PURPOSE: To determine whether a liberal transfusion strategy (≥ 9 g/dL) improves neurological outcomes in adults with acute brain injury (ABI). METHOD: We systematically searched MEDLINE, EMBASE, the Cochrane Library, and trial registries for randomized controlled trials comparing liberal (≥ 9 g/dL) vs. restrictive (≥ 7 g/dL) transfusion in adults with ABI (traumatic brain injury, subarachnoid hemorrhage, intracranial hemorrhage) and Glasgow Coma Scale ≤ 13. Frequentist, Bayesian, and trial sequential analyses were used. The primary outcome was favorable neurological status at 180 days. RESULTS: Four randomized controlled trials (N = 1853
922 liberal, 931 restrictive) were included. The pooled frequentist risk ratio (RR) for favorable neurological outcome was 0.84 (95% CI 0.65-1.09
I CONCLUSIONS: This review did not provide definitive evidence of a neurological benefit from liberal transfusion strategies in acute brain injury. Both frequentist and Bayesian analyses highlight the influence of a single trial on the overall effect estimate and heterogeneity. However, sensitivity analyses excluding this trial and focusing on studies with low risk of bias suggested that liberal transfusion strategies could improve neurological outcomes. Future research should focus on identifying patient subgroups most likely to benefit, guiding a more individualized approach.