Clinical Briefs-By Louis Kuritzky, MD

Awareness During Anaesthesia: A Prospective Case Study

Patient recall of events occurring while under operative general anesthesia is traditionally regarded as a rare event, reportedly occurring in less than 1% of individuals. On the other hand, patient concern about pain or other stressful experiences under anesthesia is commonplace, with as many as half of patients reporting such concerns. Sandin and colleagues did a prospective evaluation of patient recall of awareness during surgery by personal interview of adults older than 15 years of age (n = 11,785) who received general anesthesia in two Swedish hospitals. Interviews were taken, immediately postoperatively, at days 1-3, and days 7-14 postoperatively.

Only 18 women and seven men, (slightly < 0.2% of the total evaluated population) reported intro-anesthesia awareness. The most common underlying factor in reported awareness was the use of neuromuscular block during surgery. Patients who did not receive neuromuscular block did not report intraoperative awareness. Additionally, more than half of persons reporting operative awareness had previously experienced a similar phenomenon. Whether monitoring techniques designed to detect intraoperative awareness will actually reduce this experience will be difficult to determine, since 50,000 patients would be needed to demonstrate a halving of intraoperative awareness from the demonstrated level in this study of less than 0.2%.

Sandin RH, et al. Awareness during anaesthesia: A prospective case study. Lancet 2000;355:707-711.