Is hyperlipidemia a potential protective factor against intraoperative awareness in cardiac surgery?

Intraoperative awareness is a dreaded complication that leads to psychological sequelae such as posttraumatic stress disorder, especially in patients undergoing cardiac surgery. This study investigated the incidence of awareness among patients receiving cardiac surgery and sought to identify the risk factors contributing to intraoperative awareness.

Patients with informed consent undergoing cardiac surgery from June to September in 2012 were enrolled. At least one structured interview was performed postoperatively with the modified Brice Interview Questionnaire to identify intraoperative awareness as confirmed awareness, possible awareness, and no awareness. Confirmed awareness events reported by patients were classified into different categories with the Michigan Awareness Classification Instrument. The questionnaire results were combined with the patient medical records. A logistic regression model was used to analyze the risk factors that may have led to intraoperative awareness.

An estimated 2136 patients were included, and 1874 patients completed at least one interview. 83 patients (4.4 %) were identified as possible or confirmed awareness, among which 46 (2.5 %) reported confirmed awareness. Patients who experienced confirmed awareness were mostly of Class 1 and 2, 15 and 24 patients respectively, which represented isolated auditory and tactile perceptions. And 11 patients reported feelings of distress intraoperatively. Hyperlipidemia was associated with intraoperative awareness (OR = 0.499, 95 % CI = 0.252-0.989, p = 0.043) and using chi-square test, however, no significance was found with logistic regression.

Patients undergoing cardiac surgery are at high risk for intraoperative awareness. Distress is a common feeling in patients with intraoperative awareness. Hyperlipidemia is a potential protective factor for intraoperative awareness in cardiac surgery.