Background. Accidental awareness (AA) during general anesthesia can result in long term neuropsychiatric sequelae. The reported incidence of perioperative awareness ranged from 0.006% to 0.13%, and the critically ill patients received major surgeries carries increased risks of developing AA. Since the incidence of AA in the non-critically ill patients has not been previously reported, this study analyzed the incidence and the associated risk factors for the occurrence of AA in patients with ASA class I-III during ambulatory surgeries in a single institutional hospital.
Methods: Postanesthesia visit records (from January 2009 to December 2014) were reviewed. Patients reported to have AA were interviewed by an experienced nurse anesthetist and medical records of all patients were reviewed by the staff anesthesiologists, according to the Michigan awareness instrument and the NAP5 severity. The Poisson regression model was used for simultaneous analysis of the incidence proportion and the potential risk factors of AA.
Results: A total of 58,181 inpatients (ASA III) received general anesthesia during the 5-year period, and 16 patients were identified as definite AA. Patients received endotracheal anesthesia carried significantly higher incidence of developing AA (P= 0.015). ASA class and genders were similar between patients with and without AA. Compared with the matched controls, longer surgical time and higher educational levels were associated with increased incidence of AA. Additionally, higher mortality rate was found in patients who developed AA (18.8% vs 8.4%, AA vs matched controls, P= 0.129).
Conclusion: The overall incidence proportion of AA was 0.0275% in the non-critically ill patients received elective surgeries during general anesthesia. Endotracheal anesthesia, prolonged operation time and higher education levels were associated with increased risks for development of AA. The relationship between AA and postoperative mortality requires further investigation.

Incidence of intraoperative awareness in non-critically ill patients receiving elective surgery