The comparison between liberal and restrictive transfusion strategies has been the topic of intense debate. To date, no study that ever found that one approach was superior to the other. However, the absence of difference suggested that a restrictive transfusion policy should be preferred as this strategy helps reduce blood product exposure. In 2013, Carson et al. published the results of the MINT pilot study suggesting that the liberal transfusion strategy was associated with a trend towards fewer major cardiac events and deaths in patients with symptomatic coronary artery disease. Despite the preliminary nature of the results, this study seemed to support the adoption of a more liberal transfusion strategy in the cardiac population.
The TRICS III study is a large prospective randomised non-inferiority trial that aimed to compare the safety of a restrictive transfusion strategy (haemoglobin level <7.5 g/dL) with a liberal transfusion strategy (haemoglobin level <9.5 g/dL) in moderate to high risk patients (EuroSCORE ≥6) undergoing cardiac surgery. The primary endpoint of the study was a composite of 28-day mortality, myocardial infarction, stroke, and new onset of renal failure. The study included 5092 patients who underwent cardiac surgery at 73 sites in 19 countries; 26.1% underwent CABG surgery only, 27.7% underwent CABG with another procedure, and 46.2% underwent non-CABG surgery. In the restrictive-threshold group, 52.3% of the patients received a RBC transfusion after randomisation, as compared with 72.6% of those in the liberal-threshold group (odds ratio [OR], 0.41; 95% confidence interval [CI], 0.37-0.47; P < 0.001). Mortality was 3.0% in the restrictive-threshold group and 3.6% in the liberal-threshold group. The incidence of the primary composite endpoint was 11.4% in the restrictive transfusion group as compared with 12.5% in the liberal group (OR, 0.90; 95% CI: 0.76-1.07). The results of the TRICS III study indicate that a restrictive transfusion strategy may be adopted in moderate to high risk cardiac patients undergoing cardiac surgery. The results contrast with the preliminary results of the MINT study and the results of the TITRe2 trial, which appeared to suggest that a restrictive transfusion strategy could increase the risk of complications in patients with symptomatic coronary artery disease or in the postoperative period of elective cardiac surgery. While a restrictive transfusion strategy should be preferred also in the cardiac surgical population, physicians should however keep in mind that the definition of the optimal transfusion strategy should not only be based on a single transfusion threshold/number, but should take into account the patient’s characteristics (e.g. co-morbidities) and clinical context (e.g. active bleeding), and that one size doesn’t necessarily fit all. – David Faraoni