Indications for red blood cell transfusion in cardiac surgery: A systematic review and meta-analysis

Background: Good blood management is an important determinant of outcome incardiac surgery. Current guidelines recommend restrictive red blood cell (RBC)transfusion practice. Our objective was to systematically review the evidence fromrandomised controlled trials (RCTs) and observational studies that are used to informtransfusion decisions in adult cardiac surgery.

Methods: We searched electronic databases (PUBMED, EMBASE, Cochrane Library,DARE) from inception to May 2015, databases from specialist societies, andbibliographies of included studies and recent relevant review articles. RCTs thatevaluated the effect of liberal versus restrictive RBC transfusion threshold in cardiac andnon-cardiac surgery patients, and observational studies that evaluated the effect of RBCtransfusion compared with no transfusion on postoperative outcomes in adult cardiacsurgery patients were included. Adjusted odds ratios were pooled using fixed- andrandom-effects meta-analyses.

Findings: Data from 6 cardiac surgical RCTs (3352 patients), 19 non-cardiac surgicalRCTs (8361 patients), and 39 observational studies (232 806 patients) were included.The pooled mortality odds ratios comparing liberal versus restrictive transfusionthresholds were 0·70 (95% CI 0.49–1·02, p=0.06) and 1·10 (95% CI 0·96-1·27, p=0.16)for cardiac surgical RCTs and RCTs in settings other than cardiac surgery, respectively.By contrast, observational cohort studies in cardiac surgery found that RBC transfusioncompared with no transfusion was associated with substantially higher mortality (OR2·72; 95% CI 2·11–3·49, p<0.001) and other morbidity, although with substantialheterogeneity and small study effects.

Interpretation: Evidence from RCTs in cardiac surgery refutes findings fromobservational studies that RBC transfusion is associated with a substantially increasedrisk of mortality and morbidity. Such studies, and RCTs in non-cardiac surgery, shouldnot be used to inform treatment decisions or guidelines for cardiac surgery patients.