Adult patients undergoing surgery (14 studies, n= 8,641).
Restrictive blood transfusion strategy.
Liberal blood transfusion strategy.
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.