Prognostic Value of Bispectral Index Monitoring in Traumatic Brain Injury Patients Undergoing Decompressive Cranial Surgery

Background Predicting neurological outcomes after traumatic brain injury (TBI) remains challenging. This study investigated the prognostic utility of bispectral index (BIS) and suppression ratio (SR) monitoring in TBI patients undergoing decompressive cranial surgery. Methods We retrospectively analyzed 85 TBI patients who underwent anesthesia with BIS monitoring between January 2020 and December 2024. Patients were classified into favorable (modified Rankin Scale [mRS] 0–3) and poor (mRS 4–6) outcome groups at discharge. BIS parameters (average, minimum, maximum) and SR were compared between groups alongside clinical severity scores (Glasgow Coma Scale [GCS], American Society of Anesthesiologists [ASA] physical status, and Acute Physiology and Chronic Health Evaluation II [APACHE II]). Statistical analyses included t-tests, chi-square tests, and logistic regression. Subgroup analysis compared patients with mRS 4–5 vs. mRS 6. Results Patients with poor outcomes had significantly lower GCS (7.0 vs. 13.0, p < 0.001) and higher APACHE II and ASA scores. Mean BIS values (average, minimum, maximum) were markedly lower in the poor group (29.0 ± 14.6, 23.7 ± 13.5, 34.9 ± 15.7) than in the favorable group (41.0 ± 9.4, 36.1 ± 8.7, 47.3 ± 10.0, p < 0.001). The SR was significantly higher in the poor group (39.1 ± 24.8 vs. 6.0 ± 12.5, p < 0.001). In multivariate analysis, BIS (OR = 0.93, 95% CI 0.90–0.98) and SR (OR = 1.07, 95% CI 1.04–1.11) independently predicted poor outcomes. Among poor-outcome patients, those who died (mRS 6) showed lower BIS and higher SR than survivors (mRS 4–5) (p < 0.02). Conclusions Lower BIS and higher SR values were strongly associated with poor neurological outcomes. BIS and SR monitoring may serve as valuable adjuncts for prognostic assessment in TBI patients undergoing decompressive cranial surgery.