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

Patients undergoing cardiac surgery are among the most common recipients of allogeneic red blood cell (RBC) transfusions. However, whether restrictive RBC transfusion strategies for cardiac surgery achieve a similar clinical outcome in comparison with liberal strategies remains unclear. We searched electronic databases from inception to December 2017 for randomized controlled trials (RCTs). We calculated the risk ratios (RRs) and weighted-mean difference (MD) using a random-effects model. We included 9 RCTs with a total of 9005 patients. There was no significant difference in mortality between groups [RR 1.03; 95% confidence interval (CI) 0.74-1.45; P=0.86]. In addition, there were no significant differences between groups in the clinical outcomes of infections (RR 1.09; 95% CI 0.94-1.26; P=0.26), stroke (RR 0.98; 95% CI 0.72-1.35; P=0.91), respiratory morbidity (RR 1.05; 95% CI 0.89-1.24; P=0.58), renal morbidity (RR 1.02; 95% CI 0.94-1.09; P=0.68), myocardial infarction (RR 1.00; 95% CI 0.80-1.24; P=0.99), cardiac arrhythmia (RR 1.05; 95% CI 0.88-1.26; P=0.56), gastrointestinal morbidity (RR 1.93; 95% CI 0.81-4.63; P=0.14), or reoperation (RR 0.90; 95% CI 0.67-1.20; P=0.46). There was a significant difference in the intensive care unit length of stay (h) (MD 4.29; 95% CI 2.19-6.39, P<0.01) favoring the liberal group. However, there was no significant difference in the hospital length of stay (days) (MD 0.15; 95% CI -0.18 to 0.48; P=0.38). In conclusion, this meta-analysis showed that restrictive strategies for RBC transfusion are as safe as liberal strategies in patients undergoing cardiac surgery with regards to short-term clinical outcomes.