Awareness during general anesthesia: analysis of contributing causes aided by automatic data capture.

The cause of the awareness under general anesthesia often cannot be definitely determined from retrospective reviews of handwritten records, examinations of equipment, or interviews with clinicians. Failure to deliver the intended concentrations of anesthetic agents to the patient is one possible contributing cause for awareness. An advantage of an automated Anesthesia Information Management System (AIMS) is its ability to electronically capture and preserve case data that might otherwise be lost. We reviewed the AIMS records of 3 anesthetics in which intraoperative awareness was felt to have probably occurred. The details of the reported awareness event were temporally correlated with the anesthetic gas concentrations in an effort to determine if low concentrations were contributing factors. The data captured by the AIMS revealed low levels of inspired or expired inhalation agents during the intervals correlating with apparent patient recall. The findings suggest that failure to deliver sufficient concentrations of anesthetic gases permitted awareness events in these cases. Thus data from automated anesthesia information management in the operating room may help identify causes of awareness, and means to prevent awareness can be instituted.