation is an inadequate depth of anesthesia, but there are other risk factors. Long-term use of painkillers or misuse of medication can make patients more susceptible to this kind of experience.

Caesarean section and emergency surgery carry a higher risk of unintended awareness than other kinds of surgery, and operations at night have higher risk than those carried out during the day, the study says.

The authors recommend taking into account the risk factors identified and raising the level of vigilance among medical personnel during training, the study says.