Bispectral Index–Guided Anesthesia for Older Patients Having Non-Cardiac Surgery: A Randomized Multicenter Trial

Background: Older surgical patients are at risk because of age-related physiologic decline and comorbidities. Some 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 to IV) were randomized 1:1 to BIS-guided or routine anesthetic management. In patients assigned to BIS guidance, hypnotic depth was adjusted to maintain BIS between 40 and 60. Hypnotic depth in patients assigned to routine-care per 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, quality of life, the duration of postoperative critical care, the duration of postoperative hospitalization, unplanned ICU admission, and hospital cost. Results: Among 6982 patients (mean age 71 SD 5 years), BIS values averaged 47 (BIS-guided) versus 46 (routine). 1-year mortality was similar in BIS-guided patients 10.2% (356/3485) and routinely managed patients 10.0% (351/3497): HR 1.02, 95% CI 0.88-1.17; P = 0.812). The incidence of complications within 30 days after surgery were also comparable in each group: 10.4% versus 10.6% (RR 0.99, 95% CI 0.85-1.16; P = 0.938). No significant differences were observed in functional independence or quality of life. Conclusions: 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.