The Impact of Hemoglobin Transfusion Thresholds in Moderate-to-Severe Blunt Traumatic Brain Injury on 6-Month Neurologic Outcomes: A Systematic Review and Meta-Analysis

Introduction: Moderate-to-severe TBI (msTBI) disproportionately affects younger populations with high mortality and severe morbidity amongst survivors. A higher hemoglobin level has been suggested to improve oxygen delivery to the injured brain, and recent randomized trials revealed that more liberal hemoglobin (Hgb) transfusion thresholds may improve 6-month neurologic functional outcomes measured by Glasgow Outcome Scale Extended (GOS-E). This article aims to perform a comprehensive meta-analysis of functional neurologic outcomes and early mortality in msTBI patients with liberal (8 g/dL) versus restrictive (7 g/dL) hemoglobin (Hgb) transfusion thresholds. Methods: The Medline, Embase, and Cochrane databases were searched for primary literature concerned with msTBI and early Hgb transfusion thresholds, from inception to October 2025. Risk of bias was assessed for all selected articles. With a common-effect model, we estimated the pooled odds ratio of the primary outcome (6-month unfavorable outcome defined as GOS-E ≤ 4 or 5) and the secondary outcome (30-day mortality) for liberal versus restrictive Hgb transfusion thresholds. Results: After reviewing 484 articles, 12 met the inclusion criteria with 8 reporting 6-month functional neurological outcomes and 10 that reported 30-day mortality. After a direct comparison of 5208 cumulative patients, those with more liberal transfusion thresholds had a statistically significant reduction in unfavorable outcomes at 6 months (OR = 0.67; 95% CI [0.58–0.77]; p < 0.0001) compared to those with restrictive thresholds. Liberal transfusion thresholds showed no significant effect on 30-day mortality with the direct comparison of 4589 cumulative patients (OR = 0.93, 95% CI [0.78–1.11]). Conclusions: Higher Hgb transfusion thresholds in patients presenting with msTBI can improve functional outcomes at 6 months with a lack of significant effects on 30-day mortality.