Restrictive versus liberal red blood cell transfusion strategies for cardiac surgery: a systematic review and meta-analysis of randomized controlled trials

The equivalence of transfusion-related outcomes between restrictive and liberal red blood cell (RBC) transfusion strategies after cardiac surgery remains to be determined. This review provides an overview of the impact of restrictive RBC transfusion strategies compared with liberal transfusion strategies on the transfusion-related outcomes of postcardiac surgery patients. Studies in MEDLINE, Elsevier, Cochrane Central Register of Controlled Trials and Web of Science databases until March 2025 were searched. Studies compared the effects of restrictive RBC transfusion strategies with liberal transfusion strategies in postcardiac surgery patients were eligible. Two reviewers extracted data independently. Data including sample size, characteristics of patients, intervention and outcomes were extracted. Primary outcome was respiratory complications. Subgroup analyses were conducted by time of follow-up and Euroscore I. Review Manager 5.4 was used to evaluate the risk of bias and data. Random errors were evaluated by trial sequential analysis (TSA). Of the 4293 records identified, 13 studies compared restrictive versus liberal transfusion strategies, including 9,267 patients receiving restrictive transfusion (49.98%) and 9,275 receiving liberal transfusion (50.02%). There was no significant difference in respiratory complications between the restrictive transfusion group and the liberal transfusion group (risk ratio RR 1.07; 95% confidence interval CI 0.90–1.26; P = 0.44), but we found a statistically significant for gastrointestinal complications (RR 1.99; 95% CI 1.05–3.77; P = 0.04) and units of RBC transfusions (mean deviation MD -0.70; 95% CI -0.96–-0.43, P < 0.00001). Different transfusion strategies had no statistically significant effect on other transfusion-related outcomes. Subgroup analyses for mortality indicated that patients with low Euroscore I risk preferred restrictive transfusion (RR 1.72; 95% CI 1.16–2.57; P = 0.007). The TSA indicated insufficient number of trials and evidence to support firm conclusions. There are no significant differences in the risk of respiratory complications between restrictive and liberal transfusion strategies. However, the restrictive transfusion strategy is associated with an increased risk of gastrointestinal complications and a lower number of RBC transfusion units in patients undergoing cardiac surgery. Additionally, restrictive transfusion may reduce mortality in patients with low Euroscore I risk. Clinically, these findings support an individualized transfusion approach, in which restrictive strategies may be appropriate for selected low-risk patients, while transfusion decisions in higher-risk patients should carefully balance potential gastrointestinal risks against the benefits of blood conservation.