A study presented at ANESTHESIOLOGY 2011 in Chicago this week offered firm evidence that commonly used inhaled anesthetics such as isoflurane do not increase the incidence of postoperative delirium, which can affect how well some patients recover after surgery.

"Our study demonstrates that the use of inhaled anesthetic agents does not increase the incidence of cognitive problems such as delirium in the early postoperative period," said lead author Terri G. Monk, M.D., Duke University Health System. "This study should reassure elders that the type of general anesthesia does not affect early cognitive outcomes after surgery and that they should not avoid necessary surgery or general anesthesia if it is required for their surgery."

Previous cellular and animal studies have shown that some inhaled volatile anesthetics can cause alterations in the brain similar to those seen in dementia and Alzheimer's disease. Dr. Monk's current study is one of the first human studies to address the link between anesthesia and cognitive decline after surgery.

Her prospective study enrolled 200 adults 65 or older who were undergoing major orthopedic surgery. Before surgery, the patients were given tests to determine brain function and depression levels. During surgery, the patients received opioids with either an inhaled anesthetic (isoflurane), or intravenous anesthetic (propofol).

Postoperative delirium occurred in 12.6 percent of the patients receiving inhaled anesthesia, and 13.6 percent of the patients receiving intravenous anesthesia.

Importantly, it was found that only the patient's medical condition and cognitive status before surgery had an effect on whether he or she would experience delirium.

"These findings indicate that a patient's preoperative medical problems and the ability to process information and concentrate (executive function) and learn and remember (memory) are independent predictors of postoperative delirium; the type of general anesthesia does not influence the incidence of postoperative delirium," said Dr. Monk.

Patients who developed postoperative delirium experienced a 40 percent orthopedic failure rate, compared to a 5 percent failure rate for those patients who did not experience delirium. Previous studies have indicated that postoperative delirium is associated with longer hospital stays and increased morbidity and mortality.