Benzodiazepines and postoperative cognitive dysfunction in the elderly

Postoperative cognitive dysfunction (POCD) has been attributed to long-acting sedatives. We hypothesized that diazepam and its active metabolites could be detected in blood after surgery and correlated with POCD, I week after surgery in elderly patients. We studied 35 patients, 60 yr or older, undergoing abdominal surgery with general anaesthesia, including diazepam. Neuropsychological tests were performed before surgery and at discharge, where blood concentrations (free fraction) of benzodiazepines were also measured. POCD was found in 17 patients (48.6%). Diazepam or desmethyldiazepam was detected in 34 patients; median postoperative blood concentrations were 0.06 and 0.10 mu mol kg(-1), respectively. In a multiple regression analysis considering age, duration of anaesthesia and blood concentrations of diazepam and desmethyldiazepam, only age was found to correlate with the composite z-score (F test, P < 0.01). The postoperative cognitive dysfunction we found in elderly patients after operation could not be explained by benzodiazepine concentrations detected in blood.