BIS-Guided Anesthesia and 1-Year Mortality in Older Patients Having Non-Cardiac Surgery: A Randomized Multicenter Trial

Background: Older surgical patients face heightened risks due to age-related declines and comorbidities. Guidelines recommend Bispectral Index (BIS) monitoring to optimize anesthetic depth, but robust evidence supporting improved outcomes is lacking. Methods: We conducted a randomized, multicenter, double-blind trial across 21 tertiary care hospitals in China (March 17, 2015 to February 5, 2022). Patients aged 65 years or older scheduled for elective non-cardiac surgery (ASA I–IV) were randomized 1:1 to BIS-guided or routine anesthetic management. In the BIS group, depth of anesthesia was adjusted to maintain BIS values of 40 to 60. The routine group relied on clinical judgment with masked BIS monitors. The primary outcome was 1-year all-cause mortality. Secondary outcomes included moderate-to-severe complications within 30 days, functional independence, and quality of life. Findings: Among 6982 patients (mean age 71 [SD 5] years), BIS values averaged 47 (BIS-guided) versus 46 (routine). 1-year mortality was similar between groups: 10·2% (356/3485) in BIS-guided versus 10·0% (351/3497) in routine (HR 1·02, 95% CI 0·88-1·17; p=0·812). Complication rates were also comparable: 10·4% versus 10·6% (HR 0·99, 95% CI 0·85-1·16; p=0·938). No significant differences were found in functional independence or quality of life. Interpretation: Hypnotic depth, as assessed by BIS, was similar in patients with or without BIS-guided anesthetic titration. Anesthesiologists thus apparently titrate hypnotic depth appropriately even without BIS guidance. Unsurprisingly, outcomes including postoperative 1-year mortality and 30-day complications were similar in each group.