The Effect of Desflurane Versus Sevoflurane Versus Propofol on Postoperative Delirium in Elderly Patients Undergoing Moderate- to High-risk Major Noncardiac Surgery - a Prospective, Observer-blinded, Randomized, Clinical Trial

Background: Postoperative delirium occurs in approximately 25% of patients over the age of 60 years undergoing major noncardiac surgery and is significantly associated with an increase in postoperative neurocognitive decline, morbidity, and mortality. The prevention of postoperative delirium has been classified as a public health priority. However, so far data regarding possible intraoperative interventions to reduce the incidence of postoperative delirium is very scarce. Previous small studies compared the effect of administration of sevoflurane versus propofol for maintenance of anesthesia on postoperative delirium and found beneficial effects of volatile anesthesia for the prevention of postoperative delirium. Furthermore, in small studies the administration of desflurane led to significantly shorter recovery periods after noncardiac surgery as compared to sevoflurane. Due to the more rapid wash-in and wash-out times of desflurane as compared to sevoflurane or propofol it seems reasonable that desflurane might be beneficial for the prevention of postoperative delirium. Therefore, we evaluate the effect of maintenance of anesthesia using desflurane, sevoflurane or propofol on postoperative delirium in elderly patients undergoing moderate- to high-risk major noncardiac surgery.

Methods: We will include 1332 patients ≥ 65 years of age undergoing moderate- to high-risk major noncardiac surgery lasting at least two hours in this prospective observer-blinded randomized controlled clinical trial. After induction of anesthesia patients will be randomly assigned to receive desflurane, sevoflurane or propofol for maintenance of anesthesia. Our primary outcome will be the incidence of postoperative delirium in the first five postoperative days. Postoperative delirium will be diagnosed using the 3D-CAM or 3D-CAM-ICU in the morning and evening of the first five postoperative days as appropriate assessed by blinded study personnel. Two-interim analyses after 1/3 and 2/3 of recruitment are pre-planned.

Statistics: The primary outcome, the incidence of postoperative delirium in the first five postoperative days, will be compared between the groups using a Chi-Square-test as well as a logistic regression model for the incidence of postoperative delirium will be performed accounting for randomized group, age and other possible confounding factors.

Level of originality: Data regarding possible intraoperative interventions for the prevention of postoperative delirium are scarce. In detail, the effects of commonly used anesthetics on the incidence of postoperative delirium and neurocognitive dysfunction have only been studied in retrospective analyses or small prospective studies, which showed inconsistent results. Nevertheless, delirium is a major event after surgery and is associated with postoperative complications, worse neurocognitive recovery and increased mortality, especially in elderly patients. Thus, the results of this trial will help to choose the right anesthetic according to individual patients' requirements to reduce the risk for postoperative delirium in future.