Liberal vs. restrictive transfusion strategies for acute brain injury: a systematic review and frequentist-Bayesian meta-analysis.

Summary

Across 4 RCTs (n=1,853), liberal transfusion thresholds (hemoglobin ≥9 g/dL) did not significantly improve 180-day favorable neurological outcomes versus restrictive thresholds (≥7 g/dL). Frequentist, Bayesian, and trial sequential analyses showed that one large trial strongly influenced heterogeneity; sensitivity analyses excluding it suggested potential benefit for liberal strategies. The authors advocate subgroup-focused research to enable individualized transfusion targets.

Key Findings

• Included 4 RCTs (N=1,853): pooled RR for favorable neurological outcome with liberal vs restrictive transfusion was 0.84 (95% CI 0.65–1.09).
• Frequentist, Bayesian, and trial sequential analyses demonstrated substantial influence of a single trial on heterogeneity and effect size.
• Sensitivity analyses excluding the influential trial and restricting to low risk-of-bias studies suggested possible benefit of liberal transfusion.

Clinical Implications

Do not universally adopt a liberal hemoglobin threshold (≥9 g/dL) for ABI; a restrictive threshold (≥7 g/dL) remains reasonable for most patients. Consider individualized strategies guided by physiology (e.g., brain tissue oxygenation, anemia severity, ongoing bleeding) while awaiting subgroup-specific RCTs.

Limitations

• Only four RCTs with heterogeneity; overall effect heavily influenced by one trial.
• Potential variations in transfusion protocols, co-interventions, and ABI etiologies across studies limit generalizability and subgroup inference.

Future Directions

Conduct adequately powered, physiology-guided RCTs to identify subgroups (e.g., impaired brain oxygenation, severe anemia, ongoing bleeding) who may benefit from higher hemoglobin thresholds; consider individual patient data meta-analyses.