Comparative effects of hemodilutional anemia and transfusion during cardiopulmonary bypass on acute kidney injury: a prospective randomized study.

AIM: Acute kidney injury after cardiopulmonary bypass has been associated with dilutional anemia during surgery. We aimed both to explore if this relation is modulated by blood transfusion and to understand the postoperative contribution of protein oxidation.

METHODS: In this randomized prospective study, after ethics committee approval and informed consent, 30 patients undergoing first-time elective coronary artery bypass grafting (CABG) with hematocrit between 21% and 25% at any time during extracorporeal circulation (ECC) were randomly and equally allocated into two groups. Group I consisted of patients who received red blood cells (RBC) during ECC, while in Group II, patients did not receive any RBCs. Besides routine hemodynamic and biochemical parameters, markers of renal injury such as neutrophil gelatinase-associated lipocalin (NGAL), creatinine clearance, and protein oxidation parameters (advanced oxidative protein products [AOPP], total thiol [T-SH]) were determined in both groups.

RESULTS: (1) Both cardiovascular parameters (MAP, HR) and the hospitalization period of the transfused group were not significantly different compared to the non-transfused group (P > .05); (2) While urine NGAL level (P < .05) increased and GFR (P < .01) decreased in the transfused group compared to the preoperative period, there were no significant changes in respective parameters of the non-transfused group compared to preoperative period; (3) AOPP concentrations did not change compared to postoperative periods in both groups (P > .05). However, T-SH concentration showed a transient increased at postoperative hour 6 (P < .001 vs preoperative period) but normalized at postoperative hour 24 (P > .05 versus preoperative period).

CONCLUSION: These findings suggest that a hematocrit value over 21% during ECC is safe for renal functions. RBC transfusion just to increase hematocrit may be deleterious.