Population
Adult patients undergoing surgery (14 studies, n= 8,641).
Intervention
Restrictive blood transfusion strategy.
Comparison
Liberal blood transfusion strategy.
Outcome
There was no difference in 30-day mortality relative risk (RR) 0.96, and pooled postoperative morbidity among the studied outcomes when comparing restrictive and liberal protocols. Two trials reported worse composite outcomes with restrictive triggers. Intraoperative (RR 0.53) and perioperative (RR 0.70) blood transfusions were significantly lower in the restrictive group compared to the liberal group.