Bispectral Index-guided Anesthesia for Older Patients Having Noncardiac Surgery: A Randomized Multicenter Trial

Older surgical patients are at risk because of age-related physiologic decline and comorbidities. Some guidelines recommend Bispectral Index (BIS; Medtronic, USA) monitoring to optimize anesthetic depth, but robust evidence supporting improved outcomes is lacking.

A randomized, multicenter, double-blind trial was conducted across 21 tertiary-care hospitals in China (March 17, 2015, to February 5, 2022). Patients aged 65 yr or older scheduled for elective noncardiac surgery (American Society of Anesthesiologists [ASA] Physical Status 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-yr 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 intensive care unit admission, and hospital cost.

Among 6,982 patients (mean ± SD age, 71 ± 5 yr), BIS values averaged 47 (BIS-guided) versus 46 (routine). One-year mortality was similar in BIS-guided patients (10.2% [356 of 3,485]) and routinely managed patients (10.0% [351 of 3,497]; hazard ratio, 1.02; 95% CI, 0.88 to 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% (relative risk, 0.99; 95% CI, 0.85 to 1.16; P = 0.938). No significant differences were observed in functional independence or quality of life.

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-yr mortality and 30-day complications were similar in each group.