“…Anemia and RBC transfusion have been observed in multiple previous studies as important risk factors for AKI after cardiac surgery, but the interrelationship between these variables and AKI has not been as extensively reported. 19,20 In a single-centre observational study comprised of 2,113 propensity-score matched pairs of anemic and non-anemic patients who underwent cardiac surgery with CPB and received up to three units of perioperative RBC transfusions, the risk of AKI was increased in direct proportion to the number of transfusions in both groups, but the increase was much more pronounced in anemic patients. 7 In non-anemic patients, the AKI rate increased from 1.7% in non-transfused patients to 3.2% in those who received three units of RBCs (P = 0.1); however, in anemic patients, the rate increased from 1.8% to 6.6% (P \ 0.0001).…”