Training Level and Bispectral Index Below 40 After Propofol Induction by Anesthesiology Residents in Indonesia: A Prospective Observational Study

Abstract

Background. Excessively deep hypnosis after induction is detectable with the bispectral index (BIS), but its relation to residency training level is incompletely quantified.

Objective. To compare induction depth across seven semesters of anesthesiology residency.

Methods. This prospective observational study enrolled 21 residents (three per semester, I–VII), each managing five ASA I–II adults (n=105) in Malang, Indonesia, during April–December 2024. A standardized fentanyl–midazolam–propofol protocol was used under attending supervision. The primary outcome was BIS 2 min after intubation. Group-level analyses included sensitivity analyses for clustering and unmeasured joint distributions.

Results. In post hoc analyses, mean BIS rose by 2.47 units per semester across semesters I–V (95% CI 1.00–3.94; p=0.001), with no significant subsequent change. BIS <40 occurred after 46.7% of junior-led and 11.1% of senior-led inductions (risk difference 35.6 percentage points, 95% CI 15.0–53.9; Holm p=0.003). The difference persisted under the reported clustering and confounding sensitivity analyses. Juniors used more propofol (2.4 vs 1.9 mg/kg; p<0.001). Hypotension did not differ significantly (30.0% vs 17.8%; p=0.265); its association with BIS <40 was not identifiable.

Conclusion. Junior residents more often induced BIS <40 and used larger propofol doses. Post-induction BIS is a candidate metric for formative feedback; these observational data do not establish patient harm.