• Lisbeth A Evered, ChanMatthew T VMTVDepartment of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Hong Kong Special Administrative Region, China., Ruquan Han, ChuMandy H MMHMDepartment of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Hong Kong Special Administrative Region, China., Benny P Cheng, David A Scott, Kane O Pryor, Daniel I Sessler, Robert Veselis, Christopher Frampton, Matthew Sumner, Ade Ayeni, Paul S Myles, Douglas Campbell, Kate Leslie, and Timothy G Short.
• Department of Anesthesiology, Weill Cornell Medicine, New York, NY, USA; Department of Anaesthesia and Acute Pain Medicine, St Vincent's Hospital, Melbourne, VIC, Australia; Department of Critical Care Medicine, University of Melbourne, Melbourne, VIC, Australia. Electronic address: lae4004@med.cornell.edu.
• Br J Anaesth. 2021 Nov 1; 127 (5): 704-712.

BackgroundPostoperative delirium is a serious complication of surgery associated with prolonged hospitalisation, long-term cognitive decline, and mortality. This study aimed to determine whether targeting bispectral index (BIS) readings of 50 (light anaesthesia) was associated with a lower incidence of POD than targeting BIS readings of 35 (deep anaesthesia).MethodsThis multicentre randomised clinical trial of 655 at-risk patients undergoing major surgery from eight centres in three countries assessed delirium for 5 days postoperatively using the 3 min confusion assessment method (3D-CAM) or CAM-ICU, and cognitive screening using the Mini-Mental State Examination at baseline and discharge and the Abbreviated Mental Test score (AMTS) at 30 days and 1 yr. Patients were assigned to light or deep anaesthesia. The primary outcome was the presence of postoperative delirium on any of the first 5 postoperative days. Secondary outcomes included mortality at 1 yr, cognitive decline at discharge, cognitive impairment at 30 days and 1 yr, unplanned ICU admission, length of stay, and time in electroencephalographic burst suppression.ResultsThe incidence of postoperative delirium in the BIS 50 group was 19% and in the BIS 35 group was 28% (odds ratio 0.58 [95% confidence interval: 0.38-0.88]; P=0.010). At 1 yr, those in the BIS 50 group demonstrated significantly better cognitive function than those in the BIS 35 group (9% with AMTS ≤6 vs 20%; P<0.001).ConclusionsAmong patients undergoing major surgery, targeting light anaesthesia reduced the risk of postoperative delirium and cognitive impairment at 1 yr.Clinical Trial RegistrationACTRN12612000632897.Copyright © 2021 British Journal of Anaesthesia. Published by Elsevier Ltd. All rights reserved.

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