Dexmedetomidine Infusion Versus Placebo During Light or Deep Anesthesia on Postoperative Delirium in Older Patients Undergoing Major Noncardiac Surgery: A Pilot Randomized Factorial Trial

BACKGROUND: Postoperative delirium (POD) is common among older surgical patients and may be affected by dexmedetomidine and depth of anesthesia. We designed this pilot study to assess the feasibility of comparing dexmedetomidine with normal saline during light versus deep anesthesia on POD in older patients undergoing major noncardiac surgery.METHODS: In this pilot randomized factorial study, 80 patients aged 60 years or older undergoing major noncardiac surgery were randomized (1:1:1:1) to receive dexmedetomidine infusion 0.5 mu g/kg/h or normal saline placebo during light (bispectral index [BIS] target 55) or deep (BIS target 40) anesthesia. Feasibility end points included consent rate and dropout rate, timely enrollment, blinded study drug administration throughout surgery, no inadvertent unmasking, achieving BIS target throughout >70% of surgery duration, and the process of twice-daily POD screening. In addition, we estimated the POD incidences in the 2 control groups (placebo and deep anesthesia) and treatment effects of dexmedetomidine and light anesthesia.RESULTS: Between November 1, 2021, and June 30, 2022, 78 patients completed the trial (mean [standard deviation, SD] age, 69.6 [4.6] years; 48 male patients [62%]; dexmedetomidine-deep, n = 19; dexmedetomidine-light, n = 20; placebo-deep, n = 19; placebo-light, n = 20). This study had a high consent rate (86%) and a low dropout rate (2.5%). Average recruitment was 5 patients at each center per month. Dexmedetomidine and normal saline were administered in a blinded fashion in all patients. Unmasking did not occur in either group. Approximately 99% of patients received the scheduled study drug infusion throughout the surgery. Approximately 81% of patients achieved the BIS targets throughout >70% of the surgery duration. The scheduled twice-daily POD screening was completed without exception. Overall, 10 of the 78 patients (13%; 95% confidence interval [CI], 7%-22%) developed POD. For the 2 reference groups, POD was observed in 7 of the 39 patients (17.9%; 95% CI, 9%-32.7%) in the placebo group and 7 of the 38 patients (18.4%; 95% CI, 9.2%-33.4%) in the deep anesthesia group. Regarding the treatment effects on POD, the estimated between-group difference was -10% (95% CI, -28% to 7%) for dexmedetomidine versus placebo, and -11% (95% CI, -28% to 6%) for light versus deep anesthesia.CONCLUSIONS: The findings of this pilot study demonstrate the feasibility of assessing dexmedetomidine versus placebo during light versus deep anesthesia on POD among older patients undergoing major noncardiac surgery, and justify a multicenter randomized factorial trial.